concrete curing

• 24 to 48 hours - after inital set, forms can be removed and people can walk on the surface

• 7 days - after partial curing, traffic from vehicles and equipment is okay

• 28 days - at this point, the concrete should be fully cured

Learn more: How Long Before You Can Drive on Concrete?

WHAT IS CURING AND WHAT DOES IT DO TO THE CONCRETE?

ASTM C 1315, Type II cure & seal materials have a white pigment that helps to see what's been cured and can reflect some sunlight.Nox-Crete

Curing serves these main purposes:

• It retains moisture in the slab so that the concrete continues to gain strength.

• It delays drying shrinkage until the concrete is strong enough to resist shrinkage cracking.

• Properly curing concrete improves strength, durability, water tightness, and wear resistance.

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.