What is "CURING"?
Curing concrete is all about creating the right environment for it to develop its full strength and durability. It's not just about drying the concrete out. Here's the breakdown:
- Hydration: When you mix concrete, a chemical reaction between cement and water (hydration) starts. This reaction forms crystals that make the concrete strong.
- Moisture Matters: Curing keeps the concrete moist so this hydration process can continue. Without enough moisture, the crystals can't grow properly, and the concrete won't be as strong as it should be.
- Temperature Control: Curing also involves maintaining a moderate temperature. Too hot or too cold can slow down hydration.
Here are some ways to achieve proper curing:
- Keeping it Wet: You can cover the concrete with plastic sheeting or burlap and keep them damp by spraying them with water regularly.
- Waterproofing Sprays: Applying a curing compound can create a moisture barrier on the surface.
- Mind the Weather: In hot weather, you might need to shade the concrete if you're outdoors and use additional water. Cold weather might require using insulated blankets to maintain warmth.
Overall, curing is a crucial step in the concrete placement process. By providing the right conditions, you ensure your concrete reaches its full potential and lasts for a long time.
How Does That Relate To Concrete Worktops?
Once you have finished casting your concrete you may be tempted to down tools and leave. Don’t. You have one or two more small tasks to do.
Because concrete worktops are thin (compared to a bridge or road) there is a lot more surface area for the water to escape from.
Firstly you’re now going to cover your concrete over with plastic sheets to prevent too much water escaping for the next 12-18 hours. If too much water does escape and the concrete begins to dry, it compromises the early curing of the concrete and can weaken your it in both the long and short term.
In fact before covering with plastic, you’re going to splash or spray the concrete with plenty of water to prevent the concrete from drying at all. Don’t be mean, be liberal.
Now cover the concrete with the plastic sheets and rub the plastic sheets to “wet” them against the concrete.
The final stage of this process depends on the temperature in your workshop. If you’re lucky enough to have a heated workshop or it is the middle of summer then you will hopefully have an ambient temperature of +18degC. If its colder then the next step is even more important.
Cover your concrete and plastic with blankets to keep the heat in. In a cold workshop consider heated blankets.
Do the above and you can demould in 15-18 hours.
If you have a temperature between 15-18degC the curing process will slow but will nonetheless take place.
If you have heated blankets then they will be useful in speeding up the initial concrete curing ready for demould. Without you’ll be looking at approx 18 hours before you can demould. With heated blankets you can demould at 15 hours.
If your workspace is at 15degC or below the concrete curing process will grind to a halt. So you will need to provide assistance. The easiest way to do this is with heated blankets. Modern heated blankets are low-cost and low energy. Leave them in place and on for 15-18 hours.
If you are using heated blankets, make sure ALL of the concrete is covered.
HINT - Confucious (probably) said “A patient person will not snap concrete”. He was extremely wise. Don’t demould too soon.
HINT - after the above prescribed durations, uncover a corner of the concrete, stick your nail in. If you can’t dig into the concrete, grab a proper nail. Dig that in. If you can’t dig any concrete away, you’re ready to demould.