A parametric study on the laboratory fatigue characteristics of recycled mixes

There are not enough information about the fatigue characteristics of cold recycled mixes with bitumen emulsion and cement. In this research with the purpose of studying the fatigue characteristics of these mixes and determining the effects of different parameters, several laboratory recycled specimens containing CSS-1h bitumen emulsion and two types of cements (type I and I (PM) pozzolanic cement) have been prepared and tested. The main laboratory tests consisted of resilient modulus and indirect tensile fatigue test. After curing specimens in laboratory conditions, specimens were tested at three different temperatures and curing times. For each recycled specimen, studied parameters consisted of cement type, cement content, test temperature and curing time. According to obtained results, by increasing cement content and decreasing temperature, the slope of fatigue line will be decreased but no considerable change in fatigue behavior was occurred upon increasing the curing time. Furthermore, in comparison with reference specimens (i.e. specimens with no cement) and type I cement specimens, I (PM) cement had the mean fatigue behavior. At low initial strain levels, the fatigue life of I (PM) cement specimens were more than reference specimens and less than type I cement, whereas at high initial strain levels, the fatigue life of I (PM) cement specimens were more than type I cement and less than the reference specimens.

Research highlights
► At a constant initial strain level the fatigue life of recycled mixes was almost unchanged.
► At low initial strain levels, I (PM) cement specimens had more fatigue life than OPC.
► At high initial strain levels the reverse was true.
► By increasing cement content the slope of the fatigue line was decreased.
► The relationship between fatigue life and resilient modulus was not unique at all strain levels.