Effect of Coconut Fiber and Ground Granulated Blast Furnace Slag on the Flexural Strength, Toughness and Deformation of Foamed Concrete

To reduce environmental pollution and decrease cement consumption, ground granulated blast furnace slag (GGBS) was used as a partial replacement (10 wt.%) to produce foamed concrete. The results showed that GGBS addition did not significantly modify the flexural strength of foamed concrete, but increased its brittleness, reducing deformation at peak load by 70%. To improve these properties, coconut fibers were added (up to 0.5 vol.%) leading to higher mechanical strength and toughness. Based on the flexural strength of foamed concrete, the optimal fiber content was 0.4 vol.% depending if GGBS was added (improvement 21.3%) or not (16.7%). Coconut fibers were also found to improve the flexural toughness by two to three times compared to neat foamed concrete with or without GGBS at 2 mm of deflection. To get more information on the flexural behavior, strain gauges were used to measure the axial and transverse strains, clearly showing the positive role of coconut fiber addition on improving the mechanical properties of foamed concrete, especially for the strain energy densities. Finally, scanning electron microscopy (SEM) was used to analyze the samples morphology and explain the mechanical results.