Dynamic three-point flexural performance of unsaturated polyester polymer concrete at different curing ages

Abstract

In this study, the dynamic flexural performance of unsaturated polyester polymer concrete (UPPC) is investigated. We categorised specimens at different ages, then investigate how its flexural dynamic increase factors (DIF) relate to different ages, as well as compressive and tensile DIF. A split Hopkinson pressure bar (SHPB) is used for dynamic flexural tests under a high strain rate. The ends of the incident and transmission bars are equipped with special devices to perform a three-point flexural test. Test results indicate that the quasi-static flexural strength of the UPPC is the same as the compressive and tensile strengths, and it has a higher strength in the early stage of curing; in addition, UPPC has the same strain rate effect in the dynamic test that decreases as the curing age increases. The reason is that the unsaturated polyester resin does not react with cement thoroughly at the low curing age, and there is a weak zone. When the loading rate increases, the crack has no time to pass through the weak zone and directly penetrate the coarse aggregate. Further, the mid-span displacement of the UPPC had a strain rate effect. By comparing the fitting curves of aforementioned tests (i.e. flexural, tensile and compression test), it is clear that the flexural one shows the steepest gradient, roughly equals to the sum of compressive and tensile gradient, which means more sensitive to strain rates.