Experimental study of early continuous tension influence on concrete properties
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Abstract:
In order to study the influence of early continuous tension on the mechanical properties of concrete in the later period including concrete's axial compressive properties and cleavage strength, the tensile test of 7 series of concrete specimens which bear early continuous load is carried out, with three factors of the axial tension ratio, loaded time and concrete strength in consideration. Meanwhile, test device is designed that applied continuous tensile load on 6 prism specimens at the same time when the early age is 1.5 days. The tensile load is applied for some time then unloaded and at 28 days age the test of prism specimens' axial compressive strength is carried out. The results show that the ratio of axial tension and continuous time of load have some effects on concrete's axial compressive properties in later days. When loaded time of is 7 days, there is no obvious influence on concrete's axial compressive properties no matter what the ratio of axial tension is 0.15 or 0.3. However, when the ratio of axial tension is 0.5, prism specimens' damage is irreversible, with its initial elastic modulus, peak compressive strength decreasing and peak strain increasing. When loaded time is 14 days, the properties of the prism specimens whose axial tension ratio is 0.3 deteriorate. The lower the strength grade of concrete, the larger the early age continuous tension influence on elastic modulus, but the influences on peak stress and peak strain is relatively small. The least square method is used to get the influence coefficient, which bases on loaded time and loading conditions' effect on concrete's initial elastic modulus, peak stress and peak strain. Based on the stress-strain formula of ordinary concrete, the stress-strain formula of concrete that bear continuous loading at early ages are proposed.
