Shear behaviour of reinforced construction and demolition waste-based geopolymer concrete beams
Authors : Alper Aldemira,Saban Akdumana, Oznur Kocaera, Rafet Aktepea ,Mustafa Sahmarana , GurkanYildirima , HanadyAlmahmood, Ashraf Ashour
Abstract : Geopolymer concrete (GPC) is a promising candidate to replace conventional concrete (CC) as geopolymer concrete depends on alkali-activated binders instead of Portland cement. The elimination of cement from the mixture results in the reduction of the greenhouse gas release. From the literature, it is known that the micro-scale characteristics of the geopolymer concrete are similar to its counterparts. However, the structural performance of geopolymer elements should be investigated in detail. Therefore, in this study, the deficiently reinforced beams' structural performance was compared by conducting bending tests to determine the shear behavior of new geopolymer concrete manufactured from entirely construction and demolition wastes (CDW). In these experiments, geopolymer concrete with recycled aggregates, geopolymer concrete with natural aggregates, concrete with recycled aggregates, and concrete with natural aggregates were used in order to study the possibility of reaching fully-recycled construction materials. Three shear span-to-effective depth ratio were used to examine the different failure modes. The mechanical performances of geopolymer concretes were assessed by using load-deflection/moment-curvature curves, and crack propagations. Test results revealed that geopolymer concrete beams exhibited similar performance to the concrete beams of the same grade. Besides, the insertion of recycled aggregates caused a shift in the failure mechanism from flexure-dominated to shear-dominated, especially in specimens with larger a/d ratios. Finally, the capacity prediction performance of current codes, i.e., TS500 and ACI318, were also examined, and the calculations resulted that the current code equations had a percentage error of approximately 55% on average, although TS500 equations performed slightly better.
Keywords : Construction and demolition waste, Reduced CO2 emission, Recycled aggregate Geopolymer Shear-deficient flexural tests Sustainable construction
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Experimental Investigations on the Structural Behaviour of Reinforced Geopolymer Beams produced from Recycled Construction Materials
Authors : Saban Akduman , Oznur Kocaer , Alper Aldemir , Mustafa S¸ ahmaran a , Gürkan Yıldırım , Hanady Almahmood , Ashraf Ashour
Abstract : Concrete requires a vast amount of aggregate and cement production. Although there are some efforts in the literature to reduce the amount of Portland cement in the concrete mixture to lessen the greenhouse gas release, a limited number of studies were conducted to investigate the possibility of using this geopolymer mixtures to serve as a structural component. Therefore, this study firstly aimed to produce geopolymer concrete from construction and demolition waste-based precursors, including masonry units (red clay brick, roof tile, hollow brick, etc.) and glass. In addition, recycled aggregates produced from the concrete waste portion of the CDW were used to obtain 100% recycled construction material on the scale of the binder and aggregate phase. Then, this study investigated the possible use of this proposed geopolymer concrete to produce structural components that perform similar to conventional concrete. Therefore, the structural properties of reinforced geopolymer concrete beams produced from the recycled construction demolition wastes were evaluated in this study by conducting laboratory experiments. To this end, bending tests were performed on reinforced conventional concrete beam specimens and reinforced geopolymer concrete beam specimens. The test observations clearly showed that construction demolition waste could be recycled to produce new constructional components, considering its advantage of promoted sustainability.
Keywords : Recycled aggregate, Geopolymer, concrete Bending tests, Recycled construction materials Flexural behaviour,
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Flexural behaviour of hybrid steel-GFRP reinforced concrete continuous T-beams
Authors : Hanady Almahmood , Ashraf Ashour, Therese Sheehan
Abstract : This paper presents test results of six full scale reinforced concrete continuous T beams. One beam was reinforced with glass fibre reinforced polymer (GFRP) bars while the other five beams were reinforced with a different combination of GFRP and steel bars. The ratio of GFRP to steel reinforcement at both mid‐span and middle‐support sections was the main parameter investigated. The results showed that adding steel reinforcement to GFRP reinforced concrete T‐beams improves the flexural stiffness, ductility and serviceability in terms of crack width and deflection control. However, the moment redistribution at failure was limited because of the early yielding of steel reinforcement at a beam section that does not reach its moment capacity and could still carry more loads due to the presence of FRP reinforcement. The experimental results were compared with the ultimate moment prediction of ACI 440.2R‐17, and with the existing theoretical equations for deflection prediction. It was found that the ACI 440.2R‐17 reasonably estimated the moment capacity of both mid‐span and middle support sections. Conversely, the available theoretical deflection models underestimated the deflection of hybrid reinforced concrete T‐beams at all load stages.
Keywords : Fibre-reinforced polymer Hybrid reinforced system Continuous beams T‐section Moment redistribution
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Structural behavior investigation and durability study of concrete elements reinforced with fiber reinforced polymer (FRP) bars
Authors : Irshidat, Mohammad R, Haddad, Rami H. , Almahmoud, Hanadi
Abstract : he present paper investigates the post heating behavior of concrete beams reinforced with fiber reinforced polymer (FRP) bars, namely carbon fiber reinforced polymer (CFRP) bars and glass fiber reinforced polymer (GFRP) bars. Thirty rectangular concrete beams were prepared and cured for 28 days. Then, beams were either subjected (in duplicates) to elevated temperatures in the range (100 to 500∘C500∘C) or left at room temperature before tested under four point loading for flexural response. Experimental results showed that beams, reinforced with CFRP and GFRP bars and subjected to temperatures below 300∘C300∘C, showed better mechanical performance than that of corresponding ones with conventional reinforcing steel bars. The results also revealed that ultimate load capacity and stiffness pertaining to beams with FRP reinforcement decreased, yet their ultimate deflection and toughness increased with higher temperatures. All beams reinforced with FRP materials, except those post-heated to 500∘C500∘C, failed by concrete crushing followed by tension failure of FRP bars.
Keywords : RC beams, elevated temperatures, fiber reinforced polymer; flexural behavior
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Moment-Curvature Behaviour of Hybrid Reinforced Concrete T- Beams
Authors : Hanady Almahmood , Ashraf Ashour, Therese Sheehan
Abstract : This paper presents an analytical model to investigate the moment-curvature behaviour of hybrid reinforced concrete beams based on a developed sectional analysis. The analytical model has been validated using experimental results collected from the literature, where a good agreement between the experimental and analytical results was observed in terms of moment capacity, curvature, and modes of failure. The developed model was, then, utilized to predict the effect of different parameters on the behaviour of hybrid reinforced concrete T-beams for both sagging and hogging moments. The analytical results indicate that adding steel reinforcement to FRP T-beams enhances the ductility, the stiffness, and changes the brittle failure mode to ductile failure.
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