Production Of Self-consolidating Concrete Research Articles

Incorporation of high-volume fly ash waste and high-volume recycled alumina waste in the production of self-consolidating concrete

In this article, we considered the properties of self-consolidating concrete (SCC) into which both high-volume fly ash waste (FA) and high-volume recycled alumina waste (AW) were incorporated. FA was used as a cement substitution at 40% and 60%, and AW was used as a substitute for fine aggregate at 25%, 50%, 75%, and 100 %wt. The SCC blends were designed with the intention of creating a controlled flowing slump. In this study, the workability and mechanical properties of the blends were investigated by utilizing slump flow, J-ring flow behavior, blocking flow evaluation, V-funnel, compressive strength, and ultrasonic pulse velocity (UPV) estimations. The findings show that, compared with SCC without AW, the SCC blends that included AW required increased doses of superplasticizer and produced denser fresh concrete. With the increased cement content and altered FA content, the percentage of superplasticizer required and thickness of the fresh SCC decreased. When AW was incorporated at between 25% and 75%, its rheological and mechanical benefits became significant enough that including it in SCC became practical. Eventually, it is possible to manufacture SCC economically by using high volumes of FA and AW and even make it possible to develop green and environmentally friendly SCC.

Representing a logical grading zone for self-consolidating concrete

For an aggregate source with certain geometrical characteristics, grading can highly affect the properties of self-consolidating concrete (SCC). This paper basically focuses on the effect of using different aggregates grading on the properties of SCC. For this purpose twelve aggregate proportions with three different cement contents (450, 500 and 550), three different water-to-cement ratios (0.35, 0.4 and 0.45) and either poly-carboxylate based super-plasticizer as admixture were used. In order to examine fresh concrete properties, slump flow, U-box, L-box and V-funnel tests were carried out; for achieving hardened properties of SCC, tests were limited to compressive strength. The principal objective of this survey is to determine an acceptable aggregates grading zone which can be used in production of SCC with ideal properties. From the experimental consequences, it is observed that aggregate proportions in this zone, will result a SCC with appropriate workability and compressive strength. The optimum curves could be selected with Cu values more than 9.5.

Lowering paste volume of SCC through aggregate proportioning to reduce carbon footprint

The production of SCC (self-consolidating concrete) generally requires a fairly high paste volume, ranging typically from 35% to 40%. This is to achieve the high flowability, high segregation resistance and high passing ability needed. However, a high paste volume would lead to low dimensional stability and high carbon footprint. Hence, increasing the paste volume of an otherwise normal concrete mix is not a good method of SCC production. There is a necessity to lower the paste volume of SCC so as to avoid the adverse effects of high paste volume and reduce the carbon footprint. Herein, it is proposed to adjust the aggregate proportions to maintain the performance of the SCC while lowering the paste volume. Trial concrete mixes are tested to demonstrate how the paste volume can be lowered through aggregate proportioning. Overall, the test results reveal that with suitable aggregate proportioning, the paste volume can be lowered to as low as 26% and that the volume of aggregate particles finer than 1.18mm has major effect on the passing ability of SCC.

Properties of SCC prepared using natural pozzolana and industrial wastes as mineral fillers

The high unit cost of self-consolidating concrete (SCC) resulting from the use of conventional filler materials, such as fly ash or silica fume, has been identified as the main hindrance to its widespread use particularly at places where these materials are not available locally. To achieve economy in the production of SCC, it is highly desirable to explore possibility of using alternative materials as mineral fillers through the evaluation of technical and economic benefits of SCC made with these materials. This paper presents the results of a study conducted to evaluate the performance of ternary SCC mixtures prepared using some industrial wastes as mineral fillers which include limestone powder, cement kiln dust, bag house dust, pulverized steel slag and metakaolin, each in conjunction with natural pozzolana. The mechanical properties and durability characteristics of the SCC mixtures satisfying the requirements of self-compactability at optimally selected dosages of chemical admixtures were evaluated. Except the SCC mixture incorporating bag house dust, the early and later-age strengths of the other SCC mixtures were found to be very high. Further, the good corrosion resistance exhibited by the developed SCC mixtures showed that the high performance SCC mixtures can be prepared utilizing these industrial wastes as mineral fillers.

Adding ground sand to decrease paste volume, increase cohesiveness and improve passing ability of SCC

In the production of SCC (self-consolidating concrete), it is not easy to achieve high passing ability without sacrificing other performance attributes because the common practice of increasing the cementitious paste volume to achieve high passing ability would decrease the dimensional stability and increase the carbon footprint. In fact, at narrow gaps, the paste often flows in the front leaving the coarse aggregate particles behind to block the subsequent flow of concrete, especially if the paste does not have good cohesiveness. Hence, increasing the paste volume is not always effective in increasing the passing ability. Herein, it is proposed to keep the paste volume small and add ground sand with a mean size of 0.3mm to increase the mortar volume and cohesiveness, and improve the passing ability. Trial concrete mixes with paste volumes of 30% and 34% and different ground sand contents have been tested and the results demonstrated that the addition of ground sand would enable the achievement of high passing ability at a relatively small paste volume.

Properties of self-consolidating concrete made utilizing alternative mineral fillers

Self-consolidating concrete (SCC) is a concrete material possessing an ability to take formwork shapes and pass through congested reinforcement bars without being vibrated, making it a ‘smart concrete’ material. However, the high cost of SCC resulting from the use of mineral fillers and high cement content has been a main factor impeding the widespread use of this smart material. Consequently, there is a need to investigate the use of low cost materials in the production of SCC to ensure adoptability of SCC in concrete construction. This paper presents the results of a study conducted to develop and evaluate the performance of four SCC mixtures using different combinations of filler materials, such as silica fume, natural pozzolana and metakaolin, in conjunction with limestone powder. The developed SCC mixtures exhibited high strength (compressive, tensile, bond and elastic modulus), excellent shrinkage behavior and good durability characteristics (high corrosion resistance and related indices). The findings of this study indicated the possibility of producing cost-effective and high-performance SCC mixtures using the mineral fillers considered in this study.

Reducing cement paste volume for production of self-consolidating concrete by adding fillers

For the production of self-consolidating concrete (SCC), in order to achieve high flowability and high cohesiveness at the same time, it is often necessary to provide a fairly large cement paste volume of up to 35%. Such a large cement paste volume would lead to high cement consumption, low dimensional stability and a high carbon footprint. This paper presents a study on the feasibility of reducing the cement paste volume by adding fillers to the concrete mix. Two types of fillers, namely, limestone fines (LF) and ground sand (GS), were used. Trial concrete mixes with various amounts of LF and GS added were produced for slump flow, passing ability, sieve segregation and compressive strength tests. The results revealed that although the addition of fillers would substantially increase the superplasticiser demand, it would allow the cement paste volume to be reduced to as low as 25% while still meeting the slump flow, passing ability and segregation resistance requirements of SCC.

Guidelines for design, testing, production and construction of semi-flowable SCC for slip-form paving

A new type of self-consolidating concrete (SCC), semi-flowable SCC (SFSCC), has been developed for slip-form paving construction. Several field applications of the SFSCC have been conducted. Based on the research results, guidelines for SFSCC mix design, testing, production and construction are developed. This paper provides an overview of the guidelines. In this paper, SFSCC mix design methodology, quality control test methods and special requirements for paving equipment and operations as well as post-placement techniques are presented.

Carbon steel slag as cementitious material for self-consolidating concrete

This study deals with the recycling of carbon steel slag (CSS) to produce self-consolidating concrete (SCC). Since the chemical composition of CSS is similar to that of Portland cement or blast furnace slag (BFS), it is expected to behave similarly. In the current study, the pozzolanic activity index of CSS is examined. Furthermore, the use of CSS as a pozzolanic material to partially replace Portland cement in the production of SCC is tested. We designed concrete mixtures with different water-to-cementitious material ratios (w/cm) keeping water and superplasticizer (SP) contents constant. Results showed that the design and performance of all the concrete mixtures used in this investigation were comparable to those of SCC and high performance concrete (HPC). However, compared to ordinary plain concrete (OPC), the additional CSS content increases the setting time. In the CSS mixtures set for 90 d, compressive strengths of 86%, 134% and 121% were attained as compared to the control concrete; the corresponding w/cm ratios were 0.28, 0.32 and 0.40, respectively. Verifying the soundness of the SCC for meeting the criteria for HPC, the ultrasonic pulse velocity (UPV) of CSS was found to be comparable to that of ordinary concrete. In conclusion, the recycling of CSS can be advantageously employed in the production of SCC.

Fresh, Mechanical, and Durability Characteristics of Self-Consolidating Concrete Incorporating Volcanic Ash

Self-consolidating concrete (SCC) is known for its excellent deformability, high resistance to segregation, and use in congested reinforced concrete structures characterized by difficult casting conditions without applying vibration. The use of known mineral admixtures such as fly ash and slag cement has proved very effective in the production of nonexpensive SCC with satisfactory fresh and hardened properties. However, the use of volcanic ash (VA) in SCC is new and can provide low cost SCC. This paper presents fresh, mechanical, and durability characteristics of VA based SCC mixtures (VA-SCCs). VA-SCCs are developed by varying water-to-binder ratio, percentages of VA as cement replacement, and dosages of superplasticizer (SP). Mix design parameters are optimized to achieve minimum use of SP and optimum use of VA. The fresh concrete properties are determined from slump flow, V-funnel flow time, bleeding, air content, and segregation tests. The mechanical properties and durability characteristics such as compressive strength, freezing-thawing resistance, rapid chloride permeability, surface scaling resistance, and drying shrinkage are determined to evaluate the performance of VA-SCCs. The study produces encouraging results and confirms the production of satisfactory VA based SCC mixtures with acceptable properties. VA-SCCs having a minimum strength of 15 MPa (requirement for some structural concrete applications) can be obtained by replacing up to 50% (by mass) of cement by VA. Development of nonexpensive and environmental friendly VA-SCC with acceptable strength and durability characteristics (as illustrated in this study) is extremely helpful for the sustainable development and rehabilitation of volcanic disaster areas around the world.

Self-consolidating concrete incorporating new viscosity modifying admixtures

Self-consolidating concrete (SCC) is known for its excellent deformability, high resistance to segregation and use without applying vibration in congested reinforced concrete structures characterized by difficult casting conditions. The use of viscosity modifying admixtures (VMA) has proved very effective in stabilizing the rheology of SCC. Commercial VMAs currently available on the market are costly, which increases the cost of such a concrete. This article presents the suitability of four different types of new polysaccharide-based VMA in the development of SCC. A preliminary investigation was carried out on the rheological properties and setting times of mortar mixes with various types and dosages of VMA to study the influence and suitability of new VMAs. A more detailed study was then carried out on the SCC fresh and hardened properties such as slump flow, segregation, bleeding, flow time, setting time and compressive strength of different mixes with various dosages of an identified new VMA. The performance of various SCC mixtures with the new VMA was compared with a SCC using a commercial VMA designated as “COM” and a SCC mixture with Welan gum. The study on new VMA is encouraging and confirms the production of satisfactory SCC with acceptable fresh and hardened properties comparable with or even better than that made with commercial VMA and Welan gum. The suggested mix with 0.05% of the new Type A VMA satisfies the requirement of fresh and hardened properties of SCC and will require 7% less VMA dosage than that required in the commercial VMA mixture. The SCC with new VMA is also cost-effective.