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FAQ
How easy is it to fix a poured foundation if there is a water problem?
It is very easy and is done from the inside. No excavations or disruption to the existing landscape if it is in correctly. A high pressured epoxy is forced in to the problem crack and over time will harden stronger than the foundation itself.
Are there restrictions to the time of year you can pour concrete?
Yes and No. We can pour concrete foundations successfully down to 20 degrees. But concrete must not be poured on frozen ground. Flatwork must be covered to protect it after it is poured. All outside flatwork (drives, walks, stoops, and patios) need to be completely cured befor they are used. This takes much longer than the normal 28 days in cold weather.
Why does concrete crack?
Concrete, like all other materials, will slightly change in volume when it dries out. In typical concrete this change amounts to about 500 millionths. Translated into dimensions-this is about 1/16 of an inch in 10 feet (.4 cm in 3 meters). The reason that contractors put joints in concrete pavements and floors is to allow the concrete to crack in a neat, straight line at the joint when the volume of the concrete changes due to shrinkage.
Why do concrete surfaces flake and spall?
Concrete surfaces can flake or spall for one or more of the following reasons:
In areas of the country that are subjected to freezing and thawing the concrete should be air-entrained to resist flaking and scaling of the surface. If air-entrained concrete is not used, there will be subsequent damage to the surface. The water/cement ratio should be as low as possible to improve durability of the surface. Too much water in the mix will produce a weaker, less durable concrete that will contribute to early flaking and spalling of the surface. The finishing operations should not begin until the water sheen on the surface is gone and excess bleed water on the surface has had a chance to evaporate. If this excess water is worked into the concrete because the finishing operations are begun too soon, the concrete on the surface will have too high a water content and will be weaker and less durable. My concrete is cracking after only a short period. Is there something wrong with it and can it be repaired?
All concrete cracks. It has to crack because it contracts during the drying, curing, hardening process, and the bond between the cement paste and the aggregates is not strong enough to withstand that stress. The best way to prevent unsightly cracking is to put joints in your concrete every 2 ½ to 3 times in feet the depth of your structure in inches (4" slab should have joints every 10 to 12 feet). Uneven shifting of the substructure or subgrade can also cause cracking. This is a structural failure, as opposed to improper curing or jointing as mentioned above. Before repairing any concrete cracking, determine the source of the cracking and emedy that first. Epoxy grout is an excellent crack repair agent.
We have a situation where slabs are showing what appears to be drying cracks. They are occurring before the concrete has it's finish applied, shortly after it has been floated.
You are seeing a classic case of plastic shrinkage cracks, which occurs basically when the surface moisture dries faster than the rest of the concrete and the normal bleeding doesn't replace the surface moisture fast enough. Dry, windy, sunny days exaggerate the situation, especially when the concrete is placed on poly. the water demand increases and doesn't allow a normal bleed, which would help replenish the surface moisture from the bottom as it is being dried out on the top.
How much rebar or what size grid should be used?
It depends on the soil conditions and the expected load. A local engineer needs to answer this one. But in NW Indiana most of the towns require 2 #4 bar in footings and 2 #4 bar in walls.