Blast furnace slag has a long tradition of use in different areas of civil engineering. From the 19th century to the present day, there has been a wide range of cost-effective and environmentally friendly applications for this industrial by-product. Starting with data on the historic use of blast furnace slag and continuing to todays production rate and modern usage, this chapter presents the most common and closely investigated applications of blast furnace slag in a wide range of civil engineering areas. Blast furnace slag has latent hydraulic properties that permit its most common application as a cement additive and in concrete structures. This property also allows its application in soil stabilization and in mortar for masonry. In this chapter, the results of research conducted worldwide (laboratory and in situ) are presented to illustrate the high value of blast furnace slag as a material in civil engineering projects.
Blast furnace slag is a calcium-silicate-based product removed from the top of molten iron during its extraction from ore in a blast furnace. Usually, it is rapidly cooled to a glassy state and ground for use in construction materials (Provis etal., 2015). By the step of water quenching and out of rapid decrease in temperature, most of the compounds have not reached a stable phase. The slag retaining its former structure as a vitreous body shows good activity. From statistics, 0.31 tonne BFS is produced during the production of 1 tonne of pig iron. The discharge and accumulation of BFS not only require much labor force, raw materials, and financial investment but also pollute the environment. Thus, preparing geopolymers by using BFS for solid waste recycling, lower energy cost, and CO2 emissions is of great significance (Wang etal., 2011). In addition, the existence of BFS shows the property of reducing the permeability of the penetrant, thus enhancing the durability of geopolymers and favoring the long-term capture of heavy metals in the solidified matrix. Reactive CaO, SiO2, and Al2O3 in BFS were beneficial to the generation of geopolymers. The BFS in the AAC reacts with a soluble sodium silicate activator to form poorly crystallized CSH gel. The reaction of BFS with water is very slow, forming a hardening binder (Huang etal., 2016). The role of the alkaline activator is to accelerate the reaction, allowing the material to harden and strengthen within hours to days. This process produces the indispensable early strength in S/S products (Wang etal., 2011).
Recent studies have shown that AAC could immobilize toxic elements very well. Toxic elements, such as Zn2+, Pb2+, Cd2+, and Cr6+, could be effectively immobilized in NaOH, Na2CO3, and sodium-silicate-activated slag cements. The AAC shows superior compatibility with toxic elements (Sargent etal., 2014). Huang etal. (2016) studied the stabilization of Cr6+ by using BFS-based geopolymer. They conclude that a series of reactions such as adsorption, physical immobilization, ion exchange, neutralization, precipitation, reduction, and complex formation may be involved during the S/S process. During these reactions, the decrease of S2 in BFS makes a great difference in Cr6+ stabilization. The combined effects significantly immobilize Cr6+.
Blast furnace slag (BFS) is a by-product from iron production in blast furnaces, which are fed by a mixture of iron-ore, coke and limestone. In the process, the iron ore is reduced to iron while all remaining materials form the slag, which is tapped off as a molten liquid and cooled. Depending on the cooling method the BFS can be produced as air-cooled, granulated, expanded and pelletized (De Brito and Saika, 2013; Patel et al., 2004). A typical chemical composition of BFS is shown in Table 10.2. The main components are silica, calcium oxide, magnesium oxide, ferrite and aluminium oxides.
The air-cooled slag has very weak cementing properties, angular particle shape with surface textures from glassy to fractured when crushed. The air-cooled slag aggregates are comparable with natural aggregates but have slightly lower density and require addition of higher amount of fine particles to the concrete mix due to their angular shape. Controlled cooling process with addition of certain amounts of water or air can produce lightweight expanded or foamed products (De Brito and Saika, 2013). The palletised slag can be produced by the application of cooling and solidification processes. The obtained aggregate surface is glossier and adsorbs significantly less water in comparison with air-cooled or expanded slag aggregates. Slag quenched with water, followed by grinding showed very good cementing properties and is used as a secondary cementitious binder for Portland cement or as a primary binder in alkali activated systems.
Blast furnace slag is used successfully in mud-to-cement conversion worldwide because of its economic, technical, and environmental advantages (Pessier et al., 1994). Slag-mix slurries were used as primary, temporary abandonment and sidetrack plug cements during prospect predrilling in the Gulf of Mexico. However, the penetration rates were slower than expected when these plugs were drilled out, hence a basic study of its drilling properties was initiated.
Slag-mix, solidified mud, and conventional class H Portland cement were evaluated under controlled laboratory conditions to better understand and quantify differences in drillability between these two types of cement under realistic downhole conditions. The objectives of this study were to refine bit selection and drilling practices for more cost effective slag-mix plug drilling.
Blast furnace slag is used successfully as a mud-to-cement conversion technology in oil well cementing worldwide because of economic, technical, and environmental advantages . Slag-mix slurries were used as primary, temporary abandonment and sidetrack plug cements during prospect predrilling in the Gulf of Mexico. However, the penetration rates were slower than expected when these plugs were drilled out. Therefore a basic study concerning the drilling properties was initiated.
Slag-mix, solidified mud, and conventional class H Portland cement were evaluated under controlled laboratory conditions to better understand and quantify differences in drillability between these two types of cement under realistic downhole conditions. The objectives of this study were to refine the bit selection and drilling practices for more cost effective slag-mix plug drilling.
Molten blast furnace (BF) slag and steel slag are produced simultaneously with iron and steel manufacturing. BF slag results from smelting iron ore, coke, and fluxes during the operations of extracting iron from the iron ore. Steel slag is formed during refining operations converting crude iron into steel by combining fluxes with the nonferrous oxides and other unwanted elements in the raw materials under molten state. Slag is a nonmetallic by-product containing dominantly CaO, SiO2, MgO, and Al2O3 and their solid solutions. Knowledge of iron and steel production, the slag generation, and their properties, are of great interest and are presented in this chapter.
Expanded blast furnace slag is a small part of the supply of structural lightweight aggregates. Annual production since 1985 has been about 1 million short tons (9105t); in 1997 that was about 12% of the total lightweight aggregate construction-related usage. The amount used was only 06% of all blast furnace slag produced, and the supply seems ample for many years to come. The slag typically contains 3242% SiO2, 716% Al2O3, 3245% CaO, 0115% Fe2O, 0210% MnO, 05% MgO, and 12% S (R. S. Kalyoncu, personal communication, June 1999).
Minor blast furnace slag can be pelletized by moderate cooling. Pelletized slag is solidified by water and air quenching in conjunction with a spinning drum. Molten slag containing gas bubbles is projected through a water spray so as to form pellets. These are rounded in shape and have a smooth coated surface. However, crushing (which destroys the coating) has to be used to obtain fine particles. The bulk density of pelletized blast furnace slag is typically 850kg/m3 (55lb cf). Appropriate production control ensures the formation of crystalline material, which is preferable for use as aggregate; this is in contrast to blast furnace slag pellets used in the manufacture of blast furnace cement (Neville, 2012). Experience has shown that the coarser pellets have properties like crystalline slags and the finer pellets like vitrified slags. Subsequent to the relevant heat treatment, crystalline, vitrified, and pelletized slags undergo a mechanical processing to produce different slag products (Motz, 2002).
The pelletizing process was developed in Ontario, Canada, and one of the major types of products in Ontario, Canada (MNRO, 1992). It has been used both as lightweight aggregate and in slag cement manufacture when suitably vitrified.
Blast furnace slag (abbreviated GGBFS, for ground granulated blast furnace slag) is broadly described as a mixture of poorly crystalline phases with compositions resembling gehlenite (2CaOAl2O3SiO2) and akermanite (2CaOMgO2SiO2), as well as depolymerized calcium silicate glasses. The degree of depolymerization largely controls reactivity. As slag is generated at high temperature as a liquid in the blast furnace during iron production and subsequently quenched, its composition is essentially that of an overcharge-balanced calcium aluminosilicate framework i.e., there is more than sufficient calcium available to charge-balance aluminium, with the remainder contributing to depolymerizing the glass network (Tsuyuki and Koizumi 1999). In the context of geopolymer synthesis from slag glasses, the key glass network forming cations are Al3+ and Si4+; the divalent Ca2+ and Mg2+ act as network modifiers along with any alkalis present.
Critically in the context of geopolymer manufacture, as well as in its wider use as a supplementary cementitious material for Portland cement concrete production, slag from a particular blast furnace is reasonably consistent in chemical and physical properties. However, despite this quality control within individual locations, slag compositions do vary between specific furnaces and ores. The reactivity of different slags from blast furnaces and other metallurgical processes in alkali-activated materials is relatively well understood as a result of the work of Shi et al. (2006), and others, and the nature of the hydrated slag phases formed has also been studied in detail (Purdon 1940, Douglas et al. 1992, Richardson et al. 1994, Wang and Scrivener 1995, Puertas et al. 2000, Song et al. 2000, Fernndez-Jimnez et al. 2003, Wang and Scrivener 2003, Gruskovnjak et al. 2006, Xu et al. 2008). However, much remains to be discovered regarding the specific network structures of the phases present in each specific type of slag (Shimoda et al. 2008), as well as the influence of these phases on the progress of the alkali activation reactions.
It is also well known that the reactions of slag are dominated by small particles. Particles above 20 m in size react only slowly, while particles below 2 m react completely within approximately 24hrs in blended cements and in alkali-activated systems (Wan et al. 2004, Wang et al. 2005). Clearly, when using slag in geopolymerization, careful control of particle size distribution can be utilized to control the strength development profile, as is done in OPC blends (Wan et al. 2004).
ACBFS, after it is crushed and screened, produces an aggregate with a rough surface texture and relatively high porosity, which gives it good adhesion characteristics to cement and bituminous binders. Basic oxygen steel slag is relatively nonporous and produces a high-density aggregate with high crushing strength. The processed material is denser and stronger than BF slag. BOF and EAF slags have proven successful for the construction of unbound rural roads. Recently, road trials have been conducted in EAF and ladle slag use as road base and subbase. Ladle slag contains a high content of lime contributing to quick self-hardening, which results in a higher load-bearing capacity and a lower dust generation on rural roads and surrounding areas. Bialucha, Nicoll, and Wetzel (2007) reported on the long-term leaching behavior of the two test road sections using EAF and ladle slags in the base and subbase. The subject test road was built with two different aggregates or mixtures: (i) 40cm of natural stone as the base and 10cm of a mixture of EAF and ladle slag (1:1) in the unbound surface layer; and (ii) 50cm 100% EAF slag. The comparison of the two materials and their combination are summarized in Table 8.4. All materials are characterized concerning technical qualities, mineral and chemical composition, and leaching properties.
Laboratory and road tests were carried out to investigate the leaching behavior of the slag materials. Suction cups were used to collect the seepage water in the middle and the edge zone of both sections with either EAF slag and natural aggregate in the road base as well as 5m (16.4 ft.) to the side of the test road. The results have proved that no environmentally relevant amounts of heavy metals or salts had leached out of the material and have influence on the groundwater. Also by using the slag materials, no appreciable amounts of dust covering the road and surrounding areas was observed. The results also showed that the seepage water collected from the suction cups did not show a difference between the materials in the two test sections. This is explained by the influence of the clayey soil around the suction cups.
Vazquez et al. (2010) reported on test road sections in both unbound and cement stabilized base courses using EAF and ladle slag. The unbound granular consists of two layers of EAF and ladle slag mixtures. Each layer is 20cm (8in.) thick and aged independently for three months. The materials used are summarized in Table 8.5.
Data from Vazquez, E., Barra, M., Perez, F., Alavedra, P., Scheibmeir, E., & Bou, M. (2010). Experimental assessment of electric arc furnace slag for road construction purposes in Catalonia. In: Proceedings of the 6th European slag conference, October 2022nd, Madrid, Spain.
All the expansion test results correspond to 168h of testing. An average expansion rate on the construction site showed 2.25%, which was similar to the results tested in the laboratory. The bearing capacity tracked for 6 months in various points of the test road showed a continuous increase of the modulus.
The cement stabilized section consisted of 10cm (4in.) natural subbase course, 30cm (12in.) of hydraulic bound base course, combining 10cm of natural soil, 20cm (8 in.) of EAF and ladle slag together with 2% of cement and 16cm (5/8in.) bituminous mixture (three layers) was constructed. Table 8.6 presents the cement stabilized pavement structure. Studies also showed how mixed use of EAF and ladle slag can reduce the binding agent required in stabilized base and subbase course. The results showed that the minimum compressive strength required can be obtained by adding 2% of cement. The mixture of natural soil and EAF and ladle slag presented a higher strength than the slag alone. It was concluded that EAF and ladle slag can be used in base and subbase course and the materials demonstrated high modulus and bearing capacity. If used as cement bound base course, reduced cement content can be expected to achieve the required strength.
Data from Vazquez, E., Barra, M., Perez, F., Alavedra, P., Scheibmeir, E., & Bou, M. (2010). Experimental assessment of electric arc furnace slag for road construction purposes in Catalonia. In: Proceedings of the 6th European slag conference, October 2022nd, Madrid, Spain.
One of the nonferrous slags, nickel slag, was successfully used in highway construction (Wang et al., 2011). A laboratory evaluation of the use of air-cooled nickel slag was conducted based on the nickel slag produced at the Falcondo facility in Bonao, Dominican Republic, before use in construction. Nickel slag is a coproduct of ferronickel production that is solidified under ambient atmospheric conditions. Laterite ore is open-pit mined and then processed through a preparation, reduction, and electric furnace melting process. Molten slag is removed from one end of the furnace and ferronickel is removed from the other end for refining and shipment. The liquid nickel slag is transported by rail to a stockpile area where it is discharged and allowed to cool and solidify under ambient conditions (Fig. 8.4). This air-cooling results in some fragmentation into sizes conveniently suitable for riprap, armor stone, and gabion stone use. The fragmented air-cooled nickel slag can be crushed and screened for a variety of construction aggregate purposes, as engineered fill, granular base and subbase, and HMA coarse and fine aggregate.
Fig. 8.4. The dumped molten ferronickel slag is fragmented by thermal shock. during ambient cooling in the slag storage area (A). Fragmented sized and crushed and screened to a wide range of gradations for highway construction uses (B).
Data from Wang, G., Thompson, R., & Wang, Y. (2011). Hot mix asphalt that contains nickel slag aggregate Laboratory evaluation of use in highway construction. Journal of the Transportation Research Board, 2(2208), 18. doi:10.3141/2208-01.
Based on considerable practical positive international experience as well as satisfactory local use for several years, leachate characterization, mineralogical evaluations, and the favorable comprehensive accelerated stability and durability testing, nickel slag was given full project approval for engineered fill, granular subbase, and HMA aggregate use. Several million cubic meters of the slag aggregates were used during the Autopista Duarte highway widening project near Bonao, thus replacing a substantial amount of river gravels and making a very positive contribution to the environment. Figs. 8.5 and 8.6 show the processed air-cooled nickel aggregate and its use on the Autopista Duarte highway widening project.
Cement, in general, adhesive substances of all kinds, but, in a narrower sense, the binding materials used in building and civil engineering construction. Cements of this kind are finely ground powders that, when mixed with water, set to a hard mass. Setting and hardening result from hydration, which is a chemical combination of the cement compounds with water that yields submicroscopic crystals or a gel-like material with a high surface area. Because of their hydrating properties, constructional cements, which will even set and harden under water, are often called hydraulic cements. The most important of these is portland cement.
This article surveys the historical development of cement, its manufacture from raw materials, its composition and properties, and the testing of those properties. The focus is on portland cement, but attention also is given to other types, such as slag-containing cement and high-alumina cement. Construction cements share certain chemical constituents and processing techniques with ceramic products such as brick and tile, abrasives, and refractories. For detailed description of one of the principal applications of cement, see the article building construction.
Cements may be used alone (i.e., neat, as grouting materials), but the normal use is in mortar and concrete in which the cement is mixed with inert material known as aggregate. Mortar is cement mixed with sand or crushed stone that must be less than approximately 5 mm (0.2 inch) in size. Concrete is a mixture of cement, sand or other fine aggregate, and a coarse aggregate that for most purposes is up to 19 to 25 mm (0.75 to 1 inch) in size, but the coarse aggregate may also be as large as 150 mm (6 inches) when concrete is placed in large masses such as dams. Mortars are used for binding bricks, blocks, and stone in walls or as surface renderings. Concrete is used for a large variety of constructional purposes. Mixtures of soil and portland cement are used as a base for roads. Portland cement also is used in the manufacture of bricks, tiles, shingles, pipes, beams, railroad ties, and various extruded products. The products are prefabricated in factories and supplied ready for installation.
Quality, Strength, Reliability, Performance, and Consistency are words that are synonymous with Binani Cement, the flagship company of the Braj Binani Group. In cement matters, these qualities make Binani Cement the preferred choice for engineers, builders, and contractors. Binani Cement forms the foundation of some prestigious projects in India and abroad Dubai Metro (fully automated rail network), and the state of the art Port Khalifa at Abu Dhabi.
Binani Cement is amongst Indias reputed manufacturers of cement with a global manufacturing capacity of 11.25 million tons per annum with an integrated plant in India and China, and grinding units in Dubai. The Companys product portfolio includes:
General purpose high strength cement, which is widely used in general civil engineering construction work combines with water, sand and stone to form a durable and strong construction concrete capable of bearing great loads. Binani Cement produces OPC cement of two grades 43 and 53.
Environmental friendly and economical PPC cement is valued for its greater resistance to the attack of aggressive waters as compared to normal Portland Cement. This is the preferred choice of cement for building hydraulic structures, mass concreting works, marine structures, masonry mortars and plastering. High compressive strength, consistency in quality and accuracy in net weight of the cement bag make Binanis PPC & OPC cement the most trusted and preferred cement in the market today.
Granulated blast furnace slag is a by- product of steel plants, granulation is done by quenching with water. GGBS is used to make durable concrete structures in combination with ordinary Portland cement and/or other pozzolanic materials. It is known for its durability, extending the lifespan of buildings from fifty years to a hundred years. Binani Cement produces GGBFS of grade 120.
The Binani Cement Limited Plant was initially setup at Binanigram with a capacity of 1.65 million tons per annum (MPTA) but today, the cement capacity is 6.25 MTPA. After its success in the Indian market, Binani Cement has taken giant strides into the international arena. Today, it has manufacturing facilities in China -Shandong Binani Rongan Cement Co. Ltd. (SBRCCL) and Dubai Binani Cement Factory LLC that are setting global benchmarks.
India is the second largest cement producer in the world. India has a capacity to produce cement of around 151.2 million tones per annum. In the below article you can find the top cement companies in India.
Ambuja Cement was founded in the year 1983 and has its headquarters located in Mumbai. Ambuja Cement is well known for its eco-friendly manufacturing of Cement as an initiative for sustainability. The company was formerly known as Gujarat Ambuja Cement.
The company has a production capacity of 29.65 million tons annually. The company has around 5 manufacturing plants in India and around 8 grinding units across India. The company also offers superior products other than cement such as Ambuja roof special, Ambuja Composem, Ambuja cool wall, Ambuja Railcem and many more.
Ultratech Cement was founded in the year 1983 and has its headquarters located in Mumbai, India. Ultratech cement is the largest grey cement manufacturer in the country. It is considered to be the best cement manufacturer in the country.The company has a worldwide presence that includes countries such as UAE, Bahrain, Sri Lanka and Bangladesh.
The company is also a leading manufacturer of RMC and white cement. The company is considered to be Indias most trustworthy cement brand which offers high-quality cement types such as OPC, PPC and Portland blast furnace slag cement.
Shree Cement was founded in the year 1979 and has its headquarters located in Kolkata. Shree Cement is considered to be the third-largest cement manufacturer in India. Shree Cement has two brands under them which are Bangur Cement and Rokcstrong cement.
Shree Cement is also one of the best eco-friendly cement manufacturers in India. The company offers good quality cement at an affordable price. This attracts the customers. The company has a production capacity of 37.9 metric tonnes annually.
ACC Cement was founded in the year 1936 and has its headquarters located in Mumbai, India. ACC cement was formerly known as the Associate Cement Company. It is one of the leading cement manufacturing companies in the country.
The company has a global presence in over 80 different countries. ACC cement is one of the earliest adopters of eco-friendly cement manufacturers in India. The company has an R&D center located in Mumbai. The company has a production capacity of around 33.41 million tonnes per annum.
Birla Cement was founded in the year 1996 and has its headquarters located in Mumbai, India. Birla Cement is one of the largest cement producers in India. It is a flagship company of M.P Birla Group. The company is not just part of the cement industry but also other sectors such as jute, textile, steel, education, health sector, agricultural business, etc.
The company has around 10 cement plants located across India and a production capacity of 15.5 metric tones annually. The company has a strong presence in Central, North and East India. It offers different types of cement which are marketed under the brand names such as Perfect Plus, Multicam, Smart, etc.
Dalmia Cement was founded in the year 1939 and has its headquarters located in Delhi, India. Dalmia Cement is considered to be the fourth biggest cement company in the country in terms of installed capacity.
The company has a strong presence in the southeast, northeast and eastern parts of India. The company offers different types of cement under the brand names Konark cement, Dalmia cement and Dalima Dsp. Dalmia Bharat group has involvement in other ventures such as Cement, Thermal energy, sugar, etc.
Ramco cement is the fifth biggest cement producer in the country. The company manufactures Portland cement using the state of the art technology. The company has the capacity to produce 16.45 metric tones of cement annually.
JK Cement was founded in the year 1975 which has its headquarters located in Kanpur. JK Cement is one of the recognized cement brands in India. The company has a strong distribution network in the country with around 4000 distributors. The company has 3 cement production plants located in Gujarat and Rajasthan.
China: China National Building Materials (CNBM) subsidiary China Building Materials Academy (CBMA) has signed a knowledge sharing agreement with the Canada-based International CCS Knowledge Centre to collaborate on carbon capture technology. Their first initiative will pilot a CBMA model and front end engineering design (FEED) to a test platform with a capture capacity of around 155kg CO2/day on an active cement plant kiln. If successful, the study may see CNBM roll out CCS across its entire cement operations.
Canada: The government has granted a subsidy worth US$20m to Svante for the establishment of a Centre for Excellence for Carbon Capture, Use and Storage in Vancouver, British Columbia. The centre will consist of a filter production plant, headquarters and testing centre. The company said that it will help in the global deployment carbon capture and storage (CCS) solutions at Gigatons scale.
Vancouver is the Silicon-Valley of carbon capture technology development, said Claude Letourneau, the president and chief executive officer of Savante. Lowering the capital cost of the capture of the CO2 emitted in industrial production is critical to the worlds net-zero carbon goals. He added The carbon pulled from earth as fossil fuel needs to go back into the earth in safe CO2 storage.
Philippines: The Department of Trade and Industry (DTI) has launched a new investigation into imports of cement, currently subject to safeguarding tariffs of US$0.20/bag. The investigation follows a request by Cemex Philippines, Holcim Philippines and Republic Cement. The Viet Nam News newspaper has reported that the Vietnam National Cement Association has asked the DTI and the Philippine cement industry to consider whether imports from Vietnam did real damage. In 2020, Vietnams export cement prices fell by 15% year-on-year. Its excess production of cement was 36Mt during the year, and its clinker prices were 20% below the regional average.
Brazil: Cement sales totalled 31.5Mt in the first half of 2021, up by 16% year-on-year. The National Cement Industry Association (SNIC) attributed the growth to home renovations and new construction projects. The association has forecast total sales for 2021 of 64.2Mt, corresponding to an increase of 6% compared to 2020 levels. It expects the same segments to drive growth in 2022, though at a lower rate.
US: Colombia-based Cementos Argos subsidiary Argos USAs Newberry, Florida cement plant produced 140,000t of cement in June 2021. The plant shipped 129,000t of cement. The company says that the production figure beats its previous production record of 128,000t in June 2019 by 9%. The figure for shipments beats the previous shipment record, also from June 2019, of 121,000t by 7%.
Plant production manager Daniel Ball said, Everyone at the Newberry Plant is excited and proud to see these records being set. With the current sales climate, we are able to show the untapped potential Newberry has. This sustained sales commitment would not be possible if it wasnt for all the hard work and dedication of everyone at the plant as well as from Argos plant support staff and Argos Corporate. But with the new record set, we strive to set new records going forward.
Bolivia: Empresa Publica Productiva Cementos de Bolivia (ECEBOL) has officially restarted cement production at its integrated Oruro cement plant in Caracollo. The La Razn newspaper has reported the cost of the restart at US$8.41m. The producer received a cash injection from the government in order to enable it to restock cement bags, pay outstanding salaries and have working capital, according to Bolivian President Luis Arce. The head of state alleges that the previous administration paralysed many of the countrys public companies through mismanagement.
Steel slags (SSs) are usually classified according to the type of furnace in which they are produced. The properties of the slag depend on the type of process used to produce the crude steel, the cooling conditions of the slag and the valorisation process.
In the primary process, crude steel is produced in two ways. In the first method, the iron is produced from ore in the BF, thus, generating BF slag (BFS). BBOF slag (BOFS) is produced in the steelmaking process by using the molten iron coming from the BF. In the second method, slags are generated in the scrap-based steel industry. The first stage of the scrap-based steel industry production generates EAF slag (EAFS) and a second stage is performed to refine the molten steel. The slag produced in the LF (LFS) is the result from steel refining and, therefore, it is generally a heavy metal carrier such as chrome, lead or zinc (CEDEX Ministerio de Fomento, 2018). Table 7.1 shows the characteristics of the main slag types generated by the crude steel industry.
Another aspect that determines the physical and chemical properties of the slag is the type and speed of cooling. If the cooling of the molten slag is performed slowly, the components crystallise into stable structures producing, in most cases, a dense and inert crystalline material. However, if the cooling is rapid, its components are fixed in an amorphous structure and, therefore, the slag is unstable or active in the presence of certain substances. This is the case of the granular BF slag (GBS) which presents hydraulic properties if it is rapidly cooled and is widely used as a partial substitute of clinker in Portland cements.
There are two types of BFS, see Fig. 7.1, depending on the speed of cooling. The air-cooled slags (ABS) are subjected to a slow reduction in temperature (generally to air) and, therefore, have a crystalline structure and physico-chemical stability. Once cooled, the ABS is crushed and sieved according to the geometric characteristics required by the application. The ABS has a density of around 2.5g/cm3 and is used as a concrete aggregate, for bases, subbases and road layers (EUROSLAG; Liu et al., 2013; Nippon Slag Association). The Spanish Instruction for Structural Concrete (EHE08) (Ministerio de Fomento Gobierno de Espaa, 2008; Martn-Morales et al., 2011) only allows the use of BF ABS as aggregates, provided that the requirements regarding sulphate, sulphur and volumetric stability are met.
GBS, see Fig. 7.2, present hydraulic capacity due to its amorphous or vitreous structure. Its chemical composition is the same as that of ABS, but the structure and the stability are different. To obtain rapid cooling so as to obtain a vitreous structure, the slag is granulated. After that, the ABS is ground to sizes below 100m. ABS exhibits cementitious properties and so it is highly appreciated and used in the manufacturing of Portland cements (EUROSLAG; Liu et al., 2013; Nippon Slag Association). In Spain, 100% of produced GBS are used by the cement industry.
BOFS, see Fig. 7.3, present a high content of Fe, so its specific gravity is above 3g/cm3. This type of slag is cooled slowly to cause the crystallisation and stabilisation of its components. The most widespread use is in aggregate production for concrete and road applications (Shi, 2004; Tossavainen et al., 2007; Das et al., 2007; Juckes, 2003; Mahieux et al., 2009; Poh et al., 2006; Shen et al., 2009; Waligora et al., 2010; Xuequan et al., 1999).
The two types of EAFS are presented in Table 7.1: stainless steel (EAFS-S), Fig. 7.4 (Johnson et al., 2003; Huaiwei and Xin, 2011; Rosales et al., 2017), and crude steel (EAFS-C) (Shi, 2004; Tossavainen et al., 2007; Barra et al., 2001; Luxn et al., 2000; Manso et al., 2006; Tsakiridis et al., 2008). The main differences lie in the SiO2 and Fe contents. The high amount of oxide or metallic Fe (which could not be recovered) gives the EAFS-C, Fig. 7.5, a density which is usually above 3.5g/cm3. It is estimated that for each tonne of steel produced in this furnace, between 110 and 150kg of EAFS are generated (UNESID, 2018). When they are used as aggregates, after slow cooling, they have high compressive strength and skid resistance. EAFS have been shown to be high-performance aggregates in high-strength concrete and in road layers.
LFS, see Fig. 7.6, is commonly generated in the production of low-alloy steels and after air cooling and weathering over several days, this material is completely ground into fine white particles (Manso et al., 2005, 2013). Depending on the type of process, two types of LFS can be found. Those saturated with alumina (Tossavainen et al., 2007; Adolfsson et al., 2007; Nicolae et al., 2007; Yildirim and Prezzi, 2011) and those saturated in silica (Manso et al., 2013; Qian et al., 2002; Papayianni and Anastasiou, 2006, 2010; Branca et al., 2009; Rodriguez et al., 2009; Setin et al., 2009; Montenegro et al., 2013). They differ in their composition, having either a higher content of aluminium oxides or a higher content of silica oxide. LFS can be used as raw material in the production of cement, although special care should be taken with the content of fluorine and chlorine, which could adversely affect the properties of the clinker. It accounts for between 10% and 20% of EAFS production (UNESID, 2018).
As has been known, the major concerns with the use of BOS slag in SSBC manufacture have been associated with two issues. One is whether the BOS slag has sufficient volume stability during its service period. If the stability of SSBC is not acceptable, it will lose service significance. The second issue concerns the grindability of BOS slag used in SSBC manufacture. As is known, the main energy consumed during cement manufacture is in the process of calcining and grinding. If the energy consumed in steel slag grinding/magnetic separating is more than that for calcining and grinding of raw materials and clinker, BOS slag will lose its economic significance as an additive of blended cement. Although several papers have been published dealing with steel slag use in blended cement, few have addressed the grinding aspect and little careful laboratory investigations of steel slag grinding phenomena seem to have been done to date. It is considered that the energy consumed in relation to calcining and grinding of raw materials can be saved when using steel slags as active additive materials. However, several questions exist as to the degree of grindability of BOS slag and how it compares with OPC clinker and other materials, the suitable mill feeding size and the overall assessment of grindability.
It is well known that steel slag contains similar mineral composition to that of clinker; however, because of composition fluctuations, the slag may become unstable due to excess free CaO. GBFS possesses hydraulic properties that can only be activated in the presence of an existing basic or sulfate activator such as CaO or CaSO4 (Asaga, Shibata, Hirano, Goto, & Daimon, 1981; Duda, 1987; Narang & Chopra, 1983). Steel slag contains excess CaO that could constitute this activator. These factors comprise the premise for using steel slag as a component material for SSBC manufacture. Experiments have proven that the combined use of steel slag with GBFS and/or OPC clinker can balance the composition fluctuations in the steel slag and some CaO in the steel slag can be absorbed by GBFS, thereby preventing the occurrence of instability of SSBC specimens.
Despite differences in respective quantities of the chemical and mineral constituents that exist between steel slag and OPC clinker, steel slag can be considered comparable with OPC clinker. These differences do not affect the potential use of steel slag as an active material.
Magnetic reseparation of the steel slag can improve the efficiency of intergrinding steel slag and OPC clinker by about 50% compared with intergrinding OPC clinker and nonmagnetically reseparated steel slag. The grindability of mixtures of steel slag and OPC clinker depends on the relative content and initial pregrind size of the steel slag. No decrease in grindability was measured when less than 20% of 2.364.75mm steel slag was added to the OPC clinker.
SSBC paste specimens were inspected when cured. No cracking on the surface of the samples was observed under standard curing conditions for a period of 60 days. Two specimens of each mix, cured in water for 28 days, were treated by saturated steam at 3bar (137C) for 50min. The treatment cycle consisted of 50min presoaking (temperature and pressure build-up), 50min soaking time, followed by 50min cool down period with gradual pressure reduction. Specimens from mixes of BOF slag 1 and 2 exhibited no cracking even after 100min of treatment under the same pressure. The treatment condition is more harsh than that for testing the effect of MgO on OPC. This indicates that the addition of 10% OPC clinker can effectively prevent the occurrence of instability in SSBC (Wang, 1992).
Ratio of early to late strength: the SSBC has higher strength ratio compared with OPC, strength of SSBC at 1 year increases by 152166% of that at 28 days (45.8MPa at 28 days), whereas for OPC it takes 5 years for the strength to reach 150% of 28-day strength;
Grindability is of major importance in the manufacture of slag blended cement. In terms of grindability, BFS is slightly more abrasive than clinker and cogrinding has to be performed with care (Alanyali et al., 2009).
The laboratory results are inconclusive in determining the efficiency of intergrinding steel slag and OPC clinker. Lowrison (1974) reported the Bond index for grindability of different materials: corundum 3035; silica sand 16; cement clinker 15; slag 11 (type of slag not specified).
In a SSBC pilot study conducted by the author, although the weight retained on the 75m sieve for steel slag was higher than that for OPC after grinding, about 30% of the amount of coarse OPC particles still remained as unground particles in the ball mill. This phenomenon did not occur for the steel slag. Judging from the strength of OPC and steel slag, the hardness of steel slag should be close to that of OPC. The main reasons why steel slag may be considered to be difficult to grind may be due to the incorporation of iron scrap. In the laboratory experiments reported here, about 22% by weight of steel slag was attracted by the reseparation magnet, the separated slag particles consisting mainly of fine iron particles. Nonremoval of these materials would make the slag much more difficult to grind. Magnetic reseparation is absolutely necessary, if the steel slag is to be used for manufacture of SSBC, and to ensure that the very fine particles are removed because most of them contain impurities and iron, which affects the quality of the SSBC and decreases the grindability.
Although the grindability of steel slag is rarely covered in the literature, it is of major concern in the manufacture of SSBC. Preliminary work was carried out by using a laboratory ball mill to investigate the grindability of the steel slag and OPC clinker when ground separately and interground for periods of 30 and 60min. OPC clinker having particle sizes in the range of 8.013.2mm and steel slag having particle sizes in the range of 8.013.2mm and 2.344.75mm were used in the test. Comparative tests were performed for magnetically reseparated steel slag, ordinary steel slag, and OPC clinker. The degree of grindability was assessed by particle size distribution. Results of 30min grinding have similar trends.
when 2.364.75mm particle size steel slag is interground with OPC clinker, the grindability of the composite is better than that of OPC clinker provided that the content of steel slag in the composite is not greater than 20%.
Selective use and quantification of steel slag having suitable properties are important aspects for manufacture of SSBC. The slag should be magnetically reseparated prior to grinding for SSBC. Both too fine and too coarse particles are not suitable for SSBC. If particles are very fine, impurities such as dust might be incorporated; if they are too coarse, additional crushing will be necessary and, thus, more energy will be consumed. Particle sizes within a certain range, probably 215mm, should be selected for SSBC manufacture. The incorporation of steel slag with particle size below 5mm can benefit the grinding of OPC clinker. Other particle size materials should be used for other applications (eg, road base, etc.). The addition of steel slag, at content levels of up to 20% of total solid material, is suggested as optimum with regard to stability, economy, and strength of the blended cement.
It is well known that steel slag contains similar mineral composition to that of OPC clinker; however, because of composition fluctuations, the slag may become unstable due to excess free CaO. GBFS possesses hydraulic properties that can only be activated in the presence of an existing basic or sulfate activator such as CaO or CaS (Asaga et al., 1981; Duda, 1987; Narang & Chopra, 1983). Steel slag contains excess CaO that could constitute this activator. These factors comprise the premise for using steel slag as a component material for SSBC manufacture. Experiments have proven that the combined use of steel slag with GBFS and/or OPC clinker can balance the composition fluctuations in the steel slag and some CaO in the steel slag can be absorbed by GBFS, thereby preventing the occurrence of instability of SSBC concrete.
BOS slag is produced during steelmaking by the basic oxygen process. The manufacture of steel involves the removal of excess quantities of carbon and silicon from the iron by injection of oxygen and the addition of small quantities of other constituents that are necessary for imparting special properties to the steel. A lime or dolomite flux is used that combines with the oxidized constituents to form a slag. BOS slag is decanted off from the surface of the molten steel and is normally cooled slowly, by air-cooling or water quenching, in pits or bays prior to being dug and transported to holding areas.
Despite differences in respective quantities of the chemical and mineral constituents that exist between steel slag and OPC clinker, steel slag can be considered comparable with OPC clinker. These differences do not affect the potential use of steel slag as an active material. The main differences are summarized in Table 13.6.
The addition of steel slag to the OPC clinker has to be considered in terms of f-CaO content of steel slag, total f-CaO content of SSBC, and grindability. From the results of grindability, it is known that, from grindability considerations, the optimum addition of steel slag is below 30% of total weight of SSBC (BOS slag and OPC clinker). In addition, the total f-CaO content of SSBC should be less than 2%, which is an acceptable limit for OPC and there should also be a relationship controlling the addition of BOS slag depending on its f-CaO content. From this criterion it can be shown that, provided the relative content of steel slag is controlled, steel slags with a high free calcium oxide content can be used as an ingredient of SSBC. These steel slags would not normally be suitable for other engineering applications. The addition criterion, in terms of f-CaO content, is as follows:
For a given steel slag with 1.6% f-CaO content and OPC clinker with 0.5% f-CaO, if a mixture comprising 20% BOS slag and 10% OPC clinker is interground, the resultant SSBC will be volumetrically stable if f-CaO<2%. Substituting the values into Eq.(13.2), the f-CaO content of SSBC is 0.72%. This is less than 2%, and therefore the mix is of acceptable stability.
A SSBC contains 10% OPC clinker, with 0.5% f-CaO, and 20% BOS slag. What is the maximum allowable f-CaO for the BOS slag? Substituting into Eq.(13.4) gives an answer of 11%. This means that steel slag containing<11% f-CaO can be used in SSBC.
If steel slag is used, natural resources can be preserved in steel industrial areas. Slag can be used for various purposes. There is much more to explore about steel slag as a civil engineering material, including the following:
Steel slag is an industrial byproduct obtained from the steel manufacturing industry. It is produced in large quantities during steel-making operations that use electric arc furnaces. Steel slag can also be produced by smelting iron ore in a basic oxygen furnace. According to methods for cooling molten steel slag, steel slag is classified into five types: natural air-cooling steel slag, water-spray steel slag, water-quenching steel slag, air-quenching steel slag, and shallow box chilling steel slag [47,48]. Most steel slag contains a high content of Fe1-O and other metal oxides. Fe1-O includes FeO, Fe2O3, and Fe3O4, all of which are nonstoichiometric compounds, so Fe1-O has the properties of a semiconductor. The electrical resistivity of FeO and Fe3O4 is 5102 and 4103cm, respectively, which is basically the same as that of pitch-based carbon fiber. As a result, steel slag presents good electrically conductive properties . In addition, steel slag can be used as aggregates in concrete to replace natural aggregates, because it has favorable mechanical properties, including strong bearing and shear strength, good soundness characteristics, and high resistance to abrasion and impact. Steel slag aggregates are fairly angular, roughly cubical pieces with a flat or elongated shape (as shown in Figure2.13 ). They have a rough vesicular nature with many non-interconnected cells, which gives a greater surface area than smoother aggregates of equal volume. This feature provides an excellent bond with concrete binder. Replacing some or all natural aggregates with steel slag is helpful for reducing environmental pollution and the consumption of resources [47,48]. Therefore, steel slag is a promising kind of filler because it works as both functional filler and aggregate. The incorporation of air-quenching steel slag of 0.3155mm (in which the content of Fe1-O is over 30%) into concrete to fabricate mechanically sensitive concrete was investigated by Li etal. in 2005 ; subsequently, Jia performed a systematic study of this concrete (as shown in Figure2.14) [23,50].
Property modification of steel slag was conducted after steel slag was discharged to improve the stability of steel slag. Tests in some countries have shown that adding blast furnace slag or fly ash to the steel slag improved the stability of steel slag. Some research programs resulted in patents that were reflected in Japanese Patents (JPs). These included the addition of materials containing silicate or aluminate into steel slag during discharge (JP 74-58107); putting fine steel slag into molten blast furnace slag (JP 76-61278); adding boric acid or borate into steel slag (JP 78-43690); and mixing molten BOS slag with special steel slag containing Cr2O3 to raise the content of Cr2O3 above 2% (JP 78-30997). The aim of all of these methods is to eliminate the unstable materials in steel slag.
Steel slag has become one of the major sources of aggregates for highway pavement constructions in many state Departments of Transportations (DOTs) in the United States. In the past decades, the use of steel slag in HMA pavements has proven to be extremely successful nationwide. In particular, steel slag is one of the superior aggregates for constructing smart HMA pavements for heavy truck traffic, including SMA and thin, and ultra-thin, HMA overlays, due to its unique physical and mechanical properties, such as hardness, durability, and surface texture. Another potential use for steel slag is for high friction surface treatments (HFST) that are increasingly catching the attention of pavement engineers as an effective solution to addressing high friction demand on horizontal curves. Although steel slag does not have a PSV similar to that of calcined bauxite, its local availability and low price make it a viable aggregate source for HFST, particularly for less severe geometric conditions or relatively large scale projects (Li, 2016).
In Fig. 10.7 a 19mm thick 4.75mm dense-graded HMA pavement has been placed on an interstate highway. The aggregate is compromised of 39% steel slag by weight. The pavement has performed satisfactorily with reference to surface friction and ride quality. Fig. 10.8 shows HFST test patches of steel slag lying on a multilane highway. The test patches are composed of a layer of 13mm steel slag bonded to the existing pavement surface using a specialized resin binder. These test patches functioned very well in terms of surface friction and texture after one winter maintenance season.
For steel slag used as a coarse aggregate in a bound condition, or in a rigid matrix, such as PCC, the resulting integrity and volume stability are basically controlled by the minimum allowable stress of the matrix materials, cement mortar for instance, and the maximum expansion stress, which can be deduced from the expansion force based on appropriate modeling of steel slag particles in the matrix. A usability criterion for steel slag use in confined conditions can be developed by relating the allowable stress of a known matrix material and the maximum expansion force (stress) of a steel slag particle. Because concrete is a structurally sensitive material, one localized failure (one particle failure) will be regarded as failure of the concrete. Therefore the basic disruption model for steel slag concrete should be based on a single steel slag particle. The imperative task is to determine the expansion force of bulk steel slag and an individual steel slag particle.
From the expansion force test, if the bulk steel slag sample is placed in a rigid mold and the volume expansion is completely constrained, an internal expansion force will result. The expansion force is expressed as Fex and is defined as the resultant expansion force produced by a given volume of steel slag. The expansion force is to be proportional to the volume of slag sample; that is, the greater the volume of the steel slag, the larger the expansion force will be.
where fex is the expansion force generated by a dense compacted steel slag in a unit volume, (N/m3); Fex is the measured expansion force produced by a given volume of dense compacted steel slag, (N); and Vsl is the volume of compacted steel slag, (m3). The expansion force of a unit volume of slag given by Eq.(12.17) is equal everywhere in a given volume of steel slag; that is, fex is a constant for a given slag sample. Note that this applies only to the large amount of steel slag particles in a compacted condition; it does not apply to a single steel slag particle. The three-dimensional expansion force is monopolized by expansion of steel slag in a confined condition. Both the disruption ratio, R, and expansion force, Fex, will be used in quantifying the expansion force of steel slag.
where Fec is the expansion force produced by the coarse steel slag aggregate in one cubic meter of concrete, (N); Vsc is the volume of steel slag aggregate in one cubic meter of concrete, including air voids, based on the mix proportion, (m3). From a given concrete mix proportion, with the weight of the steel slag coarse aggregate and the density of a given steel slag, Fec can be calculated.
It is reasonable to assume that only the cracked or powdered steel slag particles that have undergone the autoclave disruption test contribute to the expansion force, and the disruption ratio is equivalent to the volumetric ratio. Therefore, the actual volume of expanded steel slag, (Vse), excluding air voids, is
where Vse is the actual volume of expanded steel slag particle in concrete, (m3); is the solid volume of spheres under tightly compacted condition, which is approximately 67% (Shergold, 1953), assuming maximum volume of single-size steel slag particles occupied the volume.
where Fss is the expansion force from a single steel slag particle, (N); Vss is the volume of the single steel slag aggregate particle, ((d3)/6) (m3); and d is the nominal particle size of the steel slag aggregate, (m). The equation is illegal when R=0; that is, when the steel slag particles are volumetric stable (disruption ratio is zero) or the aggregate is natural aggregate (disruption ratio is zero).
Steel slag is a calcium-rich industrial waste. Direct aqueous carbonation is one of the routes to slag carbonation. The reaction mechanism of direct aqueous carbonation of steel slag is first discussed. Various models have been proposed to model aqueous carbonation of steel slag. The merits and shortcomings of these models are discussed. A recently proposed slag carbonation model by Gopinath and Mehra (2016) is discussed in detail. The model considers the armoring of reaction surface by two secondary phases: pore closure in one of these layers due to product precipitation and the kinetics of the reaction at the slag core. The model is analyzed, its advantages and drawbacks are discussed, and further improvements to the model are suggested.
Solid steel slag exhibits a block, honeycomb shape and high porosity. Most steel slag consists primarily of CaO, MgO, SiO2, and FeO. In low-phosphorus steelmaking practice, the total concentration of these oxides in liquid slags is in the range of 8892%. Therefore, the steel slag can be simply represented by a CaO-MgO-SiO2-FeO quaternary system. However, the proportions of these oxides and the concentration of other minor components are highly variable and change from batch to batch (even in one plant) depending on raw materials, type of steel made, furnace conditions, and so forth.
Steel slag can be air-cooled or water quenched. Most of the steel slag production for granular materials use natural air-cooling process following magnetic separation, crushing, and screening. Air-cooled steel slag may consist of big lumps and some powder. The mineral composition of cooled steel slag varies and is related to the forming process and chemical composition. Air-cooled steel slag is composed of 2CaOSiO2, 3CaOSiO2 and mixed crystals of MgO, FeO, and MnO (ie, MgOMnOFeO), which can be expressed as RO phase. CaO can also enter the RO phase. In addition, 2CaO-Fe2O3, CaOFe2O3, CaOROSiO2, 3CaORO2SiO2, 7CaOP2O32SiO2, and some other oxides exist in steel slag (Sersale, Amicarelli, Frigione et al., 1986; Shi, 2004). It was reported that the X-ray diffraction pattern of steel slag is close to that of Portland cement clinker.
Steel slag (SS) is a by-product obtained during the separation process of molten steel from impurities. Selected physical properties of steel slag are shown in Table 10.1. Depending on the used production technology, the steel slag can be divided into a basic oxygen steel slag, an electric arc furnace slag and a ladle furnace slag (De Brito and Saika, 2013). The steel slag is used as a secondary cementitious binder, or aggregates for road construction (Sheen et al., 2013; Manso et al., 2004).
Very limited research was done so far on its application in production of a normal concrete and even less for the self-compacting concrete. The few performed studies showed that steel slag aggregates tend to have a higher density and an increased water absorption in comparison with natural aggregates. At the same time the abrasion resistance tends to be enhanced (Anastasiou and Papayianni, 2006). Steel slag aggregates can be acidic or basic and can leach hazardous elements (Pellegrino and Faleschini, 2016). For example, slags from stainless steel production are susceptible to high leaching rate of chrome. The electric arc furnace slag aggregates showed tendency to expand, which is related to the presence of certain volumetrically unstable periclase and free line (Evangelista and de Brito, 2010).
The successful establishment of iron blast-furnace plants at Newcastle and Lithgow naturally invites attention to the economic utilization of the various products and by-products arising out of the industry.
Probably the first use made of blast-furnace slag in the cement industry was not of an honourable nature, to use an almost worthless and cumbersome by-product as a not readily detectable adulterant in Portland cement, which was at that time very costly to manufacture.
The astonishing discovery was made that in many cases the adulterated cement was stronger than the original unadulterated article. It was found that chilled blast-furnace slag introduced in moderate quantity and finely ground with the cement clinker did not injure, but usually improved, the quality of the resulting cement. This mode of manufacture is recognized, especially in Germany, as a legitimate branch of the cement-making industry.
The use of slag for the manufacture of both slag cement and Portland cement has assumed very large proportions both in U.S.A. and Europeso much so that in the former country plants not well situated and equipped for cheaply making cement from clay and limestone are being forced to close down.
Slags from other than iron blast-furnaces, together with some of the latter, are not suitable for cement-making. All slags which disintegrate and fall into powder are wholly unfitted for cement-making. Those highly charged with mineral oxide compounds of sulphur, phosphorus, and large proportions of magnesia should also be at once rejected. Throughout the rest of the article iron blast-furnace slag will be simply referred to as slag.
It is necessary to suddenly chill hot molten slag in order to develop its hydraulicity and cementing power. It is well known that suddenly chilling any hot slag gives it physical and chemical properties materially differing from those which develop in unchilled slagviz., brittle and soluble in acids instead of very tough and insoluble, or almost so, in acids. Unchilled slag is almost devoid of any hydraulicity or cementing power, besides being very difficult to pulverize. Chilling slag for use in cement-making is undertaken in different ways. In all cases it is essential that the slag shall be very hot, therefore the chilling must be done as near to the furnace as practicable.
The chief method of chilling molten slag is granulation in cold water. In this method the stream of hot slag is allowed to fall into a trough containing a rapid stream of cold water, preferably introduced as a jet directed with considerable force against the stream of molten slag. The physical effect is to cause the slag to break up into porous particles, usually called slag sand. This slag sand, as it leaves the vats, contains 15 % to 45 % (usually 30 % to 40 %) of adhering water. The expense of drying the slag sand is the chief disadvantage of water-granulated slag. This method is simple, cheap, and very effective, and is the one almost universally used. It also has a great chemical advantage viz., that a very large proportion of.the sulphur and alkalis contained in the slag are eliminated from it and carried off in the water.
Another method of granulation is that the stream of slag as it issues from the furnace is struck by a jet of high-pressure steam or air, which has the effect of blowing the slag into fine threads and globules, much the same as slag wool. In this form it has the advantage of being easily pulverized by grinding machinery, but has certain inconveniences, and has fallen into disuse.
This is essentially a cement of the puzzolan type. A puzzolan material is one capable of forming a hydraulic cement on being simply mixed with lime. Puzzolan materials are largely made up of silica and alumina. Most puzzolan materials possess hydraulicity to a greater or less degree, but the addition of lime usually greatly increases their hydraulic power. Undoubtedly the most important puzzolan material is granulated slag. Some granulated slags high in lime possess, after fine-grinding, a high power of hydraulicity without the addition of slaked lime. The process of manufacture is very simple, and, in brief, is as follows:
The dried granulated slag is mixed with a predetermined quantity of dry slaked lime and ground to an impalpable powder. It is then ready for use as cement. The slag sand, after being drained, still contains a large percentage of adhering water. This adhering water must be driven off until that remaining is less than 1 %. This drying is necessary for two reasons :
(b) To admit of the material being properly ground. Either dry or wet material (i.e., wet with plenty of water) may be readily ground in suitable machines, but damp material only clogs a fine dry-grinding machine.
Properly drying the material is therefore an essential feature of the process. Rotary driers are most commonly used, and it is found in good types that one pound of coal burned as fuel will evaporate 7 lb. of adhering water.
The limestone used for making the slaked lime is preferably a pure calcium-carbonate limestone, which, after burning and slaking, falls into a fine powder. The amount of magnesia present in the limestone must be very small, the admissible limit depending on the amount of magnesia present in the slag sand. The limestone is carefully burned in a kiln, drawn, cooled, and then slaked with water. The quantity of water to be added in slaking must be carefully gauged to slake the whole of the lime, but at the same time not to leave the slaked lime in a damp condition. Damp or wet slaked lime is not admissible for the same reasons as damp or wet slag sand. The slaked lime is then screened to remove any hard lumps. The latter may be of three types-viz., under-burned, over-turned, and properly burned but not slaked. The two former, though not desirable, are hot harmful, but the last mentioned is very injurious, as it causes free lime to be present in the finished cement. Free lime causes cement to blow after it has been made up into mortar or concrete, and thus causes the material to disintegrate.
A preliminary reduction of the dried granulated slag may be made in a ball mill, and the final grinding, after the requisite amount of slake lime has been added, made in a Fuller-Lehigh mill, tube mill, or other suitable fine dry grinder. The introduction of ball-peb and similar tube mills have, however, rendered a preliminary grinding of the slag unnecessary, as the whole reduction may be done in one operation.
A ball-peb tube mill is one divided into two or three separate compartments, the first compartment containing steel balls- 3 to -5 in. in diameter, the second compartment steel balls 1 in. to 2 in. in diameter, and the finishing compartment having 7/8-in. ball-pebs; or the first compartment may have steel balls, and the finishing compartment be charged with short lengths of 1-in. diam. steel rods. These mills take feed 1 in. to 2 in. gauge, and finish off to a high degree of fineness. The slag sand being already fairly small, a two-compartment mill is sufficient for slag cement: It is essential that slag cement be ground exceedingly fine; the finished product should not contain more than 3% oversize on 100 mesh per linear inch sieve, nor more than 15 % on a 200-mesh sieve.
Lime-burning, slaking, and screening, as usually carried out, are slow, tedious, and expensive. It is essential for economical work that these operations be made as continuous as possible, and that the materials shall throughout be mechanically handled, and these are most readily attained by the use of producer gas-fired rotary limekilns, hydrating machines and mechanical screens, and the necessary bins, conveyers, elevators, &c. It is necessary for the materials fed to hydrating machines to be of small size. Shaft kilns, even of the best type, are of comparatively small capacity, require much attendant labour, have a high working cost, and do not work satisfactorily if charged with small material, as the latter chokes the draught. The rotary lime-kiln, on the other hand, is preferably fed with limestone crushed to 2-in. or smaller gauge, and has the following advantages-viz., continuous in action, economical in fuel, small amount of attendant labour, large capacity, and low working cost. The general outline of the process, with necessary bins; elevators, conveyers, &c., is as follows:
The limestone from the quarry is passed through rock-breakers and rolls, and crushed to -in. gauge. The broken material is fed continuously to a rotary kiln, the waste heat of which may be utilized for drying the slag sand. The calcined, lime is fed in weighed batches to a hydrating machine, such as the Clyde hydrator, and slaked with a gauged amount of water. The material is thoroughly turned over and mixed until the action is complete, when it is mechanically discharged. A quantity of 1000 lb. of high-grade free lime requires 450 to 500 lb; of water for the operation, producing 1200 to 1225 lb. of hydrated lime, the rest of the water having been driven off as steam by the great heat developed during slaking. The hydrated lime, which should be perfectly dry, is fed to continuous-action screens, such as the Newaygo. The separated fine material is automatically weighed and mixed with the dried slag sand and ground into a finished product as cement.
Slags used in cement-making in Great Britain and Europe vary very considerably from each other in type and composition (see Table I.) American practice, however, aims at using slags which are much more uniform in character. The slags used by the Illinois Steel Company, Chicago, may be taken as typical of American slags used for making slag cement.
This slag is higher in alumina but lower in lime than the type usually used in the U.S.A., but is very similar to many slags that have been used to make slag cement in Great Britain, France, Belgium, Germany, Spain, and Switzerland.
The amount of slaked lime that is added to the slag for grinding into cement naturally varies considerably with the type of slag used. The latter, being a by-product, its composition depends very largely upon that of the ores, fluxes, and ash of the fuel used in the blast furnaces.
Le Chatelier states that the hydraulic properties of granulated slag are due to the presence of a silico-alumino ferrite of calcium corresponding to the formula 3CaO, Al2O3, 2SiO2. This compound appears also in Portland cements, but in them it is entirely inert owing to the slow cooling it has undergone. When, however, as in the case of granulated slags, it is cooled with great suddenness, it becomes an important hydraulic agent. When go cooled it is attacked by weak acids and also by alkalis. It combines particularly with hydrated lime, and in setting gives rise to silicates and aluminates of lime identical with those which are formed by entirely different reactions during the setting of Portland cement. It is upon this property that the manufacture of slag cement, which assumes daily greater importance, is based.
Slag cements differ widely in chemical, composition from Portland cements mainly in the high percentage of Al2O3 and in their relatively low percentage of CaO, which, unless a larger proportion than is ordinarily required has been added for some special purpose, need not exceed 46% to 51%, as against 58% to 62% CaO generally present in Portland cements.
It will be seen by comparing Tables I. and II. that, despite the apparently great variations in practice, the ultimate, composition of very many finished slag cements falls within quite narrow limits, namely:
Nevertheless, many excellent British and other European slag cements have an appreciably lower percentage of CaOfor example, Cleveland cements and that quoted by Redgrave; and some are materially higher in aluminae.g., Cleveland and Seraing. Kidd, in Proc. Inst. C.E., vols. cv. and cvii., states that he had used Cleveland slag cements in marine work with most excellent results. Banks (Iron and Steel Instit., 1905) claimed that slag cements made from Cleveland slags were the strongest cements known.
Slags containing a high percentage of lime after granulation and grinding, but without the addition of slaked lime, have a very high degree of hydraulicity and strength. Attempts have been made to produce slags approaching the Portland cement compositioni.e., to make a slag which, when finely ground, would be a Portland cement. These attempts have not been successful, and were abandoned, very largely because producing, slags abnormally high in lime interfered too much with the main function of the blast furnacenamely, as a producer of pig iron.
The high lime was due to the necessity to remove sulphur from the metal, but some of the sulphur was removed from the slag during granulation. This slag, when ground, had a tensile strength of 430 lb. per sq. in. at 28 days.
Slag cements normally set very slowly compared to Portland cements. The set of slag cements may be hastened by the addition of puzzolanic materials. Of these, burned clay, certain active forms of silica, and slags high in Al2O3 are the cheapest and most generally used. Some slags used in making slag cement already contain a high percentage of Al2O3, and may not require any further regulation.
The most important method of regulation used with the low-percentage Al2O3 slag cements in the U.S.A. is the Whiting process. This process includes the use of caustic soda, caustic potash, sodium chloride, &c., added either as aqueous solution or in a dry state at some stage of the process of cement manufacture. Caustic soda 0.125 to 3% may be added, depending upon the use for which the cement is intended. It is frequently added as an aqueous solution in slaking the freshly-burnt lime.
Slag cements differ from Portland cement in requiring no preliminary seasoning. Owing to the complete hydration of the lime used in slag cement and the inert character of the silicates present, little or no change can take place in the material, even when exposed to the atmosphere for a lengthy period. Slag cement protected from actual moisture undergoes no change whatever.
Slag cements fall below high-grade Portland cements in tensile strength, but good American slag cement develops sufficient strength to pass many American specifications for Portland cement. Tested neat, they do not approach Portland cements so nearly as tested in 2 to 1 and 3 to 1 mortars.
These results would satisfy the strength requirements in. the standard Portland, cement specification of many American public bodies, but would not fulfil the requirements of the latest British standard specifications or the New South Wales Government specification.
Slag cements are deficient in resistance to mechanical wear, and are therefore not suitable for use in the surface of pavements and floors. They are well fitted for foundations and mass concrete generally, in which a high-grade strength is not necessary. They are deemed to be superior to Portland cements for making concrete to be used in or under either fresh or salt water. They are, therefore, specially suitable for use in connection with hydraulic, harbour, and marine works.
Mortar made from fat limes is, at its best, a very poor material as regards strength and setting. Such mortars, except on the surface, never set, and their hardness is little more than that due to merely drying out.
Slow-setting slag cement could with great advantage as to quality replace fat lime in making mortar for ordinary building operations, and probably also at no increased cost in districts to which freight charges would be small.
A very large portion of the Portland cement is used in Australia under conditions where its very great strength and cost are quite disproportionate to the moderate requirements of the work. There is thus, at present, a very wide unfilled gap in quality, strength, and cost between the very indifferent fat lime mortar and that made from Portland cement, which could with advantage be filled by the use of a good cheap slag cement.
Granulated slag is very extensively used in Britain, Europe, and more so in U.S.A., in the manufacture of Portland cement. The Universal Portland Cement Co. make a cement of this class, and have five mills, whose combined production is 12,000,000 barrels, or 2,000,000 tons, per year.
The mode of manufacture, chemical composition, and requirements for strength, soundness, &c., for Portland cement have been rigidly defined within narrow limits in most countries. The following particulars, from the British Standard Specification (1915), may be taken as closely representing the requirements for Portland cement in most countries. The cement shall be manufactured by intimately mixing together calcareous and argillaceous materials, burning them at a clinkering temperature, and grinding the resulting clinker so as to produce, a cement capable of complying with the other requirements of the specification. No addition of any material shall be made after burning other than calcium sulphate or water, or both (added to control the time of set). The following percentages shall not be exceededviz., insoluble residue, 1.5%; magnesia, 3%; sulphuric anhydride, 2.75 %; and loss of ignition, 3%. The proportion of lime to silica and alumina, when calculated (in chemical equivalents) by the formula CaO/SiO2 + Al2O3 shall not be greater than 2.85 or less than 2.0.
It has long been established by law and custom in most countries that a cement made from blast-furnace slag and limestone so as to comply with standard requirements of method of manufacture, chemical composition, fineness, strength, soundness, specific gravity, &c., is legitimately a Portland cement, and may be sold as such.
Most cement makers aim at producing a cement having but a small range of composition for its components. Many blast-furnace slags contain a high percentage of alumina, which, when mixed with lime, would give a cement within the proportions of lime to silica and alumina given above, but considerably higher than they desire to have. The desired proportion is obtained by adding crushed quartz or silica sand to the mixture of slag and limestone. The method of manufacture is, briefly, as follows :
The limestone is crushed to about 1-in. gauge and dried in rotary driers, using coal as a fuel, or the waste heat from the kilns may be used for this purpose. The limestone receives a preliminary grinding, and is delivered to hoppers above the scales. The slag is fed direct to driers, given a preliminary grinding, and delivered to hoppers above the scales. The limestone and slag are proportioned at the scales. The scales are preferably of the automatic electrically-operated type, interconnected, so that one cannot dump without the other. The mixed materials are very finely ground in a tube or other fine-grinding mill, then elevated to hoppers above the rotary kilns. In these kilns, using pulverized coal as fuel, the mixture attains a temperature of about 2500 Fahr., and gradually burns to a hard clinker. The clinker is seasoned for about 10 days, given a preliminary grinding, mixed with the amount of gypsum to regulate the setting, and then receives the finishing grinding in a tube or other mill. The resulting product is cement, which is carried to storage bins and bagged for distribution. There is reason to believe that portion of the foreign Portland cements imported before the war was of this origin, and readily came up to New South Wales Government standard tests.
This cement, called Eisen Portland cement in Germany, is made of a finely-ground mixture of Portland cement and granulated slag, usually in the proportion of about 3 of cement to 1 of slag. As before mentioned, this class of cement probably was at first only a fraudulently adulterated Portland cement, but it is now extensively made and sold as a separate class of cement, for which special advantages are claimed. Its development as a separate branch of the cement industry rests on the theory of Dr. Michaelis, put forward in 1876namely, that about one-third of the lime of Portland cement separates as crystalline calcium hydrates. This compound has no strengthening effect, and may have a harmful one. If this theory is correct it follows that it is desirable to add some substance which will unite with the free lime and convert it into calcium hydro-silicate or other useful compound, and thus raise the effective quantity of cement.
Ground granulated slag is used for this purpose, and may be added to Portland cement made from slag and limestone or to that made from clay and limestone. The slag is added, to the Portland cement clinker during the final grinding, so that the resulting cement mixture is very fine ground and intimately mixed. Opinion is divided as to whether the addition is a benefit or merely an adulterant. There is no doubt that in many cases it produces an article which, is sounder and stronger than the original cement. The addition of a small amount of suitable granulated slag to high-lime Portland cements would be beneficial as a safeguard against that bugbear of the danger of expansion due to free lime.
This addition should be made after clinkering and before the final grinding, so that the resulting product is very intimately mixed. Standard specifications for Portland cement prohibit any such addition, and it could only be done at the express instruction of the user.
The specific gravity of iron Portland cementnamely about 3.0is intermediate between that of slag cement and Portland cement. Iron Portland cement is received with a high degree of favour in the Continental countries of Europe.
The following are tests of (German) Eisen cement made at a time when the German specifications for Portland cement required the following strengths for 1 to 3 cement-sand mixtures at 28 daysviz., tension 227 lb., and compression 2270 lb. per sq. in. :
Probably the most important of these is that made by the Colloseus method. This cement is now being made at a number of plants in Germany, Britain, and U.S.A. In this process basic blast-iron slag is granulated in a special device, using a limited amount of aqueous solution of alkaline salts. The special salts are intimately mixed with the slag and the latter chemically and physically changed, being a porous clinker easily powdered. The chief salt is magnesium sulphate (crude Epsom salts), used as a 5% solution.
The stream of slag falls on a horizontal ribbed drum rotating at 650 r.p.m. Between the ribs are slots through which spurts the granulating solution. There is also a jet of solution just below the stream of slag. The slag is granulated as little pellets. Ungranulated slag is separated from the mass on a turn-table. Only so much solution is used that the granulated slag is perfectly dry after the operation. The slag is then treated as in the case of ordinary Portland cement clinkeri.e., no further addition of any material is made except such as is customary to regulate the setting. The sulphur content of the slag should, be low, and the amount of magnesia should be less than 3.5 to 4%.
The cement is ground very fine, specific gravity 2.97 to 3.0. Time, of setinitial, 18 to 20 minutes; final, 35 to 45 minutes. This is a very quick-setting cement when compared to the ordinary slag cement.
The slag-brick industry may be considered to be a specialized branch of the slag-cement industry, but a wider range of slags may be used. The manufacture includes bricks, pipes, and other special shapes, and the details of practice vary considerably in different works. The most usual method is to finely grind together 100 parts of dry granulated slag and 10 parts of slaked lime, giving what is really a slag cement of lower lime-content. A small amount of water is added to the material and mixed to a stiff pug and passed on to suitable brick or pipe-making machinery. The bricks or pipes are stacked to dry and harden before distributing for use. The hardening is sometimes hastened by treatment under the heat and pressure of steam. As before mentioned, some finely-ground granulated slags possess a high power of hydraulicity without the addition of slaked lime, and may be made directly into bricks.
Another important variation of process is to mix slag cement with fine slag sand which has been drained but not dried, there, being sufficient water to pug the mixture before passing to the brick machines. Well-made slag bricks are stronger than clay bricks. Slag bricks are used for ordinary building purposes, but, as they are more refractory than red-clay bricks, they are of special service in the outer walls of furnaces and for chimney stacks.
It will be seen from the foregoing brief survey of the subject that a large variety of cements may be made from suitable basic granulated iron blast-furnace slags. It has been prophesied that in a few years nearly all cement will be made by some process from blast-furnace slag.
The writer is indebted to Mr. G. D. Delprat, general manager Broken Hill Proprietary Company Limited, for kind permission to use data in connection with the blast-furnace slags made at the Newcastle iron and steel works.
Mr. G. Stephen Hart said, as Mr. Poole mentioned, chemists were still in enthusiastic disagreement as to why cements set and the chemical compounds formed, but microscopical examination showed optically different compounds named alit, belit, celit, and felit. A chilled slag differed physically from a slowly-cooled one, presumably on account of a different grouping of its atoms, as with steels cooled quickly and slowly; but to assert that slag cements on setting formed the same compounds as Portland cements seemed rather daring. It was not supported by their properties when set. The tests quoted illustrated the curious fact that in both neat and 1 to 3 mixtures slag cements were only five times as strong in compression as in tension, whilst Portland cements were ten times as strong. The neat slag cement quoted gave a strength in compression of 2830 lb. in 28 days. The New South Wales standard for Portland cement mixed with three times its weight of sand was 2250 lb. after 28 days, and the best cements gave more than double that strength in a 1 to 3 mixture ; still, there should be a use for slag cement where great strength was not neededfor example, in taking the place of mortar, as suggested by Mr. Poole. It would have a more local market, as bagging, freight, etc., would be as great as on stronger Portland cement, which could be mixed with sand where used. For the manufacture of a true Portland cement the analysis of the Newcastle slag showed it to be too high in Al2O3 compared with SiO2 for rotary-kiln practice, and mixing with siliceous material, as suggested, would tend to complicate the process. It was, therefore, mostly a question of costs. The danger of free lime in Portland cement was far less with modern rotary kilns than when old-fashioned stationary kilns were used. In those the whole charge was never properly burnt, and a gang of men had to be employed on the clinker heaps to sort out the good clinker from the bad. In cement one part of CaO could combine with 2.8 of SiO2, but only with 1 of Al2O3; therefore a siliceous cement needed a much higher percentage of lime. The old stationary kilns could not burn a highly siliceous cement, but present-day rotary-kiln practice favoured that, and he (Mr. Hart) had no doubt that every Australasian cement carried a higher percentage of lime than the example quoted in the paper. Mr W. A. Brown, in The Portland Cement Industry, published in 1916, stated that in a good Portland cement the lime should be from 60 to 67% and the silica 20 to 25%. If one part MgO was taken as equal to 1.4 parts CaO, a New Zealand cement described in a paper presented to the Institute contained CaO and MgO equivalent to 65% of CaO and 25.9% of SiO2. With reference to the strength tests in that paper, it should be remembered that briquettes made differently would give different results. The British standard specifications insisted upon briquettes being patted down with a spatula weighing 11 oz. They also demanded an increase of strength of about 10% between 7 and 28 days. New South Wales specifications used the Boehme hammera trip hammer weighing about 5 lb. which, after 150 blows, was automatically stopped. Thus, any personal factor was minimized, but briquettes so made were relatively stronger after 7 days, and, to comply with B.S.S. requirements, briquettes should be made as the B.S.S. specified.
Different cement tests were required by different Australian States, and even by different public departments in one State. That was most undesirable, as there was always the chance that one body would devise an unusual test which no cement could pass unless too bad for use, if judged by some other departments specifications.
MR, A. S. Kenyon said with regard to Portland cement he did not think that engineers were going to relax their specifications, but rather the other way. Mr. Harts candid admissions, that his company had always proved able to more than meet requirements made one inclined to stiffen them up. It was not a 10% increase, on the seven days test, that was asked for ; but that only 90% of the set should occur during the first seven days, which was a very different thing. It was not that the engineer worried about the seven days set, but that he wanted a 28 days set. With regard to slag cement, he would like to ask Mr. Poole to add a word as to the possible amount of cement they were likely to obtain from those works, whether it would equal the compression test, and whether the quality would equal that of the ordinary quality of cement in use. In other wordsWhat was the amount of commercial cement that might be made in that way in Australia ?
Mr. Poole, in reply, said he was not aware that the Commonwealth Portland cement was as high as 64% in lime. But, in speaking of free lime, he certainly did not include hydrated lime as free lime. Free lime was anhydrous calcium oxide (CaO). It was not contended that a slag cement was as good as high-class Portland cement; but it must not be forgotten that the cement made in New South Wales had grown up under, as far as he knew, the stiffest set of tests in the world. Those tests had been in vogue for quite a number of years, and cements that had grown up under them had to be very high-grade to pass. The result had been that public bodies, private engineers, and architects merely stipulated that the cement to be supplied must, come up to the New South Wales Government specification. He thought the majority of engineers did not like a very high-lime cement, because there was always a fear that it would be unsafe. No man wished to undertake an important piece of work with cement, even though it showed up well in laboratory tests, if it afterwards cracked or disintegration took place. He would prefer a cement of comparatively low-strength test, but absolutely sound in quality. As far as free lime was concerned, he did not think it was usual to test it at works. Yet certain well-known tests could be carried out at works to show the general soundness of a cement. With regard to the carrying of cement in bulk, he believed it was coming into vogue in the United States, where it was being carried, like other materials, in bulk, in proper trucks. In and around Newcastle it could be carried in bulk; but under the present system of railway trucks it would not be possible to ship it in bulk to other parts of New South Wales. They had one of the most antiquated systems of trucking in the world. When two such world-wide authorities as Michaelis and Le Chatelier disagreed as to the chemical reactions which took place during the setting of cement, it was not for those who were not expert chemists to enter into the fray. He thought that Newcastle slag could be made into a good straight-out Portland cement. He was not giving secrets away when he said that it had been examined for that purpose by one of the most progressive cement companies in Australia, and that they were quite satisfied. As to the quantity of slag cement that may be available, he could inform Mr. Kenyon that there was a company in formation ; but whether they would make a straight-out slag cement was another question. The Portland cement man did not look favourably on slag cement. It was only rarely that the full strength of Portland cement was fully utilized. As a matter of fact, outside of reinforced concrete, the great strength of Portland cement was rarely utilized. A cement of much less strength would suffice for most purposes. The output of slag cement would depend upon the output of slag from the furnace at Newcastle. There was one blast furnace now in use, and shortly a second would come into commission. The amount of slag available would be practically the quantity the furnaces produced, less what the company may require for their own particular purposes in the steel works.
Grinding-related parameters of blast furnace slag cements (BFC), such as Bond grindability, specific rate of breakage and breakage distributions were determined employing separate and intergrinding modes. Strength tests were performed on mortar specimens made by BFC prepared by these modes of grinding to the same fineness. Overall results favor the use of separate grinding mode in view of lower specific energy consumption, ease of manufacture, higher addition of slag on top of more flexible product quality arrangement.
D50 of raw steel slag decreased to around 3m by wet grinding.Compressive strength of 3m-40% can reach the level of cement at 60 d.Increased strength was ascribed to decreasing harmful pores and increasing less harm pores.
Steel slag is a solid waste generated from the steelmaking process. With a very low utilization rate of 30% in China, a high discharging cost of steel slag is inevitable so that it is imperative to dispose of steel slag by new technology. In this study, steel slag was refined by wet-grinding technology to apply on cement. The results showed that the initial setting time and final setting time were prolonged by the increased dosage of 3m steel slag. Although the viscosity of wet-grinding steel slag cement specimens increased significantly, the shear-thinning phenomenon happened by mechanical mixing. The wet-grinding specimens presented a higher hydration heat than that of raw steel slag specimens, and the microstructure of 3m-40% (3m steel slag mixed with cement as a dosage of 40%) is much denser and show more hydration products than that of raw-40% (raw steel slag mixed with cement as a dosage of 40%) which results in an enhanced compressive strength that could be guaranteed by the dosage of 20% (3 d), 30% (28 d) and 40% (60 d) under the condition of 3m steel slag incorporation with lower autogenous shrinkage. Hemicarboaluminate peak was found in wet-grinding specimens that show a higher calcium sulphoaluminate to calcium. The wet-grinding steel slag CO2 emission and cost showed a downward trend compared with cement.