ENGINEERING PROPERTIES AND ECONOMICS OF SOIL CEMENT FEEDYARD SURFACING

Abstract

Hard surfacing is being evaluated by open-lot beef cattle feedyard owners as a means to increase animal performance and improve manure quality. Soil cement, a compacted mixture of soil and Portland cement, has been used successfully for surfacing roads and airports. In this research, the engineering properties of soil cement and associated economics were evaluated using Amarillo fine sandy loam, one of the most common granular soils in the Texas Panhandle region. Soil cement specimens were prepared in compaction molds to determine the optimum moisture content and cement content for compaction. Specimens were subjected to simulated field conditions including exposure to manure for nine months. Specimens were then subjected to a series of tests: unconfined compressive strength, freezing-thawing, and wetting-drying. Unconfined compressive strength of soil cement increased linearly with cement content between 5% and 20% (R2 = 0.99). At a cement content of 7.5%, the specimens disintegrated when exposed to field conditions for nine months, while the specimens at 15% cement remained intact. Exposure to manure for nine months did not affect unconfined compressive strength or mass lost during freezing-thawing and wetting-drying. The estimated total cost for installing a 15 cm thick soil cement surface was $582 per 100 m2. The annual breakeven cost at a discount rate of 8% and payback period of five years was $146 per 100 m2. Potential annual feed conversion benefits of $330 per 100 m2 were estimated based on previous research, leaving soil cement an economically feasible option for further research and application.