High-volume Blast-furnace Slag Research Articles

Effect of wet milling activation on mechanical properties and hydration process of cement composites with blast furnace slag

In this study, blast furnace slag (BFS) was activated using water- and ethanol-assisted milling (AM). BFS-cement composites (BFS-CC) were prepared using milled BFS and cement. The effects of the activation process on the mechanical properties and hydration of BFS-CC were investigated. Results showed that water- and ethanol-AM significantly reduced the median particle size (D50) and improved the particle size distribution of BFS compared to dry milling. Water-AM increased the compressive strength of BFS-CC at 3 days by 19.9 % and decreased the compressive strength at 28 days by 6.7 %. While ethanol-AM increased the compressive strengths at 3 and 28 days by 17.2 and 22.4 %, respectively. Water-AM improved the early strength of BFS-CC, whereas ethanol-AM contributed significantly to the late strength development of BFS-CC. This study provides an effective and convenient method for regulating the mechanical properties of cement composites containing high-volume BFS.

New insights into the effects of nanosilica on transmission properties and pore structure in high-volume blast furnace slag cementitious materials

This study investigated the effect of nanosilica (NS) on the properties of high-volume blast furnace slag (HVS) cementitious materials. Results showed that HVS led to inadequate early-age development of properties, such as reduced strength and transmission properties, due to increased total porosity and porosity of pore size greater than 100 nm (P100). However, the addition of 2 wt% NS increased the hydration products and decreased the P100 of HVS containing cementitious materials. NS also increased compressive strength and decreased transmission properties of water absorption, especially at higher dosages. The reduction in water absorption was mainly due to the decrease in P100 rather than overall porosity, as shown by the strong correlation between water absorption and P100. NS was an effective additive for enhancing the properties of HVS-cementitious materials by reducing the porosity of pores larger than 100 nm, while increasing the porosity of pores smaller than 100 nm, without significant effect on total porosity.

Influence of ion chelator on pore structure, water transport and crack-healing properties of cement pastes incorporating high-volume fly ash and blast-furnace slag

This paper focuses on the influence of ion chelator (CA) on pore structure, water transport and self-healing ability of cement pastes incorporating high content fly ash (FA) and blast-furnace slag (BFS). The pore structure of pastes was measured by low-field nuclear magnetic resonance (LF-NMR). The water transport property was tested by water absorption test. The self-healing ability was assessed by water permeability and crack healing test. Results showed that the compressive strength of hardened pastes was promoted by CA, the increase rates in compressive strength of pastes were 21.9% (50%BFS), 15.7% (pure cement), 9.9% (30%FA) and 8.8% (16%FA24%BFS). CA decreased the proportion of small capillary pores (0.01–0.1 μm) in cement pastes which were more pronounced for the water absorption, the reduction rates of small capillary pores were 49.0% (50%BFS), 41.5% (pure cement), 20.2% (30%FA) and 13.0% (16%FA24%BFS). The self-healing performance of pastes with 50% BFS was most obviously improved that crack with width of 0.43 mm could be completely healed within 21d, while the relative water permeability coefficient dropped by around 80%, followed by pure cement, 30%FA and 16%FA24%BFS pastes. Notably, the morphology of the crack healing product in the blend pastes with FA and BFS was changed with the addition of CA, a large amount of lumpy and clustered calcite was generated, which promoted the compactness and content of healing products. The results of this study showed that CA could significantly improve pore structure, water transport and self-healing properties of high-volume BFS cementitious materials, which meant that CA had a better application prospect in high-volume BFS cement-based materials.

Mechanical Properties and Hydration Characteristics of Cement Composites with High-Volume Blast Furnace Slag by Wet Milling Activation

Mechanical Properties and Hydration Characteristics of Cement Composites with High-Volume Blast Furnace Slag by Wet Milling Activation

Effect of chlorine bypass system dust on fresh state properties and strength development of high-volume blast-furnace slag mortar

In this study, chlorine bypass system (CBS) dust is proposed as a new alkali activator and the feasibility of applying CBS dust for high-volume blast-furnace slag (HVBFS) mortar is confirmed. CBS is a dust-collecting system for the cement-manufacturing process that collects dust with chloride and alkali. In general, most of the collected CBS dust in South Korea is wasted. As an effort to reduce waste and incidental costs during the cement-manufacturing process, in this study, cement powder was replaced by CBS dust as an alkali activator for blast-furnace slag. From the experiment of HVBFS mortar activated with various CBS dust proportions, favourable results were observed in terms of fluidity and air content when the CBS dust replacement exceeded 5%. Additionally, regarding strength development, CBS dust was successful as an alkali activator for the latent hydraulic reaction of blast-furnace slag. Therefore, when CBS dust was used as a 5% replacement, its efficiency as an alkali activator in which a large amount of blast-furnace (HVBFS) slag was substituted under the research conditions in this study was confirmed in terms of fluidity and strength development performance.

Synergistic effect of EVA copolymer and sodium desulfurization ash on the printing performance of high volume blast furnace slag mixtures

Considering the long-term development of digital construction, a cost-effective and environmental printing material was designed with blast furnace slag as main cementitious material and sodium desulfurization ash as activator. However, weak alkaline environment lead to the insufficient 3D printability (e.g. yield stress, viscosity). Ethylene/vinyl acetate copolymer (EVA) was used to make up this defect, and it was found that there was a synergistic effect between EVA and sodium desulfurization ash (NS), which is beneficial to the improvement of the printing performance. The synergistic effect of EVA and NS was investigated in terms of fresh, hardened and microstructure properties. Experimental results show that under varying resting times and shear rates, the addition of 0.6−1.6% (i.e.by mass of binder) EVA could increase the yield stress and apparent viscosity of HVGS. Moreover, it was also found that the addition of EVA could help improve the polymerization degree of printing materials and increase the compressive strength of 28d by about 22%. To verify the practical value of the printing material, an industrial product was printed, and the maximum number of continuous printing layers can be up to 30 layers.

Improvement of Bond Strength and Durability of Recycled Aggregate Concrete Incorporating High Volume Blast Furnace Slag.

This paper aims to experimentally investigate the effects of high volume cement replacement of blast furnace slag (BFS) on the bond, strength and durability of recycled aggregate concrete (RAC). Concrete mixtures were prepared containing 0%, 15%, 30%, 45%, 60% and 75% BFS with each of recycled aggregate and natural aggregate. Measurements of the compressive and bond strength, the resistance to chloride-ion penetration and the water permeability of concrete are reported. In addition, a microhardness test was also performed to evaluate the quality of interfacial transition zone (ITZ) in concrete. Test results of the bond strength and the compressive strength of RAC mixtures, in spite of the cement replacement amount with BFS, show that the concretes result in reduced strength when compared to natural aggregate concrete (NAC) mixtures, while the strength gains for the BFS-based concrete are higher than that of the reference mixtures without BFS at long-term ages. Incorporating BFS in concrete can inherently improve the durability properties by increasing higher resistance to chloride-ion penetration and lower water permeability. This improvement in the mechanical and durability properties of the BFS-based RAC mixture may be due to the additional pozzolanic reaction of BFS, which enhances the properties of ITZ in concrete, resulting in an improvement of the strength of concrete.

41 Year Long-Term Durability of High Volume Blast-Furnace Slag Cement Concrete

41 Year Long-Term Durability of High Volume Blast-Furnace Slag Cement Concrete

Eco-friendly and cost-effective concrete utilizing high-volume blast furnace slag and demolition waste with lime

This manuscript explores the effect of ternary blend i.e. the replacements of cement, fine aggregate and coarse aggregate simultaneously with ground granulated blast furnace slag (GGBFS) and lime, granulated blast furnace slag (GBFS) and recycled coarse aggregate (RCA), respectively, on the fresh, mechanical and durability properties of concrete. Twenty-one concrete mixes having various combinations of GGBFS, lime, GBFS and RCA are prepared and characterized. Results conclude that the concrete mixes containing high volumes of RCA (up to 75%) and GBFS (up to 50%) with 60% GGBFS and 6% hydrated lime, achieve the compressive strength closer to that specified for M25 grade concrete and more than that specified for M20 grade concrete as per IS:10262 (2009). The splitting tensile, flexural and bond strengths show satisfactory performances. Durability results show that these mixes have comparable or better sulphuric acid resistance and chloride ion ingress. Also, these mixes have good cost benefit and very less environmental impact as compared to the normal concrete. Moreover, these concrete mixes save cement up to 66%, fine aggregate up to 50% and coarse aggregate up to 75% and lessen the waste disposal crisis to a greater extent which make these mixes as sustainable concrete mixes.

Use of Recycled Aggregate as Alkali Activator to Enhance Strength Development in High-Volume Blast-Furnace Slag Concrete

The aim of the research is to achieve the strength development performance of high-volume slag concrete or zero-cement concrete with 0.45 of W/B by incorporating of recycled aggregates as a cost-effective alkali activator. Based on the blast-furnace slag (BFS) based cement, like an alkali activated slag (AAS), recycled aggregates were replaced by natural aggregates and were used as an alkali activator for BFS. For compressive strength improvement in concrete, different replacement ratios of ordinary Portland cement ranged from zero to 50%, recycled fine aggregates (RFA) and recycled coarse aggregates (RCA) ranged from zero to 100% were varied. The test results indicated that recycled aggregates could be used as an alkali activator for BFS, and they were also able to help achieve about 90% of compressive strength of the concrete with natural aggregate depending on its optimum proportion with BFS.

Production of sustainable concrete utilising high-volume blast furnace slag and recycled aggregate with lime activator

Waste products from construction sector and industries have been significantly increased in the last decade, which create serious environmental problems. Therefore, their utilisation in concrete has great role in the production of sustainable concrete, preservation of natural resources and proper solid waste management. This study involves the fundamental characterisation of sustainable concrete produced using high volumes of recycled coarse aggregate (RCA) and ground granulated blast furnace slag (GGBFS) with addition of lime for its application in structural concrete members. In this investigation, at the first, the effects of lime as an alkaline activator on the mechanical and micro-structural properties of high volume GGBFS based recycled aggregate concrete (RAC) is studied in order to obtain the desired mechanical properties. From the study, the experimental results reveal that lime can be effective in activating the GGBFS and thereby, enhancing the mechanical properties such as (1) compressive strength, (2) splitting tensile strength, (3) flexural strength and (4) bond strength of high volume GGBFS based RAC. The enhancement in the above strength properties of GGBFS based RAC mixes are found to be in the range 14.02%–19.61%, 9.33%–14.07%, 10.74%–14.71% and 6.65%–14.17% for compressive, splitting tensile, flexural and bond strength, respectively. The trend of the above results is also supported by X-ray diffraction and scanning electron microscopy investigations. Secondly, the cost-effective analysis including the sensitivity analysis of cost for this concrete are carried out to ascertain its (5) economic benefit. The cost-effective analysis reveals that the cost of concrete reduces by 7.15%–11.80% for the combined use of RCA, GGBFS and lime. Thirdly, environmental impact analysis of this concrete is also performed to assess its (6) environmental benefit. It is found that the impacts on various environmental factors reduce by 32.5%–67.0% for using RCA, GGBFS and lime in concrete. Hence, it is concluded that the concrete produced using high volume of GGBFS and RCA with addition of lime activator provides the desired strength, environmental benefit by reducing the environmental impacts and minimising the waste disposal problem, economical benefit by reducing the cost and social benefit by preserving natural resources for future generation due to which this concrete becomes sustainable.

Effect of WRP and FGD gypsum on engineering properties and microstructures of HVBSM

The objective of this study is to investigate the effect of the use of waste refractory powder (WRP) and flue gas desulfurization (FGD) gypsum as an activator on the engineering properties and microstructures of high-volume blast-furnace slag mortar (HVBSM). WRP was used as a magnesium oxide (MgO) source, and FGD gypsum as a calcium sulfate source, to activate blast-furnace slag (BS). The test results indicated that, when BS alone was used for substitution, the flow was lowered compared with that of the control mixture, while the flow increased with substitution with WRP and FGD gypsum. Under the given FGD gypsum contents, the increase in WRP resulted in increased flow. The combined replacement with WRP and FGD gypsum resulted in the enhancement of the compressive strength at the age of 28 d compared to that of the control mixture. It is believed that the activation effect of FGD gypsum on BS in this study was more apparent than that of WRP. For the microstructure observations, HVBSM incorporating WRP exhibited the formation of magnesium hydroxide. In addition, HVBSM with FGD gypsum also showed larger amounts of ettringite and monosulfate hydrate, which allow HVBSM to make denser structures.

Effect of Nano Alumina on Compressive Strength and Microstructure of High Volume Slag and Slag-Fly Ash Blended Pastes

This paper presents the effect of nano alumina (NA) on compressive strength and microstructure of cement paste containing high volume blast furnace slag (BFS) contents of 70%, 80% and 90% as partial replacement of cement and combined BFS and class F fly ash (FA) contents of 70% and 80% as partial replacement of cement. FA is used at 30% as partial replacement of BFS. NA contents are varied from 1% to 4% as partial replacement of BFS and BFS-FA. Results show that the addition of NA improves the compressive strength of high volume BFS and BFS-FA pastes by 2% to 16%. The compressive strength of paste containing 69% BFS, 30% cement and 1% NA exceeded the compressive strength of control cement paste while the compressive strength of paste containing 77% BFS, 20% cement and 3% NA is 1% lower than control cement paste. NA significantly reduced the large capillary pores of >0.1 microns of high volume BFS and BFS-FA pastes. No evidence of reduction of Ca(OH)2 in high volume BFS pastes is observed due to addition of NA, however, in high volume BFS-FA paste the Ca(OH)2 is reduced due to addition of NA. Increase in intensity peaks of CAH, Ettringite and CSH in X-ray diffraction analysis is observed in high volume BFS and BFS-FA pastes due to addition of NA, which coincides with the observed more dense microstructure of high volume BFS and BFS-FA pastes containing NA than those without NA.

Effect of nano silica on compressive strength and microstructures of high volume blast furnace slag and high volume blast furnace slag-fly ash blended pastes

This paper presents the effect of nano silica (NS) on compressive strength and microstructure of cement paste containing high volume blast furnace slag (BFS) and high volume BFS-fly ash (FA) blend as partial replacement of ordinary Portland cement (OPC). Results show that high volume BFS pastes containing 60% and 70% BFS exhibited 4% higher and comparable compressive strength, respectively than control cement paste. However, about 9% and 37% reduction in compressive strength in high volume BFS pastes is observed due to use of 80% and 90% BFS, respectively. The high volume BFS-fly ash pastes containing total BFS and FA content of 60% exhibited about 5%–16% higher compressive strength than control cement paste. However, significant reduction in compressive strength is observed in higher BFS-FA blends with increasing fly ash contents. Results also show that the addition of 1–4% NS improves the compressive strength of high volume BFS paste containing 70% slag by about 9–24%. However, at higher BFS contents of 80% and 90% this improvement is even higher e.g. 11–29% and 17–41%, respectively. The NS addition also significantly improves the compressive strength of high volume BFS-FA pastes. The thermogravimetric analysis (TGA) results confirm the reduction of calcium hydroxide (CH) in high volume BFS and combined BFS-FA pastes containing NS indicating the formation of additional calcium silicate hydrate (CSH) gels in the system. The addition of NS also significantly reduced the pore volume of high volume BFS and combined BFS-FA pastes. The X-ray diffraction (XRD) analysis also confirms the reduction of intensity of CH peaks indicating its consumption in pozzolanic reaction. The scanning electron microscopy (SEM) images also confirm denser microstructure of high volume BFS and combined BFS-FA pastes containing NS compared to those without NS. By combining slag, fly ash and NS in high volumes e.g. 70–80%, the carbon footprint of cement paste is reduced significantly while maintains the similar compressive strength of control cement paste.

Development and application of a hybrid prestressed segmental concrete girder utilizing low carbon materials

A hybrid prestressed segmental concrete (HPSC) girder utilizing low carbon materials was developed in this paper. This paper introduces the hybrid prestressing concept of pre-tensioning the center segment and assembling all segments by post-tensioning, as well as the development process of the low carbon HPSC girder. First, an optimized mix proportion of 60 MPa high strength concrete containing high volume blast furnace slag was developed, then its mechanical properties and durability characteristics were evaluated. Second, the mechanical properties of 2,400 MPa high strength prestressing strands and the transfer length characteristics in pre-tensioned prestressed concrete beams were evaluated. Third, using those low carbon materials and the hybrid prestressing concept, the HPSC girders were manufactured, and their structural performance was evaluated. A 30-m long HPSC girder for highway bridges and a 35-m long HPSC girder for railway bridges were designed, manufactured, and structurally confirmed as having sufficient strength and safety. Finally, five 35-m long HPSC girders were successfully applied to an actual railway bridge for the first time.

Preparation of CaMgAl-LDHs and mesoporous silica sorbents derived from blast furnace slag for CO2 capture.

High volume blast furnace slag (BFS) resulting from iron-making activities has long been considered a burden for the environment. Despite considerable research efforts, attempts to convert BFS into high value-added products for environmental remediation are still challenging. In this study, calcium–magnesium–aluminium layered double hydroxides (CaMgAl-LDHs) and ordered mesoporous silica material (MCM-41) sorbents were simultaneously synthesized from BFS, and their CO2 adsorption performance was evaluated. Calcium (Ca), magnesium (Mg) and aluminium (Al) were selectively extracted from BFS using hydrochloric acid. Leaching conditions consisting of 2 mol L−1 acid concentration, 100 °C leaching temperature, 90 min leaching time and a solid-to-liquid ratio of 40 g L−1 achieved a high leaching ratio of Ca, Mg and Al at 88.08%, 88.59% and 82.27%, respectively. The silica-rich residue (SiO2 > 98.6 wt%) generated from the leaching process could be used as a precursor for MCM-41 preparation. Chemical composition, surface chemical bonds, morphology and textural properties of the as-synthesized CaMgAl-LDHs and MCM-41 sorbents were determined. Both the CaMgAl-LDHs and MCM-41 sorbents were found to be thermally stable and exhibited comparable adsorption uptake and rates over 20 CO2 adsorption/desorption cycles. This work demonstrated that a total solution for the utilisation of BFS can be achieved and the resulting valuable products, i.e. CaMgAl-LDHs and MCM-41 are promising sorbents for CO2 capture.

The effect of ultrahigh volume ultrafine blast furnace slag on the properties of cement pastes

The dosage of blast furnace slag (BFS) in cement is limited on account of relative low reaction rate and low early strength. Improving the early age activity of BFS is the fundamental solution for high volume BFS cementitious materials. Generally, mechanical activation is one of the main techniques to accelerate the early reaction of mineral admixtures. In this study, wet-milling and dry-separation are respectively used to prepare ultrafine BFS to improve its early reactivity. The early hydration characteristics, mechanical property, hydration products of ultrahigh volume BFS cementitious materials are analyzed to assess the efficiency of ultrafine BFS on the properties of BFS cement paste. The results show that the initial and final setting time both gradually decrease as the dry-separation BFS (GS) dosage increases, while the wet-milling BFS (WS) series present the opposite tendency. The electrical resistivity of WS specimens develops at a faster rate than that of GS specimens. Mixes containing WS, at a maximum dosage of 90%, have higher mechanical property than those with GS, resulting in an enhancement of strength. The hydration products mainly include calcium hydroxide, hydrotalcite, hydrotalcite-like phase, calcium carbonate, strätlingite, C-S-H, C-A-S-H, and akermanite.

Mechanical Properties of Steam Cured High-Strength Steel Fiber-Reinforced Concrete with High-Volume Blast Furnace Slag

In this study, the effects of water-to-binder (W/B) ratio and replacement ratio of blast furnace slag (BFS) on the compressive strength of concrete were first investigated to determine an optimized mixture. Then, using the optimized high-strength concrete (HSC) mixture, hooked steel fibers with various aspect ratios and volume fractions were used as additives and the resulting mechanical properties under compression and flexure were evaluated. Test results indicated that replacement ratios of BFS from 50 to 60% were optimal in maximizing the compressive strength of steam-cured HSCs with various W/B ratios. The use of hooked steel fibers with the aspect ratio of 80 led to better mechanical performance under both compression and flexure than those with the aspect ratio of 65. By increasing the fiber aspect ratio from 65 to 80, the hooked steel fiber volume content could be reduced by 0.25% without any significant deterioration of energy absorption capacity. Lastly, complete material models of steel-fiber-reinforced HSCs were proposed for structural design from Lee’s model and the RILEM TC 162-TDF recommendations.

탈황석고의 처리방법변화가 고로슬래그 미분말 다량 치환 모르타르의 공학적 특성에 미치는 영향

In this research, the influence of desulfurized gypsum (FGD) with different carbon removing methods of 0.3 mm sieving, and <TEX>$500^{\circ}C$</TEX> high temperature combustion on high volume blast furnace slag cement mortar was evaluated with different replacement ratios of 1 : 2, and 1 : 4 for blast furnace slag. As an experiment result, flow was generally decreased with FGD replacing while slight increased was shown with 5 to 10 % of replacement for 1 : 4 mortar. As FGD replacement, air content was reduced setting time was shortened. Compressive strength was generally decreased with 1 : 2 mortar mixtures, but for 1 : 4 mortar mixture, the highest compressive strength value was obtained when FGD was replaced about 10 % due to the generation of ettringite. Drying shrinkage was decreased and absorption rate was increased with increased FGD replacement ratio. Overall, as a carbon removing method of FGD, 0.3 mm sieving showed better results than <TEX>$500^{\circ}C$</TEX> high temperature combustion, and the mortar mixture was the most appropriate results were obtained with 1 : 4 mixture and 10 % of FGD replacement ratio.

고로슬래그가 다량 혼입된 고강도 콘크리트의 수축 특성 및 균열 잠재성 평가

고로슬래그가 다량 혼입된 고강도 콘크리트의 수축 특성 및 균열 잠재성 평가