Study On Effect Of Coarse Aggregates On Flexural Strength Of Concrete

Concrete is basically a mixture of two composite:aggregate and paste. the aggregates generally occupy 60%~75% of the concrete volume and strongly influence the concrete's freshly mixed and hardened properties, mixture proportions, and economy. The coarse aggregates act as rigid skeleton in concrete and restrict the deformation of concrete. But it is not necessary to increase the strength of coarse aggregate too much high, there exists a matching problem between the aggregates and matrix and this would influence the strength of concrete markedly, especially to high-strength concrete and lightweight concrete. The performance of the two phases is markedly different as ages increase, these dynamic changes may influence the properties (especially at early ages) of concrete. So it is of great scientific signification to study these influence.The flexural strength is the most important parameter of pavement concrete, but there are rarely systematical research results about effect of aggregates on the flexural strength of concrete at present. So this paper will study the effect of aggregate properties on flexural strength of concrete through experiment, including strength, volume percent, aggregate max-diameter, shape, grading. Study distinction of ordinary coarse aggregates, light aggregates and metal aggregates in particularly which affect flexural strength of concrete. The study is intent to explore the effect of the tow elements whose mobile distinction on flexural strength of concrete, and study the difference of enhancement between compressive strength and flexural strength of concrete caused by aggregates.The research results show that the coarse aggregate and mortar matrix has significant influence on the flexural strength of concrete, only the strength of coarse aggregate matching to those of matrix, the better effect could be achieved; also, there involves the modulus of elasticity of coarse aggregate; the influence of coarse aggregate strength on compressive strength and flexural strength are not the same, for low-strength concrete, this difference is the most noticeable; the flexural strength of concrete is effected by the content and max-diameter of coarse aggregate, and in different matrixes, the optimal values are variable; the shape and needle and rag-stone of coarse aggregate effect markedly the flexural strength of concrete, relating to the strength level of concrete; the influence of coarse aggregate grading on flexural strength of concrete shows the similar regularity.