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Show HEAT INFLUENCES CONCRETE Discovery Made That Edges Curl Up and Down in Response to Temperature Tem-perature Changes". That the edges of concrete roads curl up and down In response 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 heat. 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 causes the sides to move downward. At night w len the surface Is cool the contrr'lon causes the edges to rise slightly. The extreme movement may be as much as one-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. |