What is the difference between cement and concrete?
Although the terms cement and concrete are often used interchangeably, they are actually different materials. Concrete is the hardened, rock-like mass that we are all familiar with, and is a mixture of coarse and fine aggregates (gravel and sand), and paste.
Cement, or more correctly Portland cement, is the active binder in the paste that “glues” the aggregate particles together to give concrete its strength. Concrete hardens through a chemical process called hydration where the cement combines with the water in the mix. The hydration process actually continues for years after the concrete is placed, meaning that concrete gets stronger as it ages.
Why does concrete crack?
All concrete shrinks as it dries and loses moisture, and this shrinkage commonly results in cracks. The amount of shrinkage is typically 1/16th of an inch over a 10 foot span (5mm over a 10m length). Contractors will put joints into floors and pavement to encourage the concrete to crack in a controlled straight line as the volume changes from shrinkage.