Research on Mechanical Properties of GFRP Tube Confined Biochar Concrete Under Axial Compression
Biochar can be served as a lightweight aggregate material and its partial incorporation into con-crete can realize internal curing and filling effects,thereby enhancing the mechanical properties of cementi-tious 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 cor-rosion 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 con-tent,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 absorp-tion 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 sec-ondary 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.
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