Determination of Fatigue Life of a Granular Base Material Lightly Stabilized with Slag Lime from Indirect Diametral Tensile Testing

Abstract

Stabilization of granular materials with low percentage of slow setting binders, such as slag lime, for constructing new pavements and/or rehabilitation of existing granular pavements has economical and environmental benefits. The fatigue life of a lightly stabilized granular material under traffic type repeated or cyclic loading is an important consideration for pavement design involving this material and it is the focus of this paper. In particular, this paper examines the use of indirect diametrical tensile (IDT) testing with internal displacement measurement for determining stiffness and fatigue life of a granular base material lightly stabilized with slag-lime cementitious binder. An extensive laboratory investigation involving monotonic and cyclic load IDT testing was carried out to determine the strength, stiffness, and fatigue life of a granular material stabilized lightly with 3–5% slag lime and to establish relationships for predicting the fatigue life. Fatigue life was established using two methods, namely, the approach of determining the number of cycles for 50% reduction in the stiffness compared to the initial stiffness and the energy ratio method, and they both showed similar results. Based on the experimental results, a general fatigue model is proposed for determining the fatigue life using the static or dynamic stiffness modulus and maximum tensile strain, which is useful for mechanistic-empirical pavement design involving such materials. Empirical equations are proposed to relate the fatigue life with tensile strain and stress ratio similar to those proposed in the literature. A new model to determine the fatigue life from strain ratio is also proposed in this paper that was found to closely match the experimental data. Empirical relationships are also proposed to predict the fatigue life based on IDT strength and/or static stiffness modulus which are particularly useful in situations where resources are not available for conducting cyclic load IDT testing.