THE STUDY OF PROPERTIES OF ROAD SUBBASE MATERIAL PRODUCED FROM RECYCLED ASPHALT PAVEMENT

Abstract

     The subbase is a structural road layer that transfers vehicle loads from the road surface to other structural layers. Therefore, materials used for constructing the subbase must exhibit good engineering properties and sufficient load-bearing capacity, in line with road construction standards. This research explores the utilization of reclaimed asphalt pavement (RAP) obtained by crushing old asphalt concrete from Highway No. 101 (Kamphaeng Phet-Sukhothai route, section from Lan Krabue to Khiri Mat, Kamphaeng Phet province, Km 33+000 - Km 36+010). RAP mixed with lateritic soil from Phran Kratai district, Kamphaeng Phet province, was used as subbase material. The study involved testing the basic properties of the mixtures, with sample ratios of lateritic soil to RAP at 1:1, 2:1, and 3:1 by weight. Tests were conducted to determine compaction properties using the modified compaction test and to measure the California Bearing Ratio (C.B.R) under soaked conditions for four days. The results indicated that the optimal water content for compacting the lateritic soil mixed with RAP was 4.0%, 6.0%, and 7.6%, respectively. The corresponding C.B.R values for the load-bearing capacity of the mixtures were 9.5%, 28.4%, and 40.7%. Notably, the mix ratios of 2:1 and 3:1 met the standard criteria for subbase courses in road construction. Thus, recycling old asphalt concrete materials is an alternative replacement material, helping resolve the issue of future shortages of road construction materials.