This paper studied the influence of pre-saturated lightweight sand (LWS) on the mechanical and microstructural properties of UHPC cast with steel fiber alignment. The changes in hydration kinetics, porosity, nano-mechanical, and mechanical properties were studied. The LWS was used at 0–50% replacement volumes of total sand. Predominant fiber alignment was favored through a flow-induced casting method during casting of flexural prisms. Experiment results showed that the 28-d autogenous shrinkage was decreased from 450 to 275 μm/m with the LWS content increasing from 0 to 50%. The addition of 20% LWS led to maximum increases of 15%, 15%, and 20% in compressive strength, flexural strength, and T150, respectively, relative to UHPC made without any LWS. The use of 20% LWS combined with fiber alignment led to a synergistic effect of 45% and 40% on enhancing the flexural strength and T150, respectively, relative to UHPC without LWS and having random fiber orientation. The addition of LWS can enhance the cement hydration given the internal curing effect. Such enhanced cement hydration increased the percentage of high density and ultra-high density C–S–H from 50% to 75% and reduced the 28-d porosity from 12.5% to 9.5% with the use of 20% LWS. On the other hand, such internal curing can be overwhelmed by the introduced pores of LWS when excessive LWS was used, which led to significant increase in porosity of UHPC.
H. Huang et al., "Use of Saturated Lightweight Sand to Improve the Mechanical and Microstructural Properties of UHPC with Fiber Alignment," Cement and Concrete Composites, vol. 129, article no. 104513, Elsevier, May 2022.
The definitive version is available at https://doi.org/10.1016/j.cemconcomp.2022.104513
Civil, Architectural and Environmental Engineering
Keywords and Phrases
Fiber alignment; Lightweight sand; Mechanical properties; Microstructure; UHPC
International Standard Serial Number (ISSN)
Article - Journal
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01 May 2022