EVALUATION OF ROLLER COMPACTED CONCRETE (RCC) MIX DESIGN AND METHODS IN INDONESIA: A COMPARISON OF LABORATORY AND ON-SITE TRIALS

Abstract

Roller-compacted concrete (RCC) is an alternative method for dam construction that aims to reduce construction time and costs. Despite its advantages, RCC dams have yet to be constructed in Indonesia. While numerous guidebooks provide information on materials and mix designs, a significant challenge remains in utilizing locally accessible materials near dam sites. This research aims to determine the optimal mix design and construction method through laboratory and on-site trials while comparing the results. Laboratory trials used a pan mixer and a vibrating hammer for compaction, whereas the mock-up trial site employed a twin-shaft mixer and a vibratory roller. Samples were prepared using 15 x 30 cm cylindrical specimens and 10 x 20 cm core drills. Various amounts of cementitious material, gravel/sand fractions, and water content were investigated. Both trials revealed that a 50/50 gravel-to-sand ratio and 4% moisture content are optimal. Laboratory trials with Low Cement RCC (LCRCC, 110 kg/m³) achieved a compressive strength of 15 MPa at 150 days, while Medium Cement RCC (MCRCC, 150 and 175 kg/m³) reached 15.41 MPa and 20.86 MPa at 28 days. On-site trials with eight vibratory roller passes achieved 98.3% and 99.2% density and 80.2% and 86.4% compressive strength for MCRCC (150 and 175 kg/m³), respectively. However, large-scale mixing reduced compressive strength by 46.4% and 54.1% for MCRCC (150 and 175 kg/m³). This research highlights RCC's potential for cost and time savings in dam construction but notes unique challenges in Indonesia. Disparities between laboratory and on-site results emphasize the need for safety factors in mix designs and adapting guidebook recommendations to local materials.