Often people use the two terms cement and concrete interchangeably, believing there is no difference between the two.
However, cement is actually an ingredient of concrete. Concrete is essentially a blend of aggregates and paste. The aggregates consist of sand gravel and/or crushed stone; the paste is water and cement. Cement comprises 10 to 15 percent of the concrete mix. Over many years the cement and water harden bringing the aggregates closer together, making the concrete stronger, a process known as hydration.
This process continues on for a very long time, therefore concrete keeps getting stronger over many years.
Concrete’s volume will change slightly after it has cured. Typically concrete shrinks about 1/16 of an inch over 10 feet. Contractors put joints, wither sawcuts or expansion strips in concrete to encourage the concrete to crack in a more uniform, straight line at the joint when the concrete shrinks and changes it’s volume.
Hence why we call them Control Joints, they are employed to help control where the concrete will inevitably crack.
Concrete surfaces most often flake and/or spall because in Ontario we are exposed to severely cold weather, often fluctuating between above and below freezing. This creates a problem because exposed concrete is subjected to many freezing and thawing cycles.
In Ontario concrete needs to be air-entrained to have a stronger resistance to flaking and spalling of its surface.
The temperature is a very key part of the curing process. On hot days when concrete is curing, the heat causes excessive moisture to evaporate from the concrete. However, on the other hand if the temperature drops too close to freezing, hydration will occur at a snails pace.
This is why we always recommend using a wet-curing method, call to ask us more about the methods we employ to protect new concrete from summer heat.
Air-entrained concrete is ordinary concrete that contains controlled amounts of air in the form of microscopic bubbles. These intentionally entrained air bubbles are extremely small, this creates many tiny air pockets in the concrete. These air pockets ease internal strain and pressure on the concrete by allowing water a place to expand when it freezes.
The amount of air we use use in the mix varies, but is typically between 4 percent and 8 percent.
The primary benefit of entrained air in hardened concrete is the resistance it offers to scaling caused by de-icing salts or chemicals and freeze-thaw damage.