A fatigue life prediction method of cement-stabilized aggregates considering the effect of stress state

Abstract

Stress state is one of the factors leading to the fatigue life prediction discrepancy of cement-stabilized aggregates (CSA) in laboratory and field pavement structures, therefore, a new fatigue criterion and fatigue life prediction method characterizing this effect is needed which was proposed in this study. Experimental fatigue tests with four loading modes, including uniaxial compression (UC), uniaxial tension (UT), indirect tension (IDT), and four-point bending (FPB) were conducted in several stress levels. The results suggest that the semi-log-linear equation is suitable for all four loading modes, however, the fatigue life of CSA in tension and compression at the same stress level or stress ratio greatly differs. Inspired by the yield and failure criteria theories, bulk stress, shear stress, and principal stress were introduced to establish the fatigue criterion, and accordingly to propose a novel fatigue equation based on the semi-log-linear form, which can unify fatigue life prediction at different stress states. Since the new prediction approach is in terms of stress rather than stress ratio, the process of measuring strength at hard-to-get complex stress states is avoided. Through verification, the proposed method exhibits high agreement with the experimental results of CSA from either this study or literature, and it is capable to characterize the fatigue life difference in tensile and compressive states. Besides, the new fatigue equation was demonstrated to apply to the interpolated data from traditional fatigue curves. In accordance with the loading cycles in experimental tests with addition of considering the applicability of the semi-log-linear equation, the proposed fatigue equation of CSA was justifiably effective at the fatigue cycles of 102 to 107.