Self-compacting Concrete Mixtures Research Articles

Iron slag as fine aggregate replacement and nanosilica particles in self-compacting concrete mixtures

A study of the mechanical behavior of self-compacting concrete mixtures under sand replacement (as fine aggregate) by iron slag (residue from industrial machining) from 0.0% to 50.0% of mass, variations of water/cementitious material ratio between 0.3 and 0.5 and nano SiO2 incorporation between 0.0% and 2.0% by mass of cementitious materials is presented. Fresh state tests of slump flow were performed, and the main rheological parameters: static yield stress and plastic viscosity were determined from a rheometer. For the hardened state, compressive strength tests were performed. The study of iron slag incorporation and water/cementitious materials ratio variation was developed based on a statistical methodology of central composite design from axial points based on a 2k factorial with central points, besides a posterior analysis of variance and Tukey’s multiple comparison tests. The optimization of these variables was developed using response surface methodology on 7 days compressive strength results, from the statistical design, besides the posterior determination of nano SiO2 effects on the optimized proportions. Among the most relevant results regarding the presence of iron slag, an increase in the early age compressive strength was found, with the optimized mixture strength being more than 100% higher than mixtures without iron slag at 7 days of curing. Regarding the effect of nano SiO2 addition to the optimized mixture, a detriment of the rheological parameters and a consequent reduction of the workability were the most remarkable findings. With the obtained results, iron slag proves to be a feasible sand replacement in self-compacting concrete mixtures.

Utilization of Local Fly Ash for Producing Self-Compacting Concrete

Self-compacting concrete (SCC) mixture is an innovation that aimed to ease concrete casting due to its characteristic can be compacted by self-weight without compacting or vibrating. The original SCC mixture which first developed by Okamura contains silica fume (SF) as supplementary material. In this study, fly ash (FA) was used as supplementary cementitious material for SF substitute. The variation of FA used in the mixtures of SCC concrete was 10%, 15%, and 20% by cement weight. For all variations of FA, the results of fresh concrete tests obtained workability that satisfactory to the SCC criteria for the slump flow, V-funnel, and L-shaped box tests. Furthermore, the results of hardened concrete tests achieved the compressive strength ranging from 40 to 46 MPa. These results indicate that local Aceh FA originating from Nagan Raya can be used as supplementary cementitious material to produce SCC with the compressive strength lay in high strength concrete categories.

Underwater abrasion of steel fiber-reinforced self-compacting concrete

Hundreds of tons of concrete may be ruined due to the abrasion erosion phenomenon that takes place in several hydraulic structures. Such unfavorable action can impose high maintenance costs and reduce the life span of these structures. The high-velocity water flow which carries large amounts of sediments is basically the main cause of this phenomenon. To better understand concrete abrasion in hydraulic structures, an experimental investigation was conducted to study the underwater frictional abrasion of self-compacting concrete (SCC) using the ASTM C1138 test method. Six SCC mixtures were prepared with different design grades of 30, 40 and 50 MPa and different micro-steel fiber contents of 0, 0.5, 0.75 and 1.0%. Four fresh SCC tests were adopted, while abrasion and control tests were conducted at ages of 7, 28 and 90 days. The ASTM C1138 tests showed that increasing the mixture strength by 20 MPa improved the abrasion resistance more effectively than the inclusion of 1.0% of steel fiber. Compared to the 30 MPa plain SCC, the 90-day abrasion resistance improved by 78% for SCC with 50 MPa strength, while the inclusion of 1.0% of micro-steel fiber enhanced the resistance by only 26%.

Technological Properties of Self-Compacting Concrete Mixtures with Ground Quartz Sand

Quantitative parameters of influence of grain composition of ground quartz sand and its quantity on the workability and segregation of self-compacting fresh concrete were determined at the constant amount of mixing water and water-cement ratio. Ground quartz sand in the amount of 50-150 kg/m3 was added instead of fine and coarse aggregates with changing the amount of polycarboxylate superplasticizer. It is stated that the use of ground quartz sand of finer grinding provides higher values of workability at the same quantity of water and superplasticizer. Segregation of the fresh concrete occurs when using increased amount of ground quartz sand of coarser grinding and increased amount of superplasticizer. Experimental studies have shown the effectiveness of the use of ground quartz sand to obtain self-compacting fresh concrete of different classes of workability SF1 and SF2 as well as classes of segregation resistance SR1 and SR2. The results of the experiments allow to state that the use of ground quartz sand of coarser grinding leads to segregation of fresh concrete at its low workability, while the use of ground quartz sand of finer grinding allows to obtain fresh concrete with resistance to segregation.

Mix-design and properties of self-compacting concrete made with calcareous tuff

This paper focuses on the possibility of using calcareous tuff (CT) in self-compacting concrete (SCC) production. In concrete mixtures, CT is used as sand and its fines as partial cement replacement. Mixtures are prepared with three different sand/mortar ratios (S/M) of 0.40, 0.45 and 0.50 with a varying superplasticiser content (SP). Cement was substituted by fines of calcareous tuff (CTF) with percentages of 0, 5, 10, 15, 20, 25 and 30% for S/M ratios of 0.40 and 0.45 with a varying SP dosage up to the superplasticiser saturation dosage (SSD). The filling, passing ability and segregation resistance tests are used to assess the fresh properties of SCC. The compressive strength of SCC was also determined at 3, 7, 28 and 56 days. The results show that the use of CT improves the flowability and stability of both SCM and SCC. SCC mixtures made with CT satisfy the specifications and guidelines for SCC production. The maximum strength obtained at 28 days was with mixtures SCC incorporating 10% of CTF, which revealed clearly the good adhesion between CT and cement matrix. Finally, CT constitutes a good local eco-material, abundantly available, for the SCC design.

Experimental investigation on effects of calcined bentonite on fresh, strength and durability properties of sustainable self-compacting concrete

With the current focus on sustainable development in the civil engineering field, it is necessary to develop construction and building materials with reasonable costs and low environmental impacts in order to reduce CO2 emissions during the production of concrete, and from the cement industry as a whole. This research studies the effect of using calcined bentonite (CB) as partial replacement of Ordinary Portland Cement (OPC) on the sustainability of self-compacting concrete (SCC). The cement in SCC mixes has been replaced with two different types of CB at 0, 5, 10, 15, 20, 25 and 30% by weight. Slump flow, V-funnel flow time, L-box test and sieve stability tests are performed to evaluate the fresh properties of SCC mixtures. Various tests are used to assess the performance of SCC mixtures in hardened states, such as compressive strength, porosity accessible to water, chloride-ions penetration and gas permeability. The results showed that the use of CB in SCC mixes reduced the fresh properties of SCC and the slump flows, flow times, and segregation tests are good enough for SCC production. At a hardened state, SCC with 10–15% of CB had a higher compressive strength up to 90 days, as well as improved porosity, chloride-ions penetration and gas permeability properties. These results indicate that a CB solution will reduce CO2 emissions and make durable and eco-friendly SCC at a low cost.

Fracture and permeability properties of glass fiber reinforced self-compacting concrete with and without nanosilica

This article studied the influence of utilizing nanosilica (NS) and glass fiber (GF) on mechanical and permeability properties of self-compacting concrete (SCC) with fly-ash blended. There were three SCC series designed. This study had a constant amount of water-to-binder (w/b) ratio and total binder content which is 0.35 and 550 kg/m3, respectively. This study utilized three different percentages of nanosilica to replace cement. These percentages were 0%, 2%, and 4% by weight, respectively. The incorporation of fly ash (FA) was done by using 25% of total binder content by weight in all the SCC mixtures. Moreover, glass fiber was used as an additive material with levels of 0%, 0.35%, 0.70%, 1.0%, and 1.5%, respectively. To experimentally evaluate mechanical properties; compressive strength; static modulus of elasticity; splitting tensile strength; fracture energy, and the permeability properties of the mixtures; sorptivity index; rapid chloride permeability test (RCPT); gas permeability test were done. The results showed that with utilizing nanosilica which ranged from 0% to 4% with replacement up until 0.7% glass fiber, indicated to enhance the mechanical and permeability properties of self-compacting concrete.

Influence of accelerated carbonation curing on the properties of self-compacting concrete mixtures containing different mineral fillers

This paper presents a study on the effects of accelerated carbonation curing (ACC) on performance of self-compacting concrete (SCC) mixtures prepared using limestone powder (LSP) alone and blend of limestone powder and silica fume (SF) as mineral fillers. Specimens cast using both SCC mixtures were subjected to ACC that consisted of exposing specimens to CO2 for 10 hours under a constant pressure of 414 kPa. ACC-treated specimens were tested for evaluating effects of ACC on properties of SCC mixtures in terms of CO2 uptake, mechanical and durability properties, morphology, and mineralogy. Test results indicate that the ACC-treatment substantially enhanced the properties of both SCC mixtures. Strength of ACC-treated concrete specimens can be improved further by exposing them to air for a period of first 7 days of the ACC-treatment. ACC-treatment of LSP-SF-C was more effective than that for LSP-C. Properties of ACC-treated SCC mixtures were comparable with that of the same mixtures subjected to moist-curing for 7 days except drying shrinkage, which was higher for ACC-treated specimens than the moist-cured specimens. However, shrinkage of ACC-treated specimens after 7 days was within the permissible limit in case of LSP-C whereas 7-day shrinkage for LSP-SF-C exceeded the permissible limit of 500 µm.

Performance of self-compacting concrete comprising granite cutting waste as fine aggregate

Continuous stockpiling of granite industrial by-product enforced researchers to use this waste in a sustainable manner in concrete to reduce its adverse impacts on the ecosystem. Therefore, fresh and hardened properties of self-compacting concrete (SCC) containing granite cutting waste (GCW) were assessed in this study. The GCW was used at an increased step level replacement of 20% of fine aggregate (i.e. river sand) up to 100%. Slump flow, T500 time, V-funnel, L-box, and J-ring tests were performed to assess the fresh properties of SCC mixes, whereas, compressive strength, flexural strength, ultrasonic pulse velocity, water absorption and water permeability tests were conducted for measuring the hardened properties of SCC mixes. Results of fresh properties tests for all of the mixtures were found within the satisfactory limit as per EFNARC standard except the mix prepared with 100% GCW. The incorporation of GCW in SCC mixes showed an increment in the compressive and flexural strength at 20% replacement level and decrement in both strength characteristics beyond 20% replacement. Moreover, even at 40% replacement level, the flexural strength was found to be higher with respect to the control mix. The better impermeability characteristics and higher ultrasonic pulse velocity values of granite modified SCC mixtures were found up to 40% incorporation of GCW as compared to the control SCC mix. The scanning electron microscope and X-ray diffraction analysis also validated the results of hardened characteristics. Granite modified SCC mixtures showed satisfactory performance during fresh and hardened characteristics test, it was therefore inferred that GCW could be used efficiently to engender sustainable SCC mixes.

Experimental Investigation of Flow and Mechanical Properties of Fibrofor Fiber Reinforced Self-Compacting Concrete

Self Compacting Concrete is a material used in the construction that has excellent deformability in the fresh state and high resistance of segregation, and can be replaced and compacted under its self-weight without applying vibration which leads to substantial advantages related to better homogeneity, enhancement of working environment and improvement in the productivity by increasing the speed of construction. Concrete can be formulated with high compressive strength but always has lower tensile strength. Tensile strength and other properties of concrete can be enhanced by adding fibers due to which the workability of concrete mix reduces and in order to achieve the desired Workability super-plasticizers is added. In the present work the use of fibrofor fiber in the production of self-compacting concrete (SCC) has been studied to identify how fresh and hardened properties of SCC are affected by the addition of fibers. The fibrofor fiber of 19mm standard length is incorporated into the SCC mixtures as 0.5kg/m3, 1.0kg/m3, 1.5kg/m3of concrete. Test on fresh SCC like slump Flow test, T50, V-Funnel test, J-Ring slump test and L-Box test were performed for an understanding of flow of SCC and tests on hardened properties like flexural strength, compressive strength and split tensile strength have been conducted to identify the hardened properties of SCC produced with fibrofor fiber. A comparative study between plain concrete, SCC without fiber and SCC with fiber has been done. Mix design for M40 grade concrete has been done according to EFNARC guidelines. The results reveal that the use of fibro for fiber decreases the workability but increases the mechanical properties of SCC. The optimum volume fraction of fibrofor fiber is determined as 1kg/m3 considering the optimized flexural strength and split tensile strength based properties of SCC. Due to increase in strength properties of fiber reinforced SCC that can be used for pavement construction and various other structures such as buildings, water retaining structures, reservoir structures and tunnel etc.

The impact of time on the heat resistance of self-compacting high-performance concrete incorporated with recycled martials

The influence of time on the mechanical behavior of concrete after exposure to elevated temperatures has been studied. Twenty-one self-compacting high-performance concrete mixtures with different incorporation amounts of coarse recycled concrete aggregate (RCA) and three unprocessed waste powder materials have been tested at age of 270 days for residual compressive and flexural strength after exposure to fire. The results have been compared to the results for the same concrete, which have been studied at age of 90 days. A new parameter has been introduced for comparing the responses of concrete to elevated temperatures at different ages; this parameter was the “heat resistance” which expresses the total area under the curve of the relative residual strength (compressive or flexural) after exposing to six temperature degrees (20, 150, 300, 500, 600, and 800 °C). The results showed that the age of concrete has an influence on the response of concrete to elevated temperatures. The heat resistance of compressive strength enhanced with age but the concrete behaved with a tendency different to that at the age of 90 days. The heat resistance of flexural strength has not been affected or slightly decreased but not with more than 10% to that at the age of 90 days. The used waste powder materials were unprocessed waste fly ash, waste cellular concrete powder and waste perlite powder; they proved that using any of them up to 15% as a replacement for cement with 0% or 25% of RCA enhanced the concrete resistance for the fire with time. The main two reasons for changing of residual strength with the time were the changing of water content and the proceeding of hydration of the binder. In general, long ages testing properties of concrete simulate the real behavior of concrete structures accurately.

Mechanical Effect of Steel Fiber on the Cement Replacement Materials of Self-Compacting Concrete

The behaviors of the fresh and mechanical properties of self-compacting concrete (SCC) are different from those of normal concrete mix. Previous research has investigated the benefits of this concrete mix by incorporating different constituent materials. The current research aims to develop a steel fiber reinforcement (SFR)‒SCC mixture and to study the effectiveness of different cement replacement materials (CRMs) on the fresh and mechanical properties of the SFR‒SCC mixtures. CRMs have been used to replace cement content, and the use of different water/cement ratios may lower the cost of CRMs, which include microwave-incinerated rice husk ash, silica fume, and fly ash. Fresh behavior, such as flow and filling ability and capacity segregation, was examined by a special test in SCC on the basis of their specifications. Moreover, compressive and splitting tensile strength tests were determined to simulate the hardened behavior for the concrete specimens. Experimental findings showed that, the V-funnel and L-box were within the accepted range for SCC. Tensile and flexural strength increases upon the use of 10% silica fume were found when compared with other groups; the ideal percentage of steel fiber that should be combined in this hybrid was 2% of the total weight of the binder. Overall, steel fibers generated a heightened compressive and splitting tensile strength in the self-compacting concrete mixes.

Long-term durability of self-compacting high-performance concrete produced with waste materials

Abstract Durability tests for twenty-one self-compacting high-performance concrete (SCHPC) mixtures have been conducted to investigate the impact of using coarse recycled concrete aggregate (RCA) and three other unprocessed waste powder materials: unprocessed waste fly ash (UWFA), waste perlite powder (WPP) and waste cellular concrete powder (WCCP). Chloride migration, water penetration and absorption, freeze/thaw resistance have been investigated at different ages up to 270 days and the results showed that using RCA has no significant effect on the durability properties of SCHPC when used up to 50%. Concretes produced using UWFA or WPP as a replacement of cement mass up to 15% showed excellent durability performance regardless if the coarse aggregate used was natural aggregate (NA) or RCA. SCHPC proved it can be produced as a green concrete, where the pozzolanic activity and the amorphous waste powder materials help the concrete resist aggressive environments. Using WCCP is not recommended for the purpose of enhancing the durability of SCHPC, as well as excessive replacement amounts of either WPP or UWFA. In general, the effects of both WPP and UWFA on durability properties became more significant due to the hydration proceeding with age.

The Effect of Fine and Coarse Recycled Aggregates on Fresh and Mechanical Properties of Self-Compacting Concrete.

Today, the use of recycled aggregates as a substitute for a part of the natural aggregates in concrete production is increasing. This approach is essential because the resources for natural aggregates are decreasing in the world. In the present study, the effects of recycled concrete aggregates as a partial replacement for fine (by 50%) and coarse aggregates (by 100%) were examined in the self-compacting concrete mixtures which contain air-entraining agents and silica fumes. Two series of self-compacting concrete mixes have been prepared. In the first series, fine and coarse recycled mixtures respectively with 50% and 100% replacement with air entraining agent were used. In the second series, fine recycled (with 50% replacement) and coarse recycled (with 100% replacement) were used with silica fume. The rheological properties of the self-compacting concrete (SCC) were determined using slump-flow and J-ring tests. The tests of compressive strength, tensile strength, and compressive stress-strain behavior were performed on both series. The results indicated that air-entraining agent and silica fume have an important role in stabilization of fresh properties of the mixtures. The results of tests indicated a decrease in compressive strength, modulus of elasticity, and energy absorption of concrete mixtures containing air entrained agent. Also, the results showed that complete replacement (100%) with coarse recycled material had no significant effect on mechanical strength, while replacement with 50% fine recycled material has reduced compressive strength, tensile strength, and energy absorption.

Fresh and hardened properties of self-compacting concrete containing of cement kiln dust

There are many wastes form the cement industry among them cement kiln dust (CKD). This residue is obtained after the process of burning the raw materials of cement in the rotary kiln where it is suctioned by fans during the clinker exit of the rotary kiln. Cement dust is a major environmental and economic problem in terms of high quality air pollution ranging from (20-100) microns and the proportions of chlorides, sulphates, alkali and lime living in a way that threatens the general health of human, as well as water pollution if the waste is discharged by rivers and waterways. This investigation’s main objective is to present the potential of using CKD as a cement replacement in self-compacting concrete (SCC). Eight mixes incorporating CKD with partial cement replacement of 0%, 5%, 10%, 20%, 30%, 40%, 50% and 75% in addition to control mix were investigated. The properties of all mixture were determined. Based on the experimental program results, it was found that SCC mixture incorporating 5% to 10% of CKD was almost similar to that of control mixture. The workability of SCC concrete decreased as CKD replacement increased. This established benefits of substituting cement by CKD to make SCC.

Rheological properties, compressive strength and life cycle assessment of self-compacting concrete containing natural pumice pozzolan

Abstract In this study, the life cycle assessment (LCA), rheological properties and compressive strength of self-compacting concrete (SCC) mixtures containing natural pumice pozzolan (NPP) were evaluated. The rheological properties of SCC including filling ability, passing ability and stability against segregation were determined using slump flow, V-Funnel, L-Box, J-Ring and sieve segregation tests. The compressive strength was measured at the age of 28 and 91 days. Using the LCA tool, the life cycle of the SCC mixtures presented in this study was evaluated and global warming potential (GWP) plus air pollutant parameters (APP) including lead, VOC, CO, NOX, PM10 And SO2 were measured. The results showed that the range of calculated compressive strength is between 26 and 55 MPa, and the Euro code requirements are met for almost all mixtures on rheological properties. Also, in SCC mixtures containing 10, 20 and 30% NPP, GWP production decreased by 9.3%, 18.6% and 27.8%, and the rate of emission of AAP was decreased from 3.6 to 29.9%, respectively.

Modified fine-grained concretes based on highly filled self-compacting mixtures

In this article the results of study of rheo-technological characteristics of cement-carbonate suspensions and physical and mechanical characteristics of cement composites from highly filled self-compacting mixtures are presented. The optimal dosage of polycarboxylate superplasticizer (Melflux 5581 F) and rheologically active mineral filler (microcalcite) in cement-mineral suspensions when developing self-compacting fine-grained concrete mixtures is defined. The water demand of fine natural quartz sands using the methodology of Skramtayev and Bazhenov is studied. The compositions of self-compacting fine-grained concrete mixtures of workability class SF1 with fine natural quartz sand are developed. High physical and mechanical characteristics of fine-grained concretes from highly filled self-compacting mixtures are fixed: density in normal humidity conditions at the age of 28 days up 2393 kg/m3; bending and compressive strength at the age of 28 days up 14.9 and 115.8 MPa, respectively.

Simulation of self-compacting concrete properties containing silica quicksand using ANN models

Self-compacting concrete (SCC) mix designs exhibit complexities in their mechanical properties due to composite nature of the material and the multitude and variety of factors that affect such properties. In this paper, a set of SCC mix designs are made using silica quicksand (as filler) instead of rock powder with other required materials. The tests of fresh concrete such as the slump flow, J-ring, V-funnel, L-box tests and the hardened concrete tests are investigated and considered. The tests results are shown that, a high quality has been achieved for SCC mixture contains the quicksand and silica fume contents with low lubricant admixture dosage. The research is embodied the use of a branch of Artificial Neural Networks (ANN) as a quick and reliable alternative to such experimental testing. Results show that the ANN technique can perform as a satisfactory alternative to experimental testing to provide speedy prediction of optimum silica quicksand content must be added prior to SCC mix design. As such, proposed method for the SCC mix design are limited in scope and are approximate at best as they must rely on the results of experimental tests, which are both costly and time-consuming to perform.

Self-compacting concrete with recycled aggregates

Abstract This paper presents the results of research of self-compacting concrete produced with recycled concrete aggregates and activated filler. The physical and mechanical characteristics of coarse aggregate, grain distribution of aggregates and sand proportion in aggregate mix, design of self-compacting concrete mixture and it’s structure properties with use mathematical experiment planning method were carried out. The results indicated that optimal content of filler is 22% with 150 min of activation and 0.5% content of organic admixture. Standard consistency of composite binder has decreased from 26.5% to 22.4%. The mathematical models can be used in the design of the self-compacting concrete mixture.

Influence of time-dependent rheological properties on distinct-layer casting of self-compacting concrete

The construction quality of self-compacting concrete (SCC) is possibly degraded by the distinct-layer casting in real structures due to the time-variable rheology of cement paste. This paper aims to investigate the influence of fly ash, water to binder ratio (w/b) and retarder dosage on distinct-layer casting of self-compacting concrete (SCC). Cubic specimens were cast in two layers with different delay durations of 20, 40 min and 60 min and the interface bond strength was tested using a self-designed method. On the other hand, yield stress and viscosity of cement mortars formulated from SCC mixtures were evaluated and the flocculation states of cement pastes were observed using an opto-digital microscope. Experimental results show that a weak interface is induced by the distinct-layer casting for SCC and the interface bond strength decreases with the longer delay for casting the second layer. The addition of fly ash, higher w/b ratio or higher dosage of retarder behave favorable effects on alleviating the distinct-layer casting induced degradation of interface bond strength for SCC specimens. This is attributed to the decreasing formation of floc particles in cement paste and lower time-dependent increase of static yield stress of cement mortar matrix. Relationships between the relative interface bond strength and static yield stress or static yield stress and average floc size can be expressed by exponential equations. Therefore, the negative effect of distinct-layer casting on SCC structures can be improved by controlling the flocculation process of cement paste.