Compressive and flexural strength of fiber-reinforced foamed concrete: Effect of fiber content, curing conditions and dry density

An extensive experimental campaign was carried out to investigate the mechanical strength of fiber-reinforced lightweight foamed concrete. The considered foamed concrete was prepared with a viscosity enhancing agent that increases the cohesion and consistency of the cement paste at the fresh state (extrudable foamed concrete). The flexural strength was evaluated on almost 60 small-scale prismatic beam specimens, and the compressive strength on 100 cubic specimens in accordance with two different testing standards for comparative purposes. The effects of three different curing conditions (air, cellophane and water), three target dry densities (400, 600, 800 kg/m3), three fiber contents (0.7%, 2.0%, 5.0%), and the presence of an additional glass-fiber-reinforced-polymer (GFRP) mesh in the tensile zone of the beams (besides the short fibers) were analyzed. The polymer fibers increased the flexural capacity of the beams, especially for the low-density specimens and for the higher contents of fibers (2.0% and, above all, 5.0%), but had a negligible influence on the compressive strength. The additional GFRP mesh combined with the short fibers improved the flexural capacity considerably in all the examined conditions, turning out to be the best strategy for obtaining high mechanical strengths associated with low densities typical of ultra-lightweight concrete elements.