Mechanical properties of alkali resistant glass fabric composites for retrofitting unreinforced masonry walls

Mechanical properties of a cement-based matrix – grid (CMG) system developed for masonry rehabilitation are discussed. CMG system is a composite consisting of a sequence of layers of cement-based matrix and alkali resistant (AR)-glass coated reinforcing grid. The experimental program included tension and flexural tests of composites with special consideration to long term durability. Variables studied include effect of composite thickness, fabric orientation, and effect of accelerated aging on the tensile and flexural responses. Results indicate that samples in the cross machine direction (XMD) showed the best combination of high tensile strength (in excess of 5 MPa≅0.725 ksi) and Ultimate strain value (2.36%) as compared to the machine direction (MD) with (5 MPa≅0.725 ksi and ultimate strain of 1.8%). After 28 days of accelerated aging, tensile strengths reduced to about 3.87 MPa≅0.56 ksi for the MD and XMD directions respectively, representing average reductions of 23% and 17%. In the flexural samples, cross machine samples (XMD) show a combination of high flexural strength (15-17 MPa≅2.18-2.47 ksi) and Maximum deflection (of 15-22 mm≅0.59-0.87 in) as compared to the MD samples. Higher stiffness of fabrics in the cross machine direction due to the manufacturing process was the source of such differences in behavior. The first crack strain in flexure is as much as the ultimate tensile strength in tension for many composites. A discussion of comparison of tensile and flexural stress measures is presented.