Production Of Self-compacting Concrete Research Articles

Advanced online water content measurement for self-compacting concrete production in ready-mixed concrete plants

In ready-mixed concrete plants, the water content of self-compacting concrete (SCC) is generally controlled during the mixing process based on the stabilisation of mixer power consumption. This measurement system is however rarely calibrated, even though its signal is sensitive to the wear of mixers and the temperature of engines.The aim of this paper is to propose a calibration of mixing power as a measurement of the concrete water content that enables improving water control accuracy. A new approach based on the mixing power evolution is devised for a better determination of the signal stabilisation. The stabilisation time is then defined and considered as the necessary mixing time of each concrete batch. Experimental results obtained from 40 batches of different SCC compositions produced in a full-scale concrete plant have shown that, with the developed calibration method, the stabilisation of power consumption can be considered as a reliable indication of water content with a precision of ±3.8l/m3. It is also observed that the water-to-powder ratio (W/P) and the use of viscosity agent have significant effects on the power consumption evolution during mixing.

Reusing of marble and granite powders in self-compacting concrete for sustainable development

Huge amounts of solid wastes are generated every day from marble and granite industry. Up to now, most of these wastes are landfilled causing serious environmental problems. With increasing the environmental awareness, it is essential to explore alternative solutions to waste disposal problem. This paper investigates the possibility of using various types of waste powders, generated from marble and granite industry, as mineral additives in self-compacting concrete (SCC). For this purpose, three types of waste powders were used; marble powder, granite powder and mixed powder. The experimental program included two phases. The first phase was the preliminary investigation to optimize the amount of the used mineral additives to cement content at which the highest compressive strength is achieved with acceptable flowability. In the second phase, the fresh and hardened properties of SCC were investigated. Slump flow, V-funnel, and J-ring tests were conducted to assess the self-compactability properties of fresh concrete, while compression, splitting tensile, flexural, water absorption and sulfate attack tests in addition to microscopic investigations were conducted to evaluate its hardened characteristics. The results indicated that high volumes of the investigated waste powders (up to 50% by weight of 400 kg/m3 cement content) could be used successfully as mineral additives in the production of SCC. In general, SCC incorporating mixed powder showed the superior performance followed by granite powder mixes, while marble powder has a marginal effect on the performance of hardened concrete. However, silica fume could be used for the enhancement of marble powder performance.

Eco-Efficient Self-Compacting Concrete with Reduced Portland Cement Content and High Volume of Fly Ash and Metakaolin

The eco-efficient, self-compacting concrete (SCC) production, containing low levels of cement in its formulation, shall contribute for the constructions' sustainability due to the decrease in Portland cement use, to the use of industrial residue, for beyond the minimization of the energy needed for its placement and compaction. In this context, the present paper intends to assess the viability of SCC production with low cement levels by determining the fresh and hardened properties of concrete containing high levels of fly ash (FA) and also metakaolin (MK). Hence, 6 different concrete formulations were produced and tested: two reference concretes made with 300 and 500 kg/m3of cement; the others were produced in order to evaluate the effects of high replacement levels of cement. Cement replacement by FA of 60% and by 50% of FA plus 20% of MK were tested and the addition of hydrated lime in these two types of concrete were also studied. To evaluate the self-compacting ability slump flow test, T500, J-ring, V-funnel and L-box were performed. In the hardened state the compressive strength at 3, 7, 14, 21, 28 and 90 days of age was determined. The results showed that it is possible to produce low cement content SCC by replacing high levels of cement by mineral additions, meeting the rheological requirements for self-compacting, with moderate resistances from 25 to 30 MPa after 28 days.

The Effect of Bottom Ash on Fresh Characteristic, Compressive Strength and Water Absorption of Self-Compacting Concrete

Bottom ash is a solid residue produced through combustion process in a coal-fired power plant. It has been catogarized as a waste and usually disposed in the utility disposed site. With higher demand on the power energy, more coal-power plant are constructed and abundance of bottom ash are produced. Recently, the utilization of bottom ash in the construction industry has gained the interest of researches. Since it has similiar particle size distribution as normal sand, many attempt has been made in studying it potential use in mortar and concrete. In complementary to that, this paper presents the effect of bottom ash on fresh and hardened properties of self-compacting concrete (SCC). Bottom ash is used as fine aggregate replacing sand with replacement ratio range from 0% to 30% by volume. The effects of bottom ash on the SCC were investigated by comparing the test result of SCC mixed bottom ash with control specimens (0% of bottom ash). The test result on fresh properties of the concrete mixture revealed that, as the replacement level of bottom ash increased, the slump flow, L-box passing ratio and segregation resistance ratio (SR) decreased. Nevertheless, the slump flow time (T500) result increased with the increased of bottom ash content. The results show that the porosity and the irregular shape of the bottom ash particle has great influence on workability and viscosity of the fresh concete. The compressive strength and water absorption test are carried out on the sample at curing time of 7 and 28days. In terms of strength, the use of bottom ash in the production of SCC has increased the compressive strength of the concrete up to 15% replacement level. The increase in strength show the presence of the pozzolanic reactivity in a concrete with bottom ash particle. The water absorption rate was observed to be lower with a sample which having 10% and 15% replacement level.

Use of Unprocessed Rice Husk Ash and Pulverized Fuel Ash in the Production of Self-compacting Concrete

We investigated the properties of self-compacting concrete (SCC) mixtures comprising ternary combinations of Type 1 Portland cement (OPC), untreated rice husk ash (RHA), and pulverized fuel ash (FA). The SCC mixtures were produced with a controlled slump flow in the range between 67.5 to 72.5cm diameter with a constant total powder materials content of 550kg/m3. RHA and/or FA were used to replace in powder materials with 20 or 40 wt%. The fresh and hardened properties including water requirement, workability, density, compressive strength development and ultrasonic pulse velocity were determined. Self-compacting concrete mixtures formulated using ternary blends exhibited significant improvements in physical properties compared to SCC mixtures containing only RHA or FA.

Feasibility analysis of the reuse of waste filler of bituminous mixtures for the production of self-compacting concrete

The emergence of self-compacting concrete is a significant development in the construction industry since it greatly reduces execution time and labour costs, auxiliary resources and energy consumption. However, this type of material must continue to evolve to provide more efficient management of resources and a contribution to sustainable development. On the other hand, the possibility of revaluing the residues from one industry by reusing them as raw materials for another is nowadays seen as one of the most efficient solutions to the environmental problems caused by the construction industry. This paper conducts a feasibility analysis of the reuse of waste filler of bituminous mixtures for the production of self-compacting concrete. For that purpose, a comparative study of a reference self-compacting concrete, made with commercial filler, with another, made with recovered filler extracted from production plants of bituminous mixtures, was carried out. This article shows the results obtained after studying the behaviour of these two types of concrete both in fresh state (flowability and blocking resistance) and in hardened state (porosity, compressive strength and the evolution of carbonation depth in an accelerated carbonation process). According to the results obtained, the reuse of this waste material for the production of self-compacting concrete is not only perfectly possible but also provides the same guarantees as the usual commercial filler.

Self-compacting concrete obtained by the use of kaolin wastes

A self-compacting concrete (SCC) is characterized by its special capacity of filling ability, passing ability and resistance to segregation by the action of its own weight without the presence of other external forces. These fresh properties are obtained thanks to the use of filler, where the limestone one is mostly used. Numerous industries produce a great amount of solid wastes, some suitable for use as filler in the production of SCC. This study aimed to develop a SCC with inclusion of wastes from the manufacturing of kaolin, through an optimum dosage of kaolin wastes and superplasticizer (sp) which were well established from the experiments. The paste dosage was defined by Marsh funnel and mini-slump tests and fresh properties of concrete were measured by L box, U box, J ring, V funnel and Abrams cone. The use of kaolin wastes in SCC production is pioneering. The mix-design method used was successful and it was validated by the several fresh properties results which provided to the concrete a SCC characteristic flowing behavior. Finally, including industrial waste in SCC has brought significant environmental benefits.

Mechanical, microstructure and rheological characteristics of high performance self-compacting cement pastes and concrete containing ground clay bricks

The work aimed to utilize ground clay bricks (GCBs) in the production of self-compacting concrete. Physico-mechanical, rheological and microstructure of cement pastes and concrete were investigated. Total powder contents were 400kg/m3, the cement was replaced by GCB by 0.0, 50, 100 and 150kg/m3. The compressive strength of concrete decreased with GCB content in the absence of self-compacting concrete (SCC) admixture, whereas, increases in the presence of SCC admixture up to 28days. Increase of GCB content up to 250kg/m3, the compressive strength of concrete increases. GCB enhances the compressive strength due to the pozzolanic reaction to produce additional CSH, which precipitated in some open pores. The compressive strength of OPC pastes increase with SCC admixture up to 1.5mass%, whereas decreases with SCC admixture up to 2mass%. On the other hand, cement pastes made with 12.5% and 37.5% GCB in the expanse of OPC cement show higher compressive strength with SCC admixture at 28–1095days. The efficiency of SCC admixture decreases as GCB content increases up to 12.5%, whereas the efficiency increases with GCB content up to 37.5%. The presence of SCC superplasticizer, the microstructure displayed a more dense arrangement of microcrystalline C–S–H as the main hydration products with sheets of Ca(OH)2 as shown in the micrograph. Useful conclusions and recommendations concerning use of 30–40mass% of GCB in self-compacting concrete.

Effect of mineral admixtures on properties of self-compacting concrete

Abstract In this study, the benefits of limestone powder (LP), basalt powder (BP) and marble powder (MP) as partial replacement of Portland cement are established. Furthermore, LP, BP and MP are used directly without attempting any additional processing in the production of self-compacting concrete (SCC). The water to binder ratio is maintained at 0.33 for all mixtures. The examined properties include workability, air content, compressive strength, ultrasonic pulse velocity, and static and dynamic elastic moduli. Workability of the fresh concrete is determined by using both the slump-flow test and the L-box test. The results show that it is possible to successfully utilize waste LP, BP and MP as mineral admixtures in producing SCC. Due to its observed mechanical advantages, the employment of waste mineral admixtures improved the economical feasibility of SCC production on a unit strength basis.

Properties of self-compacting portland pozzolana and limestone blended cement concretes containing different replacement levels of slag

In order to reduce energy consumption and CO2 emission, and increase production, cement manufacturers are blending or inter-grinding mineral additives such as slag, natural pozzolana, and limestone. This paper reports on the results of an experimental study on the production of self-compacting concrete (SCC) produced with portland cement (PC), portland pozzolana (PPC) and portland limestone (PLC) blended cements. Moreover, the effect of different replacement levels (0–45%) of ground granulated blast furnace slag (GGBFS) with the PPC, PLC, and PC cements on fresh properties (such as slump flow diameter, T500 slump flow time, V-funnel flow time, L-box height ratio, setting time, and viscosity) and hardened properties (such as compressive strength and ultrasonic pulse velocity) of self-compacting concretes are investigated. From the test results, it was found that it was possible to manufacture self-compacting concretes with PPC or PLC cements with comparable or superior performance to that of PC cement. Furthermore, the use of GGBFS in plain and especially blended cement self-compacting concrete production considerably enhanced the fresh characteristics of SCCs.

Fresh and Hardened Properties of SCC Made with Different Aggregate and Mineral Admixtures

The production of self-compacting concrete (SCC) is a relatively new technology. Nowadays, the production of SCC is becoming more popular in Turkey owing to its superior properties. However, the production of SCC requires more sensitive and efficient workmanship and equipment. In addition to many other factors, such as proportioning and curing, the origin of coarse aggregate and mineral admixtures carries utmost importance in terms of fresh and mechanical properties of SCC. The effect of two mineral admixtures—fly ash and limestone powder—and two types of coarse aggregates—limestone and olivine basalt—on fresh and hardened SCC have been investigated within a series of laboratory tests. Results showed that the effect of mineral admixtures on fresh properties seems to be more dominant than the effect of aggregate type. Limestone powder and limestone aggregate combinations had superior fresh and mechanical properties compared to basalt-incorporated mixtures.

Influence of cement type on ITZ porosity and chloride resistance of self-compacting concrete

With the increasing use of self-compacting concrete (SCC) its durability has come into focus. Concerning the microstructure of concrete, the porosity in the interfacial transition zone (ITZ) is regarded as a key feature for permeability and durability. Generally, a combination of cement and mineral admixtures is used for the production of SCC. In the present study, ITZ porosity of four SCC mixtures produced with ordinary Portland cement, Portland limestone cement, slag cement and ordinary Portland cement combined with fly ash is analyzed. Additionally, the chloride migration coefficient is determined. ITZ porosity and width of the SCC mixtures are similar. The substantial differences in the chloride migration coefficients show that the binder type has a stronger influence on permeability than the pore volume in the ITZ.

Fresh properties of self-compacting rubberized concrete incorporated with fly ash

Solid waste management is one of the major environmental concerns in all over the world. High amounts of waste tires are generated each year and utilization of this waste is a big problem from the aspects of disposal, environmental pollution, and health hazards. In the production of self-compacting concrete, the incorporation of waste tires as partial replacement of aggregates is very limited. However, the use of waste tires might join the characteristics of self-compacting concrete (high flowability, high mechanical strength, low porosity, etc.) with the tough behavior of the rubber phase, thus leading to be a building material with more versatile performances. Thus, in this study, the usability of untreated crumb rubber as a partial substitute of fine aggregates with and without fly ash in the application of self-compacting concretes was investigated experimentally. For this purpose, a water–cementitious material ratio (0.35), four designated crumb rubber contents (0, 5, 15, and 25% by fine aggregate volume), and four fly ash content (0, 20, 40, and 60%) were considered as experimental parameters. Test results indicated that use of crumb rubber (CR) without fly ash (FA) aggravated the fresh properties of self-compacting rubberized concretes (SCRC) (slump flow diameter, T50 slump flow time, V-funnel flow time, L-box height ratio, initial and final setting times, and viscosity). However, the use of CR with FA amended the fresh properties of SCRC.

The Production of Self-Compacting Concrete with Normal Cement Content

The Production of Self-Compacting Concrete with Normal Cement Content

Production of Self-Compacting Concrete by Using Fine Aggregate NotConforming Local Specifications

This study aims to investigate the properties of SCC produced by locally availablematerials , and attempts have been made to increase the range of grading of fineaggregate, with fineness modulus ranging from (1.5 to 4.1) , and to study the effect of themaximum size of coarse aggregate . It also aims to study the influence of High ReactivityMetakaolin (HRM) as a partial replacement by weight of cement on the properties of freshand hardened SCC, 24 different mixes of SCC are prepared .8 mixes are considered asReference mixes which are used for comparison purposes. To determine the workability,different test methods were adopted such as slump flow, V-funnel, and L-box tests. Whenfineness modulus of fine aggregate and maximum size of coarse aggregate increase,flowability, passing ability and segregation resistance decrease as compared with smallmaximum size of aggregate and other fineness modulus. Further more, the inclusion of10% HRM as a partial replacement by weight of cement leads to decrease flow ability andincrease of viscosity. The fineness modulus (3.1) of fine aggregate gives better resultsthan other fineness modulus. The results obtained from this study, also show that it ispossible to produce SCC from local available materials which satisfy the requirement ofthis type of concrete. Moreover, the results show the possibility of using different gradingof fine aggregate with fineness modulus ranging from (1.5 to 4.1) and the effect ofchange in fineness modulus is not significant on hardened concrete properties , while it ismore significant on fresh concrete properties .

The use of quarry dust for SCC applications

Limestone powder has been the traditional material used in controlling the segregation potential and deformability of fresh self-compacting concrete (SCC). This paper deals with the utilisation of alternative materials, such as quarry dust, for SCC applications. Results from rheological measurements on pastes and concrete mixes incorporating limestone or quarry dust were compared. It was found that the quarry dust, as supplied, could be used successfully in the production of SCC. However, due to its shape and particle size distribution, mixes with quarry dust required a higher dosage of superplasticiser to achieve similar flow properties.