Curing and Sealing Concrete
All driveways in Ontario must be cured as soon as the last finishing operation is completed.
Few topics cause more confusion for users of concrete than curing and sealing. We want everyone using our products to understand these vital steps in the concrete construction process.
Concrete is a mixture of cement, sand, coarse aggregate, water and admixtures. When the cement comes in contact with water, a chemical reaction called hydration occurs. It is this chemical reaction that changes concrete from a fluid to an inflexible, strong, stone-like substance.
Cement hydration is a long term process. After 28 days, 95% of the hydration is completed, so the concrete has gained most of the compressive strength that it will achieve. However, for hydration to continue for 28 days, two conditions must be maintained:
- Sufficient temperature (above 10 degrees C.)
- Sufficient moisture
If either of these conditions is not maintained, hydration will stop, and concrete will stop gaining strength at that time. Curing is maintaining sufficient moisture and temperature for hydration.
Sealing is applying surface protection on cured concrete. For exterior applications, especially areas exposed to road chemicals, sealing should be repeated every 3-4 years with high quality sealers.
- Air Cure - this means no cure at all - okay for a footing or a basement floor perhaps, but not too smart on a driveway or exterior concrete.
- Water Cure - must keep concrete saturated - allowing it to dry out stops hydration
- Membranes - poly will leave discoloration. Kraft paper is a two part system - wet under layer and poly outer layer.
- Chemical cures - spray on chemicals - water based or solvent based.