Our company performs industrial floor repairs, and I have a long-standing argument with a co-worker about the proper way to seal joints. I've read that joint sealants should be twice as wide as they are deep so that they don't tear when the joint opens and closes. My friend disagrees. He often pours the sealant into narrow sawcuts, making the depth of the sealant far greater than the width. Which method is right?
The proper joint sealing technique depends on the service conditions of the floor. The joint sealant shape you recommend is often correct for exterior concrete that is exposed to changing temperatures because the joints open and close when the concrete expands and contracts. For these applications, a flexible sealant is commonly used. The primary function of the sealant is to prevent water and incompressible materials from entering the joint. Many industrial floor slabs, however, do not undergo much thermal movement because they are maintained at a fairly constant temperature. In addition, older floors have undergone most of their drying shrinkage, so movement at the joint is minimal. In these cases, a wide, shallow joint sealant shape is not required. Many industrial floor joints are subjected to abuse from vehicles equipped with small, hard wheels that chip away at the joint faces. The primary purpose of the joint sealant is to support the slab edges to prevent spalling. The recommended joint sealant for these applications is a semirigid epoxy.