Title: Contribution of Shrinkage Reducing Admixture and Lightweight Sand on Moist Curing Requirement for Fiber-Reinforced Ultra-High-Performance Concrete

Author(s): Le Teng, Alfred Addai-Nimoh, Kamal H. Khayat

Publication: Materials Journal

Volume:

Issue:

Appears on pages(s):

Keywords: lightweight sand; moist curing duration; shrinkage reducing admixture; ultra-high-performance concrete

DOI: 10.14359/51740566

Date: 2/8/2024

Abstract:
This study evaluates the potential to use shrinkage-reducing admixture (SRA) and pre-saturated lightweight sand (LWS) to shorten the external moist curing requirement of ultra-high-performance concrete (UHPC), which is critical in some applications where continuous moist curing is challenging. Key characteristics of UHPC prepared with and without SRA and LWS and under 3 days, 7 days, and continuous moist curing were investigated. Results indicate that the combined incorporation of 1% SRA and 17% LWS can shorten the required moist curing duration since such mixture under 3 days of moist curing exhibited low total shrinkage of 360 µε at 56 days and compressive strength of 135 MPa (19,580 psi) at 56 days and flexural strength of 18 MPa (2,610 psi) at 28 days. This mixture subjected to 3 days of moist curing also had a similar hydration degree and 25% lower capillary porosity in paste compared to the Reference UHPC prepared without any SRA and LWS and under continuous moist curing. The incorporation of 17% LWS promoted cement hydration and silica fume pozzolanic reaction to a degree similar to extending the moist curing duration from 3 to 28 days and offsetting the impact of SRA on reducing cement hydration. The lower capillary porosity in the paste compensated for the porosity induced by porous LWS to secure an acceptable level of total porosity of UHPC.