Volumetric Balance and Marshall Response of AC-WC Mixtures Incorporating Kampar River Sand as a Partial Replacement for Stone Dust

This study examined Kampar River sand as a partial replacement for stone dust in asphalt concrete-wearing course (ACWC) mixtures. The optimum binder content (OBC) was obtained by interpolating the Marshall design curve at a target VIM of 4.0%; the resulting 5.86% was rounded to 5.9% and verified with newly prepared specimens, which produced a mean VIM of 4.31%. At this OBC, replacement levels of 0, 5, 10, 15, and 20% of the fine-aggregate fraction were tested using three independent batches per condition. Recalculation with composition-specific Gsb values of 2.589, 2.588, 2.586, 2.585, and 2.583 showed that 5% replacement increased stability from 1356.13 to 1951.87 kg and Marshall quotient (MQ) from 429.56 to 626.30 kg/mm, with VMA of 15.91% and VIM of 3.68%; the 10% mixture also met all adopted criteria. The 15% mixture produced the highest stability (2063.27 kg), but the 15 and 20% mixtures failed at the minimum VMA of 15% and the specified VIM range of 3–5%. Effective binder content decreased slightly from 5.462% in the control to 5.375% at 20% replacement. Combined mechanical-volumetric screening identified the 5% mixture as the primary candidate for further testing and 10% as the highest level that passed initial screening. Because Gmm was reported as 2.401 for all mixtures, composition-specific Gmm measurements and AASHTO T 283 and T 324 testing are required before field use. The findings are preliminary because replication was limited to n = 3 per condition.