A model for resilient modulus determination of recycled mixes with bitumen emulsion and cement from ITS testing results

Typically, resilient modulus (Mr) of recycled mixes, containing bitumen emulsion and cement, will increase upon curing. Hence, assigning a design Mr for these mixes will be more complex than the case of conventional hot mixes. Furthermore, Mr testing facilities are not generally available in many project sites. Therefore, developing a model that could estimate Mr from ordinary testing methods would be quite appropriate. In this research, upon performing indirect tensile strength test (ITS) and determining Mr of specimens at different testing temperatures (−10, 5 and 25 °C) and curing times (7, 28 and 120 days), two models have been developed to estimate the Mr of recycled mixes with bitumen emulsion and two types of cements (type I and pozzolanic cement). The results showed that increased curing time and cement content and decreased testing temperature led to increased ITS and Mr values. For both tests the effect of temperature was more pronounced than two other parameters. The models were developed by two steps. First the relationship between ITS and Mr at similar testing conditions was determined for each cement type. This was done by a linear relationship. In the second step, the relationship was adjusted to consider the effects of temperature and curing time. Using the final model, Mr of studied mixes could be estimated from ITS testing results at similar or different testing conditions.