Curling of Interior Concrete Slabs-on-Grade: Cause and Repair

Abstract

During our introduction to structural engineering, the concrete slab-on-grade or floor-on-ground process was not thought of as a problem of any consequence. Further consideration acknowledged that the effect of concentrated loads on a slab supported on soil subject to compressive settlement under load was a structural problem to which a beam-on-elastic foundation approach would provide a solution. On realizing that this was a three-dimensional problem requiring detailed knowledge of both soil and concrete properties, we allowed that this was not such a simple problem. However, this is but one of several considerations in such floors. The designer has to consider the interior environment and its effect on shrinkage of the concrete, which in turn relates to control-joint spacing and the form of these joints. Joints in slabs may be susceptible to damage from use, the avoidance of which may require special treatment. Surface harness, resistance to impact and chemical attack, and resistance to wear may require special surface finishes or even two-course floors. Permeability to water vapor may affect applied-surface finishes or material stored on the floor. Excessive heat from overhead infrared heaters at loading docks can induce rapid drying shrinkage of the slab surface with consequent cracking. Arising from the development of high forklift storage racks, much attention has been given to the surface flatness of floors. This has led to special techniques for the measurement of surface flatness immediately following concrete finishing.