Please note: Javascript needs to be enabled for this form to be used.. Posted on 4th April by Ever Readymix Concrete. It will need to cure. Concrete never stops curing. However, for practical purposes and a timeframe shorter than infinity, here are some general rules of thumb where curing is concerned. Typical industrial concrete will recognise its full workable strength at the 28 day mark. For those who are laying concrete in a domestic area, like the garden, concrete is reasonably set within hours.
Bond beams, post tensioning, and other techniques are then used to create a monolithic slab that will act as a single piece and uniformly spread loads. Most of the size is for load spreading on the ground, and the ability to neglect point loads introduced by the house framing.
By making the foundation stronger than needed, the load concentration produced by large openings in the framing is ignored. Even basement walls are not that heavily loaded by backfill.
The tipping problems that occur are from a lack of lateral resistance before the floor joists are installed. I have seen basement walls fail, but they had enough curing to fall over as a unit after a fracture near the middle. Adding floor joists before any back-filling has been SOP for many years, yet occasionally seems to be ignored. I am a structural engineer and I have to chime in Pouring the walls the next day is absolutely fine. Concrete cures depending on the mix, ambient temperature, water content As long as the cure rate shows that the concrete is strong enough to handle the load the next day it will be fine.
In fact, applying force or mass--i. BTW concrete never actually completely cures year-old concrete is still getting stronger I'm always amazed. And silently smug when I see a collapse. I used to delay backfilling till the roof was framed and sheathed. But then I have persistent nightmares that the homes I build will collapse in on themselves without warning like something out of Poltergeist.
Concrete does not actually harden by "curing" nor is there any point in time when concrete would be considered "cured. Concrete naturally hardens over time by "hydration", the chemical reaction between portland cement and water in the concrete mix. In the case of a residential footing curing might consist of simply covering the concrete for 3 days. In any case the curing procedure would not normally continue beyond 5 or 7 days depending on the temperature of the air.
As long as moisture and a favorable temperature are present for hydration of the cement, the strength of new concrete continues to increase long after the early curing phase and the 28 day mark. Since the actual strength of the concrete in a residential footing is not particularly critical, testing is not required so the 28 day mark has no practical relevance in the field.
In fact, if the concrete hasn't reached the minimum strength required by code in 7 days, it's unlikely to get there. The IRC requires a concrete footing to have a minimum compression strength of 2, psi which is a low value and easy to achieve most specifications would be higher.
I won't characterize that earlier claim since it speaks for itself. As far as "respectable" architects are concerned, I have linked my grad school textbook as evidence of my training in this subject, although I would normally defer to an engineer in professional practice. The subject at hand is briefly discussed on page 5.
Of course, my book was a much older edition. It is important to understand that "curing" is an optional construction procedure rather than a physical state to be achieved. The use of phrases like "the concrete is cured" is shortspeak indicating that the desired period of moisture control is over.
The design strength is just one of many variables considered in the selection of a curing method and time period. I once had a bad batch of concrete poured in the mat foundation of a large hospital addition.
Unfortunately, it was an all day pour so it threatened to delay the project. In a big meeting of all the involved parties the concrete testing engineer announced that there was enough fly ash in the mix that steam curing might bring it up to the design specification. I had done an existing conditions survey of the adjacent buildings as part of the architectural design process and told them there was an unused steam line immediately adjacent to the bad pour.
People flew out of the trailer to tent and steam the concrete mat. When the test results came in the ready mix owner was so choked up he couldn't speak. Now there is someone who is unlikely to bad mouth engineers and architects.
Here is a link that might be useful: Concrete design textbook. So doing research to determine an effective time short of forever for measuring the strength of concrete is arbitrary? Variation will occur during assembly away from the ideal methods. We use the derating of absolute values to account for this. Choosing 28 days is far from arbitrary, but based on much research to establish a reasonable time based on mix and applications. My point was that the 28 day mark represents a testing standard based on professional concensus rather than representing the point at which the concrete work can support a load.
To say a footing cannot be partially loaded before the 28 day mark indicates a staggering misunderstanding of concrete design and construction. At any rate, it should be clear that the contractor in question either has another reason for delaying the OP's project an additional 3 weeks or he doesn't know what he is doing. Either possibility would concern me greatly. This isn't rocket science; it's just a house footing. Excellent discussion. Who the heck is Manhattan42?
He writes as if he was a pro but says things that don't make much sense. I've built 2 houses and the builder of the first did want to wait 2 weeks crawlspace. This was a tract build. Flash forward 10 years and the custom builder just kept on trucking basement. He was also the one who explained the concept of purposely slowing the cure with water The common assumptions about concrete curing are interesting.
Most people and many builders think curing is the process by which concrete becomes fully hydrated ie hydrated enough to meet the design specifications but the term only referrs to the use of techniques to prevent the evaporation of water from the concrete in order to increase the hydration in the early part of that process when most of the concrete strength is achieved. Curing is a technique for boosting concrete strength and the need for it varies with the nature of the pour.
In the case of a structural footing, little curing is necessary to meet the design specification but in the case of a slab curing techiniques are critical for strength, crack prevention, and surface quality. So, the "cure isn't slowed with water"; water spray, or other techniques, are used to guarantee greater, more complete hydration of the cement in the concrete mix during the first 2 to 7 days after the pour.
Interesting I came across this post. We had our footers poured last Thursday and rebar in place, that evening it rained all night and in to Friday morning. On Monday they had all the forms in place, Tuesday poured and today took the forms off. Temps are around 40 during the day and 30 something overnight and they are calling for snow this weekend. I only hope we have no issues in the long run and that we didn't rush things.
At this point though it's too late to worry about it. Standard engineering practice in considering the curative time for concrete or other masonry is 28 days. You should try reading the ACI documents that establish the requirements for concrete construction instead of making up a lot of specious nonsense. A national builder is building a single family home across the street from my residence. Here is what I've observed so far. The slab, footers, and foundation were poured on a Friday during a snowstorm.
The concrete was poured on top of approximately " of fresh snow. The following Monday the builders returned and started to lay block. Over the 2 day weekend, the ambient temperature never got above freezing. Is this considered acceptable building practice? Calcium Chloride can be added to the mix to allow pouring at lower temperatures, but surface protection from accelerated cooling is often still required. Temperatures will impact the speed that the concrete cures at, and colder temperatures will slow down the process.
Where there is a risk of frost and ice during the curing process, it is essential to insulate the foundations using a concrete blanket. You may be concerned about weather conditions while your concrete is curing. Curing is defined as a chemical process the concrete goes through in the days immediately after it is poured. While full strength does not occur for 28 to 60 days, depending on conditions, the building process can begin when the foundations are about 50 percent cured.
Although concrete will harden soon after pouring, it's still susceptible to damage from weight during the first four weeks.
Wait at least 24 hours before allowing foot traffic, including pets, on a newly poured sidewalk or slab, and don't drive a vehicle on a new driveway for at least 10 days. Therefore, a protective barrier known as house wrap is installed to prevent the structure of your home and its interior from getting wet, growing mold, or rotting.
Pouring Concrete vs Pouring Rain. If the rain occurs when the concrete is fresh about hours after mixing , the surface should be protected from the rain. If the finishing process was recently completed, rainwater may not cause damage as long as it is not worked into the surface and the slab is left untouched. Following are different types of foundations used in construction: Shallow foundation.
Individual footing or isolated footing. Combined footing. Strip foundation. Raft or mat foundation. Deep Foundation. Pile foundation. Drilled Shafts or caissons. For a single storey building strip foundations will typically be mm wide and at least mm deep , and for two storeys mm wide and mm deep. How long does each stage of construction take?
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