Long-term crushing performance of lightly cementitious pavement materials – update to the South African procedure

Abstract

Evaluation of the crushing (or compression) failure and associated surface deformation of lightly cementitious (stabilised) materials used for base/sub-base course in pavements has been well established in the South African pavement design practice since the 1990s. This paper presents a re-evaluation of this earlier work, focusing on expanding the empirically derived crushing performance relationships (i.e. transfer functions or damage laws) for lightly cementitious materials at in situ moisture conditions, i.e. without the adverse effect of additional or artificial water infiltration into the lightly cementitious base, which limited the practical application of the original transfer functions for significant rutting. The re-evaluation was undertaken to determine whether the original crush initiation relationship was reasonable for as-built moisture conditions and also to develop practical advanced crushing damage relationships for various rut depths developing within the base, based on the measured response of the original test sections prior to water ingress. The newly derived crush initiation relationship differs little from the original and either can be used with similar confidence. However, the new 10 mm rut relationship differs significantly from the original relationships (which were derived from the adverse statistical bound of the crush initiation data), the previous relationship should now be abandoned, and the new relationships adopted for well-protected pavements. The newly developed advanced crushing damage relationships for 5, 10, 15 and 20 mm level of deformation (“rut”) within the lightly cementitious base layers are proposed for practical application to in situ as-constructed (as built) moisture conditions.