Concrete typically takes 24 to 48 hours to dry enough for you to walk or drive on it. However, concrete drying is a continuous and fluid event, and usually reaches its full effective strength after about 28 days.
The general rule of thumb is that concrete takes about 28 days to dry for every inch of slab thickness. Within 24 to 48 hours, the concrete will be ready for foot traffic. However, as we pointed out above, the conditions must be right. You'll need low ambient relative humidity and a consistently warm temperature.
Microbial growth occurs when there's excessive moisture in the concrete and high levels of humidity in the air. Microbial growth can corrode and weaken concrete. Signs of microbiologically induced deterioration (MID) include cracking and flaking on the surface.
Technically, concrete never stops curing. In fact, concrete gets stronger and stronger as time goes on. But, as far as we're concerned, to reach a practical strength, most industrial concrete mixes have a 28 day curing period.
Due to the nature of how concrete is formed, it is a porous material that allows moisture and water vapor to migrate from below the slab to the floor above. As humidity changes throughout a day or over the course of year, moisture will travel through the concrete to areas of lower relative humidity.
Anytime that there is a higher water to cement ratio, it will decrease the strength and durability of the concrete. Water can breakdown the materials that concrete is made of. Create mold and bacteria in the concrete, and cause concrete foundations to move and shift. All of these result in cracks in the concrete.
Water is part of every concrete mixture, and even thoroughly dried slabs can absorb and release moisture content with changes in ambient relative humidity (RH). Healthy concrete slabs will still retain water vapor, but unaddressed excess moisture content leads to a host of concrete slab moisture problems.
Concrete that is not moist-cured at all dries too rapidly, and reaches less than half its potential design strength. It will also have a greater number of shrinkage cracks.
If too much rain falls into the concrete mix – or if it is laid onto wet surfaces or trenches – this will affect the mix, resulting in weak concrete. Rain falling on freshly-poured concrete can cause damage to the surface, making it bumpy and uneven.
If moisture seepage is already occurring, the most effective way to remove it is to use a dehumidifier and fans to draw out the humidity from the air. This should be done in conjunction with sealing the slab.
When concrete is dry and not sealed, it can absorb some water the same way that water escaped in the drying process. Humid environments, rain, and standing water are obvious threats. Sealing helps, but cracks exist in most concrete, and over time water can work its way in.
A definitive test that measures the amount of moisture released from the concrete requires a calcium chloride kit or a relative humidity meter. Testing with either method will tell you precisely how much moisture is present, making it possible to choose surface flooring that is appropriate.
Water facilitates the curing and hardening processes. Without it, the chemical reactions needed to form the hard crystals that give the concrete its strength can't take place.
Most specialists recommend watering the slab 5 to 10 times per day for the first seven days. Moist-cured concrete can be up to 50% stronger than dry-cured concrete.
When too little water is used or if water evaporates out too quickly, the cement never reaches a full chemical cure, causing a weakened product.
Concrete doesn't dry ... it cures.
Instead of drying, concrete instead cures. The water added to the mixture reacts or hydrates with the cement and aggregates to form the bond that creates concrete. Concrete does not need to dry out to harden as is commonly thought.
Sealer prevents moisture and other elements from seeping below the surface and negatively affecting your concrete surface.
Before applying a protective coating or other flooring materials to a concrete slab, it is critical to ensure that the moisture level inside the concrete has decreased to acceptable levels—typically ≤75% Relative Humidity (RH), 3 lbs/1000 sq. ft./24 hours MVER, or ≤5% Moisture Content (MC).
Liquid epoxy DPM for existing concrete floors
There are a number of benefits to using a liquid epoxy DPM: An epoxy liquid membrane is applied to the floor itself and creates an impermeable layer meaning that water stays in the concrete slab.
Yes, concrete does absorb water. The reason behind this is that concrete is a highly porous material that is made up of gravel, sand, cement and water. The final product appears hard but is full of pores.
Turn down the air conditioning/turn up the heat to keep the concrete floor temperature and the air temperature at similiar levels. Use a dehumidifier to remove moisture from the air and reduce the condensation. Use a penetrating sealer to seal the concrete and keep out moisture.
Freshly placed concrete should be protected from rain for at least 12 hours from its placement. After that, the rainfall rarely influences concrete properties. How much strength does concrete gain after 24 hours from its placement?
Properly curing your concrete improves strength, durability, water tightness, and resistance for many years. The first 7 days after installation you should spray the slab with water 5-10 times per day, or as often as possible. Once the concrete is poured the curing process begins immediately.
Wet the concrete, then place the plastic sheeting over it. Use bricks, boulders, or stakes to hold the plastic in place and keep small animals out. Once a day, remove the plastic sheet and wet the concrete, then replace the cover. Do this for a week for the best results.