Abstract: A method for classifying sand wherein a mixture of sand and water is introduced into a classification tank (7) partially filled with water. Depending on the weight of the sand grains, the grains of sand will precipitate at the bottom (8) of the tank (7) at graduated distances from an inlet pipe (6), the heavier particles nearest the inlet and the lighter particles farther away.To prevent large quantities of fines, i.e., sand grains between about 0.002 mm and 0.006 mm in size, from being lost by being washed out of the tank (7) together with the overflow water, the water from the tank (7) is recirculated by means of a pump (14) so that the water becomes progressively more saturated with fines, which means that larger amounts of fines will precipitate in the tank (7).Because the water is recirculated, water consumption can be reduced by 2/3, and at the same time the problem of the overflow water from the tank (7) is also reduced.

Abstract: In a sand classification tank for producing classified sand for concrete pouring purposes, i.e., sand containing predetermined fractions of sand grains of different sizes per unit of volume, a mixture of unclassified sand and water is introduced into a tank (1) partially filled with water, beneath the surface of the water, and the sand grains are deposited by sedimentation at the bottom of the tank at varying distances from the inlet, depending on their weight, such that the coarsest sand fraction will be deposited closest to, and the finest fraction or fines farthest from, the place where the sand/water mixture is introduced into the tank. For the purpose of retaining as much of the fines fraction as possible (i.e., sand grains of between 0.002 and 0.