Improving the flexural capacity of extrudable foamed concrete with glass-fiber bi-directional grid reinforcement: An experimental study

A wide experimental campaign of 40 three-point-bending tests on small-scale foamed concrete beams in the low-to-medium density range (400–800 kg/m3) is presented. The considered “extrudable foamed concrete” can keep its dimensional stability at fresh state. In order to increase the mechanical characteristics while preserving lightweight properties associated with the low densities, bi-directional grids of glass fibers are placed close to the bottom external face of the beams. Additionally, the use of short polymer fibers embedded within the cementitious matrix is investigated. Different specimen characteristics are explored, including: three curing conditions, three target dry densities, and two fiber contents. The presence of bi-directional grids increases the bending strength values for all the examined conditions: for 400 kg/m3 the increase is up to 1700%, and for higher densities is, on average, 175%. The curing condition affects the failure mode: specimens cured in water with densities higher than 600 kg/m3 exhibit a premature failure of the grid reinforcement without separation from the concrete substrate, whereas in those cured in air and cellophane typical bond failures with detachment occur. Only for densities of 800 kg/m3 the further addition of short polymer fibers produces non-negligible flexural strength increase of 31%, on average.