Optimizing Blending of Manufactured Sand with Offshore Sand Based on Physical and Virtue Characteristics

Usage of alternative fine aggregates in concrete and cement mortar has been gradually increasing by the construction industries around the world due to the escalated shortage in obtaining natural river sand. Manufactured sand and offshore sand can be considered as the principal alternatives which are consumed by most of the contractors for substituting river sand in the construction activities now. However, most of the above sand consumptions are done without deeply analyzing the conformity of the alternatives to concrete and cement mortar. The present study is executed to inspect the fitness of manufactured sand from two different high-grade metamorphic rocks, offshore sand, and blended sands of both manufactured sand types at 25%, 50% and 75% replacement levels with offshore sand to be practiced in concrete and cement mortar by scrutinizing physical properties and quality through series of characterizing experiments. Results reveal that blended sand with all replacement levels can be suitable with respect to particle characteristics such as angularity, surface texture and total specific surface. Regarding resultant particle size distribution, blended sands with 50% replacement level can be the optimum solution in reference to uniform gradation, the density of sand mix, and fineness. 50% and 75% contents of manufactured sand in combined sand types show higher loose and packing densities than river sand. Flowability under the gravity of blended sand types contain 50% to 75% of offshore sand are performed well contemplating different affecting parameters. However, increased manufactured sand content demands more water than river sand and offshore sand. Additionally, hazardous materials such as clay lumps and friable particles, fines and silt are identified within the permissible range based on the requirements by the standard available. Regarding all the above characteristics, blended sands contain two manufactured sand types with 50% replacement level with offshore sand can be suggested as the optimum substitution for river sand in terms of fresh and hardened state properties of concrete and cement mortar.