Comparative deflection hardening behavior of short fiber reinforced geopolymer composites

• Ductile fiber reinforced geopolymer composites (DFRGCs) were demonstrated.
• Matrix and composite properties of DFRGC depend on type of activator combination.
• DFRGC made by NaOH + Na2SiO3 showed superior deflection capacity and flexural strength.

This study evaluates the behavior of a recently developed ductile fiber reinforced geopolymer composite (DFRGC) exhibiting deflection hardening and multiple cracking behavior in flexure employing four different activator combinations including two Na-based and one K-based activator solutions, and one Ca-based activator combination in the form of powder. Randomly oriented short poly vinyl alcohol (PVA) fibers (2% v/v) were used to reinforce the relatively brittle low calcium (Class F) fly ash-based geopolymer matrix. The matrix and composite properties of the developed fly ash-based DFRGCs including workability of the fresh matrix, density, compressive strength, matrix fracture properties comprising elastic modulus, fracture toughness and composite crack tip toughness, and flexural behavior were evaluated. A reference ductile fiber reinforced cementitious composite (DFRCC) with water to cement ratio corresponding to the activator solution to fly ash ratio of the DFRGCs was also made for comparison. Experimental results revealed that all DFRGCs, regardless of their type of activator combinations, exhibited deflection hardening behavior accompanied by multiple fine cracks in bending. The DFRGC-Na-1 composite exhibited superior deflection capacity, matrix fracture properties, compressive and flexural strengths with significantly enhanced composite ductility and toughness.