Flexural capacity of aligned steel fiber-reinforced geopolymer composite beams

Aligned steel fibers significantly enhance the flexural capacity of geopolymer composite. However, research on the flexural capacity of aligned steel fiber-reinforced geopolymer composite (ASFRGPC) is rare. Therefore, this study investigates the flexural capacity of the ASFRGPC beam. First, geopolymer beams with different fiber layer thicknesses were prepared and four-point bending tests were carried out. On this ground, simplified flexural capacity calculation models were established for full-section and partial-section ASFRGPC beams. Then, experimental data from full-section ASFRGPC were used to determine the stress block parameters alpha(1) and beta(1). It turned out that the values of alpha(1) ranged from 0.951 to 0.987 and those of beta(1) ranged from 0.804 to 0.841. By approximating the stress block parameters alpha(1) and beta(1) as 1.0 and 0.8, the errors in the resulting flexural capacity and the depth of the compression zone are no more than 4.7% and 3.1%, respectively. Finally, experimental data from partial-section ASFRGPC were used to analyze the impact of fiber layer thickness on the flexural capacity. The results showed that as the thickness of the steel fiber layer increases, the flexural capacity initially increases until reaches a maximum and then decreases. Therefore, it indicates that there exists an optimum thickness for the steel fiber layer. It has also been found that the optimal thickness of the steel fiber layer is not a fixed value, which depends on the tensile strength of the ASFRGPC and the compressive strength of the geopolymer matrix.