Development of cement-treated base material for reducing shrinkage cracks

Abstract

This paper describes an approach to minimizing the amount of shrinkage cracking in a cement-treated base (CTB). CTB is a stiff base that features higher rutting resistance and reduced fatigue cracking because of its ability to distribute traffic loads. However, it has not been applied to asphalt pavement in South Korea because of the possibility of reflection cracks. The goal of this study was to develop a cement-treated base with a lower shrinkage and thereby prevent cracks. After factors contributing to dry shrinkage were identified and the composition and properties of each admixture were analyzed, laboratory and field tests were designed and performed. The preliminary test results suggested a mix design of 25% fly ash. The amount of cement was set at 7% for all mixes to satisfy the specification standard for allowed strength in South Korea. On the basis of the experiment results, and considering strength, shrinkage, and economic efficiency, two mix designs were selected: a mixture containing 25% fly ash and a mixture containing 25% fly ash with 10% expansive additive. The field tests focused on crack propagation suggested that the optimal mixing alternative of a cement-treated base was the mix design of 25% fly ash and 10% expansive additive.