Air-cooled Blast Furnace Slag Research Articles

Laboratory evaluation of a complex treatment technology for reducing water absorption of the pavement subbase aggregate from the blast-furnace slag

When smelting each ton of pig iron, approximately 500 kg of blast-furnace slag is formed and requires recycling. Air-cooled blast-furnace slag can be used for the manufacture of slag aggregate for the pavement subbase layers, as an alternative to natural stone aggregate. The wide use of slag in this area is limited by its high water absorption. This paper proposes a complex technology to reduce water absorption of slag aggregate. This technology includes selective crushing, which allows separating low-porosity aggregate grains from high-porosity ones, and impregnation of selected low-porosity grains with hydrophobic agent (surface hydrophobization). The results of a laboratory evaluation of this technology effectiveness are presented. Article also contains optimal parameters of this complex technological process which allowed to reduce the water absorption of the slag aggregate from 4.54% to 1.05%.

Potential Role of GGBS and ACBFS Blast Furnace Slag at 90 Days for Application in Rigid Concrete Pavements.

Incorporating blast furnace slag into the composition of paving concrete can be one of the cost-effective ways to completely eliminate by-products from the pig iron production process (approximately 70% granulated slag and 30% air-cooled slag). The possibility to reintroduce blast furnace slag back into the life cycle will provide significant support to current environmental concerns and the clearance of tailings landfills. Especially in recent years, granulated and ground blast furnace slag (GGBS) as a substitute for cement and air-cooled blast furnace slag (ACBFS) aggregates as a substitute for natural aggregates in the composition of concretes have been studied by many researchers. But concrete compositions with large amounts of incorporated blast furnace slag affect the mechanical and durability properties through the interaction between the slag, cement and water depending on the curing times. This study focuses on identifying the optimal proportions of GGBS as a supplementary cementitious material (SCM) and ACBFS aggregates as a substitute to natural sand such that the performance at 90 days of curing the concrete is similar to that of the control concrete. In addition, to minimize the costs associated with grinding GGBS, the hydration activity index (HAI) of the GGBS, the surface morphology, and the mineral components were analyzed via X-ray diffraction, scanning electron microscopy (SEM), energy dispersive spectrometry (EDX), and nuclear magnetic resonance relaxometry (NMR). The flexural strength, the basic mechanical property of road concretes, increased from 28 to 90 days by 20.72% and 20.26% for the slag concrete but by 18.58% for the reference concrete. The composite with 15% GGBS and 25% ACBFS achieved results similar to the reference concrete at 90 days; therefore, they are considered optimal percentages to replace cement and natural sand in ecological pavement concretes. The HAI of the slag powder with a specific surface area equivalent to that of Portland cement fell into strength class 80 at the age of 28 days, but at the age of 90 days, the strength class was 100. The results of this research present three important benefits: the first is the protection of the environment through the recycling of two steel industry wastes that complies with European circular economy regulations, and the second is linked to the consequent savings in the disposal costs associated with wastefully occupied warehouses and the savings in slag grinding.

The Advantages on Using GGBS and ACBFS Aggregate to Obtain an Ecological Road Concrete

This work aims to show the advantages of using GGBS (Ground Granulated Blast Furnace Slag) and ACBFS aggregate (Air-Cooled Blast Furnace Slag) on the tensile strength and durability properties of infrastructure concrete at the reference age of 28 days. Three concrete mixes were prepared: the first one was a control sample; the second one had 15% GGBS (instead of Portland cement) and 25% ACBFS (instead of natural sand); and the third had 15% GGBS (instead of Portland cement) and 50% ACBFS (instead of natural sand). The studies on mortars focused on the ratio of compressive strength (CS) in correlation with the specific surface area (obtained by the Blain method). The microstructure of the prepared mortars was examined at the age of 28 days by X-ray diffraction, SEM electron microscopy with an energy-dispersive EDX spectrometer, and NMR nuclear magnetic resonance relaxometry. The results of the tests carried out afterwards on the concretes containing slag (15% GGBS and 25% or 50% ACBFS) showed values that met high-quality criteria for exfoliation (S56 < 0.1 kg/m2), carbonation, and gelling G100 (with a loss of resistance to compression η < 25%). The slag concretes showed a degree of gelation of G100 (with a loss of compressive strength below 25%), low volume losses below 18,000 mm3/5000 mm2 (corresponding to wear class 4, grade I), and moderate penetration of chlorine ions (according to the RCPT test). All of these allow the concrete with slag (GGBS/ACBFS) to be recommended as an ecological road concrete. Our study proved that a high-class road concrete of BcR 5.0 can be obtained, with tensile strengths of a minimum 5 MPa at 28 days (the higher road concrete class in Romania, according to national standards).

Development of Geopolymer Mortars Using Air-Cooled Blast Furnace Slag and Biomass Bottom Ashes as Fine Aggregates

The aim of this study is to compare the mechanical and physical properties of different geopolymer mortars made with granulated blast furnace slag as a geopolymer source material, NaOH (8 M) as the activating solution, and three different types of fine aggregates (air-cooled blast furnace slag, biomass bottom ashes, and silica sand). The samples were made with an aggregate/geopolymer ratio of 3/1, and physical (density and mercury intrusion porosimetry), mechanical (compressive and flexural strength), and acid attack resistance were determined. When air-cooled blast furnace slag is used, the mechanical and acid attack properties are improved compared with silica sand and biomass bottom ashes because of the existence of amorphous phases in this slag, which increase the geopolymer reaction rate despite the particle size being higher than other aggregates. It can be highlighted that the use of ACBFS as a fine aggregate in geopolymer mortars produces better properties than in cement Portland mortar.

Evaluation of the effect of enrichment of slag aggregate for pavement subbase by grains density on its physical and mechanical characteristics

The article presents the results of a laboratory evaluation of the influence of the enrichment of the slag aggregate (size 20–40 mm) for road construction, obtained from the air-cooled blast furnace slag, on the grains density, on its water absorption, freeze-thaw resistance and resistance to crushing. The results of quantitative and qualitative evaluation of the obtained empirical dependences, performed using the methods of correlation analysis and approximation, are presented. Enrichment of the slag aggregate in terms of grains density makes it possible to reduce its water absorption from 4.9-6.8% to 2.19–3.13%, increase the number of repeated freeze-thaw cycles maintained without significant destruction, from 150 to 300–400, and reduce crushing value from 30-31% to 20–21%. The resulting approximation equations make it possible to predict the change in physical-mechanical characteristics with further enrichment of the slag aggregate in terms of grains density. Laboratory tests showed that the slag aggregate, pre-enriched in grain density, when used as aggregate for pavement subbase operated in continental climates with frequent natural repetition of freeze-thaw cycles, will resist the temperature fluctuations much more effectively than the high-porosity slag aggregate used without enrichment.

The Influence of Blast Furnace Slag on Cement Concrete Road by Microstructure Characterization and Assessment of Physical-Mechanical Resistances at 150/480 Days.

The results presented in this paper on the appropriateness of using of blast furnace slag (BFS) in the composition of roads make an original contribution to the development of sustainable materials with the aim to reduce the carbon footprint and the consumption of natural resources. The novelty of this work consists of determining the optimal percentage of BSF in road concrete, in order to: increase mechanical resistances, reduce contractions in the hardening process, and ensure increased corrosion resistances, even superior to classic cement-based mixtures. Thus, the physical-mechanical characteristics and the microstructure of some road concretes were studied in the laboratory for three different recipes. We kept the same amount of ground granulated blast furnace slag (GGBS) as a substitute for Portland cement, respectively three percentages of 20%, 40%, 60% air-cooled blast furnace slag (ACBFS) and crushed as sand substitute from now on called S54/20, S54/40, S54/60. Drying shrinkage, mechanical resistances, carbonation-induced corrosion, microstructure characterization of hardened concretes, and degree of crystallinity by SEM and XRD measurements were analyzed after a longer curing period of 150/480 days. The obtained results on the three BSF mixtures indicated a reduction of drying shrinkage and implicitly increased the tensile resistance by bending to 150 days well above the level of the blank composition. The degree of crystallinity and the content of the majority phases of the mineralogical compounds, albites, quartz, and tobermorite out of the three BSF samples justifies the increase in the compressive strengths at the age of 480 days in comparison with the test samples. Scanning electron microscope (SEM) and X-ray diffraction measurements showed the highest compactness and lowest portlandite crystal content for the S54/20 slag composite. Future research concerns are the realization of experimental sections in situ, the study of the influence of BFS on the elasticity module of road concrete, and the opportunity to use other green materials that can contribute to the reduction of the carbon footprint, keeping the physical and mechanical properties of road concrete at a high level.

Study on Properties of Concrete After Incorporating Waste Materials

The effects of fly ash, Air Cooled Blast Furnace Slag (ACBFS), and silica fume on cement compressive strength are examined. The compressive strength of cement concrete is studied by the addition of fly ash, air-cooled blast furnace slag (ACBFS), and silica fume. The effect of fly ash, ACBFS, and silica fume on the compressive strength of concrete was investigated. The cement content of the concrete was reduced by 25%, 22.50%, 20%, and 17.50%, respectively; fly ash was used to replace 20%, 40%, and 60% of the coarse aggregate; and fly ash was partially replaced by 2.5%, 5%, and 7.50% of the cement content. Contrarily, fly ash was left out of the mixing process for M30. The compressive strength of concrete cubes and beams aged 7 and 28 days was tested.

Recycling air-cooled blast furnace slag in fiber reinforced alkali-activated mortar

Fiber reinforced alkali-activated materials (FR-AAM) present as one type of sustainable and resilient materials. However, the thermal degradation mechanism of FR-AAM remains unclear. In this study, FR-AAM incorporating air-cooled blast furnace slag (ACBF), ground granulated blast furnace slag (GGBS) and different types of fibers (steel, glass, and polypropylene) are produced and exposed to elevated temperatures. Test results show that ACBF (replacing 30% of river sand) improved the thermal resistance of FR-AAM due to the ameliorated interfacial transition zone (ITZ) and channels for the release of vapor pressure. Relatively, steel fibers better retain mechanical performance, whilst polypropylene fibers better provide channels for the release of vapor pressure after melting. Gel decomposition and micro crack development are the main causes for the thermal deterioration of FR-AAM. Based on non-destructive tests, damage degree is proposed to quantitatively evaluate the usability and deterioration coefficient (K) is adopted to controll the strength retention of FR-AAM at high temperatures. Economically and environmentally, the development of FR-AAM is promising in shaping a sustainable and resilient future.

Effect of air-cooled blast furnace slag aggregate on mechanical properties of ultra-high-performance concrete

This research is mainly focusing on making UHPFRC lightweight, cost-effective, and environment friendly with the application of waste material. Air-cooled blast furnace slag aggregate (ACBFSA) was chosen as coarse aggregate with 30%, 50%, and 100% replacement by volume of regular limestone coarse aggregate in this study. Both straight and hooked fibers were used in mixtures of UHPFRC. The impact of coarse aggregates and dual fibers on the mechanical characteristics and fracture parameters was investigated. Fracture analysis has been widely considered as an effective way to analyze the stability of cracks, crack propagation, and safety evaluation. Compressive strength, splitting tensile strength, elastic modulus, fracture toughness, and fracture energy were all examined experimentally. Experimental results determined that concrete workability decreased with every increase in the replacement ratio of natural aggregate. The compression and splitting tensile strength was first increased at 30% replacement and then decreased at 50% and 100% replacement of NA. Flexural and fracture properties show a uniform decrease as the replacement percentage increases. It indicates that ACBFSA has low resistance against cracking which is closer to the UHPFRC without coarse aggregates. Results also prove that the low-cost and eco-friendly waste material ACBFSA can be used in UHPFRC as partially and somehow fully replacement while retaining the main properties.

Experimental investigations on substitution of natural sand in concrete with copper slag and blast furnace slag

The constant decrease in the availability of good quality natural sand across the globe has led to increasing investigations on the possibility of utilizing by-products obtained from different industries as a replacement for natural sand. Copper slag and blast furnace slag are by-products of metallurgical processes occurring during copper and pig iron production, respectively. The substitution of natural sand using copper slag and blast furnace slag in plain and reinforced concrete has been permitted in Indian Standard IS: 383-2016 up to a certain percentage as replacing natural sand in concrete. In the present study, investigations were carried out to check the feasibility of increasing copper slag and blast furnace slag as a substitution of natural sand in concrete. Conventional (Natural) sand was replaced (by volume) with copper slag (0%, 25%, 50% & 75%), Granulated Blast Furnace Slag (GBFS) (0%, 30%, 60% & 100%) and Air-Cooled Blast Furnace Slag (ACBFS) (0%, 30%, 60% & 100%). Concrete mixes were examined by substituting conventional sand with copper and blast furnace slag in different proportions and were evaluated for different mechanical properties and durabil-ity-related parameters. Leaching studies were also carried out on selected concrete samples.

Physical and Mechanical Properties of Rural-Road Pavement Concrete in South Korea Containing Air-Cooled Blast-Furnace Slag Aggregates

The purpose of this study was to assess the physical and mechanical properties of pavement concrete for rural roads of South Korea made with air-cooled slag aggregate, which is an industrial byproduct. This study assessed the physical and chemical properties according to the following performance requirements based on the design criteria of the Korea Ministry of Agriculture’s Agricultural Production Infrastructure Maintenance Business Plan and the Korea Expressway Corporation’s Highway Construction Specialized Specifications: slump of 80 mm or greater, air content of 4.5 ± 1.5%, compressive strength of at least 21 MPa, splitting tensile strength of at least 4.2 MPa, and a chloride penetration resistance of less than 4000 C. The slump, air content, compressive strength, splitting tensile strength, flexural strength, and chloride ion permeability of the aggregate-containing concretes were measured. The air-cooled slag aggregates provided the necessary physical and chemical properties and presented no environmental issues. Furthermore, the slump and air content of concrete made with the aggregates met the target values. The slump decreased and the air content increased with increasing amounts of air-cooled slag aggregate. Mechanical testing of the concretes containing air-cooled slag aggregate established that they met the performance requirements for rural road pavement.

Blast furnace slag in road construction and maintenance / Blast furnace slag in road construction and maintenance

Introduction. There is a global trend to increase the sustainability of road construction and maintenance technologies. The growing use of various industrial by-products as economical and eco-friendly construction and maintenance techniques can be observed in many countries.Problem Statement. The utilization of various forms of blast furnace slag in the road sector can be cost effective, however, several special technological measures have to be taken.PurposePresenting best practices for the use of blast furnace slag in road construction and maintenance techniques based on Hungarian and other decade-long experiences.Materials and Methods. The main types investigated are air-cooled blast furnace slag, expanded or foamed slag, pelletized slag, and granulated blast furnace slag. The utilization areas in road sector: asphalt layers, surface treatments, rut repair, hydraulically bound pavement layers, unbound base layers, frost protection layer, subgrade, cement production.Results. Presenting best practices for the use of blast furnace slag in road construction and maintenance can be beneficial for the experts of countries with limited experience in the field. Keywords: blast furnace slag, industrial by-products, road construction, road maintenance, environmental protection

Experimental study on resistance of cement concrete pavement constructed using air-cooled and water-cooled ground blast-furnace slag exposed to combined carbonation and scaling

Experimental study on resistance of cement concrete pavement constructed using air-cooled and water-cooled ground blast-furnace slag exposed to combined carbonation and scaling

Adhesion between steel slag aggregates and bituminous binder based on surface characteristics and mixture moisture resistance

Steel slag aggregates (SSA) have shown promising mechanical and physical properties for asphalt concrete application. However, SSA surface characteristics vary depending on the type of slag, which results in different binder-SSA adhesion that affects moisture damage of asphalt mixtures containing SSA. This study evaluated the adhesion in the binder-SSA system considering two typical types of slags (i.e. air-cooled blast furnace slag (ACBFS) and Linz-Donawitz steel slag (LD)) using various tests: morphological, physical, chemical, and surface energy measurements. Also, the moisture damage susceptibility of asphalt mixtures containing SSA were assessed based on two standard methods: ASTM D3625 and AASHTO T283. Test results showed strong influence of the SSA chemical composition and surface energy characteristics on the SSA-binder adhesion. LD showed a better adhesion with the asphalt binder than ACBFS due to its particular chemical and surface energy characteristics. The diminished adhesive bonding from ACBFS could be improved with proper surface treatment using additives such as hydrated lime and electrostatic precipitator powder, which change surface chemistry of ACBFS.

Experimental study on full-volume slag alkali-activated mortars: Air-cooled blast furnace slag versus machine-made sand as fine aggregates

As the industrial waste from blast furnace ironmaking, air-cooled blast furnace slag (ACBFS) puts a lot of pressure on the environment. It is becoming more and more urgent to deal with the increasing ACBFS. In this study, the concept of “full-volume slag alkali-activated mortars (FSAM)” is proposed using ground granulated water-cooled blast furnace slag (GGBS) as aluminosilicate material and ACBFS to replace machine-made sand, aiming to solve the current situation of increasing scarcity of natural resources. The characteristics of ACBFS are investigated, and its stability and heavy metal leaching all meet the requirements as a building material. The results show that the flowability and mechanical properties of FSAM are significantly enhanced with the substitution rate of ACBFS increases. Meanwhile, the incorporation of ACBFS is also beneficial to improve the compactness of the microstructure of the mortar, thereby improving the impermeability (Water, ion and gas) of FSAM. In addition, the specimen mixed with ACBFS showed good high temperature resistance due to the porous feature of the aggregate. Furthermore, using a small amount of limestone powder to replace GGBS can slightly improve the performance of FSAM. Therefore, ACBFS is recommended to be used in FSAM, which meets safety, cost and environmental benefits.

Use of air-cooled blast furnace slag as supplementary cementitious material for self-compacting concrete production

The manufacturing process of pig iron generates large amounts of slag. The slow cooling of this waste generates the air-cooled blast furnace slag (ACS). Since it is less reactive than granulated blast furnace slag (GBFS), ACS finds little use as supplementary cementitious material (SCM) and the existing studies use it only as aggregates in concrete. This work investigated the use of finely ground ACS as SCM for self-compacting concrete (SCC) production. Pastes and SCCs with GBFS, ACS in two grinding levels and limestone filler (LF) were produced, and their fresh state performance, hydration kinetics and compressive strength from 3 to 91 days were evaluated. ACS increased the yield stress and viscosity of the pastes compared with LF, also increasing the SCC’s superplasticizer content required to reach the target slump flow of 650 ± 50 mm. Nonetheless, this increase was from 0.95 up to 1.36 kg/m3 of concrete, and all the mixes presented V-funnel time of 4–6 s and were highly stable in the fresh state (VSI = 0, with no segregation/bleeding). Isothermal calorimetry indicated that ACS slightly shortened the induction period compared with LF, but led to equivalent peak values (6.7–6.9 mW/g cement). Concretes with ACS and LF had similar strengths at all ages, reaching 32 ± 1 MPa at 3 days and 41 ± 2 MPa at 91 days, indicating that no significant reaction was observed for ACS up to the later age. Furthermore, blending ACS with LF in equal proportions resulted in a SCC with fresh performance equivalent to that containing only LF, in addition to increasing the strength by about 5% at all ages. In general, ACS had comparable performance to that of LF and can be used as SCM in SCC.

Influence of Aggregate and Binder Content on the Properties of Pervious Concrete

This study introduces the experiment based on following parameters: kind of aggregate (natural river gravel and air-cooled blast furnace slag), the aggregate gradation and content of binder. Main properties such as compressive strength, void content and hydraulic conductivity of pervious concrete were investigated in the experiment. The experiment showed satisfactory results in the case of pervious concrete made of natural aggregate. Results of pervious concrete made of air-cooled blast furnace slag aggregates are perspective, however needs for some optimizations. Results confirmed the opposite relationship between compressive strength and void content/hydraulic activity. ACBFS performs worse than NA as for compressive strength, while it performs better in the case of hydraulic conductivity and void content.

Geopolymer Based on Mechanically Activated Air-cooled Blast Furnace Slag.

An efficient solution to increase the sustainability of building materials is to replace Portland cement with alkali-activated materials (AAM). Precursors for those systems are often based on water-cooled ground granulated blast furnace slags (GGBFS). Quenching of blast furnace slag can be done also by air but in that case, the final product is crystalline and with a very low reactivity. The present study aimed to evaluate the cementitious properties of a mechanically activated (MCA) air-cooled blast furnace slag (ACBFS) used as a precursor in sodium silicate alkali-activated systems. The unreactive ACBFS was processed in a planetary ball mill and its cementing performances were compared with an alkali-activated water-cooled GGBFS. Mixes based on mechanically activated ACBFS reached the 7-days compressive strength of 35 MPa and the 28-days compressive strength 45 MPa. The GGBFS-based samples showed generally higher compressive strength values.

Effects of Air-Cooled Blast Furnace Slag Aggregate on Pore Solution Chemistry of Cementitious Systems

AbstractAir-cooled blast furnace slag (ACBFS) can be used to replace naturally mined aggregates to minimize the environmental and economic costs associated with construction. This paper compares po...

Effect of Cutter Soil Mixing (CSM) method and curing pressures on the tensile strength of a treated soft clay

This study presents a set of laboratory experiments to investigate the effect of Cutter Soil Mixing (CSM) method and curing pressures on the tensile strength of a soft clay treated with Air Cooled Blast Furnace Slag (ACBFS) and Industrial Hydrated Lime (IHL). High productivity, minimum vibration, using the in-situ soil as construction material, and high level of quality control are some of the main benefits of CSM method. Three different slurries containing various percentages of ACBFS and IHL were mixed with saturated soft clay due to CSM method to enhance its tensile strength and make it suitable for the construction of deep CSM panels. To simulate high pressure due to the self-weight of the deep CSM panels in the field, a number of high pressure curing devices were designed and built in the laboratory and used for 28 and 56 day pressurised curing of the treated samples. Then an indirect tensile strength test was performed on the treated samples to investigate the effect of mixing method, ACBFS-IHL content, curing pressure and curing time on the tensile strength of the treated material. Finally, X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) analysis were conducted to investigate the microstructural and properties of the treated clay. The outcomes demonstrate that using CSM method and curing pressures along with ACBFS-IHL as a chemical stabiliser, increases the tensile strength of treated soft clay up to 35 times, which is significantly higher than the use of chemical stabiliser alone. Moreover, the microstructural analysis results revealed that the main hydration products in the clay treated with ACBFS-IHL is gismondine (C–A–S–H) which is also considered to be responsible for the higher tensile development.