In-Plane Strengthening of Unreinforced Concrete Masonry Wallettes Using ECC Shotcrete

Abstract

An experimental program was conducted to investigate the viability of using engineered cementitious composite (ECC) shotcrete as in-plane shear reinforcement for concrete masonry wallettes. Twenty-six mortared or dry-stacked ungrouted and unreinforced concrete masonry wallettes were strengthened through the application of an ECC shotcrete mix, applied either by spraying with a shotcrete machine or by hand trowelling. To determine the effect of applicator experience, ECC was applied by both a professional plasterer and amateur plasterers, with and without supervision. The in-plane shear strength of the strengthened wallettes increased between 340 and 3,471%, depending on the ECC application method. The variability of the strength increase was smaller for wallettes that had mortared joints and an ECC overlay trowelled by a professional plasterer. A set of design equations was also developed to determine the shear strength of a strengthened wallette. The design displacement ductility can be conservatively set equal to 1.9 because of the high variability in the experimentally obtained ductility values.