Three forensic investigations were conducted to determine the causes of premature pavement failure. Specific causes for both longitudinal and transverse cracking, fatigue cracking, and sulfate-induced soil heave problems were identified and verified through a series of nondestructive field and laboratory evaluation tests. Conclusions were made, and recommendations are proposed to the districts to help them select a strategic rehabilitation plan to prevent the same problems from recurring. In Case I, the transverse cracking was believed to be due to either the shrinkage cracks of the very stiff treated caliche base or the shrinkage cracks in the lime-treated subgrade. The longitudinal edge cracks were attributed to edge shrinkage cracking due to wetting and drying cycles and heavy agricultural vehicles traveling along the pavement edge. The major cause for severe fatigue cracking in Case II was identified to be the very open structure of a lightweight seal coat beneath the hot-mix asphalt surface combined with weak support of the subgrade. A lack of sufficient support for the pavement under loading facilitated its fatigue failure. On the basis of Case III, stabilization of high-sulfate-bearing soil with calcium-based stabilizers alone is not recommended because of high swell potential and low residual unconfined compressive strength. The combination of lime and fly ash proved to be the best stabilizer for the soil with high sulfate content, provided that special precautions are taken during the mix design and construction process.
Samenvatting