| Summary: | With the depletion and increasing demand of river sand, machine-made sand could be used more and more in concrete. In order to improve the properties of machine-made sand concrete, the effects of the aggregate micro fines (AMF) content, aluminum sulfate, and polypropylene fibers (PPF) on the slump, compressive strength, water permeability, and the chloride permeability coefficients were investigated through a single factor test method, and related mechanisms were analyzed. The results show that the optimum contents of AMF, aluminum sulfate, and the polypropylene fiber are 10 wt%, 1 wt%, and 0.6 kg/m<sup>3</sup>, respectively. The optimum content of AMF improved the compactness of concrete. The addition of aluminum sulfate promoted the initial formation of ettringite, and thereby improved the compressive strength and the permeability resistance. The polypropylene fiber can modify the pore structure distribution of concrete and reduce the porosity, thereby improving the impermeability of the concrete. The compressive strength of the machine-made sand concrete could be increased by more than 20%, and the water/chloride permeability coefficients could be decreased by more than 45%.
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