Application of Mount Pinatubo lahar sand as fine aggregate in controlled low-strength materials

Abstract

Fine aggregates are key components of controlled low-strength materials (CLSM). These act as structural fillers that are integrally held together by cement paste controlling the mechanical properties and strength. In general, natural sand is the most common material used in the production of CLSM. Despite their low minimum compressive strength, CLSMs are used in highway construction as an alternative to compacted backfill. However, sand supply to road and infrastructure projects may be not sustainable. Meanwhile, in the low lying areas surrounding Mount Pinatubo in Phillippines, huge volumes of pyroclastic material and ashes were deposited due to the mountain's cataclysmic eruption on 1991. To this date, the lahar washed down by the rains to the lowland municipalities and towns induce hazards during extreme rainfall events. Therefore, this study investigated the feasibility of lahar sand as fine aggregate in CLSM. Characterization of the controlled mixtures was performed via flowability, setting time, and compressive strength. Two controlled parameters (water-to-solid and cementto- water ratios) were defined to show the statistical relationship among investigated properties with the different mixture proportions. Empirical results show acceptable characteristic values for the CLSM's hardened state, making lahar sand be suitable as fine aggregates. The recommended water-to-solid and cement-to-water ratios for the CLSM mixture should be both 0.30.