Influence Of Manufactured Sand Quality Indexes On Concrete Performance

The requirement of concrete fine aggregate increases year by year. However, natural sand as traditional fine aggregate, its quality decrease and its cost increase because of over exploitation. As a result, manufactured sand has been widely applied and became the focus of current research. In this paper, the particle morphology and mineral composition of manufactured sand was tested. The combined effect of manufactured sand’s powder content and MB value on concrete and mortar performance and the influence of manufactured sand’s irregular particle shape on concrete properties were researched. The difference between the macro properties of manufactured sand concrete and river sand concrete were explained by testing the pore structure and interfacial transition zone microstructure. The research shows that:The morphology of 4.75~2.36 mm particles from different fine aggregate was tested by image analysis and laser micro system. The roundness and aspect ratio of manufactured sand are both greater than the river sand’s, its particles are irregular edge and needle-like content is high. At the micro-scale of 0.4μm laser light source, the surface roughness of river sand is higher than some kind of manufactured sand, the particle surface of river sand is rougher instead. The mineral compositions of the particles above 75μm and below 75μm of manufactured sand were analysed qualitatively, there compositions are just different in relative content.The powder content and MB value of manufactured sand are a set of interrelated quality indexes, they can’t be separated to limit. The workability of fresh concrete is affected by the change of these two indexes, but the powder content when the concrete has the largest slump is almost invariant under different MB value. The manufactured sand concrete can get good performance when the manufactured sand has high powder content(20%~10%) and low MB value(≤1.4g/kg) or high MB value(>1.4g/kg) and low powder content(10%~5%).At the same gradation and composition of powder, the irregular particle shape of manufactured sand has little influence on concrete’s workability and chloride ion permeability resistance. The river sand which particle shape is smooth obtains higher strength under the same gradation and composition of powder. The irregular particle shape of manufactured sand is not the reason why the concrete prepared by manufactured sand has high strength. But compare with the river sand which has the same gradation and composition of powder, the concrete prepared by manufactured sand obtains better frost resistance and early shrinkage resistance. However, the late shrinkage resistance is not influenced significantly.The inner pore of proto manufactured sand concrete and proto river sand concrete was tested by MIP. The microstructure and composition of interfacial transition zone were also tested by FE-SEM(EDS). The porosity of this two concrete have little difference, so they have the similar chloride ion permeability resistance. Compared with the proto river sand concrete, the pore of proto manufactured sand concrete is bigger, so its frost resistance and shrinkage resistance are worse. The interfacial transition zone of proto manufactured sand concrete is denser and has no defect, its element distribute uniformly, so its strength is higher.