Study on the Strength and Microcosmic Characteristics of C50 High-Performance Concrete (HPC) Containing Manufactured Sands

In this paper, C50 high-performance concrete (HPC) containing manufactured sand was prepared. First, three different gradations of aggregates and three different types of admixtures with significant differences in specific surface area, porosity, and water ratios were used to prepare nine groups of concrete mixtures. Second, the effect of the aggregate gradation and admixture on the workability of fresh HPC and compressive strength of hydration-hardened HPC was investigated. Finally, microscopic tests were conducted to examine the hydration product pore structure (mercury injection porosimeter (MIP)), hydration product surface appearance (scanning electron microscope (SEM)), and element qualitative analysis (energy dispersive X-ray spectrometry (EDS)), and the mechanism of the C50 HPC was discussed. The results show that the types of gradation aggregates and admixtures significantly affect the workability and strength of C50 HPC. When the slump of fresh HPC is specified, the workability of the mixture can be controlled by a homemade high-performance lignin sulfonate water reducer. The aggregate gradation biased toward the median of the gradation curve can be used to prepare the C50 HPC. In this paper, the maximum compressive strength of C50 HPC is 58.3 MPa at 90 days. In addition, the microscopic test results show that the composite compound of C50 HPC has a dense hydration product and a high bond strength interface transition zone (ITZ).

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