Hammer test is the most spread way for testing the

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Hammer test is the most spread way for testing the hardened concrete because of many reasons such that; the easy of performing the test, the device is light in weight, quite small and give approximate measurement of the resistance to pressure of manufactured concrete products. The apparatus consist of a projecting bar of solid metal connected to an internal spring. The principles on which it works are based on the rebound impact of a hammer on a piston which rests against the surface of the concrete products. The greater resistance of the concrete, the greater the rebound impact. 3
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The test is based on the principle that the rebound of an elastic mass depends on the hardness of the surface upon which it impinges, and in this case will provide information about a surface layer of the concrete defined as no more than 30mm deep. The result gives a measure of the relative hardness of this zone, and this cannot be directly related to any other property of the concrete. Energy is lost on impact due to localized crushing of the concrete and internal friction within the body of the concrete, and it is the latter, which is a function of the elastic properties of the concrete constituents, that makes theoretical evaluation of test results extremely difficult. Figure (1): Rebound Hummer The device consists of spring loaded steel mass that is automatically released against a plunger when the hammer is pressed against a concrete or a rock surface. A small sliding pointer indicates the rebound of the hammer on a graduated scale. (see Figure 1) In this experiment we test the hardness of many samples small cubes which have dimension (10*10*10) cm and with angle α = - 90, and large cube which have dimension (15*15*15) with angle α= - 90, one cylinder at angle α= - 90 and for beam at angles α= 0.
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