Why Does My Cement Stone Crack?

Curing

• Cement naturally shrinks when it dries, which means all concrete formats that contain cement, such as cement stones, will also shrink. The estimate is that concrete shrinks roughly 1/16 inch for every 10 feet during the curing process while the cement is soaking up the moisture and going through its chemical reaction, which transfers into cracks in the face of the cement stones. Hairline fractures are generally nothing to worry about.

Expansion

• The reason cement installations have expansion joints is to help with seasonal movement. Without an expansion joint, the cement will crack as the material swells in the summer months with heat and shrinks in the winter months with the cool air. These are another type of hairline crack that can appear in your cement stone and are a natural part of the process.

Water to Mix

• Human error can always introduce problems into any finish material, and if your cement stones are cracking with bits and pieces of the cement actually crumbling away from the crack, there was likely an issue with the water to dry mix ratio during the mixing process. This can be detrimental to the overall stability of the structure, so if you see crumbling along the edges of the cracks you should call an engineer to determine if you are looking at a cosmetic area where only a portion of the mix was off, or an entire bad batch that will affect your entire stone structure.

Curing Temperature

• Cement needs to be kept between 45 and 70 degrees for optimal curing conditions, and allowing it to get too cold or too hot during the drying phase can cause cosmetic cracks. Too cold and the cement will freeze, keeping the moisture from releasing into the mixture. Too hot and the moisture will evaporate too quickly. In both cases you can have cosmetic concerns where surface sections crack off the stone and maybe even peel away. Talk with your structural engineer to determine if you have cosmetic cracks or structural issues when you see sections cracking and peeling off.