Estimating the resilient modulus of crushed recycled pavement materials containing crumb rubber using the Clegg impact value

Since the determination of resilient modulus (Mr) from the repeated load triaxial test is rather complicated, due to the expensive procedure and time-consuming nature, attempts have been made to estimate it using other properties, such as the unconfined compressive strength and California bearing capacity based on empirical models. However, because of the dynamic nature of the Mr, it should be estimated by other simple-procedure dynamic properties. The Clegg hammer test has been considered as an alternative since it is not only dynamic in nature but also simple and quick. There has been no report of any previous study on correlating between CIV and Mr of construction and demolition (C&D) aggregates containing crumb rubber. In this research, a series of experiments were conducted to measure the Mr and CIV of the waste crushed rock (WCR) and recycled crushed concrete (RCC) mixed with the rubber of two different sizes and different contents (0, 0.5, 1, and 2%) for making a green pavement. The experimental results show that the CIV and Mr of both aggregates increased with the fine crumb rubber components but decreased with the coarse rubber content. The increase of CIV and Mr due to the increase of fine rubber percentage can be attributed to the filler effect of fine rubber particles that provides better interfacial bonding condition. The analytical results show that a strong correlation exists between the Mr, confining stress, deviator stress and the CIV with the R2 value ranging from 0.74 to 0.99