Tensile Strain Hardening Behavior of PVA Fiber-Reinforced Engineered Geopolymer Composite

Abstract

This paper is aimed to improve the mechanical properties (namely compressive and tensile strengths) of a recently developed fly ash-based engineered geopolymer composite (EGC) with relatively low-concentration activator combinations. In this regard, four different activator combinations (including two Na-based solutions and one K-based activator solution, and one lime-based activator combination in the form of powder) were used to develop the fly ash-based EGCs exhibiting strain hardening behavior under uniaxial tension. Randomly oriented short polyvinyl 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 EGCs [including workability of the fresh matrix, density, compressive strength, matrix fracture properties (comprising elastic modulus, fracture toughness, and composite crack tip toughness), and uniaxial tensile behavior] were evaluated. A counterpart conventional engineered cementitious composite (ECC) with a water-to-cement ratio corresponding to the activator solution to fly ash ratio of the EGCs was also made for comparison. Experimental results revealed that in fly ash-based EGCs, the use of Na-based activator combination composed of 8.0 M NaOH solution (28.6% w/w) and