In spite of its hard appearance, there are quite a few factors that can affect the quality and durability of concrete over time. Starting with the raw materials used, the environmental conditions, the art of mixing and pouring. But today, we will focus on the final step, i.e, curing because even if you have carried all the previous steps correctly but have cut corners on the last one, your end results will greatly suffer!
So what is curing?
Concrete curing is the process by which proper hydration of the newly poured concrete is secured, minimizing the loss of moisture on the surface by maintaining the temperature around the concrete between 50 degrees and 75 degrees fahrenheit. Pouring concrete in Seattle and in Houston will require very different approaches. The thicker the concrete, the longer the curing process is. That's why it is an art!
What does bad curing look like?
You will see scaling, peeling, popping, cracking on the surface. Popping is usually caused by soft aggregate. Flaking, cracking and peeling are often the result of surface water being driven into the cement. Everything is in the timing and in the right amounts!
Best curing methods:
There are several ways to ensure proper curing that fall under 2 main categories:
Water curing and membrane curing methods
1) Water curing techniques
Under this category you will find:
Ponding: for flat surfaces with easy access to water
Fogging: best used when temperatures could exceed freezing or in very dry regions
Wet covering: as the name implies, a covering is placed over the newly poured surface but well after initial hardening has occurred so that no damage is made to the curing surface.
2) Membrane Curing
If you do not have sufficient access to water on site, you may opt for membrane curing. This is often done with plastic sheeting (minimum thickness must be 0,01 mm) that will seal the surface and slow down the evaporation of water from the concrete. Make sure to extend the sheet well over the edges of the pavement or slabs.
Another option for membrane curing is the use of forming curing Compounds that can be sprayed over the surface to seal it and retain the moisture. They tipically remain on the surface for weeks to finally break down in sunlight.
When should the curing process start?
It will depend on the weather conditions (ambient temperatures), where the concrete was poured (in forms, over the groud or in water). Generally, it should be right after the chemical bonding has begun. A good rule of thumb is to never allow your concrete to dry quickly. You should monitor your work over the first 24 hours then 3 days or until it has completely set (which could take up to 28 days!).
A few more tips:
1. If you use a form, leave it during the curing process and it will serve as such as a curing agent.
2. Avoid using curing oils if you are pouring concrete indoor floors just in case some residues could prevent tile glues and other bonding products to work properly.
3. Don't overwork your concrete as it will draw more moisture to the surface and speed up evaporation.
4. Practice, practice, practice!
To find out more about special deals on concrete mixers, types of concrete mixes for particular jobs, call our experts at United Equipment Sales at (503)283-2105 or visit our website at: Unitedequipmentsales.com.
Main Source: The Art of Curing Concrete!