cement manufacturer add quartz silica sand in their cement in place of river cement,and for cement testing for their good quality they prefer standard quartz silica.why river sand avoided to mix.In place of river sand we want to use quartz silica sand for making cement mortar for plastering, bricklaying,concrete work for buildings due to its electrical resistivity with a purpose of VASTU DEVELOPMENT IN INDIA.Cracks develops much if we use river sand and cement defame due to river sand..