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A new approach for determining resilient moduli of marginal pavement base materials using the staged repeated load CBR test method

The selection of marginal materials to construct workable and durable pavement base materials requires an understanding of their resilient moduli properties. Empirical formulations have been developed previously based on quality quarried material with known performance-based behaviour. However, in recent years, there has been an increasing demand to use locally available marginal materials, which do not necessarily meet road authority specification requirements; hence it is imperative to evaluate the performance of these non-standard materials. In this study, the geotechnical properties of two marginal materials, namely limestone (Ls) and sandstone (Ss), were evaluated and compared with a high-quality rhyolite (Rh) crushed rock. In order to improve the performance of the marginal materials, each of Ls and Ss was blended with 20% Rh and 50% Rh. The geotechnical properties of individual and blended materials which were investigated included: particle size distribution, particle density, Atterberg limits, Los Angeles value, modified compaction test, California bearing ratio (CBR) and repeated load triaxial test. A novel test method termed repeated load CBR (RL-CBR) was used to investigate the performance properties of the individual materials and blends. The RL-CBR test was further developed to study the stress-dependent behaviour of the materials, termed as staged RL-CBR test. An in-depth analysis of the staged RL-CBR test confirmed the capability of this test method to determine the resilient modulus of marginal pavement base materials.