Fresh Properties Of Self-consolidating Concrete Research Articles

Influence of Admixture Source on Fresh Properties of Self-Consolidating Concrete.

The study presented herein was intended to (1) compare the optimum (minimum) dosage requirements of four different sources of polycarboxylate-based high-range water-reducing admixtures (HRWRAs) and viscosity-modifying admixtures (VMAs) in attaining slump flows of 508 mm, 635 mm, and 711 mm, and a visual stability index (VSI) of 0 (highly stable concrete) or 1 (stable concrete), and (2) assess the flowability/viscosity, stability, passing ability, and filling ability of the resulting self-consolidating concretes. The test results showed that the optimum dosage requirements to obtain a uniform slump flow and visual stability index varied among the four selected admixture sources. The required dosage amount for HRWRAs was highest for the polycarboxylate-ester (PCE) type and lowest for the polycarboxylate-acid (PCA) type. Acceptable flowability plastic viscosity dynamic and static stability, passing ability, and filling ability of self-consolidating concrete can be achieved with the proper dosing of the four studied admixture sources.

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.

Application of Artificial Intelligence to Evaluate the Fresh Properties of Self-Consolidating Concrete.

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.

Effects of nano-TiO2, nano-Al2O3, and nano-Fe2O3 on rheology, mechanical and durability properties of self-consolidating concrete (SCC): An experimental study

The objective of this study is to assess and compare the effects of different nanoparticles, namely nano-TiO2, nano-Al2O3 and nano-Fe2O3, on the performance of self-consolidating concrete (SCC) in terms of fresh, mechanical, and durability properties through performing different experiments. TiO2, Al2O3, and Fe2O3 nanoparticles with the average diameter of 18, 15, and 14 nm were used with two different contents of 3% and 5% by weight of cement. For assessing the fresh properties of SCC, slump flow, V-funnel, L-box, and column segregation tests were conducted. For the mechanical properties, compressive strength of concrete was investigated, and for the durability properties rapid chloride migration (RCM), electrical resistivity, rapid chloride penetration (RCP), and water penetration depth tests were carried out. The result showed that the workability properties of the mixes slightly improved by 3% addition of nanoparticles while increasing this value to 5% decreased the workability. For higher content of nanoparticles, the incorporation of nanoparticles in the mixes increased the water demand and consequently caused a reduction of workability.For compressive strength, nano-Fe2O3 showed a superior effect on the enhancement of strength in comparison to nano-Al2O3 and nano-TiO2. This observation was attributed to the formation of calcium ferric hydrate (C-F-H) gel in the microstructure. Moreover, the addition of all the nanoparticles resulted in an improvement of durability properties. High surface area of nanoparticles provided nucleation sites for cement particles and expedited the hydration process development. The formation of a higher content of hydration products helped the densification of microstructure. Moreover, nanoparticles controled the growth pattern of C-S-H gel, which led to the formation of a homogenous microstructure with smaller pore sizes and consequently to lower permeability against penetration of aggressive ions i.e., chloride. It is concluded that partial replacement of cement with nanoparticles on average improved the compressive strength and durability properties of SCC, but resulted in a reduction of workability.

Changes in rheology of self-consolidating concrete induced by pumping

Abstract Pumping is an easy and flexible process to place concrete inside a formwork. Many studies have recently been performed to understand and optimize the pumping process and identify the main differences between pumping of conventional vibrated concrete and self-consolidating concrete (SCC). However, due to pumping, changes in fresh concrete properties and the air-void system have been noticed. This paper describes the consequences of pumping on the fresh properties of SCC by means of two experimental pumping campaigns. In many cases, the concrete undergoes a large shear rate in the pipe, thus (re-)dispersing cement particles. This is expected to be the main cause of the observed decrease in plastic viscosity, V-Funnel flow time and pumping pressure resulting from increased flow rate or pumping time. The changes in yield stress or slump flow are anticipated to be influenced by the same phenomenon, but the final outcome is assumed to depend on the availability of residual superplasticizer in the mixing water. Pumping can cause a stable SCC to become segregating if both the yield stress and plastic viscosity decrease, or it can provoke a significant loss in filling ability, passing ability and self-consolidation of the concrete if the yield stress increases dramatically.

Ground copper slag as a supplementary cementing material and its influence on the fresh properties of self-consolidating concrete

This paper reports on an experimental programme to investigate the effect of using ground copper slag (GCS) as a replacement of cement on the fresh properties of self-consolidating concrete (SCC). Totally, seven self-compacting ground copper slag concrete (SCGCSC) mixtures were made with a fixed water–powder ratio of 0.51 in which a portion of the cement was replaced by GCS in weight ratios of 0%, 5%, 10%, 15%, 20%, 25% and 30%. The fresh properties were investigated by slump-flow, visual stability index, V-funnel, J-ring, L-box, air content, screen stability and setting time tests. The SCGCSCs were designed to give a constant slump flow of 680 ± 30 mm which was achieved by using the super-plasticiser at varying amounts. This allowed us to have a reasonable comparison of the obtained results. Totally, it has been concluded that using GCS significantly increased the workability of SCC mixtures. As the GCS increased, the slump flow is also increased at a constant amount of water and super-plasticiser, but t...

Influence of mixture composition on the properties of SCC incorporating metakaolin

This paper studies and evaluates the properties of self-consolidating concrete (SCC) containing different percentages of metakaolin (MK) by varying the mixture components and mixture proportions. In total, 32 mixtures with varied percentages of MK and mixture compositions are investigated for the effects on compressive strength, flowability, passing ability and high-range water-reducer admixture (HRWRA) demand. The percentage of MK, coarse-to-fine aggregate (C/F) ratio, coarse aggregate size, binder content and percentage of air entrained in the mixture are varied to study the influence of these variables on the fresh properties of SCC containing MK. SCC mixtures containing silica fume and SCC containing slag are also tested for comparison. The results show that increasing the percentage of MK up to 20% in SCC increases the compressive strength, viscosity, passing ability and HRWRA demand, but decreases the flowability of the mixture. In addition, the flowability of SCC mixtures improves with larger aggregate size, higher binder content and higher percentage of entrained air. The passing ability of SCC mixtures also improves with lower C/F ratio, larger aggregate size, higher binder content and the inclusion of entrained air in the mixture. The results also indicate that increasing the binder content or increasing the percentage of the entrained air has the most significant effect on improving the fresh properties of SCC mixtures.

Properties of freshly mixed carbon fibre reinforced self-consolidating concrete

This study examined the effects of discrete pitch-based carbon fibres on the fresh properties of self-consolidating concrete. Different carbon fibre reinforced self-consolidating concrete mixtures were produced incorporating 0%, 0.25%, 0.5%, 0.75% and 1% carbon fibres by concrete volume with two water-to-binder ratios (0.35 and 0.40). The flowing ability (filling ability and passing ability) of the concrete mixtures was determined with respect to slump flow, J-ring slump flow, and T50 slump flow time. The segregation resistance of the concrete mixtures was evaluated by using the sieve stability test. Visual stability index (VSI) was also used to assess the segregation resistance of concrete. Moreover, the freshly mixed concrete mixtures were tested for air content and unit weight. The hardened concretes were tested by a Scanning Electron Microscope to observe the distribution of fibres. Test results revealed that the increased amount of carbon fibres decreased the filling ability and passing ability of concrete. However, carbon fibres had no adverse effects on the segregation resistance of concrete. Also, no significant air entrapment occurred in the presence of carbon fibres. Carbon fibres were well-distributed and they slightly decreased the unit weight of concrete.

Correlations between Fresh Properties of Self-Consolidating Concrete Including Palm Oil Fuel Ash

Palm oil fuel ash (POFA) has been used successfully as a supplementary cementing material in various types of concrete. In the present study, self-consolidating concrete (SCC) was produced by using POFA as a partial replacement of ordinary portland cement (OPC). In total, sixteen SCC mixes were prepared by varying water to binder (W/B) ratio, POFA content, and high-range water reducer (HRWR). POFA was used by replacing 0–30% of OPC by weight at the W/B ratios ranging from 0.25 to 0.40. The filling ability, passing ability and segregation resistance of various SCC mixes were investigated. The filling ability was determined with respect to slump flow, 50-cm slump flow time, inverted slump cone flow spread and time, and V-funnel flow time. The passing ability was examined with respect to J-ring flow. In addition, the segregation resistance was assessed with regard to sieve segregation index and column segregation factor. Based on the data obtained, the correlations for the fresh properties of SCC were sought. The experimental findings showed strong correlations between most of the fresh properties of SCC.

Effects of recycled concrete aggregate on the fresh properties of self-consolidating concrete

Concrete wastes are generally delivered to the landfill sites for disposal. Due to increasing charges of landfill and scarcity of natural coarse aggregate (NCA), recycled concrete aggregate (RCA) derived from concrete wastes is growing interest in construction industry. In the present study, RCA was used as partial and full replacements of NCA to produce self-consolidating concrete (SCC). Different SCC mixes were produced with RCA substituting 0%, 30%, 50%, 70%, and 100% NCA by weight. The water to cement (W/C) ratio and high-range water reducer (HRWR) dosage were kept the same for all concretes. The effects of RCA on the key fresh properties such as filling ability, passing ability, and segregation resistance of SCC were investigated. The test results revealed that the filling ability and passing ability of SCC were improved for 30% and 50% RCA. The SCC mixes with 30% and 50% RCA also possessed adequate segregation resistance. In addition, strong correlations were observed for filling ability, passing ability, and segregation resistance. The overall test results suggest that RCA can be used to produce SCC substituting up to 50% NCA without affecting the key fresh properties of concrete.

Influence of Hauling Time on Fresh Properties of Self-Consolidating Concrete

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Statistical Models to Predict Fresh Properties of Self-Consolidating Concrete

In order to understand the influence of mixture parameters on concrete behaviour, a factorial design was employed in this investigation to identify the relative significance of primary mixture parameters and their coupled effects (interactions) on fresh properties of SCC that are of special interest to precast, prestressed applications. In addition to the 16 SCC mixtures employed, three SCC mixtures corresponding to the central point of the factorial design were prepared to estimate the degree of the experimental error for each of the modeled responses. The mixtures were evaluated to determine several key responses that affect the fresh properties of precast, prestressed concrete, including filling ability, passing ability, filling capacity, surface settlement, and column segregation. Mixture parameters modeled in this investigation included the binder content, binder type, w/cm, sand-to-total aggregate ratio (S/A), and dosage of thickening-type, viscosity-modifying admixture (VMA). The factorial design can identify potential mixtures with a given set of performance criteria that can be tried in the laboratory, hence simplifying the test protocol needed to optimize SCC.

Effects of Hauling Time on Air-Entrained Self-Consolidating Concrete

Self-consolidating concrete (SCC) is a highly flowable concrete that is characteristically sensitive to mixing and hauling variables such as transportation time. In real-world applications, lengthy hauling times are often necessary for transportation to the job site and can result in deviations in the fresh properties of SCC. In this investigation, air-entrained SCCs were developed at a constant water-to-cementitious material ratio (w/cm) of 0.40 and air content of 6% for 3 distinct slump flows of 559, 635, and 711 mm (22, 25, and 28 in.). Test results revealed that the slump flow losses up to 39% were recorded after 90 minutes of hauling time. The air content increased with hauling time, ranging from 2.6-4.8%. The air void characteristics improved with hauling time, with an average increase in specific surface of 9.5 mm–1 (241.3 in.–1) and an average decrease in spacing factor of 64 μm (0.0025 in.).

Influence of paste/mortar rheology on the flow characteristics of high-volume fly ash self-consolidating concrete

Self-consolidating concrete (SCC) is known for its excellent deformability, high resistance to segregation and use without applying vibration in congested reinforced concrete structures characterised by difficult casting conditions. The rheology of paste and mortar is important to understand the flow behaviour of SCC. The current paper presents the results of a comprehensive investigation to establish correlations among the rheological parameters of paste/mortar (such as yield stress and plastic viscosity) and the fresh properties of concrete mixtures incorporating high volumes of fly ash (FA) (such as slump flow, flow time, filling capacity and segregation index) in order to predict the flow behaviour of corresponding SCC. The specific Marsh cone flow time of paste and fresh properties of concrete were also correlated. Twenty-one mixtures of paste, mortar, and concrete with four variables such as total binder content (350–450 kg/m3), percentage of FA as cement replacement (30–60% by mass), percentage of superplasticiser (SP) (0·1 to 0·6% by solid mass), and water-to-binder ratio (w/b) (0·33–0·45) were investigated. An attempt had been made to identify the range of rheological parameters of paste and mortar to achieve desired fresh properties such as flowability and self-consolidation of corresponding SCC. The prediction of the rheological parameters of paste/mortar is relatively easy compared with the prediction of the fresh properties of SCC. Establishment of correlations among the rheological parameters of paste/mortar and fresh properties of SCC can save time and energy associated with the mix proportioning of a satisfactory FA SCC.

Development of high-volume low-lime and high-lime fly-ash-incorporated self-consolidating concrete

The current article presents an experimental study on the use of two types of fly ash (low lime and high lime) as mineral admixtures in producing self-consolidating concrete (SCC) with the objective of assessing the effects of both types of fly ash on the fresh and hardened properties of SCCs. Within the scope of an experimental programme, SCCs were prepared by keeping the total mass of cementitious materials constant at 500 kg/m3, in which 30, 40, 50, 60 or 70% of cement, by mass, was replaced by high-lime and low-lime fly ash. The workability-related fresh properties of SCCs were observed through slump flow time and diameter, V-funnel flow time, L-box height ratio, GTM sieve stability test and the rheological parameters (relative yield stress and relative plastic viscosity). Setting times and temperature rise of SCCs were also determined as part of fresh properties. The hardened properties that were monitored for a year included the compressive strength, ultrasonic pulse velocity, drying shrinkage and chloride permeability. It was observed that the geometry and surface characteristics of fly ash affected the workability properties of SCC mixtures. Nonetheless, the compressive strength of SCC mixtures with 30–40% low-lime fly ash replacement was slightly greater than the control SCC mixture at the end of the year, as the amount of fly ash replacement increased losses in compressive strength. As a result of this experimental study, it could be concluded that SCCs incorporating a fly ash replacement of 70% could be produced with improved fresh and permeation properties and sufficient compressive strength.