Self-compacting Concrete Beams Research Articles

A Proposed Model and Performance Study on Prefabricated Cage-Reinforced Self-compacting Concrete Deep Beams

A Proposed Model and Performance Study on Prefabricated Cage-Reinforced Self-compacting Concrete Deep Beams

Effect of strengthening by carbon fiber reinforced polymer sheets on the flexural behavior of reinforced self-compacting concrete beams under repeated loads

This study investigates the effect of strengthening self-compacted concrete (SCC) beams using CFRP sheets on flexural behaviour subjected to repeated loads. During the experiment, six rectangular reinforced SCC beams were evaluated; two were reference beams without strengthening, while the remaining four were strengthened with CFRP sheets. The beam’s length, depth, and width are 2100 mm, 300 mm, and 200 mm, respectively. A monotonic load was applied to one of the reference beams, while repeated loads were applied to the remaining (compression cyclic loads). The main parameters studied in this experimental work were the type of loading (monotonic and repeated), the positions of strengthening and the dimensions of CFRP sheets. The flexural behaviour of these beams was investigated through experimental examination by recording the ultimate load and maximum deflection. Meanwhile, the cracks’ pattern and failure modes were observed. The findings of the present study demonstrated that the limited cycles of repeated loads have marginal effect on the flexural behaviour of the beams. This results in an ultimate load reduction of no more than 11%. It was also noted that SCC beams strengthened using CFRP sheets subjected to repeated loads significantly affected the flexural behaviour of these beams. Consequently, the ultimate load of the strengthened beams was improved by up to 18%. Besides, the maximum deflection of the strengthened SCC beams was reduced by 45% compared to those without strengthening. Using strengthening throughout the beams’ entire width and length that are subjected to repeated loads improved their ultimate load to surpass that of non-strengthened beams under monotonic loads by as much as 7%.

Shear performance of polypropylene fiber reinforced high-strength self-compacting concrete beams

This paper consists of two parts, the first one look for producing self-compacting polypropylene fibrous concrete (PFSCC) with reasonable passing, filling and flow abilities and segregation resistance. Limestone powder with particle size less than 75μm was used to increase the fines fraction in the mix. The second part of this study, deals with the effect of adding polypropylene fibers and the shear strength of self-compacted reinforced concrete beams. Eighteen beams were cast which were 1.8 m long, 150 mm wide, and with overall depth of 200 mm. Four volume percentages of polypropylene fibers were used, 0, 0.1, 0.2 and 0.3 percent of cementitious materials weight. The test results showed that the polypropylene fibers have not serious adverse effect on the fresh properties and this effect was reduced by using plasticizer. Moreover, although the polypropylene fibers improved the tension properties of the hardened concrete, don`t have impact on compression properties. The test results showed that the presence of polypropylene fibers increased the cracking shear stress and the shear strength and this increase depends on the volume fraction of the fibers.

Investigation of optimized machine learning models with PSO for forecasting the shear capacity of steel fiber-reinforced SCC beams with/out stirrups

This article presents a comprehensive investigation of the applicability of optimized machine learning (ML) models with particle swarm optimization (PSO) for forecasting the shear strength of steel fiber-reinforced self-compacting concrete (SFR-SCC) beams with/without stirrups in engineering applications. Firstly, a database containing the results of 101 specimens with nine input features is adopted to train the models. As ML models such as random forest (RF), adaptive boosting regression (AdaBoost), extreme gradient boosting (XGBoost), support vector regression (SVR), and K-nearest neighbors regression (KNN) are considered, whereas the hyper-parameters of these models are set as default by the sklearn module. On the other hand, PSO-ML models (PSO-RF, PSO-AdaBoost, PSO-XGBoost, PSO-SVR, and PSO–KNN) are constructed using particle swarm optimization to find the optimal combination of the hyper-parameters of these default ML models. Afterwards, the forecasting ability of each model is extensively assessed using various performance metrics, error analysis, and score analysis, and the model with the best forecasting ability is determined and compared with existing empirical models. Moreover, Shapley additive explanation (SHAP) analysis is also utilized to ensure the interpretability of the forecasting models and to overcome the “black box” problem of ML methods. Lastly, based on the best forecasting model developed in this study, a graphical user interface (GUI) has been developed to easily forecast the shear strength of SFR-SCC beams in practical applications. The results of the study clearly illustrate that PSO-ML models exhibit better forecasting capabilities than default models. It can be emphasized from here that the PSO algorithm can be an effective tool to improve the performance of ML models. It should also be pointed out that the use of PSO in simpler algorithms instead of tree-based models can further improve forecasting efficiency. On the other hand, the PSO-RF model has the best performance, with a lower error value and a high final score. And this makes it a more reliable option for predicting the shear strength of the SFR-SCC beams compared to empirical equations. In addition, according to the results of SHAP feature importance analysis, the most important input parameters affecting the shear strength of SFR-SCC beams are stirrup rebar ratio (ρv), stirrup yield strength (fyv) and longitudinal rebar ratio (ρt). This information can assist engineers in paying special attention to these features in their design and assessment processes.

Shear Strength of Hybrid Fiber Reinforced Self-Compacting Concrete Beams

Self-compacting concrete has constructive advantages over conventional concrete, such as reducing labor and construction time, mainly because of its fluidity in the fresh state. However, in the hardened state, it maintains low performance when tensioned, and the fibers can be added to the mixture, maintaining a portion of the resistance after cracking. Steel fibers are usually added to concrete, but recently synthetic fibers have been used, due to their lower cost and non-corrosive nature, but with lower tensile strength. Thus, by combining the two types of fibers, the benefits of each material can be used. This work presents the results of an experimental program to evaluate the effect of the hybridization of metallic and synthetic fibers on the shear strength of self-compacting concrete beams without stirrups. The results demonstrate that both steel and hybrid fibers result in greater shear strength compared with the reference concrete without fibers before shear crack formation; however, the greatest advantages are attributed to post-cracking residual strength. The experimental results were compared with estimates calculated using equations published in the literature, demonstrating the feasibility of using some existing equations for concretes with the addition of hybrid fibers.

Monitoring temperature and hydration by mortar sensors made of nanomodified Portland cement

Mortar beams incorporating carbon nanofibers (CNFs), which were synthesized in situ on Portland cement particles, were used to produce nanomodified Portland cement sensors (SmartCem sensors). SmartCem sensors exhibited an electrical response comparable to a thermistor with a temperature coefficient of resistivity of − 0.0152/ °C. The highest temperature sensing was obtained for the SmartCem sensor, which contained ~ 0.271 wt.% of CNFs. The calculated temperature sensitivity was approximately 11.76% higher in comparison with the mortar beam containing only unmodified Portland cement. SmartCem sensors were used to monitor the cement hydration in large-scale self-compacting concrete beams. The measurements were conducted after casting for 7 days. Additionally, commercially available thermocouple and humidity sensors were used as references. The results showed that changes in electrical resistivity measured by the SmartCem sensor were well aligned with the ongoing hydration processes.

Shear performance of lightweight SCC composite beam internally reinforced with CFRP laminate stirrups and GFRP bars: Experimental and analytical study

This research demonstrates the structure feasibility of using carbon fiber reinforced polymer (CFRP) laminate stirrups as a form of transverse reinforcement in shear deficient GFRP reinforced lightweight self-compacting concrete (LWSCC) beams. An experimental study performed on eight full-scale shear deficient beam specimens. One beam served as the reference specimen and remaining beam specimens were internally reinforced with impregnated CFRP laminate stirrups. The parameters investigated in this study were the stirrup configuration, number of layers, stirrup spacing and width. Specimen tested under two-point loading and all results in term of load-deflection response as well as their failure modes were reported. All tested specimens failed due to shear compression failure mode along with the rupture of CFRP laminate stirrups, and the inclusion of CFRP laminate stirrups has significantly enhanced the nominal capacity of LWSCC beams ranged from 91%− 200% over control specimen. Shear strengths of the tested specimens were also theoretically predicted using different design standards. Comparison between the experimental and predicted shear strength has shown that ACI 440.1R-15, CSA S806–12, and CSA S6–14 provided the closest prediction. Therefore, it has been concluded that CFRP laminate stirrups can be used as a transverse reinforcement in GFRP reinforced LWSCC beams.

Shear strengthening performance of fiber reinforced lightweight SCC beams

In recent years, the demand for fiber reinforced lightweight concrete (FLWC) has increased rapidly to make high-strength, durable and lightweight structures. The strengthening behaviour of FLWC has never been studied in the literature and currently there are no standard guidelines for strengthened FLWC beams. Therefore, the main aim and objective of the current experimental study is to investigate the shear behaviour of fiber reinforced lightweight self-compacting concrete (FLWSCC) beams externally strengthened with CFRP strips. Six full-scale reinforced concrete (RC) beams were tested under four-point bending with varying CFRP strip spacing, number of layers, and configuration. One additional beam served as the control specimen to compare the performance of the strengthened specimens. The experimental results indicated that the external CFRP strips enhanced the strength and stiffness of the strengthened FLWSCC specimens. The strength enhancement ranged from 12% to 91% and pull out of steel fiber and debonding of CFRP strips was the predominant mode of failure in the control and strengthened specimens. The presence of steel fibers in the concrete has increased the shear strength of concrete and limits the external contribution of CFRP strips. Furthermore, all the experimental results were compared with theoretically predicted shear capacities using various FRP design standards for external strengthening. All the design standards have overestimated the shear capacity of FLWSCC specimens and CNR-DT (2013) design standard was found to be the most conservative as compared to other design standards. In addition, a lightweight modification factor has been recommended for strengthened FLWSCC beams

Torsion Improvement of Reinforced Self-Compacting Concrete Beams Using Epoxy Injection and CFRP

Few researchers have investigated the internal torsional reinforcement of box timbers, so little research has been conducted on this particular fortification method. The primary objective is to find out the possibility of adding a certain percentage of RCA to the NC mixtures, as well as verifying the success achieved in repairing the cracks that occurred as a result of torsion with CFRP or injecting with epoxy, which has not been addressed in previous research and literature reviews. This study reinforces reinforced SCC box columns subjected to complete torsion with CFRP sheets and epoxy resin injections. Four reinforced SCC specimens (the first beam with 0%, the second beam with 33.3%, the third beam with 67.7%, and the fourth beam with 100% RCA by weight) were subjected to pure torsion until failure. The dimensions and reinforcement of every specimen are identical. In addition, the applied torque-twist angle relationship at the midspan and end span was investigated. Bending experiments were performed to establish load-deflection curves and assess failure modes. After structural rehabilitation, all beams exhibited increased rigidity values, according to the results. Epoxy resin and CFRP sheet contributed to the specimens' increased ultimate load. The ultimate strength of RCA beams strengthened with CFRP and injected with epoxy increased. The specimens' flexural strength was considerably enhanced by the combination of surface roughness and fracture injection, and the effectiveness of using RCA was very good; it could be replaced with NCA in concrete mixtures, according to the ratio and need. Doi: 10.28991/CEJ-2023-09-11-05 Full Text: PDF

Structural Performance of Lightweight Fiber Reinforced Polystyrene Aggregate Self-Compacted Concrete Beams

This study aims to investigate experimentally the flexural behavior of lightweight Self-Compacted Concrete (SCC) beams made by Expanded Polystyrene (EPS) concrete and reinforced with rebars and steel fibers. To achieve the aims of this study, seven simply supported EPS lightweight fiber-reinforced concrete beams were fabricated and tested up to failure to study the effects of EPS content and the volume fraction of the steel fibers on their flexural behavior. The tested specimens were divided into two groups with one additional reference beam to be cast without using EPS or steel fibers. In the first group, three lightweight specimens were constructed using 25% EPS beads and were reinforced with 0%, 0.75%, and 1.5% steel fiber volume fractions. The second group is similar to the first group but was fabricated using 50% EPS beads. The test results showed that the mechanical properties of the hardened concrete were significantly reduced due to polystyrene EPS beads with some enhancement when steel fibers were added to the concrete mix. The flexure strength of EPS-LWT concrete beams was significantly reduced due to the polystyrene EPS beads. Furthermore, the results revealed remarkable enhancement in the flexure strength of the tested beams due to the steel fiber reinforcement.

Effect of Manufactured Sand Content on the Flexural Performance of Self-Compacting Lightweight Aggregate Concrete Beams

Effect of Manufactured Sand Content on the Flexural Performance of Self-Compacting Lightweight Aggregate Concrete Beams

Retracted: Electrochemical Preparation of Recycled Self-Compacting Concrete Composite Beams and Their Application in Prefabricated Buildings

Retracted: Electrochemical Preparation of Recycled Self-Compacting Concrete Composite Beams and Their Application in Prefabricated Buildings

Shear behaviour of SWSS-SCC beams reinforced with GFRP bars and Stirrups: Experimental and analytical investigations

This paper presents a study of shear behaviour of sea-water and sea sand self-compacting concrete (SWSS-SCC) beams reinforced with glass fibre reinforced polymer (GFRP) bars and stirrups. Nine full-scale beams were conducted and tested under four-point loading up to failure. The investigated experimental variables were the shear-span ratio, configuration of GFRP stirrups, type of the concrete, longitudinal reinforcement ratio and beam depth. The crack pattern, failure mode, load–deflection response, load–strain response and shear capacity of concrete beams were discussed. It is evident in the test results that the ultimate shear capacity of test specimens is enhanced by reducing the shear-span ratio, using the GFRP stirrups, improving the longitudinal FRP reinforcement ratio and increasing the beam depth. The shear behaviours of SWSS-SCC beam reinforced by GFRP bars and stirrups were found to be similar to that of fresh-water and river sand self-compacting concrete (FWRS-SCC) beam. The ultimate shear capacity of the test beams was predicted by the theoretical models reported in the literature. In addition, the effect of the experimental parameters on shear capacity was discussed and the theoretical models of shear strength were evaluated based on the summarized database. It is found that the nominal shear strength is barely affected by the axial compressive strength and is optimal when the longitudinal reinforcement ratio is about 2%. The CSA-S806 2012 specification has more accurate prediction results for the shear capacity of concrete beams reinforced with FRP bars and stirrups.

Structural assessment of Basalt FRP reinforced self-compacting geopolymer concrete using artificial neural network (ANN) modelling

Basalt FRP geopolymer composites are considered a sustainable solution to address the conventional OPC-Steel composite structures' structural and environmental concerns, especially the increased carbon emissions and structural deterioration due to corrosion attacks. Recent research on novel composites reports the superior performance of these FRP-geopolymer concrete structural applications reporting high strength and durability. However, the existing design guidelines do not accurately predict the flexural capacity and strength characteristics, which hinders the broader use of FRP-based geopolymer composites. This study aims to develop a prediction tool to help the researchers model the structural performance of the novel FRP-geopolymer composite based on modern machine learning algorithms. It shall address the lack of data on novel composites' structural and long-term performance in various exposure conditions. This paper thus reports the suitability of Artificial Neural Network (ANN) based models to accurately predict the flexural strength of Basalt FRP reinforced self-compacting geopolymer concrete beams under various exposure conditions. The ANN model is trained and validated against the experimental data from the long-term study conducted on the beam specimens subjected to one-year ambient and marine exposures. The ANN prediction model developed in this study reported close agreement with the experimental data showing better prediction accuracy than the existing empirical and numerical models.

Flexural Behavior of Self-Compacting Concrete Beams with Steel Fiber Reinforcement with B500 Ribbed Rebar

Flexural Behavior of Self-Compacting Concrete Beams with Steel Fiber Reinforcement with B500 Ribbed Rebar

Flexural Behaviour of SCC Beams Incorporating Industrial Wastes

Abstract: Self-Compacting Concrete (SCC) is a concrete form developed in Japan. Because of its novelty, this form of concrete differs from traditional concrete. Compaction is required for conventional concrete, but not for SCC which is utilized in substantially reinforced constructions where it is challenging to compact concrete. Industrial wastes such as Fly Ash (FA) and Cement Kiln Dust (CKD) [which contaminate the environment] are used as partial replacements for cement, and, Granite Powder (GP) and Eco Sand (EC) are used as partial replacements for M-sand. The optimum mix proportions of casted beams obtained by Taguchi method are SCC1 (FA30%), SCC2 (FA25%+CKD5%), SCC3 (FA30%+GP20%), SCC4 (FA25%+CKD5%+GP20%), SCC5 (FA30%+EC10%), and SCC6 (FA25%+CKD5%+EC10%). For each composition, the flexural behavior of SCC beams is experimentally investigated. Experimental work is verified by FEM analysis using the ABAQUS software. When the outcomes from the experimental and numerical analysis are compared, it is evident that SCC6 outperformed other mixes in terms of flexure

Structural behavior of reinforced lightweight self‐compacting concrete beams using expanded polystyrene as coarse aggregate and containing polyethylene terephthalate fibers

AbstractThrough this study, an attempt was made to produce concrete beams from self‐compacting concrete (SCC) contain expanded polystyrene (EPS) beads as coarse aggregate and waste plastic fibers (WPFs) produced from cutting disposed packing straps in site. The beams were designed according to ACI‐318‐14, where three different reinforcement ratios were chosen for the purpose of checking the conductance of thresholds made of this type of environmentally friendly concrete under bending loads. The use of EPS with WPFs had a significant positive effect in reducing the density of concrete, and the highest percentage of reduction was equal to (38.46%). Using WPFs had a positive effect in increasing the flexural toughness of concrete prisms, and the maximum increment was equal to (180%) compared with these made from the reference mix. The results proved the possibility of producing lightweight concrete from the use of EPS waste and WPFs, three of which are structurally can be classified as lightweight concrete combination of normal weight and lightweight aggregates according to specifications requirements of ASTM330/330M‐14. Reinforced lightweight SCC beams behaved under flexural loads similar to the reinforced concrete beams made from normal weight concrete counterparts under flexural loads.

Load-displacement characteristics of self-compacting steel fiber reinforced concrete beams

Measurements of ductility in steel-fiber (SF)-reinforced self-compacting concrete (SCC) are rarely studied, despite the fact that many studies have concentrated on enhancing our understanding of the ductility index of the reinforced concrete element. The objective of this analysis is to evaluate the resilience of SCC beams strengthened with SF in the face of impact loads. All together, twelve reinforced SCC beams (six beams per set) were subjected to flexural tests (with and without steel fibers). In this investigation, the use of three different concrete strengths (designated as M30, M60, and M90) and two different steel ratios (qmin and qmax.) were carried out. The ductility Energy index (μE). of the experimented SCC beams is calculated from the load–displacement curves (P). The results demonstrate that beam deformation and the resulting restricted cracking can be avoided thanks to the increased flexural toughness of the fibrous self-compacting concrete beam samples. Fibrous material growth to SCC is also shown to be highly efficient. Its flexural strength, ductility index, and energy dissipation rate are all ductility energy index (μE.). Steel fibre content, steel reinforcement to concrete, and concrete compressive strength all contribute to the material's flexural strength.

Performance of hybrid steel fiber-reinforced self-compacting concrete RC beam under flexure

Hybrid steel fiber-reinforced self-compacting concrete (HSFRSCC) has desirable properties for improving the performance of structures. But the literature is sparse on the flexural performance of the reinforced concrete (RC) beam reinforced with hybrid fibers. The impact of the combined action of micro- and hooked-end steel fibers on the flexural performance of the SCC beam to which mineral admixtures and superplasticisers have been added to improve their workability is investigated in this study. In the experiment, beam specimens, reinforced with micro-steel and hooked-end fibers, with a compressive strength of 60 and 80 MPa and of size 150×230×3000 mm were prepared. The results clearly demonstrate that the flexural performance of the SCC beam significantly improved with the addition of hybrid steel fibers. The combination of 0.5% of hooked-end steel fibers and 0.25% of micro-steel fibers offers a better flexural performance than the addition of hybrid fibers in other proportions. Adding hybrid steel fibers in RCSCC beam increases the beam’s load- and moment-carrying capacities by 40.64% and 40%, respectively, compared to the RCSCC beam without hybrid steel fibers. The crack spacing and crack width are also reduced by 16–45% and 25–75%.

An Investigation on Eco Friendly Self-Compacting Concrete Using Spent Catalyst and Development of Structural Elements

The theme of this initiative is "Waste to Wealth." Construction materials, particularly concrete, need to have better qualities, including strength, rigidity, durability, and ductility, because Oman's construction industry is expanding. Self-compacting concrete (SCC) has more benefits than regular concrete, including better workability. The major focus of this study is the C30-grade SCC for the control mix, spent catalyst (zeolite catalyst)-based SCC, and the development of the RC beam's flexural behavior employing control and spent catalyst-based SCC. The preliminary study and the main study are the two study outcomes included in this project. Preliminary research involves creating four mixtures with various dosages of 3%, 6%, 9%, and 12% in order to optimize spent catalyst in C30 grade concrete. All of the cubes undergo a 28-day curing test. The cubes' compressive strength is tested in order to establish the ideal dosage, which is 9%. Develop a C30 grade control modified design mix in accordance with SCC and optimize chemical admixtures such as superplasticizer (SP) at different dosages, like 2, 2.5, 3, and 3.5%, using various trials and tests (slump flow, L-box, J-ring, V-funnel, and U-box tests), as well as the optimized dosage of spent catalyst (SC). The main study includes six singly reinforced RC beams with dimensions of 750 (L)×100 (B)×150 mm (D) that were cast and tested in the laboratory. After a 28-day curing period, two specimens were placed under a two-point loading setup, with the remaining two samples receiving the optimum dosages of spent catalyst and superplasticizer. All of the beams were tested using a Universal Testing Machine (UTM) with a 1000 kN capability. From the preliminary study, partial substitution of cement in control concrete of grade C30 using spent catalyst (SC), it was found that the 9% optimum dosage produces greater compressive strength compared to other doses, which are almost 10% rises at 28 days of curing period. Based on a different test, it was discovered that the optimum dose of 3% SP gave closer agreement and satisfied the need for SCC as per the BS standard. The load-carrying capability of the SCC beams is almost 21.7% higher than that of the control beams. Comparing the SCC beams to the control beams, their deflection was reduced by about 26% at the same load level, and their ductility rose by almost 33%. Comparatively to the control beam, the stiffness of 21.6% of SCC also rises. According to test results, the SCC beam performs better in every way when superplasticizer and spent catalyst are used at the recommended dosage. Doi: 10.28991/CEJ-2023-09-05-08 Full Text: PDF