Investigation and Prediction Model for the Dynamic Modulus of Asphalt Emulsion Cold Recycled Mixtures

The stiffness characteristics of four types of asphalt emulsion cold recycled mixtures (AECRMs) were evaluated using the simple performance test (SPT). Factors influencing the dynamic modulus and the applicability of the Witczak model were investigated. Based on the time-temperature superposition principle, the dynamic modulus |E*| master curves of recycled mixtures were constructed using nonlinear-least squares regression techniques. Statistical significance on the basis of one-way analysis of variance was evaluated as a function of cement, aggregate gradation, frequency, temperature, and confining pressure. The Witczak model is suitable for AECRMs and cement-treated AECRMs, and its prediction accuracy was improved by modifying the original Witczak model. The accuracy of the predicted models was evaluated on the basis of the statistical analysis. The one-way analysis of variance results indicated that the constructed master curves were consistent with the experimental test data. Frequency and temperature significantly affected the dynamic modulus, while confining pressure was not significant. Cement and aggregate gradation had a significant effect on the dynamic modulus at high temperatures or at low frequencies, while the effect was not significant at low temperatures or at high frequencies. Furthermore, the results of the statistical analysis showed that the modified and the original Witczak models resulted in a satisfactory fit between the predicted |E*| results and the laboratory measured |E*| data. The modified Witczak model was more accurate than the original model for AECRM.