In spite of the availability of different models proposed to predict the shear capacity of reinforced concrete (RC) beams strengthened in shear using fabric reinforced cementitious matrix (FRCM) system, accurately predicting this value remains a challenge. The simplified compression field theory has shown to accurately predict the shear capacity of RC beams. This paper presents an analytical model based on the simplified compression field theory for predicting the shear capacity of RC beams strengthened in shear using FRCM strengthening system. The model has been validated against a data series of over sixty RC beams strengthened in shear using different FRCM types with different strengthening configuration and orientation. The results showed that the model can reasonably predict the load carrying capacity of the beams. The ratio of theoretically predicted and experimental results for the load carrying capacity ranged between 0.67 and 1.33 while average of this ratio was 1.01 with a coefficient of variation of 0.16.
The focus of this work was to study the reactivity of glass powder of a certain fineness by using a new experimental approach and to establish specifications for the use of glass powder as a pozzolanic material in concrete by developing glass powder hydration reaction equations. Experiments were carried out to determine the different quantities and proportions of glass powder, calcium hydroxide and water to establish the hydration reaction. Models that describe the hydration of the glass powder with and without calcium hydroxide are also developed in this paper. The developed models are validated using the results of the experiments. Using these models, predictions of the structure of the hydration products are obtained.
Abstract In this study, steel reinforced grout (SRG) is proposed for shear strengthening of reinforced concrete (RC) beams using the near‐surface embedded (NSE) technique. It is believed based on several research contributions in the literature that the NSE technique precludes or delays the onset of premature debonding and achieves higher strength increase in strengthened beams compared to the externally bonded (EB) counterpart. The tests conducted in this study used 13 RC beams to determine the shear behavior of RC beams strengthened in shear using SRG. The effect of the strengthening technique (NSE versus EB), SRG fabric density, strengthening scheme (side‐bonded vs. U‐wrapped), and the strengthening configuration (continuous vs. discontinuous) on RC shear enhancement was studied. The strengthening effectiveness of the SRG system was assessed in terms of the shear capacity, failure mechanism, load‐deflection response, and strain results. The NSE‐SRG increased the beam shear strength by an average of 100%, alleviated SRG debonding, and enhanced the deformation characteristics. The average increase in the shear strength of the EB‐SRG strengthened beam was 54% and 105% for the continuous and discontinuous SRG strips, respectively. An analytical model is proposed to predict the shear capacity of both the NSE‐SRG and EB‐SRG strengthened beams and give accurate and safe predictions.
Exiting literature revealed that fabric reinforced cementitious matrix (FRCM) is a promising material for the strengthening of shear deficient reinforced concrete (RC) beams. However, most of the available experimental studies are devoted to the use of FRCM system for the strengthening of slender beams and limited literature is available on the strengthening of deep beams using FRCM system. Moreover, there is no available literature on the analytical modelling of FRCM-strengthened deep beams. In this paper, a simple strut and tie model (STM) has been used to predict the ultimate load carrying capacity of RC deep beams strengthened in shear using FRCM system. The model accounts for the internal transverse reinforcement ratio and axial rigidity of the FRCM system. The proposed model is validated against an experimental results of RC deep beams strengthened with different types of FRCM system available in the literature.
The externally bonded (EB) fabric reinforced cementitious matrix (FRCM) has successfully been used as a structural strengthening for various applications including flexural and shear strengthening of reinforced concrete (RC) beams, flexural strengthening of RC slabs and column confinement. However, the EB-FRCM system is characterized by poor FRCM/concrete bond leading to premature debonding of FRCM off the concrete substrate, particularly for thicker FRCM. The present paper reports on an experimental study on the efficacy of a pioneer form of hybrid near surface embedded and externally bonded technique using FRCM composites (NSEEB-FRCM) for shear strengthening of RC beams. With such a technique, higher thickness of FRCM composites can be applied with less likelihood of debonding that is normally experienced when using the EB-FRCM system. Thirteen shear-deficient medium-scale RC beams were constructed, strengthened in shear and tested under three-point bending test. The test parameters were: (a) FRCM type (polyparaphenylene benzobisoxazole, carbon, and glass), (b) strengthening configuration (full versus intermittent strips), and (c) number of fabric layers. The percentage enhancement in the shear capacity of the beams ranged from 43% to 114% indicating the successful implementation of the strengthening methods provided. An average enhancement in shear capacity of 83%, 72% and 62% were observed in carbon FRCM, glass FRCM and PBO-FRCM, respectively. The failure mode of the strengthened specimens was sensitive to the type and configuration of FRCM in addition to the number of FRCM layers. The strengthening systems also resulted in higher deflection at failure and energy absorption value of the strengthened beams with an average of 94% and 204% relative to the reference specimen, respectively.
Abstract The field of reinforced concrete (RC) strengthening continues to evolve as the construction industry seeks cost‐effective and sustainable alternatives to structural replacement. This study, therefore, aimed to comprehensively investigate the pioneering application of steel‐reinforced grout (SRG) for strengthening large‐scale, 3.5‐meter‐long continuous RC beams. The main purpose was to explore the complex interplay among SRG density, the number of SRG layers, and the steel reinforcement ratio, and to assess their collective impact on the structural performance of the strengthened beams. Extensive experimental testing was carried out on 10 large‐scale RC continuous beams, including two pristine beams serving as references. The experimental findings demonstrated significant enhancements in the load‐carrying capacity of the strengthened beams, achieving increases ranging from 24% to 104% compared to the corresponding reference beams. Although a reduction in ductility was observed, this emphasized the need to optimize the balance between strength and deformation in the strengthened members. The use of low‐density SRG proved remarkably effective, providing superior bonding and higher efficiency, while high‐density SRG exhibited slightly lower performance due to reduced matrix penetration. Additionally, the number of SRG layers was found to play a crucial role in boosting the load capacity, with more pronounced effects in beams with lower steel reinforcement ratios. To complement the experimental investigation, two theoretical models based on the SRG effective strain were developed and validated against the experimental results. The close agreement between the models and the experimental data underscores their potential as practical tools for the design and optimization of SRG‐strengthened beams, thereby contributing critical insights for engineering applications.
This paper reports on the feasibility of using fabric-reinforced cementitious matrix (FRCM) systems to rehabilitate corrosion-damaged reinforced concrete (RC) beams.Seven large-scale RC beams were constructed and tested to failure under four-point load configuration.Six beams were subjected to an accelerated corrosion process for 70 days to obtain an estimated mass loss of 10% in the tensile steel reinforcing bars.One virgin beam and one corroded unrepaired beam were used as benchmarks for comparison purpose.The other five corroded beams were repaired before applying the FRCM system.The test parameters included the number of fabric plies (1, 2, and 4) and the strengthening schemes (endanchored bottom flexural strips and fully U-wrapped flexural strips).Test results showed that corrosion insignificantly reduced the yield and the ultimate strength of the specimen.However, the corroded specimen failed to meet the provisions of the ACI 318 code for crack width criteria.The use of FRCM increased the ultimate capacity of corroded beams between 6% and 46% and their yield strength up to 20% in comparison with those of the control virgin beam.The specimens repaired with U-wrapped FRCM strips showed higher capacity and higher ductility than those repaired with the end-anchored bottom strips having similar number of layers.A higher gain in the flexural capacity and a lower ductility index were reported for specimens with higher amount of FRCM layers.
This paper presents the efficacy of a new technique of fabric reinforced cementitious matrix (FRCM) for the strengthening of shear deficient reinforced concrete (RC) beams. This technique involves embedding the FRCM composites in the concrete cover and is referred to as “near surface embedded” FRCM (NSE-FRCM) technique. Five (5) medium scale rectangular RC beams of width × depth × length of 150 × 330 × 2100 mm were constructed and tested under displacement controlled with three-point loading. One beam was kept unstrengthen as a control specimen whereas the other four beams were strengthened with different types and configurations of the NSE-FRCM system. The test parameters were: (a) geometric configuration (intermittent strips of NSE-FRCM versus full NSE-FRCM plate), and (b) fabric types (carbon versus glass fabrics). The test results indicated that the NSE-FRCM technique can successfully be used to significantly enhance the shear capacity of the strengthened beams. The strengthened specimens exhibited an average enhancement in the shear capacity of 62% over the unstrengthen beam. The full NSE-FRCM plate showed higher enhancement in the shear strength compared to that for the intermittent NSE-FRCM configuration. Moreover, the specimens strengthened with carbon FRCM showed higher shear capacity compared to that with glass FRCM counterparts.
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The use of seawater and recycled coarse aggregate (RCA) in concrete mixtures leads to the production of a very sustainable concrete. The potential risk of steel reinforcement corrosion (due to chloride in the seawater) in such mixtures may be eliminated when considering plain concrete or noncorrosive reinforcement (e.g., fiber-reinforced polymer). This study investigated the fresh and hardened properties of a proposed green concrete mixed using seawater and recycled coarse aggregates. Two different concrete mixtures were studied, namely conventional concrete (Mix 1) and seawater-mixed concrete with RCA (Mix 2). Blast furnace slag was used as supplementary cementitious material at a 65% replacement level in both concrete mixtures. Fresh and hardened properties of the two concretes, including workability, strength gain, drying shrinkage, permeability, and microstructure, were characterized and compared. The results suggest that the use of seawater and RCA together has negative effects on concrete performance. Compared with the reference (Mix 1), Mix 2 concrete had approximately 5% lower density, 25% lower slump flow, 50% lower setting time, 33% lower strength gain, 10% higher drying shrinkage, 60% higher water absorption, and 100% higher charge passed (in rapid chloride permeability tests). Consequently, strategies to improve the performance of such concretes, such as a reduction in the water:cementitious materials ratio and the use of chemical admixtures, are suggested. These strategies, however, may somewhat reduce the green aspect of the proposed seawater-mixed concrete with RCA.
