Online Measurement of the Grain Size Distribution of Sand 0–4 mm used for the production of concrete

Abstract

AbstractAn apparatus is described for the fast and automatic measurement of the grain size distribution of sand ranging from 0 to 4 mm. A sample of sand continuously introduced at a rate of 30 g/min is separated by the apparatus into seven fractions of 0–0.063, 0.063–0.125, 0.125–0.25, 0.25–0.5, 0.5–1, 1–2, and 2–4 mm. The amount of sand in each of these fractions is determined and the results are given in time intervals of 1 minute. The sand is separated in a separation chamber through which water streams in a horizontal laminar flow. The samples are separated according to their settling velocities. The four coarse fractions descend to the bottom of the chamber. They are collected and weighed under water. The three fine fractions remain suspended in three effluent water streams. The quantity of sand is measured in flow cells by absorption of laser light. Control of the system as well as the collection and processing of the measured data are done by means of an electronic control unit and a microcomputer.