Understanding the micro-characteristics and mechanical behavior of more sustainable UHP-ECC with both recycled aggregate and recycled powder from concrete waste
Zhiming Ma, Yuanhui Wu, Bo Wang, Chaofeng Liang, Youchao Zhang, Changqing Wang, Changqing Wang
Abstract
This study comprehensively investigated the properties of more sustainable ultra-high-performance engineered cementitious composites (UHP-ECC) incorporating recycled aggregate (RA) and recycled powder (RP) as the substitution for silica sand and cement-GGBS. Replacing high volume of cement-GGBS with RP weakened the hydration reaction, causing a reduction in the hydration products and micro-structure. Incorporating a moderate dosage of RA and RP had a minimal effect on the UHP-ECC strength, but the strength decreased with high-content RA and RP incorporation. The mechanical strength degradation caused by RP incorporation was more pronounced than that induced by RS incorporation. The 28-day compressive strengths of UHP-ECC, RA-100SS, RP-70CEM+70GGBS and 100SS+70CEM+70GGBS were 101.6, 86.0, 72.6 and 62.2 MPa. Under uniaxial tensile load, incorporating a moderate dosage of RA and RP improved tensile stress and strain capacity, whereas excessive incorporation reduced the tensile stress of UHP-ECC. Fully recycled UHP-ECC with both RA and RP exhibited good uniaxial tensile behavior. The tensile stresses of UHP-ECC, 100SS+10CEM+10GGBS, 100SS+30CEM+30GGBS, and 100SS+70CEM+70GGBS are 12.4, 10.2, 9.3 and 5.3 MPa; while their tensile strain capacities are 6.5%, 7.2%, 7.4%, and 6.6%, respectively.