Performance of Self-Consolidating High-Strength Mortars Developed from Portland Pozzolana Cement for Precast Applications

摘要

In this study, the performance of self-consolidating high-strength mortars (SCHSMs) produced using portland pozzolana cement (PPC) was evaluated for use in precast concrete applications. The applications may include using SCHSMs (1) for making thin sections with adequate strength and toughness, (2) as a patch material with better adhesion properties with substrate concrete, (3) as a sandwich layer or repair material in newly or existing concrete beams in the tension zone for improved ultimate strengths, and (4) for specialized precast concrete applications demanding high strength. The tests conducted include compressive, flexure, impact, shear strength, and toughness using standard or developed test procedures. Results from the investigation suggested that SCHSMs from PPC can be used for developing complicated sections such as I-specimens; however, significant strength reduction was observed compared with that of equivalent cube specimens. SCHSMs with 0.6% fiber addition showed higher ultimate strength, with toughness and impact energy several times higher than the respective specimens without fibers. The shear bond strength of SCHSMs containing PPC showed higher strength than mixtures made with ordinary portland cement (OPC) or OPC+silica fume blend. In addition, conventional beams made with a part layer of SCHSMs containing PPC provided higher ultimate strength and strains compared with beams made with a part layer of OPC. The heat-cured SCHSMs provided 56%-110% higher early-age strengths than normal water-cured SCHSMs, but the use of high temperature at 140℃ or 200℃ for 2 days negatively affected the later-age strengths. The shortlisting of curing regimes for PPC mixtures considering both early-age strength and later-age strength for precast concrete was not possible within the heat-curing regimes investigated. The optimized heat-curing regime for OPC may not necessarily be the optimized one for PPC mixtures.