Tension stiffening and cracking behavior of FRP-reinforced self-compacting concrete with high-volume fly ash (HVFA-SCC)

It is more durable and sustainable to construct infrastructures with fiber-reinforced polymer (FRP) reinforcements and high-volume fly ash self-compacting concrete (HVFA-SCC). This study investigates the tension stiffening and cracking behavior of FRP-reinforced HVFA-SCC by conducting tensile tests on ten specimens with different FRP types and surface treatments, bar diameters , and reinforcement ratios. The specimens featuring too shallow spiral wound heights or lacking sand coating on the FRP bars exhibited a significantly smaller ascending slope during the pre-cracking stage. An increase in the reinforcement ratio led to a decrease in initial cracking stress; however, utilizing different types of FRP bars with similar sizes and mechanical properties did not result in notable differences in tension stiffening responses. The mean values of the maximum and minimum crack spacing to average crack spacing ratios for the key specimens were 1.37 and 0.61, respectively, which closely aligned with the theoretical values, whereas the mean maximum crack width to average crack width ratio was 1.94. With slight modifications, the code-based constitutive models by CEB-FIP MC78 and EC2–04 could effectively simulate the tension stiffening responses of the specimens, particularly in estimating the initial cracking stresses. These findings suggest that employing FRP bars with excessively shallow spiral wound heights or inadequate surface treatments may compromise stiffness in tension or bending structural elements. Furthermore, the study confirms that, with minimal alterations, the constitutive models developed for reinforced concrete with steel bars can still be applied to FRP-reinforced HVFA-SCC. • FRP bars with too shallow spiral heights or without sand coating had much smaller initial ascending slopes. • Increasing the reinforcement ratio may decrease the initial cracking stress. • A steeper descending concrete curve indicated less energy dissipated by concrete, and thus a poorer tension stiffening effect. • The constitutive models by CEB-FIP MC78 and EC2–04 had good performance.