Self-consolidating Concrete Beams Research Articles

Shear behavior of self-consolidating concrete deep beams reinforced with hybrid of steel and GFRP bars

This paper experimentally investigates the dowel action contribution of longitudinal reinforcement, a hybrid of steel and GFRP bars (usually adopted for avoiding corrosion of steel bars), in concrete deep beams for different reinforcement schemes. The self-consolidating concrete without and with steel fibers (0.9 % and 1.2 % by volume) was used. Sixteen simply supported deep beams of 140 × 300 (depth) × 1500 mm were tested under the two-point loads. A model is developed to predict the shear capacity of deep beams without web reinforcement, taking into consideration the dowel action contribution of longitudinal reinforcement, which is a hybrid of steel and GFRP rebars. The results showed a significant dowel action contribution of steel as well as GFRP rebars to beam shear strength. However, the use of a hybrid system of steel and GFRP bars caused a reduction in the dowel action of steel bars due to their combined action.

Assessment of concrete shear resistance of lightweight SCC beams containing scoria aggregates

Lightweight self-consolidating concrete (LWSCC) has become a construction material that combines the benefits of lightweight concrete (LWC) and self-consolidating concrete (SCC). However, this combination may affect the shear resistance of structural members made with such concrete. This paper evaluates the shear resistance and performance of LWSCC beams. Eight full-scale beams without stirrups were fabricated and tested to failure. Seven beams were constructed using LWSCC and one was cast using normalweight self-consolidating concrete (NWSCC). Natural lightweight coarse and fine scoria aggregates were used in preparing the concrete mix. The beams were tested over a simply supported span in a two-point loading configuration. The test parameters comprised the type of aggregates, the reinforcement ratio of longitudinal steel bars, the shear span-to-depth ratio, and the depth of the beam. The experimental results showed that employing scoria aggregates in the mix resulted in beams with a reduced self-weight, where the obtained unit weight of LWSCC was 1800 kg/m3. Compared to the beam with NWSCC, the counterpart beam with LWSCC showed 25% lower shear strength. Additionally, the LWSCC beam experienced a reduction of 20% in the flexural cracking load while the beam showed a larger number of cracks at failure. The shear strength of the beams was predicted using the relevant shear design provisions of the American Concrete Institute building code ACI 318, the Canadian standard CSA-A23.3, and Eurocode 2. The ACI 318 method provided more reliable and conservative estimates for the shear capacity of the tested beams.

Flexural Behavior and Serviceability Performance of Lightweight Self-Consolidating Concrete Beams Reinforced with Basalt Fiber-Reinforced Polymer Bars

Flexural Behavior and Serviceability Performance of Lightweight Self-Consolidating Concrete Beams Reinforced with Basalt Fiber-Reinforced Polymer Bars

Performance of Lightweight Self-Consolidating Concrete Beams Reinforced with Glass Fiber-Reinforced Polymer Bars without Stirrups under Shear

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Shear strengthening performance of GFRP reinforced lightweight SCC beams: Experimental and analytical study

Light weight construction using Glass Fibre-Reinforced Polymer (GFRP) bars and structural light weight concrete (LWC) have increased recently and offers a wide spectrum of advantages over traditional normal weight concrete (NWC) structures. However, the shear strengthening and rehabilitation performance of LWC beams reinforced with GFRP bars is very limited and currently there are no guidelines related to it. Therefore, this study presents the results of an experimental investigation on the shear strengthening behaviour of lightweight self-consolidating concrete (LWSCC) beams reinforced with GFRP bars. The test parameters studied in the experimental program were the longitudinal reinforcement ratio and strip configuration or orientation. A total of twelve shear deficient GFRP reinforced beams were prepared with a shear span to depth ratio of 3.12 and subjected to static four-point bending. Five beams in each series were externally strengthened with different configurations of Carbon Fibre-Reinforced Polymer (CFRP) strips and one beam served as a control specimen to compare the performance of the strengthened specimens. Crack patterns, load–displacement response curves, and strain in the external CFRP strips were recorded until the failure ultimate load. The results of the experimental study indicated that the external CFRP strips improved the nominal shear capacity of GFRP reinforced LWSCC beams, and the contribution of external CFRP strips was sensitive to the reinforcement ratio. The nominal shear capacity of the strengthened specimens increased from 33.3 to 168% compared to the control specimen. U-wraps with horizontal strips in the compression and tension zone were the most effective configuration, showing the highest increase in shear strength compared to other strengthened specimens. Moreover, the shear capacity was theoretically predicted using different Fiber-Reinforced Polymer (FRP) design standards and guidelines which were compared with the experimental results. All the FRP design standards have overestimated the shear capacity of LWSCC beams, and a modified equation with a set of recommendations was proposed based on the experimental study. In addition, a reduction factor of 0.75 is recommended for conservative design.

Experimental Study of the Shear Behavior and Shear Strength of Hybrid Fiber-Reinforced SCC Rectangular Beams

Based on the investigation on the workability of macro-mono-steel fibers and macro-hybrid fiber-reinforced self-consolidating concrete, a series of simply supported hybrid fiber-reinforced self-consolidating concrete rectangular beams with four-point vertical load were analyzed by using experiments. Influences of steel fibers and hybrid fibers with various dosages on the shear strength and failure mode of reinforced concrete beams are analyzed. This work finds that hybrid fibers can evidently enhance the shear strength. The failure mode of the beam can be changed from a brittle shear failure into a ductile flexural mechanism due to enough hybrid fibers added. The mechanical behavior of the hybrid fiber-reinforced self-consolidating concrete beam is much better than that of macro-mono-steel fiber-reinforced self-consolidating concrete. Hybrid fibers combined with stirrups show the synergistic response and that is a good way of reinforcement for self-consolidating concrete members. The ultimate shear load of beams with hybrid fibers and/or shear reinforcement can be predicted by the σ-w design method suitably.

The use of GPR to investigate the effect of steel fiber distribution on the mechanical behavior of FRC

The present work focuses on the steel fiber distribution in self-consolidating concrete short beams. The objective is to assess the feasibility of the ground penetrating radar (GPR) in evaluating the homogeneity of fibers within concrete materials, for use in testing laboratories to study the modes of placing and compaction employed for preparing specimens during quality control or material development. Self-consolidating concrete beams were cast, tested, and evaluated. A GPR survey employing a concrete scanning system with a shielded 1.2 GHz center frequency was performed on self-consolidating casted short beams just before a monotonic four-point bending test was carried out. After failure, a representative short beam was cut and the resulting slices were photographed to obtain the position and distribution of the steel fibers. Results were processed using dedicated software and an integrated analysis was accomplished. The digital and processed images correlated well with the GPR mappings in a single radar trace mode. In particular, the GPR amplitude provides information on the steel fiber density that was used as reinforcement in concrete specimens.

Flexural Strength and Serviceability of GFRP-Reinforced Lightweight Self-Consolidating Concrete Beams

Flexural Strength and Serviceability of GFRP-Reinforced Lightweight Self-Consolidating Concrete Beams

Bond-dependent coefficient and cracking behavior of lightweight self-consolidating concrete (LWSCC) beams reinforced with glass- and basalt-FRP bars

Crack width is one of the issues that can often control the design of flexural elements reinforced with fiber-reinforced polymer (FRP) bars due to the relatively low modulus of elasticity. This paper aims at investigating the cracking behavior of lightweight self-consolidating concrete (LWSCC) beams reinforced with glass- and basalt-FRP (GFRP and BFRP) bars and evaluating the bond-dependent coefficient (kb) values. Fifteen reinforced concrete specimens 200 mm in width, 300 mm in height, and 3100 mm in length were prepared and tested up to failure. Twelve specimens were made using LWSCC, while the other three were made with normal-weight concrete (NWC) as reference specimens. The test variables were concrete density (LWSCC and NWC); reinforcement type (GFRP and BFRP bars) with various surface conditions (sand-coated and helically grooved); and longitudinal reinforcement ratio. The experimental results show that the FRP-reinforced LWSCC (FRP-LWSCC) beams exhibited cracking behavior similar to that of the counterpart FRP-reinforced NWC (FRP-NWC) beams. The FRP-LWSCC beams had a linear crack response up to failure by concrete crushing, regardless of the amount and surface condition of the FRP reinforcement. Moreover, the recorded crack widths of the FRP-LWSCC beams are presented and compared to those predicted according to FRP design provisions. The comparisons indicate that the crack widths of the FRP-LWSCC beams can be estimated with the FRP design provisions with a variable degree of conservativeness. Furthermore, the determination of the kb factor reveals that the sand-coated GFRP and BFRP bars yielded smaller kb values than the helically grooved GFRP and BFRP bars.

Flexural Performance and Ductility of Expanded Slate Lightweight Self-Consolidating Concrete Beams

Flexural Performance and Ductility of Expanded Slate Lightweight Self-Consolidating Concrete Beams

Performance of lightweight SCC beams strengthened with rubberized engineered cementitious composite in shear

This study evaluated the shear behavior of lightweight self-consolidating concrete (LWSCC) beams strengthened with rubberized engineered cementitious composite (RECC). The RECC in this investigation, was developed with crumb RECC (CRECC) or powder RECC (PRECC). Four reinforced LWSCC beams layered with either CRECC or PRECC at the tension or compression zone, were constructed with no stirrups and tested in shear. Another three beams fully cast with LWSCC, CRECC, and PRECC, were tested for comparison. The performance of all tested beams was evaluated through different aspects including cracking behaviour, failure modes, ultimate shear load, post-diagonal cracking resistance, deformability, and energy absorption capacity. The experimental results indicated that strengthening LWSCC beams with either a CRECC or PRECC layer improved their ultimate shear strength, deformability, and energy absorption capacity without significant increase in their self-weight. The highest improvement in the shear behavior of the LWSCC beams was recorded when the CRECC or PRECC layer was located at the compression zone. Meanwhile, placing the RECC layer at the tension zone helped to enhance the cracking resistance, which indicates better protection for tensile reinforcing bars. The results also indicated that powder rubber seemed to be more efficient in developing RECC with higher fresh and mechanical properties compared to crumb rubber. The shear capacity of the tested composites was successfully estimated using a new model proposed based on a modification of the Eurocode’s equation.

Flexural Behavior of Lightweight Self-Consolidating Concrete Beams Strengthened with Engineered Cementitious Composite

Flexural Behavior of Lightweight Self-Consolidating Concrete Beams Strengthened with Engineered Cementitious Composite

Shear Behavior of Lightweight Self-Consolidating Concrete Beams Containing Coarse and Fine Lightweight Aggregates

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Strengthening and Repair of Self Compacting Concrete Beams( Dept.C )

While there is abundant research information on ordinary concrete beams strengthening or repairing with FRP, relatively little data on the behavior of self-consolidating concrete (SCC) is available. Carbon Fiber Reinforced Polymers laminates (CFRP) was investigated for strengthening and repairing SCC and high strength self compacting concrete (HSSCC) beams subjected to one midpoint load in in order to compared to beams made of normal concrete (NC) and normal high strength self compacting concrete (NHSSCC) at the same conditions respectively. To demonstrate the concept, this paper presents results of a laboratory investigation of 24 beams (150x200x1600 mm) on the behavior of self compacting concrete strengthening and repairing with one layer of CFRP laminate and subjected to one midpoint load, including the effect of using 8 different mixes to study the effect of mix proportions on rapped CFRP beams behavior. Test results showed that the addition of CFRP laminate to the tension surface of the beams demonstrated significantly improvement in stiffness and ultimate load capacity of beams. The response of control and strengthened beams were compared and evaluated by experimental and theoretical calculations. It was observed that ductility indexes of SCC and HSSCC beams were more efficient than NC and NHSC respectively. Load carrying capacity of control, strengthening and repairing self compacting concrete beams was closed to traditional concrete beams (about 90-95%). The paper also highlighted the crack pattern of all cases of beams which indicated more distribution and smaller crack amplitude for strengthened beams with respected to the control beams.

Performance of engineered cementitious composite covered or wrapped self-consolidating concrete beams under corrosion

In this study, effect of Engineered Cementitious Composite (ECC) covering and wrapping on corrosion resistance and structural performance of un-corroded and corroded shear beams made of self-consolidating concrete (SCC) and light weight SCC (LWSCC) has been extensively investigated. An accelerated corrosion test on beams has been performed to reach the required high degrees of corrosion (30–40% of rebar mass loss). Both corrosion and structural performance of corroded beams has been assessed and analysed. The structural performance of un-corroded and corroded beams has also been compared. The corrosion performance has been evaluated in terms of current flow, half cell potential, actual rebar mass loss, reduction in diameter etc. The structural performance has been assessed and compared in terms of load–deflection behaviour, 1st flexure/diagonal cracking load, ultimate failure load, post cracking shear resistance, ductility and energy absorption capacity, failure load and failure modes. Composite beams with ECC covering exhibited superior corrosion resistance and post-corrosion structural performance as compared to full depth SCC or LWSCC counterparts. The performance of ECC wrapped composite beams has been found to be better than those with covering. Overall, ECC can be used as covering or wrapping in conventional SCC/LWSCC beams to enhance their corrosion resistance performance significantly.

Shear capacity of self-consolidating concrete beams

An improved analytical model to predict the ultimate shear capacity of a self-consolidating concrete (SCC) flexural member is presented. SCC behaves differently to normal concrete because of its unique composition and mix proportions, which alter the shear resisting mechanisms in the member. SCC has found a wide range of applications due to its excellent deformability and high resistance to segregation and bleeding, but the lack of an adequate model that could help analysts predict the shear capacity of SCC beams is one of the main barriers to its acceptance in routine design practice. The model presented in this paper was developed considering all the factors that influence the shear capacity of SCC beams. The test results of an experimental study conducted to validate the accuracy of the proposed model are also provided in this paper; the model's efficacy was also checked using test results reported by other researchers. The results predicted by the model showed good agreement with the experimental test data.

Experimental verification and simulation of fracture behavior of CFRP reinforced self-consolidating concrete beams with initial notch

The current study presents numerical and experimental approaches in the assessment of fracture behavior of self-consolidating concrete beams strengthened with carbon fiber-reinforced polymer (CFRP) lamina. The failure modes, mid-span displacement, and the load-bearing capacity of specimens with initial notches at mid-span are analyzed by varying the notch length and the beam height. Furthermore, the effects of variations in CFRP and concrete mechanical properties, bond strength, and notch location are examined by using the non-linear finite element analysis. Findings reveal that stress concentration in concrete and CFRP, in the vicinity of initial notch, as well as the failure of specimens occur as a result of CFRP debonding and crack extension. Moreover, it is observed that load- mid-span displacement curves are characterized by two peak load points strength. At the first stage, the applied load increases up to one peak value and then at the second stage there is a drop in the load-caring capacity. The applied load is then improved to another peak value due to the relatively high cohesive effect of the CFRP sheet at the third stage. Among different variables, the second peak load shows higher sensitivity to variations of the elastic modulus of CFRP, and bond strength at interface. As the notch approaches the beam support, and hence the relative distance from mid-span changes from 0 to 2/3, the two peak loads are respectively escalated by 116 and 58%, and thus the inclined crack propagates toward mid-span.

Development length of prestressing strand in self-consolidating concrete vs. conventional concrete: Experimental study

An experimental investigation was conducted to compare the development lengths of prestressing strand in self-consolidating concrete (SCC) and conventional concrete (CC). Development lengths and bond performance of 12.5 mm diameter, Grade 270 prestressing strand were evaluated using rectangular beams and the North American Strand Producers (NASP) test for both normal and high strength CC and SCC mixes. (The NASP test has now been formally adopted as ASTM A1081.) Results indicate that the current AASHTO and ACI equations for development length are conservative for both SCC and CC mixes. All development length test beams failed in flexure due to concrete crushing and exceeded the calculated nominal moment by 10–15%. Furthermore, all the SCC and CC beams showed negligible strand end slip during testing. Overall, SCC and CC appeared to exhibit comparable development lengths.

Experimental investigation on shear resistance of self-consolidating concrete beams

Abstract Self-consolidating concrete stands out for its high fluidity and stability, which are obtained by the reduction of the coarse aggregate dimensions and content in the mixture and also by the addition of superplasticizer and viscosity modifiers. An experimental test program was carried out to evaluate the influence of these particularities of self-consolidating concrete mixtures on the shear capacity of beams with shear reinforcement. Four mixtures of self-compacting concrete and two mixtures of conventionally vibrated concrete with different coarse aggregate size and volume were used for the production of beams to be tested under flexure. The experimental results were compared to those estimated by the ACI-318, CAN A23.3, EC-2 and NBR 6118 design codes. The results demonstrated that the reduction of coarse aggregate dimensions and content in self-compacting concrete mixture did not significantly influence the ultimate shear strength. The shear strengths obtained experimentally were considered adequate to codes estimates, for both concrete types.

Shear behavior of novel hybrid composite beams made of self-consolidating concrete and engineered cementitious composites

Shear performances of hybrid composite beams, a combination of two different layers of self-consolidating concrete (SCC) and engineered cementitious composites (ECC) were investigated. Composite beams were made with two different ECC to SCC depth ratios. Full depth beams, consisting of a single layer of either SCC or ECC, were also made and tested to compare their performance with respect to that of hybrid composite beams. Both full depth and composite beams were made with and without shear reinforcement. The performance of shear beams was evaluated in terms of load-deflection response, first diagonal crack load, post-cracking shear resistance, energy absorption, and ductility index. Compared to the full depth SCC and full depth ECC beams, non-shear reinforced hybrid composite beams showed higher ductility and energy absorption capacity which indicates suitability of hybrid composite to be used in earthquake resisting elements. Hybrid composite beams also showed higher number of cracks with lower crack width. Code based equations and other design specifications were found to be conservative in predicting shear strength of hybrid composite beams. However, the theoretical capacity was found to be higher than that of experimental shear resistance in case of full depth ECC beams.