One of the fundamentals of cement manufacturing is to ensure the right chemical composition of the cement raw mill. A raw mill with a superior fineness and well-controlled chemical composition using as advanced control system can improve the cement quality and define critical cement craft parameters.
Amrit Cement uses the best of raw materials and has an enviable infrastructure supported by advanced technologies to ensure supreme cement quality. Physical and chemical analysis of clinker cement and fly ash with Bureau of Indian Standard Specifications by experts from India and Overseas ensures excellence in its product offerings.
Limestone from mines are brought to plant site and stored in the yard then fed to dump hopper of primary crusher by mixing high-grade and low-grade limestone in defined proportion to meet the quality norms.
The primary crusher is designed with 350 TPH and secondary crusher is installed to reduce the limestone size to further meet the process requirement before reaching the longitudinal stock piles. Longitudinal stacking method is also termed as Chevron Method to improve the consistency while re-claiming.
The stacker and re-claimer are designed for stocking and extraction of limestone and other corrective materials are fed in to respective hopper. Underneath the hoppers weight feeders are installed to make the proportions of desired mixing ratio.
The main raw materials required for manufacturing clinker and cement are Limestone, Clay and Laterite. All the raw materials are stored in respective hoppers and underneath the weight feeders are installed to make the mix proportion.
The above mix proportion is ground in Raw mill at 110 118TPH (Ball mill) to achieve desired fineness and fed into CF silo (continuous Flow silo concreted, capacity 4500MTs) where extraction and filling takes place simultaneously. This kind of system is well-proven for uniform feed to kiln to avoid the variation in burning system.
Our manufacturing facility houses technologically advanced Stacker Reclaimer System for pre-blending and homogenizing the raw mill. This process ensures a fully auto-controlled and homogeneous raw material quality output.
Raw material blending process is an essential part of the cement production process. The main purpose of the process is to guarantee a certain oxide composition for the raw meal at the outlet of the mill by regulating the four raw materials. But the chemical compositions of raw materials vary from time to time, resulting in difficulties to control the oxide compositions to a predefined value. Therefore, a novel algorithm to estimate the chemical compositions of the raw materials is developed. The paper mainly consists of two parts. In model construction part, a novel constrained least square model is proposed to overcome the deviation introduced by long-term drift of the material components, and the model parameters are estimated with an online strategy. And in validation part, the approach is implemented to two examples including datasets from simulation model and the actual industrial process. The final results show the effectiveness of the proposed method.
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word cement traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder.
The reason why cement can sets and hardens independently is its hydraulic property. When cement is mixed with water, the chemical reaction occurs and produces hydration products, such as C-S-H gel, calcium hydroxide, ettringite and monosulfoaluminate. The C-S-H gel is the main material to bind different particles and resulting in the engineering strength which is needed as a construction material.Since the set and hardening process of cement is chemical reaction, so we can get cement set under water.
It is common to see another name of cement that is Portland cement, because concrete made with cement resembled natural stone from the Isle of Portland. It worthy to note that first cement is produced by early Greeks and Romans from volcanic ash mixed with slaked lime. Unfortunately, this art was lost during the Middle Ages. The modern cement, Portland cement, is developed in England by bricklayer Joseph Aspdin in early 1800s.
The exact composition of slag varies over a range. In general, factors that determine the suitability of slag for usage in composite cement mainly include the fineness of grinding, glass content and the chemical composition.
Like most of other cement materials, the reactivity of slag is influenced by its surface area. Increased surface area leads to better strength development and more water requirement; however, the fineness of slag is limited from practical aspects, such as economic and performance considerations, setting time and shrinkage. The following table shows typical fineness data of market slag in some countries.
During the quenching process, the liquid slag forms glassy and crystalline contents. Practical glass content of slag depends on the cooling rate, in general, rapid rate results in high glass content. The main difference between glass content and crystal content of slag is that the former part has a latent hydraulic property that makes the glass content of slag a very important factor affecting the engineering performance of slag cement.
As for the relationship between hydraulicity and glass content, increasing glass content of slag improves its hydraulicity; however, research data that slag samples with 30-65% glass contents are still suitable has not shown exact correlation between them. Due to this uncertainty, most international standards classify slag reactivity by testing its direct strength rather than requiring minimum glass content. But from a practical standpoint, the glass content of slag should exceeds 90% to guarantee satisfactory properties.
As stated above, the chemical composition of slag is mainly the four components, namely, MgO, Al2O3, SiO2, and CaO.From a metallurgical standpoint, slag can be sorted as either basic or acidic, and the more basic of slag, the greater its hydraulic activity in the presence of alkaline activators, Lea also reported that the hydraulic values of slag increase with the increasing CaO/SiO2 ratio up to a limiting value (not precisely stated). Further, in European Standard EN 197-1:1992 and British Standards, the ratio of the mass MgO plus CaO to SiO2 must exceed 1.0, by which the high alkalinity is guaranteed and otherwise the slag would be hydraulically inactive.
With a constant CaO/SiO2 ratio, the strength of hydrated slag increases with the Al2O3 content, and a large amount of Al2O3 can compensate the deficiency of CaO. Further research, by a regression analysis of compressive strength on composition using a wide range of west European slags, showed that increase in Al2O3 content above 13% tended to increase the early strengths but to decrease late strengths. Moreover, the content of Al2O3 also influences the sulfate resistance of slag concrete.
The influence of MgO as a replacement of CaO seems depending on both the basicity and the MgO content of slag. Variations in the MgO content up to 8-10% may have little effect on strength development, but high content have an adverse effect. It also reported that MgO in amount up to 11% was quantitatively equivalent to CaO. Frearon and Higgins reported that to get a satisfactory sulfate resistance the content of MgO should be about 13%.
Many researchers attempted to quantify the reactivity of slag considering the four major components together. Among these results, ratio (CaO+MgO+Al2O3)/SiO2 is the simplest and most widely used one. It was observed that the hydraulic activity of slags increases with the increasing contents of CaO, MgO and Al2O3 but decreases with the increasing content of SiO2. Furthermore, minimum values for this ratio, such as 1.0 (Germany) and 1.4 (Japan) have already been adopted in some countries standard specifications.
Apart from the four major components, there are also some minor components that may have important effect on the properties of slag, such as MnO is always negative, P2O5 and alkalis are more complicated.
Mark Bediako, Eric Opoku Amankwah, "Analysis of Chemical Composition of Portland Cement in Ghana: A Key to Understand the Behavior of Cement", Advances in Materials Science and Engineering, vol. 2015, Article ID 349401, 5 pages, 2015. https://doi.org/10.1155/2015/349401
The performance of Portland cement in concrete or mortar formation is very well influenced by chemical compositions among other factors. Many engineers usually have little information on the chemical compositions of cement in making decisions for the choice of commercially available Portland cement in Ghana. This work analyzed five different brands of Portland cement in Ghana, namely, Ghacem ordinary Portland cement (OPC) and Portland limestone cement (PLC), CSIR-BRRI Pozzomix, Dangote OPC, and Diamond PLC. The chemical compositions were analyzed with X-Ray Fluorescence (XRF) spectrometer. Students -test was used to test the significance of the variation in chemical composition between standard literature values and each of the commercial cement brands. Analysis of variance (ANOVA) was also used to establish the extent of variations between chemical compositions and brand name of the all commercial Portland cement brands. Students -test results showed that there were no significant differences between standard chemical composition values and that of commercial Portland cement. The ANOVA results also indicated that each brand of commercial Portland cement varies in terms of chemical composition; however, the specific brands of cement had no significant differences. The study recommended that using any brand of cement in Ghana was good for any construction works be it concrete or mortar formation.
Portland cement is without any argument among the most important and necessary materials in the world. Without it, the construction industry that utilizes huge tonnages of concrete annually would struggle to survive. Besides this, concrete is rated as the second most highly consumed product after water . It is known that some developed countries depend on the construction industry as one of the main pillars for the growth of their economies. In developing economies, the construction industry provides many jobs for people in both the formal and the informal sectors. Any shortfall that stagnates the construction industry usually leads to serious economic slump.
The Ghanaian construction industry depends hugely on Portland cement for almost every type of construction including bridges, offices, and residential facilities . It is estimated that approximately four million tonnes was utilized in 2014. The prediction is that cement consumption may hit a record high of about five million tonnes by 2020. In Ghana, until 2002, the cement industry was monopolized by Ghana cement manufacturers (Ghacem). After the breakdown of the monopoly, the cement industry has witnessed the influx of many other sources of cement products. Some of these Portland cement products are imported from China, India, and other western European countries. Currently the cement market is diverse and huge and therefore customers have the power to make choices. Available Portland cement products that builders depend on are normally the brands from Ghacem, West Africa cement manufacturers (Wacem), and the Dangote cement. The Ghanaian cement market in recent years has seen the influx of minor entrants like Fortress, and so forth.
The breakdown of cement monopoly which allowed the entrance of other brands of cement is currently creating a major problem for builders in making the best and preferred choice of cement for their constructional work. Engineers and other related building professionals are always confronted with the tough task of selecting the best cement brand in the Ghanaian cement market. The reason for this is because usually masons who normally use the cement products give out various complains to clients who are the main financiers. Sometimes masons complaints are justified; however, the details of their complaints really lack engineering basis.
Most Ghanaian engineers in construction which is largely made of mostly civil engineers make their preferred choice of Portland cement based on strength classification. However, other information such as chemical composition, mineralogical, and even physical properties could be used to corroborate with strength in making good decisions on the best cement in the market. This could be an important key for the selection of best performing cement. In this work, commonly used available Portland cement in the Ghanaian cement market was analyzed in terms of its oxide composition. The main aim of the study was to determine the extent of variation that exists between the commercially available cement and standard literature requirements. In achieving the main aim of the work, the study was guided by this hypothesis Is there any major differences between the chemical compositions of Ghanaian commercial Portland cement and standard requirements from literature?
Portland cement is the most commonly utilized cement in almost every part of the world. The understanding of the embodiment of Portland cement could lead to a more sustainable concrete and mortar design. It chemically reacts with water to attain setting and hardening properties when used in the construction of buildings, roads, bridges, and other structures. Portland cement was patented by Joseph Aspdin in 1824 and was named after the cliffs on the isle of Portland in England .
The production of Portland cement is made by the calcination of a mixture of a calcareous and an argillaceous material at a temperature around 1450C . Calcareous substances are of calcium oxide origin usually found in limestone, chalk, or oyster shells whereas argillaceous substances are of silicate and aluminate origin predominantly found in clays, shale, and slags . The calcination process between well-proportioned argillaceous and calcareous substances leads to the production of clinker. Portland cement is obtained when the produced clinker is mixed together with a predefined ratio of gypsum and milled together in a ball mill.
The chemical composition of Portland cement involves both major and minor oxides . The major oxides include CaO, SiO2, Al2O3, and Fe2O3 whereas the minor oxides also include MgO, SO3, and some alkali oxides (K2O and Na2O) and sometimes the inclusion of other compounds, P2O5, Cl, TiO2, MnO3, and so forth . Each of the oxides performs unique work during cement hydration; however, each content of the oxide must be in the right quantity during proportioning of raw materials . Lea  provided the required oxide composition of Portland cement (see Table 1). A deviation from standard specifications of the oxide composition may lead to unsoundness and sometimes failure of concrete structures. Many experienced authors have shown that cement oxides which fall very close to the average values are more suitable to maintain concrete integrity [8, 9].
During cement hydration CaO in conjunction with SiO2, Al2O3, and Fe2O3 leads to hardening of Portland cement due to the formation of calcium aluminosilicates and aluminoferrite hydrate. With Portland cement, an increased presence of MgO (greater than 2%) may be detrimental to the soundness of cement, especially at late ages. High percentage of SO3 tends to cause unsoundness of cement. For the Americans in their standard, ASTM C618 limits SO3 to 4% and 5% whilst the Indian standard limits SO3 to 2.75%. Alkalis at higher levels and in the presence of moisture gives rise to reactions with certain types of aggregates to produce gel which expands and gives rise to cracking in mortars and concretes.
Sometimes Loss on Ignition (LOI) is classified as a component of chemical composition. LOI indicates the amount of unburnt carbon in the material. However, in some instances it may not necessarily be a measure or indication of carbon content. It may be burning away of residual calcite, bound water molecules, and clay materials . High LOI content may be detrimental to concrete and mortar. It is also known that a high value of LOI results in increased water requirement and dosage of super plasticizer usage in mortar and concrete . Maximum LOI values for both American and Indian standards for common pozzolanic material are 10% and 12%, respectively.
The Portland cement analyzed was five main available commercial cement brands in Ghana which included Ghacem OPC (Class 42.5N) and PLC (Class 32.5R), BRRI Pozzomix, Dangote brand (Class 42.5R), and Diamond brand (Class 42.5N). These brands of cement were obtained in 50kg bags from a cement distribution outlet in Kumasi, the second biggest city of Ghana. A representative sample of about 20g was taken from the bulk 50kg bags as received from the factory for the chemical analysis.
The chemical compositions were performed with the X-Ray Fluorescence (XRF) by the name Spectro X-Lab 2000, at the Ghana geological survey in Accra. The XRF machine uses a polarized energy dispersion. About 4g of the cement sample was mixed with about 0.09g of wax. The mixture was milled in a milling machine (RETSCH Mixer Miller (MM 301)) for about three minutes to produce a homogeneous mixture, obtaining a particle size of about 60m. The mixture was placed in a dice and placed under the press pellet equipment (SPECAC hydraulic press). The equipment produced a pellet and was then placed in the Spectro X-Lab instrument. The major and other minor oxides were described in graphical histogram presentation. The chemical compositions of each sample were performed three times. The average values of each brand cement were analyzed against the average composition of cement provided by Lea  using Students -test at alpha () value of 0.05. The hypothesis made for the -test waswhere and are the mean values of average composition by Lea  and commercial Portland cement, respectively.
After Students -test, analysis of variance (ANOVA) was used to determine the extent of variation that existed in commonly used Portland cement in Ghana. The hypothesis that was established was thatwhere , , , , and are the mean values of Ghacem OPC, Ghacem PLC, CSIR-BRRI Pozzomix, Dangote OPC, and Diamond PLC. The alpha () value used for the ANOVA test was 0.05.
Figures 1(a)1(e) present the chemical compositions of the commercial cement available in Ghana. The figure showed the major and the minor oxides present in the Portland cement. A comparison with each cement brand indicated variations in the chemical compositions existing between them. From Figure 1, the predominant oxide compositions were CaO followed by SiO2, Al2O3, and then Fe2O3 in that order. The minor oxides included MgO, Na2O, K2O, MnO, TiO2, P2O5, and SO3. The compositions of the various oxides in the commercial Portland cement shown in Figure 1 fall within the requirements of cement oxide compositions provided by Lea  and Neville  who also obtained similar compositions but at different percentages in their studies.
Table 2 presents the predictive () values and remarks of Students -test performed between the average chemical composition values provided by Lea  and each of the commercial Portland cement brands. All the values indicated that the test failed to reject the hypothesis that there is any significant effect between the average literature composition values and the commercial Portland cement. This indicated that commercial Portland cement in Ghana is well within and without any major deviation from accepted generalized standard specifications.
Table 3 presents the results of the ANOVA test performed among commercial Portland cement brands. The results gave a predictive value of approximately for the rows which represented the chemical compositions whereas that for the columns was approximately 0.85 representing the various brands of the commercial Portland cement. The predictive values indicated that there exists a significant difference with respect to the chemical compositions among cement brands. The variation in chemical composition may be attributed to the differences in the proportioning of raw materials and the nature of production used to produce Portland cement. However, with respect to Portland cement brands, any of them could be used for construction since there were no significant differences.
The chemical compositions of commonly used Portland cement in Ghana were analyzed with both spectroscopic analysis and statistical tools. Generally, Students -test results confirmed that, with regards to chemical composition, all commonly used cement in the country has no deviation from standard requirements prescribed from the literature. This therefore shows that any of the commercial cement brands is very suitable for construction or concrete works. However, the Anova output indicated that each brand of commercial Portland cement has individual variations with respect to chemical composition. This is due to the differences that exist with individual factory proportioning of raw materials for Portland cement production.
Copyright 2015 Mark Bediako and Eric Opoku Amankwah. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Ancient Romans were probably the first to use concrete a word of Latin origin based on hydraulic cement that is a material which hardens under water. This property and the related property of not undergoing chemical change by water in later life are most important and have contributed to the widespread use of concrete as a building material.
Portland cement is the name given to a cement obtained by intimately mixing together calcareous and argillaceous, or other silica-, alumina-, and iron oxide-bearing materials, burning them at a clinkering temperature, and grinding the resulting clinker.
The definitions of the original British and new European Standards and of the American Standards are on those lines; no material, other than gypsum, water, and grinding aids may be added after burning.
These compounds interact with one another in the kiln to form a series of more complex products, and, apart from a small residue of uncombined lime which has not had sufficient time to react, a state of chemical equilibrium is reached.
The properties of this amorphous material, known as glass, differ considerably from those of crystalline compounds of a nominally similar chemical composition. Another complication arises from the interaction of the liquid part of the clinker with the crystalline compounds already present.
Calculation of the compound composition of commercial cements: the potential composition is calculated from the measured quantities of oxides present in the clinker as if full crystallization of equilibrium products had taken place.
The calculation of the potential composition of Portland cement is based on the work of R. H. Bogue and others, and is often referred to as Bogue composition. Bogues equations for the percentages of main compounds in cement are given below. The terms in brackets represent the percentage of the given oxide in the total mass of cement.
They have been found to react with some aggregates, the pro ducts of the alkali-aggregate reaction causing disintegration of the concrete (see page 267), and have also been observed to affect the rate of the gain of strength of cement.
Two terms used in require explanation. The insoluble residue, determined by treating with hydrochloric acid, is a measure of adulteration of cement, largely arising from impurities in gypsum. BS EN 197-1 limits the insoluble residue to 5 per cent of the mass of cement and filler; for cement, the ASTM C 150 limit is 0.75 per cent. The loss on ignition shows
the extent of carbonation and hydration of free lime and free magnesia due to the exposure of cement to the atmosphere. The specified limit both of ASTM C 150-05 and of BS EN 197-1 is 3 per cent, except for ASTM Type IV cement (2.5 per cent) and cements with fillers of BS EN (5 per cent). Since hydrated free lime is innocuous, for a given free lime content of cement, a greater loss on ignition is really advantageous.