Shear behavior of reinforced slag-based geopolymer concrete T-shaped beams

The lack of comprehensive and systematic research, coupled with the absence of established design modeling, hinders the practical application of geopolymer concrete (GC) T-beams in engineering projects. To address the above issues, this study investigated the shear behavior of reinforced GC T-beams. Beam shear tests were performed on 21 GC T-beams and 3 conventional reinforced concrete (RC) T-beams under three-point loading. The test parameters were the concrete type, concrete strength, flange configuration, shear span-to-depth ratio, longitudinal reinforcement ratio, and stirrup spacing. The test results showed that the GC T-beams had similar crack propagation, failure mode, and shear resistance to RC T-beams, but their stiffness and diagonal cracking load were less than those of the counterpart RC T-beams. Increasing the flange thickness-to-effective beam depth ratio from 0.24 to 0.48 increased the shear resistance of GC T-beams. As the shear span-to-depth ratio decreased, the shear resistance of GC T-beams significantly increased, and the failure mode changed from flexural failure to shear compression failure and diagonal tension failure. An increase in the diameter of longitudinal bars from 20 mm to 25 mm or the stirrup spacing decreased from 275 mm to 75 mm also led to a significant increase in the shear resistance of GC T-beams. Current design codes for RC T-beams underestimated the shear resistance of GC T-beams. Consequently, this study proposed a model capable of more accurately predicting the shear strength of GC T-beams by addressing the aforementioned parameters.