Stiffness, Strength, and Performance of Unbound Aggregate Material: Application of South African HVS and Laboratory Results to California Flexible Pavements

this report is to illustrate the effect of the level of compaction and the degree of saturation on the stiffness, strength, and plastic deformation of unbound aggregate layers based on information obtained from HVS and laboratory testing in South Africa. The results will permit extrapolation of Goal 1 and Goal 5 results to other California materials and structures. The information presented in this report also contributes towards the improved understanding and modeling of the behavior of unbound aggregate material for mechanisticempirical design purposes. The scope of the information presented herein is limited to the aggregate used for pavement base and subbase layers. A comparison of California and South Africa specifications for base and subbase aggregate material is presented to identify possible similar material categories for which it is thought similar response and behavior will be exhibited. HVS tests that were performed on pavements with unbound aggregate base layers were identified and the deflection and permanent deformation responses of these test sections were extracted from the CSIR HVS database to be evaluated in terms of the objective of this report. Data from laboratory projects that were performed in association with the HVS program in South Africa in addition to the HVS data are presented in order to facilitate a more detailed evaluation of the effect of density and degree of saturation on the stiffness, strength, and plastic deformation of unbound aggregate material. 2.0 CALIFORNIA AND SOUTH AFRICA AGGREGATE The California and South Africa materials classification systems distinguish between different aggregate classes or categories. In the case of the California material specification, a distinction is made between aggregates for base and subbase ..