Engineering Properties and Economics of Soil Cement Feedyard Surfacing

Abstract

Soil cement, a compacted mixture of soil and portland cement, has been used successfully in the past forsurfacing roads and airports. Hard surfacing is being evaluated by open-lot beef cattle feedyard owners as ameans to improve manure quality and increase animal performance. In this research, the engineeringproperties and economics of using soil cement were evaluated using Amarillo fine sandy loam, one of themost common granular soils in the Texas Panhandle region. Soil cement specimens were prepared incompaction molds to determine the optimum moisture content and cement content for compaction.Specimens were subjected to field conditions including exposure to manure for nine months, then subjectedto unconfined compressive strength tests, freezing-thawing tests, and wetting-drying tests. The unconfinedcompressive strength of soil cement increased linearly with cement content between 5 and 20 percent(R 2 =0.99). At a cement content of 7.5 percent, the specimens disintegrated when exposed to field conditionsfor nine months, while the specimens at 15 percent cement stayed intact. Exposure to manure for ninemonths did not affect unconfined compressive strength or mass lost during freezing-thawing and wetting-drying.The total cost for installing a 15 cm thick soil cement surface was estimated to be $8,110 per pen.The annual breakeven cost at a discount rate of 8% and payback period of five years was $2,031 per pen.Based on documented benefits from related research, potential returns of $5,200 per pen might be realizedfrom improved animal performance.