Search Results (28)

This systematic review and meta-analysis per PRISMA 2020 addresses the use of recycled concrete aggregates as a replacement for aggregates in self-consolidating concrete for structural and non-structural use. It provides a comprehensive evaluation of the available research and offers a synthesised overview of the potential use of recycled concrete aggregate in self-consolidating concrete beyond standardised replacement levels. A total of 256 research papers were obtained from different databases, and after a detailed content review, only 24 unique experimental research studies fulfilled the review criteria. Data were extracted on recycled concrete aggregate source, pre-treatment, replacement ratio, mix proportions, fresh properties, strength, stiffness, and durability. It was observed across all studies that the recycled concrete aggregates originated from precast concrete rejected elements with a low water-to-cement ratio, producing an equal or stronger concrete than the reference concrete in the studies; however, none of the studies included in this research resulted in a higher modulus of elasticity than the corresponding reference concrete. Additionally, moderate aggregate replacement (20–50%) preserved the workability, whereas high replacements (75–100%) affected fresh concrete properties as well as increased shrinkage and creep. The inclusion of fine recycled concrete aggregate in addition to coarse recycled concrete aggregate has a larger effect on lowering compressive strength and stiffness in the concrete. Overall, high-quality coarse recycled concrete aggregate (precast rejects or screened demolition waste)—an aggregate replacement level of around 50%—facilitates the production of sustainable self-consolidating concrete, whereas full replacement requires aggregate pre-treatment and a carefully optimised mix design. Full article

This article presents the results of a study on the influence of a three-level dispersed composition of the clinker component of a binder, which includes coarse, medium, and fine fractions, on the physical and mechanical properties of self-compacting concrete (SCC). One of the current challenges in SCC technology is enhancing its durability and resistance to aggressive environments while maintaining self-consolidating properties. Addressing this challenge holds significant engineering importance, especially for infrastructure under freeze–thaw cycles and chemical exposure. The work aimed to determine the optimal polyfractional composition that ensures the maximum packing density of cement binder particles and to assess the changes in the operational characteristics of SCC. A software and calculation complex featuring a three-dimensional modeling algorithm, Drop and Roll, was used to select the optimal composition. Experimental studies were conducted for mixtures with varying fraction contents, differing in average particle sizes of 12 μm, 6.6 μm, and 4.9 μm. It was found that the optimum composition, consisting of 15% of the 1500 cm²/g fraction, 75% of the 3000 cm²/g fraction, and 10% of the 4500 cm²/g fraction, contributes to an increase in compressive strength of 26%, bending strength of 10%, a times two increase in freeze-thaw resistance, a decrease in water absorption, and an improvement in chemical resistance to aggressive environments. The results confirm the effectiveness of optimizing the grain composition of the binder to enhance the durability and performance characteristics of SCC used in aggressive conditions. Full article

The rapid progression in concrete technology and the emphasis on improving the mechanical characteristics and durability of concrete, as well as the need for skilled workers, were key factors that led to the fabrication of self-consolidating concrete (SCC). The primary advantage of SCC is the elimination of vibrations during construction. This experimental study investigates the effect of nano-silica, nano-clay, and micro-silica with ratios of 2% and 4% on the properties of SCC. To reach this aim, rheological tests (flow slump, V-shape funnel, U-shaped box, and L-shaped box tests), mechanical tests (compressive strength, tensile strength, and flexural strength test), and durability tests (freezing, abrasion, and permeability tests) were carried out. The results demonstrated that the mechanical characteristics and durability of the concrete were enhanced by increasing the nano-silica content up to 4% of the cement weight. Also, the increase in the nano-clay content produced suitable results for SCC in terms of mechanical and durability aspects. However, as the nano-material ratio increases, the amount of superplasticizer also increased to ensure the proper workability of the SCC. Full article

There is a growing demand for sustainable solutions in civil engineering concerning the carbon footprint of cementitious composites. Alkali-Activated Binders (AAB) are materials with great potential to replace ordinary Portland cement (OPC), with similar strength levels and lower environmental impact. Despite their improved environmental performance, their durability remains a gap in the literature, influenced by aspects of mechanical behavior, physical properties, and microstructure. This paper aims to assess the impact of steel slag aggregates and curing temperature of a proposed AAB based concrete formulation by characterizing fresh state, mechanical behavior, and microstructure. The proposed AAB is composed of fly ash (FA) and basic oxygen furnace (BOF) steel slag (SS) as precursors, sodium silicate and sodium hydroxide solution as activators, in total replacement of OPC, using baosteel slag short flow (BSSF) SS as aggregate in comparison with natural aggregate. The concrete formulation was designed to achieve a high-performance concrete (HPC) and a self-compacting concrete (SCC) behavior. Mechanical characterization encompassed hardened (compressive strength and Young’s modulus), fresh state (J-ring, slump flow, and T50), and durability tests (scanning electronic microscopy, water penetration under pressure, and chloride ion penetration). The compressive strength (64.1 ± 3.6 MPa) achieves the requirements of HPC, while the fresh state results fulfill the SCC requirements as well, with a spread diameter from 550 mm to 650 mm (SF-1 class). However, the flow time ranges from 3.5 s to 13.8 s. There was evidence of high chloride penetrability, affected by the lower electrical resistance inherent to the material. Otherwise, there was a low water penetration under pressure (3.5 cm), which indicates a well-consolidated microstructure with low connected porosity. Therefore, the durability assessment demonstrated a divergence in the results. These results indicate that the current durability tests of cementitious materials are not feasible for AAB, requiring adapted procedures for AAB composite characterization. Full article

This study explores the influence of different concentrations of recycled concrete aggregate (RCA) on the fresh and hardened properties of self-consolidating concrete (SCC) in order to assess the structural suitability of the use of RCA in a precast concrete plant. The study particularly emphasizes the early strength of the produced concrete. The RCA was sourced from crushed concrete used in roadway applications and was sieved to replicate the characteristics of natural aggregate. Five different SCC mixes were produced, with RCA substituting 0%, 10%, 30%, 50%, and 70% of the natural coarse aggregate (NCA) by weight. For each different mix design, the hardened properties tested were the compressive strength and tensile strength. The fresh properties investigated were the passing and filling ability. Additionally, aggregate properties including grain size distribution and absorption of coarse aggregate were studied. The selected mix design follows a typical well-graded self-consolidating concrete mix with 28-day strength of 8000 psi (55.16 MPa). It was found that replacing up to 50% of the NCA with RCA improves the early strength of concrete without a significant impact on the fresh and hardened concrete properties. Full article

Self-consolidating concrete (SCC) is renowned for its outstanding workability and ability to seamlessly flow into intricate structures with minimal vibrations, achieved through the incorporation of chemical admixtures. This study pioneers an innovative approach by exploring the use of the cost-effective and readily available plant extract aloe vera mucilage (AVM) as a bio-admixture for SCC. The primary objective is to assess the impact of AVM on SCC formulations, including those comprising ordinary Portland cement (OPC) and blended cement LC³ (clinker 50%, calcined waste clay 30%, limestone 15%, gypsum 5%). AVM is applied at varying dosages at up to 10%. Findings reveal that LC³ exhibits lower consistency, reduced slump values, and extended initial and final setting times compared to OPC. With increasing plasticizer dosage, V-funnel and L-box values decrease. Notably, OPC samples with both plasticizers outperform LC³ in compressive strength at 7, 14, and 28 days. Significantly, a 2.5% AVM dosage demonstrates enhanced compressive strength in both OPC and LC³ samples. In summary, this research positions AVM as an innovative and comparable alternative to commercial plasticizers, contributing to reduced yield stress and increased slump flow in SCC. Full article

In this paper, the mechanical properties and bond strength of composite samples that consist of a conductive concrete (CC) layer and a self-consolidated concrete (SCC) layer are investigated. The bond strength study includes two parameters: (1) surface preparation and (2) casting and testing directions. The surface preparation study shows that, compared to the other methods in this study, the shear key method is the most suitable surface preparation method to fully utilize the CC in a composite. Moreover, the casting direction study reveals that the strength is heavily dependent on the type of test used along with CC’s layer positioning. The flexural strength study confirms that positioning the CC mix in the tensile region is beneficial since it can increase the flexural strength of a structure because of the hybrid steel fibers included in the mixture. Finally, different codes/specifications and published theoretical results are used to predict the CC’s mechanical properties, and the predictions are not as accurate as the SCC predictions, which can be attributed to the presence of conductive fillers in the CC mix. Full article

This paper presents an experimental investigation of the bond strength of reinforcing steel bars in tension in self-consolidating concrete (SCC). The effects of the reinforcing bar’s location, orientation, size, and coating on the bond strength with SCC were studied and compared to those with conventionally vibrated concrete (CVC). Several SCC mixtures were developed to cover a wide range of applications/components and material types. The fresh properties of the SCC mixtures were determined to evaluate their filling ability, passing ability and stability. Two hundred and thirty-four pull-out tests of rebars embedded in cubes, wall panels and slabs were conducted. Almost half of the tests were conducted to evaluate the bond with SCC and the other half with CVC. Load–slippage relationships were measured for each test. Pull-out test results were analyzed, and the bond strength was reported in two values: critical strength, which corresponds to slippage of 0.01 in. *0.25 mm); and ultimate strength, which corresponds to the maximum load. The critical strength of SCC and CVC were compared against the ACI 318-19 provisions and comparisons between the ultimate strength of SCC and CVC were conducted. The comparisons indicated that SCC has lower bond strength with vertical rebars than CVC, and a 1.3 development length modification factor is recommended. A similar conclusion applies to epoxy-coated and large diameter rebars. Also, SCC with high slump flow has shown a less top-bar effect than that of CVC. Full article

Self-consolidating concrete (SCC) has been used extensively in the construction industry because of its advanced characteristics of a highly flowable mixture and the ability to be consolidated under its own weight. One of the main challenges is the high content of OPC used in the production process. This research focuses on developing sustainable, high-strength self-consolidating concrete (SCC) by incorporating high levels of supplementary cementitious materials. The overarching purpose of this study is to replace OPC partially by up to 71% by using fly ash, GGBS, and microsilica to produce high-strength and durable SCC. Two groups of mixtures were designed to replace OPC. The first group contained 14%, 23.4%, and 32.77% fly ash and 6.4% microsilica. The second group contained 32.77%, 46.81%, and 65.5% GGBS and 6.4% microsilica. The fresh properties were investigated using the slump, V-funnel, L-box, and J-ring tests. The hardened properties were assessed using a compressive strength test, while water permeability, water absorption, and rapid chloride penetration tests were used to evaluate the durability. The innovation of this experimental work was introducing SCC with an unconventional mixture that can achieve highly durable and high-strength concrete. The results showed the feasibility of SCC by incorporating high volumes of fly ash and GGBS without compromising compressive strength and durability. Full article

Self-Compacting Concrete (SCC), a high-performance concrete with exceptional fluidity and cohesiveness, has gained popularity recently. The consolidation qualities and durability demands of this material require the application of Supplemental Cementitious Materials (SCMs). Alccofine is a type of additive material that has the potential to increase SCC characteristics while lowering the environmental effect of Portland cement manufacturing. In light of these facts, this study focused on the fresh, strength, and durability properties of SCC by partially replacing cement with varying percentages of alccofine such as 0%, 10%, 20%, 30%, 40%, 50%, and 60%. The fresh properties are examined using slump flow, T₅₀, V-funnel, and L-box as per ISO 1920-13. The mechanical and durability properties were investigated, such as compressive strength test, modulus of rupture, Young’s modulus of concrete and water absorption, sorptivity, sulphate resistance, and acid resistance, and were compared with conventional SCC. Results indicated that the replacement of 30% alccofine exhibited superior performance in both the strength and durability properties compared to other mixes. Full article

The addition of steel fiber to self-consolidating concrete (SCC) may considerably prolong concrete cracking time and improve its deforming performance. Current studies mainly apply high content micro-steel fibers to improve the mechanical performance of SCC whilst assuring its workability, however, there are still very few studies concerning the influence of a mixture of a high content of micro-steel fibers with ordinary steel fibers on the performance of SCC. Thus, this paper conducted experimental studies on micro-steel fiber and ordinary-sized steel fiber hybrid reinforced self-consolidating concrete (MOSCC). Plain self-consolidating concrete (PSCC), micro-steel fiber reinforced self-consolidating concrete (MSCC), and ordinary-sized steel fiber reinforced self-consolidating concrete (OSCC) are proposed for comparison with MOSCC in respects of workability and mechanical performance. Test results show that the hybrid micro-steel fiber and ordinary steel fiber highly enhance the compressive strength, flexural strength, and ductility of SCC as well as maintaining its workability. This paper provides reference to the improvement of the mechanical performance of SCC material and the enhancement of crack resistance of concrete structures. Full article

Self-consolidating concrete (SCC) is a well-known type of concrete, which has been employed in different structural applications due to providing desirable properties. Different studies have been performed to obtain a sustainable mix design and enhance the fresh properties of SCC. In this study, an adaptive neuro-fuzzy inference system (ANFIS) algorithm is developed to predict the superplasticizer (SP) demand and select the most significant parameter of the fresh properties of optimum mix design. For this purpose, a comprehensive database consisting of verified test results of SCC incorporating cement replacement powders including pumice, slag, and fly ash (FA) has been employed. In this regard, at first, fresh properties tests including the J-ring, V-funnel, U-box, and different time interval slump values were considered to collect the datasets. At the second stage, five models of ANFIS were adjusted and the most precise method for predicting the SP demand was identified. The correlation coefficient (R²), Pearson’s correlation coefficient (r), Nash–Sutcliffe efficiency (NSE), root mean square error (RMSE), mean absolute error (MAE), and Wilmot’s index of agreement (WI) were used as the measures of precision. Later, the most effective parameters on the prediction of SP demand were evaluated by the developed ANFIS. Based on the analytical results, the employed algorithm was successfully able to predict the SP demand of SCC with high accuracy. Finally, it was deduced that the V-funnel test is the most reliable method for estimating the SP demand value and a significant parameter for SCC mix design as it led to the lowest training root mean square error (RMSE) compared to other non-destructive testing methods. Full article

Self-Compacting Concrete (SCC) is a unique kind of concrete that tends to consolidate in terms of its weight. In this study, the prime target is to investigate the durability properties of SCC developed using eco-friendly economical waste binding materials as partial replacement to costly cement. This circular economy concept will not only help in the development of green concrete but will also help to improve the climatic condition by reducing the use and production of cement. An economical design methodology has been applied to produce environmentally friendly construction material. This research focuses on the application of Alum Sludge (AS) and Brick Dust (BD) in Self-Compacting Concrete (SCC). Both materials are waste materials containing binding properties. Performance of SCC developed using these two materials was tested considering mechanical properties of concrete using the destructive testing technique. Results showed that BD and AS can be utilized for up to 12% and 9% of replacement of cement, respectively, to achieve equal or higher compressive, tensile, and flexural strength. The application of BD and AS has demonstrated a subsequent improvement of SCC’s mechanical properties, i.e., compressive, tensile, and flexural strength. This study will help the production of composite green materials with the help of eco-friendly and economical waste materials for sustainable infrastructure development. Full article

This paper numerically investigates the required superplasticizer (SP) demand for self-consolidating concrete (SCC) as a valuable information source to obtain a durable SCC. In this regard, an adaptive neuro-fuzzy inference system (ANFIS) is integrated with three metaheuristic algorithms to evaluate a dataset from non-destructive tests. Hence, five different non-destructive testing methods, including J-ring test, V-funnel test, U-box test, 3 min slump value and 50 min slump (T50) value were performed. Then, three metaheuristic algorithms, namely particle swarm optimization (PSO), ant colony optimization (ACO) and differential evolution optimization (DEO), were considered to predict the SP demand of SCC mixtures. To compare the optimization algorithms, ANFIS parameters were kept constant (clusters = 10, train samples = 70% and test samples = 30%). The metaheuristic parameters were adjusted, and each algorithm was tuned to attain the best performance. In general, it was found that the ANFIS method is a good base to be combined with other optimization algorithms. The results indicated that hybrid algorithms (ANFIS-PSO, ANFIS-DEO and ANFIS-ACO) can be used as reliable prediction methods and considered as an alternative for experimental techniques. In order to perform a reliable analogy of the developed algorithms, three evaluation criteria were employed, including root mean square error (RMSE), Pearson correlation coefficient (r) and determination regression coefficient (R²). As a result, the ANFIS-PSO algorithm represented the most accurate prediction of SP demand with RMSE = 0.0633, r = 0.9387 and R² = 0.9871 in the testing phase. Full article

Supplementary cementitious materials (SCMs) and fillers play an important role in enhancing the mechanical properties and durability of concrete. SCMs and fillers are commonly used in self-consolidating concrete (SCC) mixtures to also enhance their rheological properties. However, these additives could have significant effects on the viscoelastic properties of concrete. Existing models for predicting creep and drying shrinkage of concrete do not consider the effect of SCM/filler on the predicted values. This study evaluates existing creep and drying shrinkage models, including AASHTO LRFD, ACI209, CEB-FIP MC90-99, B3, and GL2000, for SCC mixtures with different SCMs/fillers. Forty SCC mixtures were proportioned for different cast-in-place bridge components and tested for drying shrinkage. A set of eight SCC mixtures with the highest paste content was tested for creep. Shrinkage and creep test results indicated that AASHTO LRFD provides better creep prediction than the other models for SCC with different SCMs/fillers. Although all models underestimate drying shrinkage of SCC with different SCMs/fillers, the GL2000, CEB-FIP MC90-99, and ACI 209 models provide better prediction than AASHTO LRFD and B3 models. Additionally, SCC mixtures with limestone powder filler exhibited the highest creep, while those with class C fly ash exhibited the highest drying shrinkage. Full article