Experimental Study On Mechanical Properties Of A New Type Of Concrete

In recent years, high performance pumping concrete is widely used in various engineering construction fields relying on its demonstrated superiority in high-rise building construction. In practice, however, serious early-age cracking is common phenomenon existing in cast-in-place pumping concrete structure and many practices show that most of the "early cracks" are caused by the large structural shrinkage deformation that is resulted in surplus cement mortar. Concrete is a multiphase man-made material composed of coarse aggregate, mortar and interfacial transition zone between them. As the strength skeleton of concrete, coarse aggregates are usually the structural units with the highest intensity, the best volume stability and durability. Generally speaking, increasing the volume content of coarse aggregate within a specific range, there are different degrees of improvement on the mechanical properties, volume stability and durability of concrete, which can also have a positive impact on terms of energy-saving emission reduction and cost savings. It is one of the important measures to develop green concrete and achieve sustainable development of building resources and environment.In this paper, a new type of concrete mixing process is applied to high slump concrete, in which different graded coarse aggregates are thrown into the high slump concrete before concrete into the mold. It is to design a new kind of concrete with coarse aggregate at lower costs instead of part of cementing materials.This paper mainly studies the effect of volume content of coarse aggregate on the basic mechanical properties of high slump concrete. Firstly, high slump concrete with low and middle strength (C30, C40and C50) which is commonly used in structural engineering is prepared. The slumps are180mm to200mm. As the scattering-filling volume fraction increases, the concrete slump losses are measured to analyze pouring feasibility of the new type of concrete. Then according to the tests of cube compressive strength, axial compressive strength, splitting tensile strength, bending strength, elasticity modulus and axial compressive load-displacement curve, the paper analyzed the influence of scattering-filling volume fraction of coarse aggregate on the mechanical properties of high slump concrete. In the tests, we take scattering-filling volume fraction among0%,10%,15%,20%and25%(where0%stands for the ordinary concrete with the same water-binder ratio to the new type of concrete for comparison). The results show that the new type of concrete mixing process does have different degrees of improvement to the mechanical properties of high slump concrete. However, there isn’t a monotonically increasing relationship between the scattering-filling volume fraction of coarse aggregate and mechanical properties but the presence of a optimum scattering-filling volume fraction of coarse aggregate. Taking everything together, the optimum scattering-filling volume fraction is15%obtained in this paper.Finally, quantitative analysis of advantages in cost saving and environmental protection for the new type of concrete is taken through the material cost analysis and CO2emissions analysis of the big slump concrete per cube.