Performance of concrete sidewalks: field studies

This article examines the different failure modes of concrete sidewalks through an extensive field survey of sidewalk inventories in major cities in the Canadian Prairies. The major form of sidewalk damage is longitudinal cracks. There was no correlation of either the liquid limit or the plastic limit of the soil beneath the sidewalk with the type of sidewalk damage observed in each city. However, the extent of longitudinal sidewalk damage increases when the sidewalks are founded on soils with high plasticity index. Two failure modes (hogging and sagging) are closely examined through the analysis of observed vertical surface movements to explain the occurrence of longitudinal cracks. It is concluded that the rigid body movements (both uniform vertical movement and tilt) are mainly a consequence of frost penetration beneath the sidewalk. Uniform vertical movement is not very sensitive to moisture changes in the soil underneath the sidewalk. The dominant mode of deformation for sidewalks is hogging. The seasonal temperatures have considerable impact on the interaction of the sidewalk with the underlying soil, but an indirect estimate of the flexural strain or differential movement ratio is not sufficient to determine if they are large enough to exceed the tensile strain of concrete.