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Show HEAT INFLUENCES CONCRETE Discovery Made That Edjes Curl Up and Down in Response to Temperature Tem-perature Changts. That the edges of concrete roads curl up and down in i espouse to changes In temperature Is the discovery discov-ery recently made by the bureau of public roads of the United States Department De-partment of Agriculture in the course of experiments at the department's experimental farm at Arlington, Va. Curling Is caused by the unequal expansion ex-pansion and contraction of the upper and lower sides of the concrete slab under the Influence of hect. It has been observed during the middle of the day when the surface of the road becomes hot It expands more than the cooler underside and cause.i the sides to move downward. At night when the surface Is cool the contraction causes the edges to rise slightly. The extreme movement may be as much as line-tenth of an inch. While the warping of the concrete Is not In Itself detrimental to the road, It may lead to failure of the surface under the wheels of vehicles which travel over It when parts of It are not resting on the ground. |