Influences of Saturated Surface-Dry Recycled Fine Aggregate on Fluidity and Strength of Ultra-High Performance Concrete

Abstract

Abstract: In order to investigate the influence of the content of saturated surface-dry recycled fine aggregate on the fluidity and strength of ultra-high performance concrete (UHPC), the UHPC with various recycled fine aggregate contents (0%, 25%, 50%, 75%, and 100%, by mass fraction) in the saturated surface-dry state were designed under the same net water-binder ratio, and the fluidity and strength under standard curing at various ages of the UHPC were tested. The mechanism was revealed by SEM and MIP et al. The study results show that, with the increase of the recycled fine aggregate content, the friction between particles increases, and more cement slurry are needed to wrap and fill the surface of recycled fine aggregate, resulting in the decrease of the fluidity of UHPC. With the increase of the content of recycled fine aggregate, the total water-binder ratio increases, and the length of ITZ₂ (the interfacial transition zone between the old fine aggregate and the old cement matrix) and ITZ₃ (the interfacial transition zone between the old cement matrix and the UHPC matrix) increase, the amount of micro-cracks increase, and the harmful hole and multi-harmful hole content increase, and the compactness of UHPC decreases, and therefore the flexural strength and compressive strength of UHPC decrease.

Key words: recycled fine aggregate, ultra-high performance concrete, fluidity, strength, pore structure, interfacial transition zone

CLC Number:

TU521

CHEN Zhiwu. Influences of Saturated Surface-Dry Recycled Fine Aggregate on Fluidity and Strength of Ultra-High Performance Concrete[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2021, 40(5): 1503-1509.

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