玻璃纤维增强复合材料管约束生物炭混凝土柱轴压性能研究

Research on Mechanical Properties of GFRP Tube Confined Biochar Concrete Under Axial Compression

生物炭可作为一种轻骨料,部分掺入混凝土中可有效提供内固化及填充效应,成为一种潜在的碳捕捉和封存技术,但由于生物炭高孔隙率的微观结构,导致生物炭混凝土存在强度低、耐腐蚀性差及稳定性差等问题。本研究提出采用玻璃纤维增强复合材料(GFRP)管约束生物炭混凝土,开展GFRP管约束生物炭混凝土的轴压性能试验研究,设计参数主要包括:GFRP管的厚度(层数)、生物炭掺量及生物炭吸水率,着重分析各试件的轴向应力-应变曲线、环向应变-轴向应变曲线、屈服应力、极限应变及环向断裂应变等指标。研究结果表明:在相同生物炭掺量及吸水率的前提下,GFRP管约束生物炭混凝土试件的极限抗压强度相对于未约束试件可提升490.4%~563.3%,约束试件的极限应变也大幅提升,且约束试件屈服应力、应变远远大于未约束试件的屈服应力、应变,说明GFRP管的约束有效提高了生物炭混凝土的强度及变形能力;随着生物炭掺量的增加,约束试件的屈服应力降低,但轴向极限应变增大;而生物炭吸水率的增加则导致约束试件的屈服荷载提高,但极限应变减小;GFRP管的层数增加,使得GFRP管约束生物炭混凝土的二次刚度提升,其环向应变-轴向应变曲线弹性段和二次刚度段无明显过渡点,说明GFRP管与生物炭混凝土协同工作性能良好。

Biochar can be served as a lightweight aggregate material and its partial incorporation into concrete can realize internal curing and filling effects,thereby enhancing the mechanical properties of cementitious materials.It represents a potential carbon capture and sequestration technique.However,due to the high porosity of biochar’s microstructure,biochar concrete faces challenges such as low strength,poor corrosion resistance,and instability.This study proposed the use of Glass Fiber Reinforced Polymer(GFRP)tubes to confine biochar concrete,and the axial compression tests on GFRP tube-confined biochar concrete were performed,with design parameters including GFRP tube thickness(number of layers),biochar content,and biochar water absorption rate.Emphasis was placed on analyzing the axial stress-strain curves,circumferential strain-axial strain curves,yielding stress,ultimate strain,and circumferential fracture strain of each specimen.The results indicated that,under the premise of same biochar content and water absorption rate,the ultimate compressive strength of GFRP-confined biochar concrete specimens increased by 490.4%to 563.3%compared to that of unconfined specimens.The ultimate strain of confined specimens also significantly increased,and the yielding stress and strain of the confined specimens were much greater then those of unconfined specimens,indicating that GFRP confinement significantly improves the bearing capacity and deformation performance of biochar concrete.With increasing biochar content,the peak stress of confined specimens decreased while the axial ultimate strain increased.On the other hand,an increase in biochar water absorption rate led to an increase in the yielding load of confined specimens but a decrease in the ultimate strain.Additionally,an increase in the number of layers of GFRP tubes enhanced the secondary stiffness of confined specimens.The circumferential strain-axial strain curve exhibited no obvious transition point between the elastic segment and the linear segment,indicating that three was a good synergy between FRP tubes and biochar concrete.