Bulking of sand

        The presence of moisture in sand increases the volume  of sand. This is  due to fact that  moisture causes film  of water around the sand particles  which result in  the increase of volume  of sand. For a  moisture content of 5 to 8  percent, the increase in  volume may  be about 5 to 8 percent, depending upon the grading of sand. The finer the  material, the  more will be the increase in volume for a given moisture content. This  phenomenon is known as bulking of sand.  

         When  moisture content  is  increased by  adding  more water, sand particles pack near each other and  the amount of bulking of sand is decreased. Thus the dry  sand and the sand completely  flooded with  water have  practically  the same  volume.