Identification of the optimum replacement ratio of quarry dust as a substitute for sand and cement in cement plastering

Abstract

River sand and cement are important construction materials, but their scarcity creates significant challenges for the construction industry. Quarry dust is being explored as a possible alternative, as crushed rock is a common aggregate source in Sri Lanka. Therefore, this study focuses on determining the possibility of using quarry dust as a partial replacement for cement and river sand in plastering mortar. Selected Manampitiya river sand and quarry dust from four quarries were subjected to sieve analysis (ASTM C136). Four quarry dust samples obtained from two different crusher types (cone crusher and vertical shaft impact crusher) were sieved to separate 0.1-2.36 mm particles and <0.1 mm particles to replace with sand and cement, respectively. Plastering mortar’s cement-sand ratio was selected as 1:5 and developed in 12 mix proportions, varying the replacement of sand with quarry dust (0.1-2.36 mm particles) at 0%, 33%, 50% and 100%, as well as the replacement of cement with quarry dust (<0.1 mm particles) at 0%, 5% and 10%. The flow table test (ASTM C1437) was performed for each mix proportion to obtain the water-cement ratio of plastering mortar, which gives acceptable workability (105-115 mm). Four 50 mm cubic specimens from each mix proportion were prepared according to the obtained water-cement ratio. The cubic compression test (ASTM C109M) and water absorption test (ASTM C140) were performed for the cubic specimens after the completion of the 28-day curing period. Results indicate that the sand and quarry dust samples analysed are poorly graded. An increase in quarry dust in the plastering mortar reduced the workability, but it reached an acceptable range with a water-cement ratio of 1.1-1.2. All tested specimens indicate compressive strength >3 MPa, which was the minimum strength required for plastering. The compressive strength results indicate that the cement replacement can be further increased with 100% sand replacement. The durability of plaster slightly reduces with an increase in quarry dust proportion, indicating a maximum of 2.4% increment in water absorption for a 100% sand-replaced, 10% cement-replaced specimen compared to a specimen made from 100% sand. Furthermore, 100% sand replacement can achieve a cost reduction of 27%. Hence, it is recommended to replace sand 100% with quarry dust 0.1-2.36 mm particles for cement plastering.