Adding air to the concrete (air entrainment) allows the concrete to withstand freezing and thawing cycles as it provides room for the water present in concrete to expand without putting stresses on the concrete itself.
ACI provides guidelines as suggestions or recommendations on the water content to provide the desired compressive strength. Never add more water than what is necessary to provide the desired workability. More water equals lowered strength.
There are many causes for cracking in concrete. Concrete goes through many changes as it hydrates or hardens. Allowing the concrete to harden and achieve strength before these stresses arise will eliminate a large portion of these cracks. Proper curing, a good mix design, use of shrinkage-reducing admixtures and the addition of fibers are all good ways to help minimize some types of cracking.
Concrete can be placed in a wide range of ambient conditions. ACI guidelines explain the range of these conditions. Avoid placing concrete below 40°F or above 120°F without proper protective measures. Also avoid windy conditions without a wind break as this will expose the fresh concrete to premature surface drying, which can lead to cracking or a weakened surface that is prone to “dusting” and discoloration.
Concrete is very good in compression but poor in tension. Reinforcement allows the concrete structure to maintain its compressive integrity while still providing good resistance to tensile or flexural stresses.
Admixtures enable concrete producers and placers to easily mix, place and/or finish the concrete in multiple environments and conditions. Admixtures also provide a way to produce higher-quality concrete without increasing the cementitious content of the concrete mixture, which keeps the cost of the concrete down.
Curing is one of the most important steps in protecting your concrete and ensuring a long service life. The use of sprinklers, wet burlap and curing agents allow the concrete to gain structural integrity (strength) while protecting it from premature surface drying. Utilizing curing compounds and using sealing agents are the best ways to keep the concrete surface protected from the environment and ambient conditions, which would otherwise deteriorate the concrete surface.
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