Recently Building Forensics International (BFI) had a project where a number of homes in a specific housing tract experienced random cracking throughout their garage slabs, driveways and foundation slabs. A BFI investigative team examined and investigated the slabs to determination the reason for the random cracking.
This project is a reminder of the importance of control joints help dictate where the cracking will occur, because cracking in concrete slabs will occur. Concrete, with or without joints, cracks when it hardens and dries as dependably as ice cream (another perishable product) melts when it rises above its originally fresh frozen storage temperature. Whether randomly occurring, or within joints, cracks occur despite the presence of control joints.
When control joints are wisely installed in the concrete, these joints are specifically intended to weaken the slab at the jointed area so that treated slabs crack within the joint where intended, rather than between joints in some random and unattractive way. Nonetheless, some random cracks occur even if control joints are used, both within the control joints and away from them. This is because concrete slabs shrink as they dry over time and react with materials around and supporting them and environmental conditions. As a direct consequence, cracks occur at all locations where stresses (mostly from shrinkage, but there are many others) exceed strength. So, Plaintiffs report random cracks they observe as defects, even though concrete is expected to crack. In this Project, substantial precautions were taken to reduce the manifestation of cracking, but for any given concrete flat work, achieving the elimination of random cracking is simply not possible.
BFI Staff Writer ~