Compost Amended Soil Treatment for Mitigating Highway Shoulder Desiccation Cracks

Certain types of compost materials have fibrous characteristics that exhibit moisture affinity suggesting that they could be used to stabilize expansive soils to control desiccation cracks. In order to understand shrinkage cracking control mechanisms of compost amended soils, a field study was designed with two compost types, dairy manure compost (DMC) and biosolids compost (BSC). Composts were mixed with topsoil at different proportions to form four types of compost manufactured topsoils (CMTs). Seventeen CMT test plots of different treatment widths and thicknesses including a control plot with no CMT cover material were constructed at Stephenville, Tex. and these sections were heavily instrumented with moisture and temperature sensors. Data from sensors, digital image based surface cracking studies, visual observations of shoulder cracking, and surficial erosion surveys of all test sections were collected and statistically analyzed and these results indicated that the BSC amendments provided the best subsoil enhancements by controlling moisture and temperature fluctuations from the high temperature environment, thereby reducing shrinkage cracks in subsoils and in the adjacent paved highway shoulders. The DMCs were less effective in mitigating shrinkage cracking due to low amounts of fibrous or organic matter. Both design and construction specifications for CMTs were also developed. This application will enhance recycling efforts by converting wastes into usable compost, mitigate future pavement cracking, and lessen premature maintenance costs.