Laboratory fatigue models for recycled mixes with bitumen emulsion and cement

The role of cement in cold recycled mixes with bitumen emulsion (CRME) have been extensively investigated. In most cases it is affirmed that cement will stiffen the mix and will decrease its moisture sensivity and temperature susceptibility and will increase its resistance against permanent deformation. Nevertheless the effect of cement on the fatigue properties of these mixes is not clearly understood. Because of crystalline nature of the pozzolanic bonds, cemented materials tend to be brittle which can reduce the flexibility and fatigue life of recycled mixes. In this research in order to develope fatigue models for these mixes, extensive indirect tensile fatigue and resilient modulus tests were performed at different temperatures (varying from −10 to 25 °C) and curing times (varying from 7 to 120 days). Test results showed that the effects of cement on fatigue life of mixes is related to the initial strain level assumed in testing. At 300 microstrain level and above, the addition of cement caused a reduction in fatigue life, whereas below 300 microstrain the reverse was true. Finally based on laboratory testing results distinct models were established for different boundary strain levels.