The Cyclic Loading of Normal Concrete in a Specific Stress Range

This research presents a study about the effect of static cyclic loading at compression on the properties of normal concrete, which are: the modulus of elasticity, the compressive strength and the ultimate strain. The static cyclic loading of concrete is achieved by loading-unloading-reloading at compression, for a short duration, in a specific stress range and for a few number of cycles. Experimental program includes tests for sixteen concrete specimens with maximum compressive strength 30 MPa. Twelve of the specimens are tested under a static cyclic loading, at the stress range (40 to 80) percent of the maximum compressive strength. The four remaining specimens are tested under uniaxial loading till failure. The cyclic loading is carried out for a few number of cycles, which is determined with (5, 10, 15, 20) cycles. Analytical part of this study is based on mathematical formulations for the stress-strain response, which are developed from the test results, in order to get the properties of concrete. A comparison between the properties of concrete in the two cases of loading (cyclic and uniaxial), is carried out. The results show an obvious improvement in the properties of concrete under cyclic loading, when achieved in the specific stress range (40 to 80) percent of the maximum strength, and for the number of cycles 15 or 20 cycles. The improvement in the properties of normal concrete under cyclic loading is the fundamental for the application of this kind of loading on High-Strength concrete. Hence, the cyclic loading causes an increase in the ultimate strain of normal concrete, so it may be of greater efficacy in High-Strength concrete.