how long do cement dry

how long does it take for concrete to dry - bob vila

A: Sounds like you have a fun project ahead of you! Concrete is one of the strongest and most durable construction materials around, but in order for it to reach its peak strength, it needs to dry gradually. This drying process, known as hydration, begins the moment you mix water with the dry concrete mix, giving you limited time to get the wet concrete into the forms before it hardens. Hydration continues over the next few weeks, progressing through a number of stages until the concrete is completely cured.

During the drying process, rock-hard crystals develop within the concrete that bind the sand and gravel components firmly together. If the concrete dries too quickly, the finished project wont be as strong as it should be. Read on to find out how much time you have to pour and finish the concrete slab and what you can do during each stage to make your project a success.

With most concrete mixes, such as Quikrete Ready-To-Use Concrete Mix (in the yellow bag) , you can expect to have about an hour of work time to get the concrete shoveled into the forms, spread out, vibrated, and leveled before the mix begins to harden. During this time, its vital that everyone who is working on the project knows what their job is and that they work somewhat quickly. You wont have time to run out and buy an extra bag of concrete so make sure you have enough before you start the pour, as well as all the necessary tools (shovels, concrete rakes, screed board, floats, trowels, a broom, an edger, and a groover).

In hot, dry weather, especially if youre pouring under the blazing sun, the heat can draw water out of wet concrete quickly, reducing pour time to as little as 30 minutes, so its best to pour on a day when the temperature is between 60- and 80-degrees Fahrenheit. If you do have to pour in hot weather, the following tips will help extend pour time:

When pouring concrete, plan to spend half of the work time on the pouring process, and the other half on the finishing process. If the concrete mix has an approximate one hour of work time (work time is listed on the bag), plan to spend no more than 30 minutes on the actual pouring and screeding process, so you have adequate time to finish the slab.

To start the finishing process, you must screed the surface. Screeding is the process of removing excess concrete by leveling the top level of the slab. A 24 is commonly used to do this, but whatever tool you use must be longer than the width of the area. To complete the process, move the straight edge in a sawing motion across the area to leave it flat. One pass is each direction is usually enough to achieve the desired result.

Finishing fresh concrete involves floating the surface with a concrete float to smooth it out and push large rocks down, hand-troweling around the edges where the float misses, using an edging tool to create rounded edges, adding a broom-finish texture to reduce slipperiness, and then using a grooving tool to create control joints. The larger the slab is, the longer it will take to finish, so take that into account and work quickly, and recruit extra help if needed. If the concrete begins hardening, skip the control joints and work on smoothing and brushing the surface and smoothing the edges. You can always cut the control joints the next day with a concrete saw.

With basic concrete mix, you can usually walk on the slab about 24 hours after finishing the surface. If you need to be able to walk on it sooner, you may want to go with a fast-setting type of concrete, such as Quikrete QMax Pro Concrete Mix that offers a walk-on time of just three hours.

High-strength mixes can come with longer walk-on times, so youll need to read the particulars on the concrete bag. If youre pouring an early high-strength mix, such as Quikrete 5000, while the work time is shorter, about 45 minutes, the concrete should not be walked on before 10 to 12 hours. Because different mixes differ in work time and walk-on time, its important to use only one type of mix in your project. Dont blend different mixes in the same pour.

By keeping the new concrete from drying too quickly, youll have a stronger slaband this is where curing comes in. You can slow the drying process by spraying the new slab frequently with water for the first seven days to keep it damp. Known as moist curing, this will help ensure that the moisture deep within the slab is not drawn to the surface too quickly where it can evaporate.

Of course, not everyone has the opportunity to spray down new concrete multiple times during the first week to keep it damp. If this applies to you, no worries. You can apply a curing product, such as Quikrete Acrylic Concrete Cure & Seal, to the surface of just-finished concrete in order to keep the water within from evaporating and causing the concrete to dry too quickly. Acrylic Cure & Seal can be applied to the surface of the slab with a roller or garden sprayer just as soon as the concrete hardens and the surface sheen disappears.

By the time a week has passed the concrete will have reached approximately 90 percent of its final strength, and its usually safe to drive on it. If you have a large size vehicle, however, such as a 1-ton pickup truck, its a good idea to wait a few days or even a week longer.

Although the bulk of the hydration process takes place in the hours and days immediately after the pour, concrete needs 28 days to fully dry. While the slab will harden and lighten in color before 28 days, dont be fooled into thinking its done hydrating. If you plan to stain or paint the concrete, doing so before the process is complete can result in changes in the stain color or the paint peeling off.

Disclosure: BobVila.com participates in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for publishers to earn fees by linking to Amazon.com and affiliated sites.

3 ways to make cement - wikihow

This article was co-authored by Gerber Ortiz-Vega. Gerber Ortiz-Vega is a Masonry Specialist and the Founder of GO Masonry LLC, a masonry company based in Northern Virginia. Gerber specializes in providing brick and stone laying services, concrete installations, and masonry repairs. Gerber has over four years of experience running GO Masonry and over ten years of general masonry work experience. He earned a BA in Marketing from the University of Mary Washington in 2017. There are 12 references cited in this article, which can be found at the bottom of the page. This article has been viewed 106,751 times.

The words cement and concrete are used interchangeably, but thats not technically correct. Cement, in fact, is one of several ingredients that are combined to make concrete. Cement is a powdery, dry substance that makes concrete when its mixed with water, gravel, and sand.[1] X Research source Instead of buying a bagged mix, you can try making your own cement by obtaining and burning limestone. Also, in an emergency, you can make whats known as survival cement -- although it should really be "survival concrete" -- by combining mud and grass.

Expert Trick: If you're working on a project where you'll have a concrete finish, measure out 3 parts concrete, then add 1 part water. If you're making a concrete foundation for a retaining wall or a post, the concrete can be a little more wet, because the finish won't matter as much.

To make cement from scratch, buy or collect limestone and break it into 2 inch chunks. Put the chunks into a kiln, set the kiln to 900 C, and let the limestone bake for 4-5 hours. Be sure to wear a respirator when you pull out the limestone, then let it cool completely. Once it's cool, slip on work gloves and crumble the limestone into a fine powder with your hands. The resulting powder is cement, which you can mix with water, sand, and gravel to make concrete! For more tips, including how to use a cement mix to make concrete, or advice on how to make "survival cement" from mud and grass, read on! Did this summary help you?YesNo

replacing the cement between flagstones | devine escapes

I took some photos during a recent flagstone repair job, and thought Id put together a tutorial on how to repair flagstone, part of my continuing DIY flagstone series. Please note, that if you need individual help with your flagstone project, I now offer DIY phone consultation services.

Flagstone patio set in cement. The patio, In Ambler Pennsylvania, has a few years on it and now most of the mortar in between the stones is all cracked up. In fact, there were no sections of unbroken mortar that were longer than 10 inches. As such, my prescription was complete removal of all mortar from between the flagstones and replacement with new, type S masonry mortar.

So the first thing to do is remove the old mortar. The way you do that will depend on the project. How big are the joints, how broken up are they, are they regular straight lines, or is the flagstone irregular and natural shaped? Either way, the tool kit that I use will generally be the same: an angle grinder with a four and a half inch diamond blade on it and a hammer and chisel, maybe a large flat head screw driver.

One way to remove the old cracked up mortar is to take your angle grinder and cut a line through the center of the mortar.only as deep as the cement joint. You do not need to cut all the way down into the concrete. A inch deep will do it.

After that you can take a chisel and hold it at a forty five degree angle, and come at the joint from the sides. Strike down upon the mortar from the right side and then from the left. Should pop out fairly easily. Again, the method you use will greatly be determined by the shape and size and condition of your mortar joint.

This was an 800 square foot patio. We used different technique on different sections, but the above method worked for most of it. Some areas, the mortar had enough cracks in it and was loose enough that we could just wedge a small chiselor a large flat-head screwdriverand just pry out the loose mortar.

Really, most of the joints could have been removed with just a hammer and chisel. And that sounds attractive, right? Less noise, less dust, more eco. However.A) that would have taken awhile longer and B) many stones would have popped loose that way. Using the hammer and chisel creates greater impact. Now if we bust up the stones and have to re-lay themthats more work, more cement, less eco. So well usually try using just the chiselwhen too many stone pop up loose, we switch to the grinder.

PLEASE NOTE: there are other methods, and other tools that can be used to remove the old mortar, this is just one method, and not appropriate for all flagstone patio repair jobs. Anyway, repointing a patio is a lot of work, so lets just keep going then.

But before we get to learning how-to repoint our flagstone patio, you need to clean out them joints, remove any loose mortar that might be remaining and clean out the dust. My usual method is alternating turns with the leaf blower and the hose. Use a broom to pick up any larger bits of old mortar that is still on the patio. Blow out all the dust, then spray it down, then blow it out again. Your mortar will not adhere to dust, so whatever method you use, just be sure to get them joints clean.

I like to use a fairly dry mix of mortar for this type of work. Masons call this a stiff mix, or a tight mix. I go just a tiny bit wetter than crumblywell, maybe a little bit crumbly. This makes less of a mess, than wet mortar will. Also, since the cement is fairly dry, I can really push it down into them cracks. With a wetter mortar, if you push it down hard, or even just go to smooth it out too much, youll push the moisture up to the surfacewhich will cause problems, such as spalling and cracking, later. Drier stuff is easier to clean and will be stronger. Years down the road, this patio will still be in good condition.

***I need to go back and edit this post with photos and description of my current method. First I need new photos! Anyway, Ive discussed re-pointing flagstone and other paving with other masonry contractorsI partially wrote this article in order to present my method, self taught, to other masons and see what they had to offer. Since then, Ive modified my technique. Ive been experimenting with using much more dry mortar. This cuts way down on the clean-up time. Use really really dry mortar. Just add enough water that the mortar all looks darkened, but is not actually damp. Pile it up around the joints, one foot or so at a time..work it into the joints with your tuck pointerpress it in really good..my old way, the way outlined above works finebut I believe the really dry method provides just as much strength and durability and much less clean-up.

UPDATE: my new method of re-pointing flagstone is described here. Basically its the same as before, only with a much more dry mortar mix, firmer pressing-down with the narrow trowel, and much less extensive cleaning afterwardsc

Other methods that I have encountered have varying degrees of easebut do not provide much durability. I do NOT approve of any methods that use a) too much water, or b) is not compacted enough, pushed down into the joint really well. The mortar, whether you are using the super dry method or and other dry method, must not be plastic. It can be bone dry, crumbly, or slightly dampbut it must be more dry than a block laying mix. The cement you use to lay a cinderblock is just way too wet for grade level application.

Another super dry method involves just sweeping the mortar into your joints. I know guys who fit their dimensional ((pattern-cut)) as tight as possible, with 8th inch or less gapsand then they sweep dry mortar mix into the joints and then lightly mist it. Later on pressure washing any haze. This method is easy.but since the mortar never gets pushed down into their, never gets properly compactedIm just not feeling it. Not my style. Will crack up.

So do some other work for awhile and return to the newly filled flagstone joint a couple hours later, or however long it takes, until when the joint has become thumbprint dry. Heat and humidity and how loose or tight your mortar mix was will determine how long this takes.on a perfect 70 degree day, you may be able to work all morning, filling the joints with mortar, and then after lunch you can go back amd sponge off the joints a second time. This is because your first pass with the sponge, when the joints were fresh, got up the majority of the spilled mortar. To try and get it 100 percent clean when the mortar is freshwill make a mess.

Sponging down the joint itself (when it is thumbprint hard) will also fill minor gaps that you may leave behind with the trow. Look, Im pretty good with a trowbut still, little tiny spots can get left, little voids, about one quarter the size of a match headlittle spots, usually along the edge of the stone, not in the middle of the joint. These are spots where water can infiltrate, and cause a mortar joint to fail, sometimes within just a few years. Worse still, that water could even get underneath your flagstones, cause thing to pop up and come loose.

Im not really sure how many masons use a sponge technique like I do. What I do know however is that when I come in to repair these jobs, I always find little tiny gaps in the mortarlittle tiny gaps like the ones that I myself sometimes leave behind with my trowbut that I always correct, with the sponge.

Thank you for taking the time to read this article on how to repoint flagstone patios. Now go forth into the world and repair some old flagstone patios, like a pro, like a real stone mason. Like Devin Devine.

I wouldnt recommend sealing any grade level masonry. 1. it can make the flagstone slippery and 2. it can trap moisture. Once the top of the stone is sealed, the bottom of the stone and mortar are both still porous and can take on moisture from the groundbut now that water can not be shed through evaporation. This can potentially cause problems.

Hi, Our flagstone patio grout is more broken up than the image you show here. Im sure moisture was seeped down underneath. Is it worth spending the money to repoint it? Its a large area and Im certain it will be an expensive project.

Usually repairing is much cheaper than replacing and a patio needs to be in bad bad shape, before repairing is just not worth it. Having said that, a repair doesnt have much value, unless it is carried by a skilled stone mason.

Thanks Devin for the tips. I was about to repair a few gaps in my pool surround and then I read your keep it dry grout recommendation. I also went out and bout a tuck pointing trowel. Appreciate your advice.

Theres too much here that I dont know. Theres cracked mortar and the flagstones are on a bed of sand. So.was the patio built on a base of sand and then the joints mortared? Thats not the right way to build a stone patio. Or, is the stone patio is on a concrete foundation and the mortar between the stones has cracked, while the mortar beneath the stones has crumbled up and became sand? This happens often, when the mortar joints on a stone patio crack, often theres a few stones that have mortar beneath them that has degraded and become sandy. In the latter caselift up the stone, clean out the loose mortar/sand. Remove enough material so that you can re-set the stone in about an inch of mortar. In the former casetheres probably a few things wrong (too thin stone probably, too wide joints I bet, also stone dust is better than sand, for leveling flagstones) and the remediation may be more complex. Have a pro look at it, Set up a phone/email consultation with me, in that case. Hope that helps!

Original material was Type M mortar mixed with red sand, providing a beige color. Re-pointed by different mason three years ago with gray mortar (not sure what type) and match was awful. Now, about 20-25% of the patio has cracked mortar and a bunch of loose stones. Areas under decks looks brand new.

1. What is the best way to match the existing mortar? 2. What is the best method to re-lay the loose stones? 3. With this much cracking, should I consider a total re-grout? 4. What type of sealer do you recommend for this?

1. I show up with brown and, yellow sand, white sand. Grey Portland cement, sometimes white Portland cement to. I experiment with different sand combinations, to try and get the best matchlet samples dry. Check them. Tip! You can mix up a sample, then compare it to the old mortardampening the old mortar will give a better comparison, so youre not comparing dry to wet. But let it fully dry to be sure. Also, be aware the new mortar will get lighter as it dries.then get a degree or two lighter still, over a few days/week.

2. Set up a phone consultation to go into detail about things like this.clean out old mortar, get it nice a clean. Complicated projectyou might do well to hire a pro, or set up a 60 minute phone consult with me.or keep reading articles/ watching videos.

4. No sealer! Unessesary and can trap moisture. Underneath, it is absorbing ground water, but it cant evaporate. Might make flagstone slippery. No evidence that it helps longevity. Sealer not recommended for grade-level stone work.

Thanks for this really great. My patio just has a few 3 to 6 inch joint gaps where the mortar has cracked and comes out after just power washingmaybe 10 or so on a 2030 foot patio.how much of the existing mortar do I have to remove ? Clearly anything loose but I dont want to create a huge job. Thanks Fred

Cant say for sure without seeing the patio, but it sounds like you have maybe 1-3% of the joints failing. If Im looking at a patio with a small percent of joints failing, Ill usually end up recommending that the loose material be removed, anything cracked be grinded out and patched as well. Really, every job is different and I can only offer general guidelines, at best, as there is BUT, generally speaking, Id replace the loose stuff, cracked stuff, and Id look for anywhere where the mortar has separated from the stone at all, at patch those areas too. Good luck!

Wow I wish I could show you my slate patio. As far as I can tell it was not done properly. It was done by the previous owners. Some tiles arent slate Im sure as they have basically disintegrated over time. Looking at trying to fix it as it does look nice in some spots. Are the tactics you use here similar to what I could do to fix my patio? Can I make a quality repair with out starting from scratch? Thanks in advance.

I really couldnt say, without seeing the job. It sounds like a complicated fix, one that you probably should seek out a professional for. Consider hiring a professional. If you just want a professional opinion and advice before going DIY, then I do offer phone/email consultations:

Is your walkway on a concrete foundation? If so, use mortar (which is made from cement and sand). If your walkway is on a grave base, then use stone dust/quarter inch minus/pathway fines/whatever they call the stuff in your area.

Youre just what the doctor ordered. I have an old (50 plus years) flagstone patio natural flags large and small. They are set on concrete. Just about all the joints are loose and have filled in with dirt and many weeds.so my thought is to scrape them all out, pressure wash the whole thing and then repoint with cement. Ill send you a before and after pic have been wanting to do this for years and now maybe i have the time. Thanks for the informative blog.

From what youre telling me, youre going to have someor a lotof flagstones that are loose. When you removed the old mortar, youll find flagstones that are loose, and will need to be re-set in mortar. Looking forward to the before and after pics. Good luck!

Ive recently had a flagstone patio installed and while most of the job went well the two sides of the patio mortar dont match. One side is a preferred light grey and the other is a sandy color. Im estimating at least 250 sqft does not come even remotely close. Would you request the contractor to come back and redo all of the mortar that doesnt match or just deal with it? I can forward pics of youd like.

If it were me..I wouldnt install a new wet laid patio. Go dry lay. Seriously. Read some posts https://www.devineescapes.com good, qality stuff. But if I was repairing a mortared patio (something that I do often, because they often fail) then my mortar would match. And if there was an coloration issue, Id sure want my client to ask me about it. Talk to your contractor.

That depends. If more than half of the mortar is crumbly, then Id just remove all of it. If less than half of the mortar is broken up, then you can leave the good stuff where it is and just remove/replace the broken stuff. Color matching will be an issue though. New mortar tends to be white/gray, whereas the old stuff is probably a yellow/gray/brown. Buy some dye and pre-mixed mortar or go all-out and buy portland cement plus different types of sand and maybe some dye tooand mix up some test batches. Spread a small bit of each batch on a piece of cardboard and set in in the sun to dry fast and give you an idea how close the color match is. Good luck!

Thank you for your very informative guide. I had my patio re-pointed last year. The mortar is flaking off. This started shortly after the repair, prior to winter or bad weather. He ground the old mortar out, pressure washed it and cleaned it then re-pointed it. He used a masonry cement type S white mortar and added flex con. The mason, who also repaired a sandstone walk without any issues, doesnt know why the flagstone repair isnt holding up. He will redo the work, but we dont want to repeat the problem. Do you have any suggestions? How long should a repair last if properly done?

a) wash out the joints really good before re-pointing. Grind/chip out the old joints, then sweep, then leaf blower, then hosethen repeat the blower and the hose again. Or multiple passes with the hose if you dont have a blower. Mortar will not stick to a dusty surface and dust can hide, down in them cracks between your walkway/patio stones.

b) dont mix your mortar too wet. Mix it dryer than you think. Sometimes I mix it even dryer than dryer than you think, and mix it so its still powery, only barely damp, and only sticking together when pushed down into the joint with pressure. Soupy, over-wet mortar will flake up. Like-wise, a only somewhat damp mortar will flake up if over-worked. You work the surface of that mortar with your trowel too much, and you will bring all the moisture to the surface, making the surface mortar over-wetand over-wet mortar will flake up.

Hi Devin. I have a question regarding flagstone steps. The mortar on most is loose and the mortar on one of the risers has crumbled. One stone on a flat landing is loose and wobbly. Can I use Type S to reset the loose stone or would I use Portland cement? Thank you for your time.

What a miracle that I stumbled across this post! I was about to destroy my patio without knowing that the joints shouldnt be sealed! It never ocurred to meso I just sealed the entire patio in order to keep the new grout from staining. I sealed the old grout as well in this process, so it looks like I need to act fast. Ive never heard the terms pointing or do I know about different grades of mortars. I guess I have my work cutout. Not something Im looking forward tohowever, sealing the stone didnt make it slippery at all. If I can suggest adding a handful of playground sand to the sealer to keep it from slippingit works. Just a bit as you go to add an element of grip. Most of all I really want to thank you for your post. You saved me from destroying my 650 sq foot4 yr old patio. A $70k patio when you add in the waterfall. I owe you!

Hi I followed your advice and bought a bag of Sakrete Mortar/stucco mix type S at home depot. After using few times I feel there is too much sand to produce a smooth joint surface. If I am using the wrong product, what should I pick.? Should I make my own mix of portland and sand? Thank you

Idkhow smooth are you looking for? Wetter mortar is easier to get rather smooth, but I dont do that, myself, as wetter mortar is weaker. More water when mixing, equals lighter/more porous weaker when dry.

xypex | concrete waterproofing using crystalline technology

The ambitious $368-million Atlanta Water Program has successfully converted a defunct granite quarry into a 2.4 billion gallon reservoir and extended the citys drinking water reserve supply from a mere 3 days to more than 30. Xypex Admix C-500 was added to the concrete for two critical flow control channels in order to help the city meet its 100-year longevity goal for the new structures.

The seaside city of Largo needed a way to restore crumbling concrete at the heart of its wastewater treatment plant. In consultation with a local engineering firm, the city chose to restore the plants biological nutrient removal (BNR) trains using the single-step Xypex Megamix II with Bio-San instead of a time-consuming multi-step alternative.

how to mix cement: 11 steps (with pictures) - wikihow

This article was co-authored by Gerber Ortiz-Vega. Gerber Ortiz-Vega is a Masonry Specialist and the Founder of GO Masonry LLC, a masonry company based in Northern Virginia. Gerber specializes in providing brick and stone laying services, concrete installations, and masonry repairs. Gerber has over four years of experience running GO Masonry and over ten years of general masonry work experience. He earned a BA in Marketing from the University of Mary Washington in 2017. wikiHow marks an article as reader-approved once it receives enough positive feedback. In this case, 80% of readers who voted found the article helpful, earning it our reader-approved status. This article has been viewed 570,382 times.

Whenever a project calls for a hard, permanent binding material, most professional and independent builders use cement. Before using cement, you need to mix it with sand and stone. While this process can seem overwhelming, it's fairly simple with the right tools. You can mix your cement in a wheelbarrow using a spade or shovel before applying it to the area you're paving.

To mix cement, start by combining 1 part cement, 2 parts sand, and 4 parts gravel in a large bucket or wheelbarrow. Next, make a small crater in this mixture and add half a bucket of water. Mix the cement with a shovel and add more water until its formed a smooth paste similar to peanut butter. Then, use the cement for your project and clean your supplies as soon as possible so the cement doesnt dry on your tools. For tips from our Home Improvement reviewer on what to do if your cement turns out too soupy, read on! Did this summary help you?YesNo

how long does it take for a concrete driveway to dry?

A concrete driveway takes 24 to 48 hours to dry. Walking on the driveway without damaging the concrete is possible after this time. Even though concrete is solid after two days, there are still time limits on what the driveway can handle.

A concrete driveway takes 24 to 48 hours to dry. Walking on the driveway without damaging the concrete is possible after this time. Even though concrete is solid after two days, there are still time limits on what the driveway can handle.

It is not advisable to use skateboards or bicycles on the driveway between day two and day seven. Concrete hardens enough to drive on after one week but only for normal-sized vehicles. For the first month after a concrete driveway is poured, it continues to harden. It typically reaches full driving capacity for any size vehicle after 30 days.

It is not advisable to use skateboards or bicycles on the driveway between day two and day seven. Concrete hardens enough to drive on after one week but only for normal-sized vehicles. For the first month after a concrete driveway is poured, it continues to harden. It typically reaches full driving capacity for any size vehicle after 30 days.

how long does cement take to dry?

The weather has a large effect on how quickly cement completes the curing process. Factors such as rainfall, sunlight, wind and humidity are all contributors. Treatment of newly poured cement depends greatly on the weather conditions as moisture imbalances can cause cracking as the cement dries. Concrete will cure harder and stronger if it is allowed to dry slowly. If conditions are moderate, covering the cement with plastic protects it. If temperatures are 80 degrees or above, frequently watering it down with a garden hose keeps it moist and prevents cracking. In the right conditions, concrete will reach about 90 percent of the curing process within a week.

The weather has a large effect on how quickly cement completes the curing process. Factors such as rainfall, sunlight, wind and humidity are all contributors. Treatment of newly poured cement depends greatly on the weather conditions as moisture imbalances can cause cracking as the cement dries. Concrete will cure harder and stronger if it is allowed to dry slowly. If conditions are moderate, covering the cement with plastic protects it. If temperatures are 80 degrees or above, frequently watering it down with a garden hose keeps it moist and prevents cracking. In the right conditions, concrete will reach about 90 percent of the curing process within a week.

There are accelerator products on the market that help to speed up the drying process. Accelerators are chemicals added to a concrete mix that reduce the set time by increasing the rate of hydration. There is also Portland cement, which sets and hardens due to a chemical interaction with water. The curing process is the most important step in achieving strong and even cement.

There are accelerator products on the market that help to speed up the drying process. Accelerators are chemicals added to a concrete mix that reduce the set time by increasing the rate of hydration. There is also Portland cement, which sets and hardens due to a chemical interaction with water. The curing process is the most important step in achieving strong and even cement.

curing concrete - how long it takes & how to cure - the concrete network

In the first week or so after concrete is poured, you must maintain the proper temperature and dampness for proper curing. Curing is easy to skip in the instant but that will have a major impact on the quality of your finished work.

While curing is important for all concrete, the problems that arise from not curing are most obvious with horizontal surfaces. An uncured slab, whether decorative or plain gray, is likely to develop a pattern of fine cracks (called crazing) and once it's in use the surface will have low strength that can result in a dusting surface that has little resistance to abrasion.

The entire curing period of concrete takes about a month, but your concrete will be ready for use sooner. Each project will vary slightly due to differences in the weather, concrete mix and placement and finishing techniques.

When most people think of curing, they think only of maintaining moisture on the surface of the concrete. But curing is more than that-it is giving the concrete what it needs to gain strength properly. Concrete strength depends on the growth of crystals within the matrix of the concrete. These crystals grow from a reaction between Portland cement and water-a reaction known as hydration. If there isn't enough water, the crystals can't grow and the concrete doesn't develop the strength it should. If there is enough water, the crystals grow out like tiny rock-hard fingers wrapping around the sand and gravel in the mix and intertwining with one another. Almost sounds like a horror movie-our concrete baby has turned into a monster!

The other important aspect of curing is temperature-the concrete can't be too cold or too hot. As fresh concrete gets cooler, the hydration reaction slows down. The temperature of the concrete is what's important here, not necessarily the air temperature. Below about 50 F, hydration slows down a lot; below about 40 F, it virtually stops.

Hot concrete has the opposite problem: the reaction goes too fast, and since the reaction is exothermic (produces heat), it can quickly cause temperature differentials within the concrete that can lead to cracking. And cement that reacts too quickly doesn't have time for the crystals to grow properly so it doesn't develop as much strength as it should.

So in the soon-to-be famous movie, the Cement Monster That Enveloped the World, all the puny earthlings need to do to save civilization is get the concrete too cold, too hot, or too dry and he turns into a weakling. Our objective, though, is to help him envelope the earth and to make him as strong as possible!

So the objective is to keep our young and impressionable concrete damp and at the right temperature (ideally between 50 and 85 F). The most frequently overlooked curing aspect is keeping exposed concrete surfaces moist while they are hydrating. Most concrete, especially most decorative concrete, will have plenty of water initially in the mix to completely hydrate the cement. The problem is that if the exposed surfaces dry out then the concrete can't hydrate and our young concrete ends up with very sensitive skin-easily scratched and sometimes actually dusty.

There are three phases of curing and the length of time each lasts depends on the concrete and the environmental conditions. Check out Figure 1.6 in ACI 308, Guide to Curing Concrete, to see how this works:

During initial set, the rate at which the bleed water evaporates depends on a combination of factors: air temperature and humidity, concrete temperature, and wind velocity. The classic, and still best way to estimate the rate of evaporation is the Menzel/NRMCA nomograph-an easy-to-use chart that combines all of these factors. You can get this nomongraph out of ACI 308 or it's also available in an excellent piece in the March 2007 Concrete International, "Estimating Evaporation Rates to Prevent Plastic Shrinkage Cracking." You can also estimate evaporation rates using a free online program developed by Luke Snell and Amir Munir.

So you use these methods to figure out how fast the bleed water is evaporating--if it's greater than 0.2 pounds per square foot per hour, then initial curing is necessary because the concrete will be drying out. In the next section we'll discuss how to do initial curing.

After initial set, the concrete surface still needs moisture and now there's no bleed water. This is when you really need to cure the concrete. You need to assume that your concrete needs to be cured-it does! You don't want your perfect baby concrete to turn into a juvenile delinquent, do you?

Now let's narrow this conversation down a bit. Let's talk only about horizontal concrete and only about the moisture part of curing. To learn more about working in temperature extremes get a copy of ACI 305, Hot Weather Concreting or ACI 306, Cold Weather Concreting.

Let's also narrow things down to curing of colored concrete. We'll define that as any concrete with color, whether integral or dry-shake, whether it is going to be stamped or not. First, and most importantly, colored concrete is not really different than any other concrete, it needs exactly the same treatment to end up with quality concrete. Some of the methods, though, need to be a bit different since appearance is so much more important than it is for an industrial slab.

There are three ways to cure concrete: either we add water to the surface to replace the water that is evaporating or we seal the concrete to prevent the water from evaporating in the first place or we do both. Note that adding water to the surface is NOT adding water that will be worked into the concrete mix--that would increase the water-cement ratio of the surface concrete and weaken it, ruining all our curing efforts.

You need to think about initial curing when the bleed water is evaporating too rapidly to keep the surface wet prior to initial set. Traditionally that has been specified at greater than 0.2 pounds per square foot per hour. Many mixes today bleed at much lower rates than this, so if there is less bleed water then the evaporation limit needs to be set lower-more like 0.05 to 0.1 pounds per square foot per hour. The best approach for decorative concrete is to try to alter conditions so you don't need to do initial curing: block the wind, keep the sun off the concrete, get cooler concrete. If that's not possible, fogging just enough to keep the surface damp is possible, but the simplest approach is to use evaporation retardant. This chemical can be sprayed on to form a thin membrane on the surface that prevents the water from evaporating. It completely dissipates during finishing operations. Keep some of this around for dry windy conditions.

Water curing can be done after the slab pour by building dams with soil around the house and flooding the slab. The enclosed area is continually flooded with water. Ideally, the slab could be water cured for 7 days.Some builders on a tight schedule water cure for 3 days as this achieves approximately 80% of the benefit of water curing for 7 days.

how long does concrete take to set? | concrete setting times

If you really want to know the truth, concrete never stops curing; it continually hardens forever. However, for practical purposes, it reaches a point where further hardening will be so slow it becomes unnoticeable. In this article, we cover the basics of what you need to know if youre asking the question, how long does concrete take to set?

The continual hardening occurs because cement particles react with the water in the mix (hydration), and as long as cement is in contact with moisture, even minuscule bubbles, it will continue to form bonds. This is minimal after full strength is achieved, but it is continual.

In standard industrial cases, full strength concrete is recognized at 28 days. At seven days, you should have concrete that is curedto 70% full strength or greater. But to answer the question of, How long does concrete take to set?concrete setting time is generally 24 to 48 hours. At this point the neighborhood dog will not leave his footprints in it, but you should keep it clear of heavy equipment during this time period. Most mixes are cured at 28 days.

If you are wondering about how long concrete takes to set, asolution for your concrete setting needsis a concrete heating or cooling blanket. But not all blankets are created equal. Consider the following two types of solutions to the effects of hot and cold:

If conditions are cold, concrete curing blankets provide a manageable way to cure concrete effectively and confidently. Powerblanket curing blankets increase production by rapidly curing with consistent, even heat.

Realize that just because you have a concrete curing blanket doesnt mean you have a solution. The type of blanket and how that blanket is used will have a massive impact on your concrete. Read more about curing blankets here.

It sure was nice when you said that it will generally take 24-48 hours for the concrete to set. My dad is planning to have ready mix concrete delivered to his house. He said that hes planning to install a concrete driveway. Its important for him to keep the exterior part of his house to be organized and appealing. Since he wants his driveway to not be damaged while curing, Ill share this with him.

What about fence post brackets set into concrete? How long should one wait before fixing the wooden posts onto the brackets? My worry is that the heavy(ish) posts will exert a lot of leverage on the bracket and especially the pin underneath that actually sits in the setting concrete when Im getting them vertical and putting in the screws. Would 7 days be long enough to wait?

Just for the record! I have poured Cement under water successfully. I was asked to lay a Pylon for a small jetty many years ago and was unsure how to begin the job. I then struck on the idea that I should use a length of 6 / 150mm Pipe, as the water was around 36 deep and I needed to ensure stability my decision was to set it 18 to 24 in the river bottom and used a high pressure portable water pump to dig the pipe in by forcing water down the pipe and blasting the Graver and dirt out from beneath the pipe opening. I then braced the pipe and back filled it with a Strong cement dry cement mixture roughly allowing for some of the Cement Powder to wash away is the process. Having finished the pour I then back filled the gap about the pipe base and left the whole thing for a week to set. Keep in mind that in hot weather keeping cement moist allows for a slower drying time to gain a strong job and once the the mix had been laid there was no way for water to get in or out of the pipe once the mix began to go OFF. This a fairly rough way to do the job I did as there is no way to regulate the mixture as you will be laying as the only control you will have is by using its weight to displace the water in the pipe so make your best guess at the Mix quantities and do not mess about with the pour get it in and done as fast as possible (For you) and walk away. Trust too Providence you got it right. Through Floods and drought that pier is still standing 20 years later. Did I get it right?? Only time will tell