Flexural strength and failure of geopolymer concrete beams reinforced with carbon fibre-reinforced polymer bars

• Published in: Construction & building materials 2020-01, Vol.231, p.117185, Article 117185
• Main Authors: Ahmed, Hemn Qader, Jaf, Dilshad Kakasor, Yaseen, Sinan Abdulkhaleq
• Format: Article
• Language: English
• Subjects: Carbon fibre-reinforced polymer bar; Flexural strength; Geopolymer concrete; Sustainability
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2019.117185

•Geopolymer concrete beams with low rebar ratio recorded significant deformation.•Concrete compressive strength had a significant effect on the first crack of GPC beams.•The CFRP-RGPC beams had more deflection than CFRP-ROPC beams.•Number of cracks in the CFRP-RGPC beams was higher than that in the CFRP-ROPC.•CFRP-ROPC beams obtained a higher value of crack width compared with CFRP-RGPC. Geopolymer concrete with carbon fibre-reinforced polymer bars can provide a good construction system with high sustainability, high durability and appropriate strength. Few studies have used a combination of these materials, especially the carbon fibre-reinforced polymer bar. The present investigation obtains the flexural strength and behaviour of geopolymer concrete and ordinary Portland concrete beams reinforced with carbon fibre-reinforced polymer bars. Twelve beams consisting of nine geopolymer concrete and three ordinary Portland concrete beams were cast and investigated by using the four-point bending test over an effective span of 2000 mm. Reinforcement ratio, compressive strength and concrete types were taken as the variables. First cracking load, ultimate load, load-deflection behaviour, load-strain curve, crack width, number of cracks and modes of failure, were studied. Experimental results were compared with the proposed equations provided by ACI 440.1R-15, CSA S806-12 and the proposed method. Results showed the decrease of deflection and increase of first cracking load with the increase of compressive strength, a slight increase in the deflection of geopolymer concrete beams and nearly the same value of ultimate load were observed; geopolymer concrete beams also recorded a lower value of crack width compared with ordinary Portland concrete beams. ACI 440.1R-15 and CSA S806-12 underestimated the flexural strength of the beams, while the proposed method which based on the parabolic stress block predicted more accurately.