Compressive and Time-Dependent Strength of Concrete Masonry Constructed with Type M Mortar and Grouts Containing High Volume of Fly Ash and Slag

摘要

A testing program was conducted to determine whether concrete masonry prisms constructed with Type M mortar and grouts containing high volumes of supplemental cementitious materials (SCMs) could meet minimum masonry compressive strength requirements. Research focused on replacing portland cement (PC) with Class F fly ash and ground-granulated blast-furnace slag (GGBFS) in quantities larger than those currently allowed by technical standards. In addition, the research evaluated the development of the compressive strength of the prisms with time. Thus, specimens were tested at 14, 28, 42, 56, and 90 days. The control prism group contained grout with only PC. In the second prism group, the grout had Class F fly ash replacing PC at rates of 45, 55, and 65% while in the third prism group the grout had Class F fly ash and GGBFS combinations replacing PC at rates of 65, 75, and 85%. The compressive strength of all prisms exceeded the minimum compressive strength requirement of 10.34 MPa (1500 psi) at 28 days, although the 65% fly ash grout mixture itself did not meet the minimum grout compressive strength of 13.79 MPa (2000 psi) at 28 days. A lower estimate of the ultimate strength of grouted prisms constructed with grouts containing high volumes of SCM can be estimated by multiplying the strength measured at 14 days by 1.2 and 1.3 for prisms with binary and ternary grouts, respectively.