Composting is recognized as one of the innovative ways of recycling organic waste materials, by converting organic materials to innocuous materials that could be effectively used in various day to day applications. Because of its moisture affinity and fibrous characteristics, it is theorized that compost could be used to stabilize expansive soils to control desiccation cracks on unpaved highway shoulders. In order to understand possible mechanisms of this stabilization, a field study was planned and conducted. Two composts, Dairy Manure Compost (DMC) and Biosolids Compost (BSC), were used. Both composts were mixed with the local subsoils at different proportions to form different types of Compost Manufactured Topsoils (CMTs) as shoulder cover materials. Several properties including erodability and shrinkability characteristics are studied while evaluating the CMTs performance in field conditions. During the field phase, data was collected from embedded moisture and temperature sensors, digital image surface cracking studies, visual observations of paved shoulder cracking, and surficial erosion surveys of all sixteen CMT test plots and one control test plot. The field data was collected and analyzed with statistical comparison tests, which indicated that the BSC amendments provided the best subsoil enhancements by controlling moisture and temperature fluctuations from surrounding environments and thereby reducing shrinkage cracking in subsoils and in adjacent paved shoulders. The DMCs were less effective in mitigating shrinkage cracking, due to low amounts of organic contents, also resulting in erosion problems.
Abstract