| Shoulder cracking due to movements of underlying expansive soil subgrades leads to softening and weakening of bases and subgrades. This is because these shoulder cracks allow moisture infiltration which can eventually result in pavement cracking in longitudinal and transverse directions. Effective remediation methods need to be applied immediately to mitigate shoulder cracking; otherwise, this cracking could result in the poor performance of adjacent travel lanes. Mechanical and chemical stabilization methods have proven ineffective with respect to cost and performance aspects of treating shoulder subgrades. Encapsulation of expansive subgrades either by geomembranes or by chemical grouts to limit moisture fluctuations in subsoils is an effective method, but it is costly.; In this research, three types of inexpensive recycled materials, both in pure and blended forms, were used as shoulder covers. These materials, due to their hydrophilic and low permeability properties, will limit both moisture fluctuations in underlying subgrades and hence mitigate shrinkage cracking in covers and subsoils. These materials are dairy manure, composted biosolids and lime treated biosolids. Swell tests, shrinkage bar tests, direct shear tests and permeability tests were conducted on compost manufactured topsoils and these results indicate that these materials exhibit low shrinkage strains, moderate strength, high swell strain potentials and low permeability properties. These results are analyzed to determine optimum compaction characteristics for field studies. These future field studies provide specifications for the construction of CMT's as shoulder covers. As a part of the research, subgrade soil from Stephenville, Texas was used as control soil. |
