Cracks form in swelling soils in Texas generally during the dry conditions in summer and winter. Uncontrolled cracks in the soil extend to the subgrades beneath the paved shoulders and ultimately under the pavements. A pavement with considerable cracking from subsoil movements will deteriorate faster and will develop ruts and alligator cracks. Crack sealing in Texas has proved to be costly and ineffective since the materials do not last more than three years, and many fail after only one year. A Texas DOT-sponsored research project investigated the potential benefit of treating swelling soils with compost to mitigate cracking.

The study found that new cracked areas on the paved shoulder and the pavement next to biosolids compost (BSC)-treated swelling soils developed on average less than 50 percent as often as those observed for the control section. Moisture and temperature data, elevation surveys, and visual observations indicated that BSC treatment has mitigated the cracking of soil and pavement.

Ongoing life-cycle cost analysis comparing the compost treatment of soils versus crack sealing will provide better insight into the long-term performance of the two methods. However, Texas DOT is confident enough in the technique''s benefits to be considering implementation of the BSC stabilization method as a pavement preservation technique on most highway reconstruction and maintenance projects in all 25 of its districts. In addition to the maintenance savings, the technique may also serve as a way for the United States to use some of the 8 million tons of biosolids and 32 million tons of manures it generates annually. Almost 40 percent of biosolids and approximately 50 percent of manures are disposed in landfills.

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