The objectives of this study were to determine the resilient modulus of two recycled roadway materials: recycled pavement material (RPM) and road surface gravel (RSG) with and without cement and cement kiln dust (CKD) stabilization. The resilient modulus was determined by conducting Large Scale Model Experiments (LSME) designed to replicate field conditions, and compared with the resilient modulus determined from the laboratory test method described by NCHRP 1-28A. Results of wet-dry and freeze-thaw durability tests were used to select a portland cement content of 4% by weight and a CKD content of 10% by weight to chemically stabilize RPM and RSG. The stiffness at curing times of 7 and 28 days was evaluated, and the summary resilient modulus (SMR) corresponding to a bulk stress of 208 kPa was used to calculate AASHTO base layer coefficients for use in pavement layer thickness design. A conventional base course material specified as a Class 5 material gradation employed in Minnesota, and similar to AASHTO grading C, was used as a reference material. This study has shown that the addition of cement or CKD can significantly improve the stiffness of RPM and RSG, having the potential to allow greater use of recycled roadway materials in the reconstruction of roads, minimizing construction costs and environmental impacts. However, the low durability of materials mixed with CKD should be investigated further, because the expansion may be damaging to pavement structures.
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