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Axial compressive performance of sustainable BFRP-confined rectangular columns using recycled brick aggregates
(2025-10-01)
Suthumma, Chisanuphong
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Ejaz, Ali
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Iqbal, Muhammad Jawed
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Yooprasertchai, Ekkachai
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Hussain, Qudeer
This study examines the mechanical behavior of basalt FRP confined rectangular concrete columns using crushed brick aggregates, addressing a research gap. While previous work focused on circular and square columns, this is the first to explore rectangular ones. The use of waste brick aggregates promotes sustainability. The study aims to assess the mechanical properties, expecting improvements in strength and ductility, and could lead to broader applications of basalt FRP. A total of 32 rectangular specimens were tested to evaluate the influence of aggregate type, concrete grade, and number of BFRP layers (0, 2, 4, and 6) on axial compressive performance. Results showed that BFRP confinement significantly enhanced strength and ductility, with maximum gains of 81% in strength and 230% in strain observed in low-strength natural aggregate concrete. Although recycled brick aggregate concrete (RBAC) exhibited lower stiffness, BFRP still provided up to 23% strength improvement. The effectiveness of confinement reduced with increasing unconfined strength. Post-peak analysis revealed that additional BFRP layers delayed stiffness degradation, promoting more ductile failure. Experimental elastic modulus closely matched ACI predictions in natural aggregate (NA) specimens but was overestimated in RBAC due to its higher porosity. The findings demonstrate the viability of BFRP confinement for enhancing the structural performance of sustainable concrete, while emphasizing the need for aggregate-specific design considerations. Design-oriented modelling was adopted to predict the complete stress-strain response of BFRP-confined concrete incorporating both natural and recycled brick coarse aggregates. A two-branch idealization of the compressive response was performed. Several key points were identified and predicted by using nonlinear regression analysis. The proposed approach closely predicted the response of BFRP-confined concrete.
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Modeling and comparative analysis of sustainable cotton rope confinement: Full vs. STrip wrapping for enhanced concrete strength and ductility
(2025-07-01)
Saingam, Panumas
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Gadagamma, Chaitanya Krishna
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Hussain, Qudeer
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Hlaing, Hnin Hnin
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Suwannatrai, Rawirot
The rise of natural FRPs as ecological alternatives to synthetic ones has highlighted the need for studies on partial confinement using cotton ropes, which offer cost-effective, low-carbon solutions with high rupture strain. Unlike full confinement, partial confinement through cotton rope strips can efficiently strengthen deteriorated concrete sections with reduced material usage. Despite possessing several advantages, the partial confinement by cotton on concrete has not been investigated. This study addresses the gap by investigating the performance of cotton rope strips and developing analytical models to predict their structural impact. This study tested cylindrical concrete specimens of two strengths, strengthened with cotton rope in either complete wrapping (Group 1) or strip wrapping (Group 2). Each group was further divided by concrete strength and included one unstrengthened specimen, and three strengthened with one, two, or three layers of cotton rope. Experimental results revealed that cotton rope wraps effectively confined the concrete, enhancing load-bearing capacity and improving ultimate compressive strength by 9.97–152.10 % and ultimate strain by 188.00 % to 1488.89 %. The compressive stress vs. strain behavior exhibited an initial stiff elastic ascent followed by a parabolic transition. The second branch of the response, either ascending or descending, was significantly improved with an increased confinement ratio. Type-I failure was characterized by an ascending second branch in the compressive stress vs. strain curve, while Type-II failure exhibited a descending second branch. Four specimens demonstrated Type-I failure (L-2F, L-3F, H-3F, and L-3S), predominantly in full configurations and with lower unconfined compressive strength. The modulus of the second branch improved with an increased confinement ratio, transitioning from Type-II to Type-I failure near a ratio of approximately 0.50. Regression analysis provided equations of various key points along the compressive response with R² values greater than 0.90, highlighting a strong dependence on the confinement ratio. The Popovics model effectively predicted the first part of the compressive response, with predicted curves closely matching experimental results.
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Large rupture strain cotton ropes hybridized with affordable fiberglass chopped strand mat sheets for enhanced compressive behavior of reinforced concrete columns
(2024-11-15)
Saingam, Panumas
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Gadagamma, Chaitanya Krishna
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Hussain, Qudeer
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Ejaz, Ali
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Hlaing, Hnin Hnin
The hybrid confinement system combines various fiber types within a single matrix, allowing for the adjustment of volumetric ratios to optimize confinement performance. Synthetic FRPs are more expensive and have a higher carbon footprint due to significant CO<inf>2</inf> emissions during production. In response, this study presents an innovative hybrid confinement approach using two natural materials: cotton ropes and FSMS (CFS) to improve concrete strength and ductility. Specimens, standardized at 300 mm height and 150 mm diameter with longitudinal steel bars and stirrups, were divided into two groups based on CFS configurations. The stress-strain response of CFS-confined concrete displayed distinctive behavior: an initial parabolic phase leading to peak compressive stress (ultimate strength), followed by a linearly degrading phase. Across all subgroups, CFS confinement significantly enhanced ultimate strength and corresponding compressive strains, with Subgroup 2A achieving the highest improvements of 246 % in ultimate strength and 1477 % in strain. Moreover, the ductility gain was reported as high as 20 for CFS-confined concrete. A non-proportional enhancement in the compressive behavior was observed with the increase in confinement ratio. Predictive models were developed for the idealized two-branch response of CFS-confined concrete, encompassing expressions based on nonlinear regression for ultimate strength, corresponding strain, ultimate strain, and elastic modulus. Two existing models were modified to trach each branch of the response. Integrating these two adjusted models closely replicated the experimental compressive curves.
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Role of surface silanols and confinements of siliceous MFI supports on stability of active Ga species for ethane dehydrogenation
(2022-05-25)
Prakobtham, Kittipong
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Choojun, Kittisak
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Promchana, Pratya
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Sattayaporn, Suchinda
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Sooknoi, Tawan
Effect of surface silanol and confinement of siliceous MFI supports on the anchoring stability of active Ga species was demonstrated for ethane dehydrogenation. The catalysts were prepared by impregnation of Ga(NO<inf>3</inf>)<inf>3</inf> solution on siliceous MFI (Si/Al >500) and amorphous SiO<inf>2</inf>, and characterized by XRD, XRF, SEM-EDX, H<inf>2</inf>-TPR, NH<inf>3</inf>-TPD, in situ XANES, and EXAFS. Extra-framework Ga3+ species were present with different dispersions and reducibility, depending on the surface silanols. Proximity of the silanols within the surface confinement played an essential role on anchoring stability of the extra-framework Ga3+ species. All Ga catalysts provided > 93% ethylene selectivity with appreciable TOF ~60 h−1 for ethane dehydrogenation at 650°C. In situ XANES, EXAFS, and H<inf>2</inf>-TPR suggested that the highly dispersed extra-framework Ga3+ species could exist as dimeric Ga oxide [Ga<inf>2</inf>O<inf>2</inf>]2+ species. This active site could be reversibly interconverted with the less active [HGaOH]+ species under the H<inf>2</inf> flow.

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