Shear Behavior of Geopolymer Concrete Slender Beams

Abstract

This study investigates the shear behavior of slender steel-reinforced geopolymer concrete (GPC) beams with the shear span to effective depth ratio (a/d) of 4.5 and 5.0. To investigate the effect of shear reinforcement, two ordinary Portland cement concrete (OPC) beams and two GPC beams without shear reinforcement, and two OPC beams and two GPC beams reinforced with shear stirrups were cast. All beams were 150 mm wide and 225 mm deep with lengths of 1770 mm (a/d=4.5) and 1950 mm (a/d=5). The beams were tested under a three-point bending test. The experimental results showed that OPC and GPC beams without and with shear reinforcements exhibited similar crack propagation and failure mechanism. The midspan deflections of GPC beams were greater than OPC beams. The normalized shear resistance of OPC and GPC beams with a/d ratio 4.5 was greater than 4% and 30%, respectively, than beams with a/d ratio 5. OPC beams showed a greater decrease in shear resistance with an increasing a/d ratio compared to GPC beams. The shear resistances computed using empirical relationships available in various OPC design codes including AC1-318-14, AC1-318-19, fib-10 and JSCE-07 underestimated the experimental shear resistance of both OPC and GPC beams. In addition, the environmental assessment of OPC and GPC beams exhibited that GPC beams emit about 34% lower embodied CO2 emissions than OPC beams.

Experimental and Analytical Investigations on Shear Performance of Ambient-Cured Reinforced Geopolymer Concrete Beams

“…Similar findings were also reported by Slowik [29], Ismail et al [31], Wu et al [36], Visintin et al [37], and Tauqir et al [12] that increasing 𝑎/𝑑 ratios decreased the shear strength of beams. Moreover, the pure diagonal shear compression failure was observed in OPCCB, while the failure pattern in GPCB changed from shear to shear-flexure with increasing 𝑎/𝑑 ratio from 1.5 to 4.0 [29,31,36,37,69].…”

“…In JSCE Guidelines for Concrete Structures-2007 (JSCE 2007 [43]), the V c of steelreinforced concrete beams is calculated using Equation (12).…”

“…In the last decade, numerous studies investigated either partial or complete replacement of Portland cement with various aluminosilicate materials, such as fly ash, rice husk ash, metakaolin, etc., to produce geopolymer concrete (GPC) [12][13][14][15]. These materials are industrial waste obtained from construction, minerals, energy, and steel industries.…”

“…Geopolymers are formed by the chemical reaction between aluminosilicate materials and alkaline activator solutions during the geopolymerization phenomenon. In this reaction, 3D polymeric ring structures of aluminosilicate (Si-O-Al-O) are formed, which condenses to give strength to the geopolymers [12].…”

“…Other studies showed that the shear strength of oven-cured GPC beams reduced by 50-55% as the a/d ratio was increased from 1.5 to 4.0 [15,36]. Moreover, limited studies investigated the influence of a/d ratio on the shear strength of ambient-cured GPC beams and reported a 30% decrease in shear strength with increasing a/d ratios from 2.0 to 6.0 [12,[37][38][39]. Therefore, in this study, the shear performance of ambient-cured reinforced GPC beams is investigated by considering the effect of a/d ratios of 1.6, 2.9, and 4.3, and a comparison is made with the corresponding OPCC beams.…”