Characteristics studies on engineering properties of river sand substitutes for conventional concrete and mortar works

Abstract

The main sand source of construction industry in Sri Lanka is river sand. However, being a developing country, the demand for river sand increases gradually. Based on engineering computations, sand demand for 2013 was estimated to be 12,266,186m3. The GSMB currently keeps records of all the licenses issued for sand mining and transportation, and according to these records the approximate annual sand supply is 7,132,631m3(GSMB records), which is far below the estimated demand. The difference may compensate by to illegal mining. Thus, this kind of unrestricted harvesting of sand is resulting in heavy rates of soil erosion; land degradation; increased river-water turbidity; lowered water tables; salinity intrusion in the lower reaches of rivers. Further, over use of river sand for construction industry has various undesirable social and ecological consequences. As a solution for this, various alternatives such as offshore sand, quarry dust, manufactured sand, dune sand, washed soil, waste building material, broken glass and blast furnace slag have been identified by various countries. Thus, this study attempts to identify suitable alternatives for river sand to mitigate the environmental issues related to river sand mining in Sri Lanka. In this project, we use manufacture sand, quarry dust, beach sand and off shore sand to test the suitability for conventional concrete and mortar works. Basically testing for concrete strength using uniaxial compressive strength and check grading of all river sand substitutes are performed. In addition to that two types of sand were mixed in various ratios and check those concrete and mortars for the compressive strength test to find the best mix ratio of sand for construction purposes. Finally those results were compared with strength of concrete for which river sand was used.