Self-consolidating Concrete Mixes Research Articles

Evaluation of aggregate segregation in self-consolidating concrete using 3D point cloud analysis

Self-consolidating concrete (SCC) is a widely used construction material known for its high workability. In general, the proportion of chemical admixture in SCC is higher than that of standard concrete, making it more susceptible to the segregation due to its low aggregate bearing capacity. To test the aggregate segregation, a variety of qualitative and quantitative methods have been proposed for either fresh or hardened SCC; however, the conventional methods are difficult to accurately investigate the segregation in advance of the construction. This study presents a novel method for evaluating the degree of segregation in fresh SCC at an early stage using point cloud data obtained from scanning the surface of SCC slump flow. The acquired point cloud provides three-dimensional (3D) spatial information, which can be used to calculate various parameters, including diameter, maximum height, and curvature. In particular, the volume of the segregation suspicious region (VSSR) is proposed to quantify the aggregate segregation of the fresh SCC. The reliability of the proposed method is evaluated by comparing the obtained spread diamters with those of the manual inspection, in which the average error is minimal (i.e., approximately 2.4%). Furthermore, the overall performance is compared with standardized qualitative tests and validated through digital image processing on hardened SCC samples, showing good agreement between the VSSR and the degree of segregation obtained from the image analysis. This method offers a comprehensive and efficient tool to assess segregation in the fresh SCC, contributing to improved quality control and optimization of SCC mix designs.

Analysis and Development of Innovative Concrete Compositions in the Republic of Bashkortostan

Self-consolidating concrete mix (SCC) is the innovative construction material meeting strict and current requirements. Due to high flowability thereof and own weight it is able to flow within and around the formwork with no vibration. The “Construction Materials” department at the Ufa State Petroleum Technological University together with experts from the “Reinforced Concrete and Masonry Structures” department at the Moscow National Research State University of Civil Engineering made a range of experiments for making compositions of the modern innovative concrete mix. Regional materials were taken as the original ones to be used for concrete compositions. Fresh concrete consistency, flowability (by slump and cone flow diameter), concrete life time, delamination by amount of bleeding water, strength of tested samples at 4, 7, 28 days of standard curing, density of hardened samples were monitored during the experiments. Under the laboratory results SCC recipes for В25, В30, В35, В40, В45 compressive strength grade were prepared. Laboratory SCC compositions by compressive strength for В25-В45 grade complied with the required technological characteristics. Under practical application of SCC some peculiarities were identified in the technology of making and pouring thereof to be considered to prevent defects in cast-in-situ constructions.

Comparing and evaluating influence of nylon fiber and fly ash in self compacting concrete

Self-consolidating concrete (SCC) is a special concrete that is highly flow able, non-segregating and self-expanding. Self-compacted concrete (SCC) is poured into the formwork without compaction and fills the formwork by its own weight. SCC is considered to have many advantages. Compared with conventional concrete as improved Construction quality, faster construction activity, lower cost etc. This project was carried out to evaluate the effects of addition of nylon fiber and fly ash on the fresh and hardened properties of SCC mixes. In this project, concrete mixes with nylon fiber of 0.5%, 1.5%, 2.5%, and fly ash with 0%, 15%, 30% and 45% were used to determine its permeability, flow Capacity, evaluated on the basis of and separation resistance, slump flow, L-box and V-funnel tests. After 3 days, 14 days, 28 days of curing SCC cylinders, compressive and splitting tensile strength were tested. The test results show that nylon fibers increase permeability but decrease the filling capacity and segregation resistance of SCC. Furthermore, it can be concluded that after 3 days, 14 days, 28 days of curing, the test of concrete samples showed that the addition of nylon fiber up to 2.0% of cement by volume increased the compressive strength of SCC. Strength, improves tensile strength but 2.5%. Nylon fiber reduces the compressive strength, tensile strength of hardened SCC.

Variability of Lightweight Aggregate Source: Effect on the Development of High Strength Lightweight SCC Matrix Blended with Normal Weight Aggregate

Structural lightweight concrete is a valuable alternative to normal weight concrete. Concrete prepared with coarse lightweight aggregate provides reduction of a structure self-weight and better structural performance in regions prone to seismic activities. However, variability of the coarse lightweight aggregate affects production and properties of the concrete. In addition, availability of the aggregate influences the long-term use and stability in the construction industry. Lightweight aggregate is imported from Iran, Turkey, Saudi Arabia, UK, and Greece to the United Arab Emirates (UAE) and has been used in structural and non-structural applications. This paper presents the development of a self-consolidating high strength lightweight concrete (SCHSLWC) matrix with available materials in UAE. Specific gravity, unit weight, gradation, particles’ shape and absorption were used during the development and selection of aggregates source. In addition, percentage of normal weight aggregate that could be used to improve the matrix was optimized. Results of the experimental investigation showed that self-consolidating concrete mixes with more than 50 MPa cube compressive strength could be produced with aggregates having specific gravity factors in the range of 1.15 to 1.4. Additionally, up to 12% per volume of the coarse lightweight aggregate could be replaced by normal weight coarse aggregate while maintaining a unit weight less than 2000 kg/m3.

A comparative study of natural pozzolan and fly ash: Investigation on abrasion resistance and transport properties of self-consolidating concrete

• Potential for use of natural pozzolans in self-consolidating concrete (SCC) was investigated. • Performance of natural pozzolan and fly ash in self-consolidating concrete was compared. • Mechanical and transport properties, drying shrinkage, and abrasion resistance of concrete were investigated. • Natural pozzolans performed at the same level of fly ash showing a proper replacement for fly ash in SCC. This study compared the influence of natural pozzolan with fly ash, as Supplementary Cementitious Material (SCMs), on properties of Self-Consolidating Concrete (SCC) with particular focus on abrasion resistance and transport properties. Natural pozzolan and fly ash replaced a portion of portland cement at the levels of 0, 15, 22.5, 30, and 37.5% by mass. A set of comprehensive experimental program was devised to measure fresh properties (slump flow, J-ring, T 50 and U-box), mechanical properties (compressive strength and modulus of elasticity), drying shrinkage, transport properties (rapid chloride penetration and rapid chloride migration tests, water permeability and absorption, and capillary water absorption) and depth of wear. Overall, the results indicated that replacing 15 and 22.5% of portland cement with SCM, decreased final depth of wear for SCC mixes. However, the observed improvements were diminished with increases in dosage of SCM. Use of SCMs led to similar or improved performance in terms of mechanical and transport properties, specifically at later ages of curing, showing potential for use of fly ash and natural pozzolan in SCC. Considering all the tests carried out, natural pozzolan performed at the same level of fly ash showing its great potential for use in SCC to achieve the same performance. This is of great importance considering the shortage of fly ash in recent years.

PRODUCTION OF LOW-COST SELF-CONSOLIDATING CONCRETE (SCC) USING MANUFACTURED AGGREGATES

Limitations to the sources of aggregates and the unavailability of sand is becoming a problematic issue for concrete production. A novel technology of manufactured aggregates can produce well graded round aggregates that can substitute natural aggregates while maintaining the same characteristics needed and preserving the resources. Self-Consolidating Concrete (SCC) using manufactured aggregates is assessed in this experimental work to understand the variability of workability properties and mechanical properties with the changes in w/c ratio and percentages of Coarse Aggregates and Manufactured Sand to Natural Sand in order to choose the best mixture that satisfies an adequate overall performance. Targeting compressive strength improvement, the SCC mixes included the use of Silica Fume (SF) and Polycarboxylate Superplasticizer which exhibited a strength improvement when compared to normal SCC. After performing 6 different trial mixtures, the use of manufactured rounded aggregates of percentages 73% from total fine aggregates proportion, 2.7% of Polycarboxylate superplasticizer, and around 8% Silica Fume (SF) from total cementitious materials can succeed in reaching high strength concrete with optimum mechanical properties and a noticeable workability improvement when compared to natural aggregates.

Influence of Mixture Proportions on Fresh and Mechanical Properties of Self-consolidating Concrete

Self-consolidating concrete (SCC) is a concrete that able to flow and consolidate under its own weight, and it is cohesive enough to fill spaces of almost any size and shape without segregation or bleeding. In this study, workability and strength characteristics of seven SCC mixes were examined and compared with two additional vibrated mixes of normal and high strength. For this purpose, the flowability, deformability, and passing ability of fresh concrete mixes were tested through slump test, slump flow, T500, and the J-ring tests. Furthermore, the hardened concrete specimens were tested for mechanical properties with the variation in shape and size of the specimens at six different ages. The results revealed that addition of micro-silica is more effective in improving concrete workability and strength than blended micro-silica and fly ash. A well-designed SCC could have an excellent flow (730 mm) and passing ability (ΔH = 4 mm), without sacrificing the early strength (22.3 MPa in 1 day), or long-term strength (107.7 MPa in 90 days). Results also showed that the compressive strength and the tensile strength of SCC mixes were less affected by specimen shape and size compared to conventional concrete mixes.

Utilizing Artificial Intelligence to Predict the Superplasticizer Demand of Self-Consolidating Concrete Incorporating Pumice, Slag, and Fly Ash Powders.

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.

Combined Recycling of White Rice Husk Ash as Cement Replacement and Metal Furnace Slag as Coarse-Aggregate Replacement to Produce Self-Consolidating Concrete

According to empirical evidence, high levels of energy and considerable amounts of natural resources are used in the production of concrete. Given the context, this study explores self-consolidating concrete (SCC) that includes rice husk ash (RHA) and metal furnace slag (MFS) as an alternative to cement and the natural aggregates in standard SCC mixes. In this study, mixture designs are investigated with 20 wt.% of RHA, 10–30 wt.% of MFS and water-to-powder material ratios of 0.30 and 0.40. Based on the findings regarding the fresh-state, hardened-state, and durability properties of the resulting SCC mixes, it is evident that the use of RHA and MFS can significantly improve the properties of concrete. The highest compressive strength was achieved for SCC with 20 wt.% RHA and 10 wt.% MFS. This outcome should be used as a basis for further investigations into the production of concrete materials that are both high-performance and sustainable.

Compressive Strength, Splitting Tensile Strength, and Chloride Penetration Resistance of Concrete with Supplementary Cementitious Materials

This article presents the outcomes of a study that examined the durability and mechanical characteristics of self-consolidating concrete (SCC) mix in which a percentage of the required ordinary Portland cement (OPC) was substituted with either fly ash or ground granulated blast furnace slag (GGBS). The first part of the study evaluates the chloride penetration resistance and compressive strength of SCC mixes in which OPC in a designed control mix was partially replaced in a series of mixes by fly ash in percentages ranging from 10% to 40%. It noted that replacing OPC with fly ash at each of the four percentages studies improved chloride resistance of concrete compared to the control mix made of 100% OPC as binder. The 40% fly ash mix was the best performer in terms of resistance to chloride migration in contrast with the 100% OPC mix. Samples prepared using the 40% fly ash mix SCC mixes had the lowest compressive strength after 7 days of moist curing. However, the 28-day compressive strength of 40% fly ash mix was a healthy 55.75 MPa, only slightly lower than the 100% OPC mix. Tests also showed that adding 2% or fewer basalt fibres to the SCC mix in which 40% of OPC improves concrete resistance to chloride migration in contrast with the 40% fly ash mix that didn’t contain basalt fibres. This paper also reports the relationship between splitting tensile strength and compressive strength of SCC mixes in which up to 80% of OPC was substituted with GGBS. A total of eight mixes were produced by varying the amounts of GGBS used to replace the OPC content of the control mix. The fresh properties were assessed through the flow test, visual stability index (VSI), and the T50. An empirical relationship was developed to predict the splitting tensile strength based on 28-day compressive strength, and its accuracy was evaluated in comparison to formulas in various design codes.

An experimental study on transfer length of prestressing strand in self-consolidating concrete

Due to its economic advantages, the use of self-consolidating concrete (SCC) has increased rapidly in recent years. However, because SCC mixes typically have decreased amounts of coarse aggregate and high amounts of admixtures, industry members have expressed concerns that the bond of prestressing strand in SCC may be compromised.Therefore, the objective of this research program was to investigate the transfer lengths of prestressing strand in SCC. Transfer lengths of 12.5 mm diameter (0.5-in.), Grade 270 prestressing strand were evaluated using rectangular beams constructed from normal and high strength conventional concrete and SCC mixes. Strain readings over 56 days were used to calculate transfer lengths of beams. Results indicated that bond performance of SCC is superior to conventional concrete and that AASHTO and ACI equations for transfer length were generally conservative.

Effects of steel fibers on flexural strength and impact resistance for self-consolidating concrete plates

Self-Consolidating Concrete (SCC) can be considered as a major innovative satiric expansion in the future of concrete materials and technology during the recent three decades. It has evolved to make adequate compaction with easy concrete placement in constructions, which have overcrowded the restricted zones and reinforcement. This research aims to experimentally study the effect of steel fibers volumetric ratio (Vf ) and effect of chicken wire in enhancement of the behavior of the normal strength SCC. Two types of SCC concrete mixes were prepared and cast for this purpose. One of them was normal strength SSC to serve as a reference mix, while 0.75 % of steel fibers was used in the second one. Slump-flow test, L-box, J-ring and V-funnel tests had been done to investigate the properties of fresh SCC. Compressive strength of the reference SCC was about (33.5MPa) and for 0.75% steel fibers SCC was about (39.7MPa). In addition to that, six identical plate’s specimens of (400×400×20) mm were cast and tested to study the effect of steel fibers and chicken wire on the impact load resistance and flexural load of SCC. Results show that the impact load resistance for steel fibers SCC concrete had been increased by about 60% compared with the reference normal strength SCC mix, while an increase in impact load resistance for SCC of about 50% was gained by using chicken wire mesh. It was noted that the use of 0.75% steel fibers-SCC and chicken wire-SCC plates show an increase in impact resistance and flexural strength by about 20% and 2% compared to the reference normal strength SCC, respectively. The results also indicate that using steel fibers is useful in holding up the formation of transverse cracks and providing affirmative restraint to the successive growth of cracks of plate’s specimens.

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.

Comparative study on direct shear behavior of manufactured and recycled shredded tyre steel fiber reinforced self-consolidating concrete

This article presents the experimental study on the shear behavior of self-consolidating concrete (SCC) reinforced with recycled steel fibers (RSF), obtained from scrap tyres and manufactured steel fibers (MSF). A total of seven mixes were prepared viz SCC with no fiber as control mix, SCC with the inclusion of MSF with 0.5%, 1.0% and 1.5% volume fraction and RSF with varying volume fractions of 0.5%, 1%, and 1.5%. To increase the workability and viscosity of SCC, fly ash and silica fume (SF) was added in an appropriate proportion. The use of these materials promotes the sustainable use of waste. It was observed that the shear strength of SCC mix with RSF improved as compared to that of plain SCC but decreased as compared to SCC with MSF. A statistical model based on experimental data has been developed for predicting the shear strength of SCC containing MSF and RSF. An attempt has been made to predict the shear strength of mixes used in studies available in the literature.

Optimization of high-strength self-consolidating concrete mix design using an improved Taguchi optimization method

Since many parameters are involved in the concrete mix design, finding the optimal mixing design has always been a problem for concrete engineers. In this research, the Taguchi optimization method is improved to model to optimum mix design of the high strength self-consolidating concrete (HSSCC). For this purpose, at first different quality criteria and the parameters influencing them were defined based on the available literature. The Taguchi approach was then utilized to generate an the orthogonal array of the parameters. The experimental tests were then conducted according to the suggested design array in order to obtain the experimental data for each and every single scenario. The Best-Worst method is then adopted for pairwise comparisons of the quality criteria and experiments as such to obtain the overall weights of experiments with respect to each quality characteristics. Analysis of variance was also utilized to appraise the effective factors and the optimal mixture design. It was found that the proposed method was efficient in obtaining the optimal mixture design of the manufacturing process according to decision makers’ preferences. The experimental results indicated a significant improvement in the total quality of concrete compared to the decision maker’s estimated mixture design. The cement amount, water to cementitious ratio and mixing time are the most significant parameters affecting the concrete mix design.

Bond performance of prestressing strand in self-consolidating concrete

An experimental investigation was conducted to study the bond of prestressing strand in self-consolidating concrete (SCC). The bond of 12.5-mm-diameter (0.5 in.), Grade 270 prestressing strand was evaluated using both the large block pullout test (LBPT) and the North American Strand Producers (NASP) test for both normal and high strength conventional concrete (CC) and SCC mixes. (The NASP test has now been formally adopted as ASTM A1081.) Results indicated that there was a strong correlation between the NASP and LBPT pullout loads in this study (R2 = 0.93). Furthermore, the NASP and LBPT pullout loads can be considered fairly accurate with respect to relative bond between strands, but in terms of absolute bond and rejecting or accepting strand based on set limits, the NASP test passed all three types while the LBPT only passed one out of the three. In addition, the statistical data analysis (both parametric and nonparametric) confirmed that SCC mixes had higher bond strength than the CC mixes.

Characterising the segregation of self-consolidating concrete using ultrasonic pulse velocity

Segregation is the unintentional separation of the fresh components of concrete or mortar, which can have negative impacts on the mechanical, transport and durability properties of the cured product. The problem is acute in self-consolidating concrete (SCC), because of its high fluidity level. To help evaluate segregation, this paper investigates the potential of using ultrasonic pulse velocity (UPV) as a means to identify and characterise segregation in traditional and SCC mixes. Fourteen different concrete mixes were tested using standard techniques (sieve and column) in comparison with the UPV-based test proposed herein. Six of the 14 concrete mixtures were stable, as indicated by having sieve segregation indices lower than 15% and segregation resistances (f) higher than 95%. These six stable samples displayed UPV segregation index values (fu) approaching 100%. The remaining samples were found to be unstable concretes with sieve segregation index values higher than 15% and resistance index values lower than 65%. These concretes could also be clearly identified as unstable by a UPV segregation index lower than 80%. The UPV method provides a clean, quick and easy nondestructive alternative for testing segregation of both fresh and hardened concrete.

Modeling chloride penetration in self-consolidating concrete using artificial neural network combined with artificial bee colony algorithm

This paper examines the robustness of a feed forward artificial neural network combined with an artificial bee colony algorithm (FF-ABC) in the prediction of chloride penetration in self-consolidating concretes. To this end, several self-consolidating concrete mixes were made using various mix proportions, and their rapid chloride penetrations (RCPT) were measured. The mix proportions and RCPT results were used as input and output variables, respectively, to train and test the proposed method. To verify accuracy of the FF-ABC model, its performance was compared to linear regression, genetic algorithm (GA), and particle swarm optimization (PSO) models. This comparison was conducted in three stages of training, validation, and testing. Results of this study indicate higher reliability of the FF-ABC model in comparison with the statistical, GA, and PSO models.

Fundamental Fresh State Properties of Self-Consolidating Concrete: A Meta-Analysis of Mix Designs

The study reported in this paper is the first meta-analysis aimed at obtaining statistical models for the fresh state behavior of self-consolidating concrete (SCC) mixes which effectively reproduce the complex relationships between mix design and fresh state performance. A database compiled with data from more than 120 different sources was analyzed. This study proves that SCC fresh state performance is determined by three fundamental, uncorrelated properties: flow time, flow spread, and resistance to segregation, which constitute a robust mathematical framework for the optimization of SCC mixes. The models obtained for these fundamental properties have proved consistent and reproduce very well the general trends and interactions implicit in SCC mix design recommendations, which in effect constitute the mathematical validation of recommendations well sanctioned by practice. It has been proved that, if no supplementary cementitious materials (SCMs) are used, there is a remarkably narrow margin in which the three fundamental properties of fresh SCC mixes can be simultaneously optimized. The most stable mixes were found to be associated with sand-to-coarse aggregate ratios of at least 1.1. The flowability of SCC mixes in terms of both flow times and flow spread can be optimized when the following conditions concur: w/c ratio of 0.45, SCMs content below 100 kg/m3, and sand content not lower than 750 kg/m3. Furthermore, it was also proved that, in general, it is best to keep the dosages of superplasticizers (HRWRs) and viscosity-modifying agents (VMAs) below 1.7% and 0.7%, respectively, subject of course to variation across the different types of products available.

Behaviours of sustainable self-consolidating concrete exposed to elevated temperatures

The collapse of the structures may be initiated by fire, which is considered one of the most severe risks. However, there are several conditions in which structures may be exposed to elevated temperatures such as nuclear applications; factory procedures; and fires in tunnels or buildings due to accidents or terrorist attacks. Recently, Self-Consolidating Concrete (SCC) has become more broadly used, and there is thus a need to recognise its behaviours when subjected to elevated temperatures, particularly in terms of sustainable SCC. Seven sustainable SCC mixes were thus investigated in this study, each incorporating certain green materials (Portland limestone cement, high volume Class F fly ash, and locally available cement kiln dust (CKD)). All mixes were subjected to temperature levels of 200 °C, 400 °C, 600 °C, and 800 °C for two hours and cooled to room temperature either slowly (air cooling) or rapidly (water cooling). The residual (compressive, splitting, and flexural) strengths and modulus of elasticity were calculated. The results indicated that SCCs with high volumes of Class F fly ash showed the best performance when subjected to elevated temperature.