George Stimpson

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Which is heavier, wet or dry sand?

Dry sand is heavier, measure for measure, than wet sand—up to a certain percentage of moisture. A cubic foot of average wet river sand weighs from twelve to fifteen pounds less than a cubic foot of the same sand when dry. One who buys a cubic yard of damp sand by measure will get less than one who buys an equal volume of dry sand. When specified standard of concrete is required contractors fill a barrow level with dry sand, but they are permitted to heap the barrow with wet sand. Sand dampened moderately increases in volume out of all proportion to the amount of water added. Consequently any given measure of moist sand weighs less than the same measure of dry sand. This bulking or "piling" of sand is due to a film of water that forms around the individual grains and prevents them from flowing together. As a general rule fine sand bulks more with the addition of water than coarse sand does. From a dry condition to about 5 percent of moisture sand bulks greatly. This bulking, however, is governed by the percentage of moisture and does not continue indefinitely with the addition of water. According to the United States Bureau of Roads, if sand is thoroughly saturated so that all the voids are filled with water, it in approximates its original weight, measure for measure. A cubic foot of sand having a moisture content of about 14 percent weighs about the same as an equal measure of dry sand. In other words, when sufficient water is incorporated the saturated sand is equivalent to weight to the same bulk of dry sand. To illustrate: Suppose a cubic [page 64] yard measure is filled with dry sand and then water is poured slowly, into it until the sand reaches the saturation point; or, suppose the measure is first filled about one-third full of water and the sand is thy added slowly until the measure is full. The measure will weigh about the same as if it were full of dry sand. Engineers call this process "inundation."