THE WACO PONDING PROJECT

This report presents results of field studies conducted between 1957 and 1972 on the effectiveness of ponding and lime stabilization of clay subgrade to minimize volume change beneath portland cement concrete pavements. Potential vertical rise (PVR) was calculated to identify sections in need of ponding, and the relationship of PVR to roughness and heaving of pavement is presented. The thickness of asphaltic concrete overlay required for pavement over untreated subgrade is compared to that required for concrete pavement over lime-stabilized subgrade, some of which was ponded. Although a study of underdrains was not intended as part of this project, it became noticeable that the result of connecting perforated underdrains to ditch drop inlets was to increase heaving and overlay repair thicknesses. A method for determining desired moisture content is presented, and it correlates fairly well with moisture contents obtained from below pavement after several years.