Effect of Curing Age on Tensile Properties of Fly Ash Based Engineered Geopolymer Composites (FA-EGC) by Uniaxial Tensile Test and Ultrasonic Pulse Velocity Method

Abstract

Tensile properties of fly ash based engineered geopolymer composites (FA-EGC) at different curing ages were studied by uniaxial tensile test and ultrasonic pulse velocity (UPV) methods, which included uniaxial tensile properties, the correlation between ultrasonic pulse velocity and tensile properties, and characteristic parameters of microcracks. The experimental results show that obvious strain hardening behavior can be found in FA-EGC at different curing ages. With the increase of curing age, the tensile strength increases, the tensile strain decreases and the toughness becomes worse. The UPV of FA-EGC increases with curing age, and a strong correlation can be found between tensile strength and UPV. With the increase of curing age, the average crack width of FA-EGC decreases and the total number of cracks increases. This is because the strength of geopolymer increases fast at early age, thus the later strength development of FA-EGC tend to be stable. At the same time, the bond strength between fiber and matrix, and the friction of fiber/matrix interface continue to increase with curing age, thus the bridging effect of fiber is gradually strengthened. In conclusion, the increase of curing age is beneficial to the development of tensile properties of FA-EGC.

Keywords

engineered geopolymer composites (EGC) / tensile properties / ultrasonic pulse velocity (UPV) / characteristic parameters of microcracks

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