Search

The use of alkali-activated composites and alternative aggregates reduces the carbon dioxide emissions of the construction industry and mitigates the problem of aggregate depletion. However, published investigations into non-cement composites containing ferronickel slag powder (FSP) and blast-furnace slag fine aggregate (BSA) are limited. The aim of this study was thus to assess the mechanical properties and durability of non-cement composites containing FSP and BSA. The mix with 10% FSP and 25% BSA was found to have the highest 28-day compressive strength, of approximately 42.2 MPa. For the mixes with 5% FSP, the 28-day compressive strength increased with an increase in BSA content. Charge-passed tests revealed that, after 7 days, the sample with 5% FSP and 50% BSA exhibited a total charge of approximately 907 C, classifying it as 'very low' according to ASTM C1202. By 56 days, the total charge for this sample reached a value of approximately 120 C, close to 'negligible' as per ASTM C1202. It was thus concluded that an appropriate BSA content effectively enhances the mechanical properties and durability of non-cement composites. [ABSTRACT FROM AUTHOR]

The alkali-activation of blast-furnace slags (BFSs) is a topic largely studied today. However, some types of activators, more environmentally friendly, have been less studied such as alkali-sulphate activators. In this study, the effect of four alkali-sulphate activators (Na2SO4, K2SO4, MgSO4, CaSO4.2H2O) is investigated to better understand the effect of cations (Na+, K+, Mg2+, Ca2+) and of a high content of sulphate ions (SO42−) on the hydration process of BFS and the nature of the hydrates. To reach this objective, a large experimental campaign is carried out to characterize the pore solution, the hydration products and the kinetics of the chemical reactions. As the temperature seriously affects the hydration advancement, the activation energy coefficient is also determined experimentally to compare the results as function of the equivalent time. Finally, a new method is proposed to determine the evolution of the hydration degree of BFSs, a key parameter for predicting the evolution of the hydrates through a thermodynamic modeling. The results indicate that the use of sodium sulphate results in faster hydration kinetics and shorter setting times due to a higher pH of their pore solution, leading to a larger rate of C-A-S-H type gel precipitation from the initial setting time to the long term and a higher hydration advancement. These hydration products are characterized by a higher content of Na+ and a denser rim around the surface of anhydrous particles. The effect of K2SO4, MgSO4 and CaSO4.2H2O on the BFS activation efficiency is limited compared to Na2SO4 due to their lower rate of C-S-H type gel evolution at early age. It is directly related to the pH of the pore solution and the effect of cations on the nature of hydrates. However, the compressive fis research study, a large strength beyond 28 days is more significant for mortars activated with Na2SO4 and MgSO4, satisfying the strength requirement of the repaired mortars (R2 and R3) due to the larger contents of C-(N)-A-S-H/M-S-H-type gels, ettringite and hydrotalcite. [ABSTRACT FROM AUTHOR]

The low activity of stainless steel slag (SSS), primarily attributed to its high γ-C2S and low C3S content, impedes its effective utilisation. A thermochemical high-temperature reconstruction method using lime and bauxite as tempering agents to regulate the mineral phase was investigated in this work. Through an array of tests and analytical techniques, including compressive strength tests, activity index evaluation, X-ray diffraction, scanning electron microscopy and hydration heat analysis, the impacts of the calcium/silicon mass (CSM) ratio and the sintering temperature on the mechanical properties and activity of reconstituted SSS mortar were examined. It was found that, at a CSM ratio of 4.2 and a sintering temperature of 1290°C, the reconstructed slag demonstrated optimal mechanical properties and activity, yielding compressive strengths of 43.69 MPa and 62.58 MPa at 7 days and 28 days, respectively, with remarkable 28-day activity index of 143.49%. The proposed thermochemical high-temperature reconstruction method ingeniously employs high temperature to increase the content of C3S while rapid cooling prevents alteration of the C2S crystalline structure. This innovation significantly enhanced the mechanical properties and activity of the SSS, offering promising avenues to increase its utilisation rate. [ABSTRACT FROM AUTHOR]

A study was undertaken to evaluate the embodied greenhouse gas emissions of four different design options for the foundation of a residential modular building in the East Midlands, UK. The assessment considered the embodied carbon dioxide equivalent of material production (without and with Portland cement replacement using ground granulated blast-furnace slag), transportation, construction works (such as soil excavation) and plant usage on site and off site. The findings indicated that helical piles and reinforced concrete slabs supported with expanded polystyrene were the most sustainable options (in terms of embodied emissions) compared with conventional strip and pad foundations. This study provides valuable insight into considerations and constraints that may arise when evaluating the sustainability of modular building foundations. It offers practical guidance for decision makers in the modular construction sector seeking to mitigate the environmental impact of their geotechnical design. [ABSTRACT FROM AUTHOR]

Conobea scoparioides (Plantaginaceae) is an herbaceous plant known as "pataqueira" that grows wild in seasonally wet areas of the Amazon region. It is used for aromatic baths and anti-protozoan remedies by the Brazilian Amazon native people. The main volatile compounds identified in the essential oil of "Pataqueira" were the phenolic monoterpenes thymol and thymol methyl ether and their precursors, the monoterpene hydrocarbons α-phellandrene and p-cymene. A hydrotalcite synthesized from blast-furnace slag exhibited a 3:2 (Mg/Al) molar ratio, and this layered double hydroxide (LDH) was evaluated as a catalyst in converting the main monoterpenes of the "Pataqueira" oil. This action significantly increased the thymol content, from 41% to 95%, associated with the percentual reduction in other main components, such as thymol methyl ether, α-phellandrene, and p-cymene. The LDH reaction showed a strong tendency towards producing hydroxylated derivatives, and its behavior was similar to the hypothetical plant biosynthetic pathway, which leads to the production of the monoterpenes of "Pataqueira" oil. Thymol and its derivatives are potent antiseptics applied in pharmaceutical and hygienic products as antibacterial, antifungal, and antioxidant properties, among others. The present work reports a natural source with a high thymol content in aromatic plants from the Amazon, with evident economic value. [ABSTRACT FROM AUTHOR]

This paper assesses the suitability of geopolymers (GPs) for use as adhesives for ceramic tile fixing, including their compliance to the relevant EN 12004 specification. Two series prepared with different percentages of metakaolin (MK), blast-furnace slag (BFS), and limestone materials activated by an alkaline NaOH/Na2SiO3 solution are investigated. Tested properties included the thixotropy, setting, compressive strength, open time, and adhesion bond strength under different exposure conditions (that is, dry, wet, heat, or freezing-and-thawing cycles). Compared to cement-based mortars containing adjusted proportions of cellulose and redispersible polymers, the GPs exhibited higher thixotropy, reflecting additional energy for spreading the material over the substrate, yet better maintenance of the alternating patterns of ripples and grooves at rest. The bond strengths tested under different exposure conditions were remarkably high for the MK-based GP, given the fine MK particle sizes that foster geopolymerization and crosslinking of solid bonds in the hardened structure. The BFS-based GP exhibited relatively lower bond strengths (compared to MK) due to coarser particles. Such results can be of interest to civil engineers and manufacturers of ready-to-use building materials that aim at reducing the portland cement footprint while assuring performance and sustainability of tiling applications. [ABSTRACT FROM AUTHOR]

The ubiquitous use of Portland cement in construction is accompanied by significant energy consumption and environmental impact. Geopolymeric cement has emerged as a sustainable alternative, boasting mechanical properties that are potentially favorable and a notably lower environmental footprint. This study evaluates the mechanical, physical, microstructural, and durability characteristics of geopolymer mortars synthesized from local aluminosilicate precursors--namely metakaolin (MK) and granulated blast-furnace slag (GBFS)--activated with sodium silicate solutions of varying molar ratios (1.2 to 2). Mechanical parameters assessed include compressive and flexural strengths and dynamic modulus, while physical properties encompass workability and porosity. Microstructural analysis was conducted, and durability was gauged through compressive strength reduction and alkalinity loss following sulfuric acid exposure. The performances of these geopolymer mortars were juxtaposed with those of conventional Portland cement mortar. It was revealed that an optimal geopolymer formulation incorporates 75% aluminosilicate material and 25% alkaline solution, with a liquid-to-solid ratio of 0.5 and a sodium silicate solution molar ratio (SiO2/Na2O) of 1.8. This specific formulation yielded a compressive strength that surpassed that of the Portland cement mortar and displayed comparable porosity and resistance to compressive strength reduction postacid exposure. [ABSTRACT FROM AUTHOR]

This study compares greenhouse gas (GHG) emissions, embodied energy, and air pollutant emissions of alkali-activated mortars and conventional portland cement (PC)-based mortars. Alkali-activated materials (AAMs) do not require the use of PC to offer cementitious properties; these materials can valorize industrial waste streams and noncementitious natural resources. In this work, several AAMs containing blast-furnace slag and natural pozzolans were examined. Comparisons were drawn both based on the production on 1 m3 of material and based on ratios of GHG emissions to mortar strength. To facilitate robust assessments, mechanical and material properties were determined. GHG emissions, embodied energy, and nitrogen oxides (NOx), sulfur oxides (SOx), carbon monoxide (CO), and lead (Pb) emissions for the alkali-activated mortars were lower than their conventional counterparts. However, the AAMs exhibited higher volatile organic compound (VOC) and particulate matter 10 microns or smaller (PM10) emissions. When ratios of GHG emissions to strength were examined, results indicated that the lower environmental impacts of AAMs could be desirable relative to PC mortars, even when the AAMs displayed lower mechanical strength. These findings suggest that, depending on application, AAMs could contribute to environmental impact-mitigation strategies.

The dissolution rates of alkali-activated fly ash (FA) and alkali-activated slag in hydrochloric acid (HCl) with various pH values were investigated. The geopolymerisation reaction degree of alkali-activated FA/slag (AAFS) can be determined based on the content of hydrochloric-acid-insoluble matter, so X-ray fluorescence, X-ray diffraction and Fourier-transformed infrared spectroscopy were used to analyse the hydrochloric-acid-insoluble matter of the alkali-activated FA and alkali-activated slag. Acid dissolution tests on the AAFS showed that the addition of slag increased the geopolymerisation degree of FA in most cases. For a certain slag content, the reaction degree of FA decreased with an increase in the modulus of the activator and increased with an increase in the liquid/solid ratio. An increase in activator concentration had a greater effect when the slag content was low. At low activator concentrations, the reaction degree of FA increased with an increase in slag content. The slag content corresponding to the highest reaction degree of the FA gradually reduced with an increase in activator concentration. [ABSTRACT FROM AUTHOR]

This study investigated the performance of two alkali-activated concretes (AACs) subjected to marine exposure for 2 years. The AACs were synthesized from a low-calcium Class F fly ash (FA) and a blast-furnace slag. Concrete specimens were exposed in a marine environment in a port facility in southern Australia for 2 years. The specimens were subject to a range of nondestructive testing (NDT) techniques, including resistivity, Schmidt hammer, and ultrasonic pulse velocity (UPV) tests. In addition, chloride diffusion coefficients were calculated from concrete cores taken from specimens exposed in the marine environment. Microscopy analysis was undertaken using Fourier-transform infrared (FT-IR), nuclear magnetic resonance (NMR), and thermogravimetric analysis (TGA), and comparative data were taken on laboratory specimens at 28 days. Furthermore, the chloride diffusion coefficients were compared with the results of standard laboratory tests undertaken on the control samples at 28 days, including rapid chloride permeability testing (RCPT) using a 10-V driving voltage, an NT Build 492 test, and a bulk diffusion test, to determine the relationship between the 28-day laboratory tests results and the site performance. The data showed good correlation between the predicted performance based on the 28 day laboratory tests and the 2-year site data. The chloride diffusion of the ground granulated blast-furnace slag (GGBS) concrete agreed very accurately with the predicted value from the modified RCPT test, whereas the performance of FA concrete was superior to that predicted. [ABSTRACT FROM AUTHOR]

A decisive aspect of site evaluation for construction is the presence of anthropogenic materials occurring in the geological environment. The geotechnical properties of blast-furnace slag were investigated as a potential substitute for aggregates in the construction industry. The basic geotechnical parameters of the slag were determined, which are critical for evaluating its stability, environmental impact, and usability in geotechnical construction. The research focused on monitoring the physical and mechanical properties of the two samples, and also included mineralogical analysis. The obtained results demonstrated that the slag belongs to the category of poorly graded gravel, G2/GP, and gravel with an admixture of fine-grained soil, G3/G-F. In addition, other important parameters, such as the water disintegration of the slag aggregate, the minimum and maximum bulk densities, the California bearing ratio (CBR), the oedometric modulus (Eoed), and shear tests (the angle of internal friction φ and cohesion c), were determined. The results from this paper provide important information for the proper management of blast-furnace slag so to minimize its environmental impact and achieve sustainability in the mining industry. At the same time, it enables a better understanding of the use of slag as a substitute for aggregates in geotechnical tasks. Despite its local importance in relation to the investigated case, the presented study has significant educational and scientific value for the construction sector, where it is necessary to evaluate anthropogenic activities and materials. [ABSTRACT FROM AUTHOR]

Formulating alkali-activated binders requires a clear understanding of the role of activator concentration and source material composition on product formation and strength gain. Alkali activation of a low-calcium fly ash (FA) binder with slag replacements at 30% and 50% by mass was evaluated. The reactivity and compressive strength gain of the activated binders were evaluated using activating solutions with different sodium hydroxide molarities (SHMs). An increase in SHM produced a higher compressive strength of the activated binder. The primary reaction product formed in the activated binder was calcium silicate hydrate with aluminium substitution (C-(A)-S-H). An increase in SHM led to an increase in C-(A)-S-H content and a reduction in porosity. The slag contributed to early reactivity of the binder and the initial strength development, while the FA contributed to the later age strength by silica enrichment of the C-(A)-S-H. While increasing the SHM produced an increase in early reactivity, the sodium did not directly contribute to the formation of the reaction product. The sodium from the alkaline activator was not chemically bound to the C-(A)-S-H and could be removed by leaching in water. An increase in basicity with SHM enhanced the contribution of the low-calcium FA, leading to higher silica enrichment of the C-(A)-S-H. [ABSTRACT FROM AUTHOR]

Conobea scoparioides (Plantaginaceae) is an herbaceous plant known as “pataqueira” that grows wild in seasonally wet areas of the Amazon region. It is used for aromatic baths and anti-protozoan remedies by the Brazilian Amazon native people. The main volatile compounds identified in the essential oil of “Pataqueira” were the phenolic monoterpenes thymol and thymol methyl ether and their precursors, the monoterpene hydrocarbons α-phellandrene and p-cymene. A hydrotalcite synthesized from blast-furnace slag exhibited a 3:2 (Mg/Al) molar ratio, and this layered double hydroxide (LDH) was evaluated as a catalyst in converting the main monoterpenes of the “Pataqueira” oil. This action significantly increased the thymol content, from 41% to 95%, associated with the percentual reduction in other main components, such as thymol methyl ether, α-phellandrene, and p-cymene. The LDH reaction showed a strong tendency towards producing hydroxylated derivatives, and its behavior was similar to the hypothetical plant biosynthetic pathway, which leads to the production of the monoterpenes of “Pataqueira” oil. Thymol and its derivatives are potent antiseptics applied in pharmaceutical and hygienic products as antibacterial, antifungal, and antioxidant properties, among others. The present work reports a natural source with a high thymol content in aromatic plants from the Amazon, with evident economic value.

In order to realize the synergistic utilization of calcium silicon slag, fly ash and blast-furnace slag, this paper researched on hydration mechanism of calcium silicon slag composite geopolymer through preparation experiments of the calcium silicon slag composite geopolymer under different ratio of fly ash / blast-furnace slag.The results show that the calcium silicate slag base geopolymer is a binary composite cementitious material mainly composed of C—S—H and C(N)—A—S—H, which is formed by the hydration of β-calcium silicate itself and alkali-activated hydration.Compared with crystalline minerals, glass minerals are more prone to reaction with Ca(OH)2 and sodium silicate, resulting in a large amount of unreacted mullite remaining in the hydrates of 7 d when the fly ash / blast-furnace slag ratio is more than 0.5, but the mullite will continue to hydrate with the extension of curing time, and worm-like tetranatrolite and strip-like beidellite will be formed at 28 d.At the same time, when fly ash / blast-furnace slag ratio is 1.0, micromorphology of calcium silicate slag composite geopolymer is the most evenly distributed and dense, and its 28 d compressive strength reaches maximum 37.9 MPa.So, it indicates that the best synergistic effect among calcium silicon slag, fly ash and blast-furnace slag can be released under this condition.

Blast furnace slag-based geopolymer mortars strengthened with human hair fibers were synthesized in the present study. The mixture of NaOH and Na2SiO3 was used as activating solution. Zero percent, 0.25%, 0.5%, 0.75%, 1%, and 1.25% hair fibers were added by weight of slag. Several analytical approaches, including compressive strength, flexural strength, P-wave velocity, bulk density, porosity, water absorption, infrared spectroscopy, X-ray diffraction, and scanning electron microscopy, were used to assess the physicomechanical and microstructural characteristics of the geopolymer mortars. Overall, the results found revealed that the incorporation of human hair fibers into the slag-based geopolymer matrix brought about a noticeable improvement in the mechanical characteristics of the geopolymer mortars. Similarly, based on FTIR analysis, the geopolymer mortar is characterized by the presence of three principal bonds, namely, the stretching of Al-O, a shift of the absorption band of the Si-O-Si (Al), and the stretching of the O-C-O. Likewise, the mineralogical analysis shows that quartz and calcite are two crystalline phases dominant in the geopolymer matrix. In addition, SEM-EDS analysis shows a dense and continuous morphology devoid of microcracks with a few pores existing on the matrix surface with perfect integration of the hair fiber in the geopolymer matrix. According to these relevant properties, the synthesized geopolymers have potential applications as a suitable substitute for many Portland cement-based materials whose manufacture is energy-consuming and polluting. [ABSTRACT FROM AUTHOR]

In order to investigate the influence of SiC on the composition and structure of mixed slag (blast-furnace slag: steel slag = 1:9), the chemical composition, equilibrium-phase composition, and microscopic morphological characteristics and elemental distribution in the microscopic region of the SiC-reagent-tempered slag samples were analyzed by X-ray diffractometer (XRD), FactSage7.1 thermodynamic analysis software, scanning electron microscope, and energy spectrum analyzer. It was found that the main physical phases of the tempered slag samples were magnesia–silica–calcite (Ca3Mg(SiO4)2, C3MS2), calcium–aluminum yellow feldspar (Ca2Al2SiO7, C2AS), C2S, and iron alloy. Theoretical calculations suggest that the experimental temperature should be higher than 1500 °C to facilitate the combination of P5+ with Fe and Mn in the liquid phase to form an alloy, reduce the P5+ content in the tempered slag, and create conditions for the self-powdering of the conditioned slag. The doping of the SiC reagent can increase the liquid phase line temperature and reduce the binary basicity in the liquid phase; the liquid phase line temperatures were 1150 °C, 1200 °C, and 1300 °C and the basicities in the liquid phase were 4.68, 4.13, and 3.10 for the doping amounts of 3%, 4%, and 5% of the SiC reagent, respectively. The mixed slag doped with 4% SiC reagent achieves self-powdering and reduction of ferroalloys during the air-cooling and cooling processes, realizing the purpose of "resource utilization" of blast-furnace slag and steel slag. [ABSTRACT FROM AUTHOR]

The article proposes a technological line for recycling the blast-furnace slag. This line makes it possible to obtain the crushed stone for road building, which has high water and frost resistance. The design of replaceable working equipment of a single-bucket excavator, with replaceable working tools for loosening frozen slag in dumps and preparing it for use in road building, is proposed. The results of testing the manufactured replacement working equipment are presented. The results of mathematical processing of experimental data using the approximation method are presented, as well. [ABSTRACT FROM AUTHOR]

This article discusses the engineering and computational methodology of designing the main units of a blast-furnace slag dry granulation plant with a capacity of 1 million tons of slags per year, also intended for the recovery of slag heat. This plant can replace the slag wet granulation plant at blast furnace No. 5 at the iron and steel works of Severstal of the same capacity. The method can be used to estimate the radius and rotation frequency of the disk for spraying a slag, mechanical power to the disk drive, granulation chamber (GC) diameter that ensures the solidification of slag droplets, temperature of slag granules at the outlet of the GC, amount of heat transferred by convection to the air and by radiation to the walls of the GC, flow rate of air supplied to cool the slag, changes in the temperatures of the slag and air on fluidized bed grates (FBGs), size of these grates, loss of air pressure in the plant, and power consumption for the fan drive, amount of slag heat disposed of in the plant, and possible generation of electricity due to it. Recommendations on the shape of the side wall of the GC are given. The findings revealed that for a plant with a capacity of 1 million tons of slags per year with a diameter of granules no more than 2 mm, the disk radius should be approximately 0.2 m, with a rotation frequency of 500 rpm and disk drive power of 5.1 kW. The required diameter of the GC at the flight speed of slag droplets of 10.4 m/s is approximately 14.4 m. The slag is cooled in the GC from 1500℃ to 1030℃ and then to 150℃ on three FBGs. Cooling air with a flow rate of 34.8 nm3/s in FBGs is heated to 640℃ and then to 800℃ in the GC. The fan drive power for is approximately 40 kW. In the plant, approximately 43 MW of heat can be disposed for steam generation, and up to 18.5 MW of electricity can be obtained due to it. [ABSTRACT FROM AUTHOR]

Concrete structures exposed to high levels of chemical attacks are assigned to exposure class XA3, which recommends separate concrete protection or a special expert solution to ensure durability. Due to the partial substitution of Portland cement by blast-furnace slag, an increased resistance to acid attacks could be achieved within the framework of a research project. The technical and ecological advantages of cements containing granulated blast-furnace slag were exploited through chemical, granulometric and concrete technological optimizations. Despite extensive parameters, a statistical test design (DoE) was able to limit the experimental effort, thus defining principles for the conception of binder systems with increased chemical resistance.Mortar prisms indicated that the use of (ultrafine) blast-furnace slags (up to 13,000 cm2/g according to Blaine) with a broad particle size distribution can have a positive effect both on the capillary/gel pore ratio and on the calcium hydroxide content in the cement stone. Furthermore, the chemical composition of the blast-furnace slag as well as the water-binder ratio are decisive influencing factors for the acid-resistance, which was confirmed in accelerated acid resistance tests on concretes (pH-stat method). After 13 weeks of storing concrete specimens in sulfuric acid (H2SO4, pH 3.5), reduced damage depths and lower weight losses were observed compared to conventional binder compositions. The results serve as a basis for the development of highly acid-resistant concretes using blast-furnace slag-containing binder systems. Currently, the acid resistance of those concretes is being investigated in a long-term study by outsourcing representative test specimens into the Emscher sewer.

In this research, the mechanical properties and durability of sulfur concrete with two different waste aggregates were evaluated. The waste aggregates included ground granulated blast-furnace slag and waste marble powder. The properties of sulfur concrete were also compared with those of the conventional binder concretes (i.e., Portland cement concrete and sulfate-resistant cement concrete). The durability parameters included measuring water absorption capacity and resistance to different harsh chemical environments (5% HCl solution, 5 Molar NaOH solution, and 16% NaCl solution). It was found that sulfur concrete made with slag as aggregate exhibited the maximum strength, i.e., about 2 times higher than that of Portland cement concrete and sulfate-resistant cement concrete. Sulfur concrete made with slag and marble waste powder showed superior mechanical performance compared to that made with river sand. Thus, sulfur binder develops more favorable properties with eco-friendly fillers than it develops with natural sand. In harsh chloride and acidic environment, sulfur concrete with slag powder exhibited about 90–95% lesser mass loss than Portland cement concrete. [ABSTRACT FROM AUTHOR]

One-part geopolymers are a greener alternative to Portland cement and are more suitable in engineering applications compared with two-part geopolymers. The effects of mechanical activation on the properties and the mechanism of the pozzolanic reaction of fly ash (FA)/slag-based geopolymer paste prepared using the one-part method were studied. Simple mixing was used for the control group and the effect of mechanical activation on the macroscopic properties of geopolymers was studied using tests for compressive strength, fluidity and setting times. The effect of mechanical activation on the pozzolanic reaction of geopolymers was assessed using isothermal calorimetry, X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetric analysis. The results showed that the 28-day compressive strength of the geopolymer formed by mechanical activation was 26% higher than that of the geopolymer prepared using simple mixing. Workability and fluidity were also enhanced. The reactivity of the precursor was improved by mechanical activation, particularly for the FA. The mechanically activated FA experienced a pozzolanic reaction within 7 days, while the undisturbed FA produced pozzolanic activity after 14–28 days. In addition, mechanical activation lessened the carbonisation of the one-part FA/slag-based geopolymer The implications of these results in terms of the influence of mechanical activation on pozzolanic activity are discussed. [ABSTRACT FROM AUTHOR]

Alkali-activated materials (AAMs) are regarded as an alternative cementitious material for Portland cement with regards to sustainable development in construction. The purpose of this work is to investigate the properties of activated blast-furnace slag (BFS)–steel slag (SS) with sodium carbonate (NC), taking into account BFS fineness and Na2O equivalent. The hydration was investigated by rheological behavior and pH development. The hydrates were characterized by TG-DTG and XRD, and the microstructure was analyzed by SEM and MIP. Results showed that the rheology of activated BFS-SS pastes was well-fitted with the H-B model and affected by BFS fineness and NC mixture ratio. It was found that BFS fineness and NC ratio played a crucial role in the initial alkalinity of SS-BFS-based pastes. As such, lower BFS fineness and higher NC ratio can dramatically accelerate the formation of reaction products to endow higher mechanical strength of BFS-SS pastes. However, the effect of NC ratio on the microstructure development of BFS-SS based AAMs was more obvious than BFS fineness. [ABSTRACT FROM AUTHOR]

Ground blast-furnace slag is one of the waste products available in Ukraine and other countries. It is obtained at metallurgical enterprises in huge quantities and can be efficiently used for concrete production. The article is devoted to obtaining experimental-statistical models of the influence of technological factors that determine the composition of self-compacting concrete (SCC) based on ground blast-furnace slag and polycarboxylate superplasticizer on compressive strength, tensile strength, prismatic strength, elastic modulus and crack resistance. Analysis of the investigated factors' influence on the specified SCC properties is carried out and positive influence of blast-furnace slag and superplasticizer simultaneous action on durability and deformation characteristics is studied. A design method of SCC composition design using the obtained mathematical models is developed. It allows for the consideration of a set of necessary parameters simultaneously. A numerical example is given. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Concrete structures exposed to high levels of chemical attacks are assigned to exposure class XA3, which recommends separate concrete protection or a special expert solution to ensure durability. Due to the partial substitution of Portland cement by blast-furnace slag, an increased resistance to acid attacks could be achieved within the framework of a research project. The technical and ecological advantages of cements containing granulated blast-furnace slag were exploited through chemical, granulometric and concrete technological optimizations. Despite extensive parameters, a statistical test design (DoE) was able to limit the experimental effort, thus defining principles for the conception of binder systems with increased chemical resistance.Mortar prisms indicated that the use of (ultrafine) blast-furnace slags (up to 13,000 cm²/g according to Blaine) with a broad particle size distribution can have a positive effect both on the capillary/gel pore ratio and on the calcium hydroxide content in the cement stone. Furthermore, the chemical composition of the blast-furnace slag as well as the water-binder ratio are decisive influencing factors for the acid-resistance, which was confirmed in accelerated acid resistance tests on concretes (pH-stat method). After 13 weeks of storing concrete specimens in sulfuric acid (H2SO4, pH 3.5), reduced damage depths and lower weight losses were observed compared to conventional binder compositions. The results serve as a basis for the development of highly acid-resistant concretes using blast-furnace slag-containing binder systems. Currently, the acid resistance of those concretes is being investigated in a long-term study by outsourcing representative test specimens into the Emscher sewer. [ABSTRACT FROM AUTHOR]

The effect of a fixed ratio of different additives on the carbonation behavior of ground-granulated blast-furnace slag (shortened as slag) activated with a fixed concentration of Na2SO4 was investigated. Slag was activated by 1% (Na2O-equivalent) Na2SO4 (M0) and partially replaced with 10%, by weight, of one of the following additives: limestone powder (LS10), fly ash (FA10), portland cement (PC10), silica fume (SF10), metakaolin (MK10), and hydrated lime (HL10). The compressive strength values were measured and compared with those activated with the traditional common activators. After 28 days of curing, the pastes were exposed to 5% concentration of CO2 coupled with 20 ± 1°C and 65% surrounding temperature and relative humidity, respectively, for different durations of 2, 4, and 8 weeks. Compressive strength, pH value, and carbonation depth of carbonated specimens were determined and compared with noncarbonated ones exposed to the same conditions but at a natural CO2 concentration. The results were analyzed with special tools to determine the different phases. The results revealed that it is possible to increase the carbonation resistance of slag activated with Na2SO4 by using some additives. The specimens of LS10 exhibited the highest carbonation depth, while SF10 specimens exhibited the lowest carbonation depth. The remaining additives showed intermediate results between LS10 and SF10. [ABSTRACT FROM AUTHOR]

Foam concrete is lightweight concrete. It has been proven to be more environmentally beneficial than conventional concrete because it uses less natural resources. Besides, saving natural resources and making effective use of industrial waste as aggregate in concrete is a pressing issue. Currently, the effective use of industrial waste is of interest to many researchers. As a result, the current study seeks to investigate alternative fines sources by examining the impact of granular blast furnace slag as a substitute for sand aggregate on the properties of foam concrete. This paper builds on the author’s earlier research into the impact of blast furnace slag on the properties of foam concrete. In total, four foam concrete mixtures with densities of 1700 kg/m3 and 900 kg/m3 and sand replacement amounts of 100% blast furnace slag were created. GOST has been used to measure the compressive strength, elastic modulus, and porosity of foam concrete. According to the findings, using blast furnace slag instead of sand makes foam concrete thicker and less porous. These findings result in higher foam concrete compressive strength and elastic modulus. Furthermore, the author used Hoff’s equation and Zheng’s equation to calculate theoretical porosity and compare it to observed porosity. The measured results indicate that the theoretical and measured porosity have a reasonably close relationship.

This paper focuses on the effectiveness in the improvement of clay soils of using geopolymers of fly ash (FA), metakaolin (MK), or blast furnace slag, activated by an alkaline solution of sodium hydroxide (NaOH), sodium silicate (Na2SiO3), or a mixture of both. The unconfined compressive strength (UCS) of samples cured for 1, 7, and 28 days was determined, and X-ray fluorescence (XRF), X-ray diffraction (XRD), and Fourier-transform infrared (FTIR) spectroscopy were performed to record the mechanical, chemical, and mineralogical behaviors of the stabilized soils. The results showed an increase from 149.72 kPa (untreated clay) to 460.06 kPa for the clay soil treated with NaOH after 1 day of hardening. The highest UCS was obtained using a MK-based geopolymer (MKG) at 28 days. Oedometric testing showed a reduction in the swelling potential of the clay soil and a decrease in the swelling pressure from 600 to 300 kPa. It was found that all the tested treatments significantly improved the geotechnical properties of the clay soil. However, the MKG treatment was most effective in terms of increased resistance, while the FA-based geopolymer (FAG) provided better results in terms of reducing swelling. [ABSTRACT FROM AUTHOR]

• The viscosity of high titanium content blast furnace slag was studied. • Melting temperature first decreases and then increases with increasing TiO 2. • Crystallization degree of slag under different quenching conditions was studied. • The viscous-flow activation energy of slag was determined by the W-F equation. • The relationship between slag viscosity and structure was discussed. As a raw material for ironmaking, vanadium-bearing titanomagnetite will leads to an increase in the TiO 2 content of blast-furnace slag and deteriorates the metallurgical properties of the slag. In this study, the effect of TiO 2 content on the viscosity of CaO-SiO 2 –8.25 %MgO-15 %Al 2 O 3 -TiO 2 slag system at fixed w (CaO)/ w (SiO 2) ratio of 1.2 was investigated, and Raman spectroscopy focusing on the relationship between the structure of high TiO 2 -bearing blast furnace slag and viscosity was performed. The findings showed that under the experimental condition, the viscosity of slag decreases with the increase of TiO 2 content over a range of 20 to 35 %. The melting temperature of slag increases first and then decreases after w (TiO 2) is higher than 30 %. The viscous-flow activation energy of slag decreases with the increase of TiO 2 content, which has a concomitant variation corresponding with the results of the effect of TiO 2 on viscosity. The analysis of Raman spectroscopy results reveals that the blast-furnace slag system is dominated by [SiO 4 ]4- network structure. As the TiO 2 content increases, more and more Ti4+ enters the silica-oxygen tetrahedral network structure, disrupting the Si-O-Si bond to form the [TiO 4 ]4- structural unit and a small portion of the [TiO 6 ]8- structural unit. The NBO/Si value of the Si4+ in the tetrahedron unit as an index for the degree of depolymerization of slags increased from 1.62 to 2.60 as the TiO 2 content increased, the slag structure was gradually simplified and the slag viscosity was gradually decreased. [ABSTRACT FROM AUTHOR]

After ordinary Portland cement (OPC) concrete, geopolymer concrete (GPC) is the most advanced form of concrete. GPC has many advantages including improved strength and durability properties. High early age strength and ambient curing of GPC helps to reduce the construction time. Factors such as binder materials, alkali-activated solution, and curing methods control GPC's strength properties. Moreover, when industrial byproducts such as fly ash and ground granulated blast-furnace slag (GGBS) are added to GPC, this leads to advantages such as reduced carbon dioxide emission, ability to reuse of waste materials, thus saving valuable lands from getting converted into dump yards, cost reduction, and so on. Moreover, the energy required for the extraction of raw materials is also reduced. In this paper, GPC's strength and durability characteristics, its mix design procedure, its effect of fibers on mechanical properties, and its structural performance are comprehensively reviewed. Moreover, the development of high-strength GPC using fly ash with sodium hydroxide as an alkaline solution under oven curing condition is highlighted. To develop GPC from different binder materials, trial and error methods are proposed. Rangan's mix design procedure is used for fly ash-based GPC. Moreover, the inclusion of fibers, it was found, improves the ductile nature of GPC. Suggestions and scope for future GPC-related research are also included. [ABSTRACT FROM AUTHOR]

The possibility of preparing cementitious materials by the alkali-activated method using Yellow River sediment (The second largest river in China) as raw material and the modification effect on different slag addition were investigated. Sodium silicate and calcium hydroxide were used as the activator, and the specimens were prepared by the press molding method. The hydration process, hydration products, pore characteristics, and mechanical properties were investigated using SEM/EDS, FTIR, TG/DTG, XRD, MIP, and uniaxial compressive strength experiments, respectively. The results showed that the compressive strength of the modified yellow river silt-based cementitious material was significantly increased when the water glass dosage was 12 wt% (Ms=1.8)) and the slag dosage was 40%, and its 90-day maximum compressive strength could reach 53 MPa. [ABSTRACT FROM AUTHOR]

The resistance of alkaline‐activated silico‐manganese fume (SMF) and blast furnace slag (BSF)‐based mortar, prepared by varying BFS and NaOHaq composition, during 20 weeks of exposure to 5% sulfuric acid (H2SO4aq) of initial pH = 0.24 and pure water (controlled) was studied. The deterioration was monitored by visual, alkalinity, mass, compressive strength and microstructural tests. The set of specimens synthesized included: (a) BFS‐free high alkaline, (b) SMF‐BFS blended high alkaline, and (c) SMF‐BFS blended mild alkaline system. Their residual strengths after 20 weeks of acid exposure were 20.1, 18.6, and 16%, respectively. BFS‐free specimens exhibited high resistance to acid attack due to the dearth of Ca in SMF. BFS‐admixed mild alkali system resulted formation of more gypsum and dealumination attributed to incomplete dissolution of Ca grains leading to severe spalling. BFS‐admixed high alkaline system underwent moderate resistance due to dense microstructure formed by additional C‐S‐H, K‐A‐S‐H, and C‐Mn‐H gel which enhanced retention of the polymerized framework. [ABSTRACT FROM AUTHOR]

The radionuclide composition of the fractions of dump and granular blast-furnace slags from Ukrainian enterprises, their compliance with the radiation safety standards of Ukraine and international radiological indicators were determined. The blast-furnace slag contains natural radionuclides: 226Ra, 232Th and 40K. All investigated slags correspond to the safe level of international radiological indicators, belong to the first class of radiation hazard (Ukraine) and can be used in construction without restrictions. A direct correlation between the acidity of slag fractions and the increase in radiological parameters was determined. The hypothesis was proposed about radionuclide sorption on the negatively charged surface of the slag particles. [ABSTRACT FROM AUTHOR]

This research evaluated the bond behavior of reinforcement and the mechanical characteristics in a reactive powder concrete (RPC) replacing 35% cement with blast-furnace slag. Pullout tests were performed at the ages of 3, 7, 28, 56, 63, and 91 days on cylindrical samples. The embedded length used was double the diameter of the bar. At 3 days it presented compressive strength of 41% of the maximum obtained, which was 123.06 MPa at 91 days. There was an increase in strength until the age of 56 days and after stabilization of the curves. In pullout tests, it was noticed the considerable influence of the rib, because in tests with plain bars, the bond force was below 20% of the results with ribbed bar, which reached 54.38 MPa of strength. The compression curve was similar to the bond curve. Underestimated values were observed when the researchers' equations were applied to calculate the maximum bond strength. [ABSTRACT FROM AUTHOR]

Featured Application: In this paper, the idea of the sustainability of durable solutions is very much present. The effect of four pozzolanic materials employed in four percentages in mortars made with two different reactive aggregates is assessed regarding alkali-silica reaction (ASR). The findings encountered here will help to optimize the cement-based materials mix design. The increased use of industrial wastes and by-products to produce concretes and blended cements is a lever to achieve carbon neutrality. Furthermore, they could improve their durability. Some pozzolanic additions can minimize the alkali-silica reaction (ASR), which is a well-known deleterious process that occurs between some reactive aggregates and the alkaline pore solution found in mortars and concretes. This work quantifies the efficiency of four pozzolanic materials (natural pozzolan, P, siliceous coal fly ash, V, silica fume, D, and blast-furnace slag, S) assessed by means of compressive strength testing, open porosity, ASR-expansion measurements, and SEM microscopy. Accelerated expansion tests were performed in mortar bars with a cement/sand ratio of 1/2.25 and a water/cement ratio of 0.47, two reactive aggregates and a non-reactive one. The major contributions of this paper are: (i) The more aggregate reactivity is, the higher ASR mitigation level was found when additions were added and (ii) The best additions for ASR inhibition are silica fume and fly ash. [ABSTRACT FROM AUTHOR]

Carbon dioxide mineralization for the disposition of blast‐furnace slag is an important method for reducing CO2 emissions and simultaneously dealing with solid waste from the steel industry. However, due to the stable structures and properties of blast‐furnace slag, low mineralization reaction efficiency is a key issue in this process and hinders industrial applications. This work presents a method for enhancing the CO2 mineralization reaction by the addition of salt solutions (e.g., NaCl 1 mol · L−1) in the slurry of the blast‐furnace slag (<75 μm). The results showed that CO2 mineralization efficiency could be greatly improved with a high CO2 storage amount of ∼280 kgCO2 · tBFS−1 at a liquid‐solid ratio (L/S ratio) of 10, a temperature of 150°C and CO2 pressure of 3 MPa. The mineralization process was systematically characterized to identify the mechanism for mineralization enhancement by saline solution. The results indicated that saline solution could accelerate the dissolution of Ca2+ in blast‐furnace slag, reduce the activity of water, and lead to high acidity in the solution, and thus facilitate mineralization and improve the reaction rate. The NaCl solution was not consumed and could be recycled in the process, suggesting that this approach could use the brine and saline water as the medium for solid waste treatment and CO2 emission reduction in high energy‐consuming industries such as mineral processing, power plants, and the steel industry. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Copyright of Scientific Bulletin of National Mining University is the property of National Mining University, State Higher Educational Institution and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Two series of hydraulic concretes were prepared with alternative and sustainable composite binders of mineral calcium sulfate hemihydrate or waste anhydrite fluorgypsum, both supplemented with granulated blast-furnace slag, and fly ash or silica fume. The mixtures with 300 and 400 kg m−3 of binder cured for up to 360 days showed strengths of up to 30 MPa and hydraulic character. The microstructural configuration, characterized by SEM, EDS and XRD, indicated that the precipitated framework of gypsum crystals was stable under water after being engulfed by C–S–H like products formed by the reactions of the slag, pozzolanas and Portland cement. Ettringite was identified and assumed in moderate amounts in some samples, indicating the sulphatic activation for the slag and fly ash. The environmental impact assessed by a simple LCA indicated that the studied concretes release GHG in average 64.6 or 81.3 kgCO 2 eq·m−3 depending on the binder content, which is up to 5.3 times lower relative to conventional Portland cement mixtures. Depending on the distances travelled, freight was an important factor of GHG, while grinding and sieving were very low. [Display omitted] • Sustainable concretes made with gypsum-blast furnace slag-pozzolanas were studied. • Good mechanical strength was developed while maintaining insolubility under water. • Dihydrate, C–S–H and ettringite were the main hydration products. • Mixes generate up to 5.3 times less greenhouse gas emissions than Portland cement. • This study constitutes the basis for extensive research on gypsum-based concretes. [ABSTRACT FROM AUTHOR]

• To effectively mobilize the pozzolanic ability of the new green binders, the main components (FA, GBA, and BFS) need to be activated by the activators. • The strength behavior was a function of the G/R ratio. • The red mud in the new green binders FA(G/R), GBA(G/R), BFS(G/R) enhanced the early strengths of stabilized RGS mixtures. Meanwhile, phosphogypsum strongly enhanced to the long-term strengths. • The hardened RGS mixtures stabilized by the new green binders were classified as nonhazardous materials. In this study, residual granitic soil (RGS) was stabilized by using various new green binders (i.e., fly ash (FA), ground bottom ash (GBA), blast-furnace slag (BFS) activated by lime (L), phosphogymsum (G), and red mud (R)). As a result, these new green binders developed from industrial by-products led to a significant improvement in engineering properties of RGS. Interestingly, the red mud amount in the new green binders enhanced the early strength while phosphogypsum enhanced the 28-day strength. A series of strength, microstructure, and environmental tests were carried out to prove the feasibility of these new green binders in RGS stabilization. [ABSTRACT FROM AUTHOR]

Supersulfated cements (SSC) are normally produced from granulated blast-furnace slags having high-alumina content. However, such slags are not produced in North America. In this study, SSC mixtures were produced using two different slags, one high in alumina content (13%) and the other low in alumina content (7%). The purpose of this study was to investigate the differences in hydration mechanisms of SSC produced with the two types of slag. The low-alumina slag SSC mixtures showed a lower degree of slag hydration and quantities of hydration products formed (C–S–H and ettringite), ultimately resulting in higher porosity and poor mechanical performance of the SSC mixtures compared to high-alumina slag mixtures. A better mechanical performance of SSC mixtures made with low-alumina slag may be achieved by increasing its rate of glass slag dissolution. [ABSTRACT FROM AUTHOR]

• Sprayed concrete containing slag reaches strength requirements of classes J 1 and J 2. • Accelerators activate slag and the matrix achieves a proper hydration behavior. • Slag does not influence hydration negatively after 3 h when accelerators are added. Cement replacement by additions is crucial to produce sprayed concrete with proper mechanical properties and durability. The use of blast-furnace slag to produce sprayed concrete for tunnel linings may be restricted due to its low reactivity. In this context, the objective of this study is to evaluate the chemical and mechanical properties of sprayed concrete produced with cement and blast-furnace slag as a partial cement replacement. Hydration kinetics were characterized by isothermal calorimetry, X-ray diffraction and evolution of temperature, while mechanical properties were evaluated by needle penetration resistance and compressive strength of extracted cores. Results showed that slag was activated by the accelerators employed and the minimum strength specified for a J 2 class from 10 to 60 min and at 24 h was achieved. Therefore, blast-furnace slag may be used in sprayed concrete applications when the average strength evolution class is specified. [ABSTRACT FROM AUTHOR]

Geopolymer concrete (GPC) is attracting increasing attention due to its potential to replace ordinary Portland cement (OPC) concrete to reduce the carbon dioxide emissions from cement production. Although extensive research has been conducted in this area since the 1970s, its applications in engineering practice are still very limited. This paper briefly reviews the recent developments of GPC and its properties at ambient and elevated temperatures. It was found that GPC generally exhibits comparative properties to OPC concrete at ambient temperature. In contrast, GPC often has better fire performance and superior durability. Therefore, GPC could be advantageously used to improve the fire performance and durability of buildings and infrastructure. While a lot of aluminosilicate raw materials (such as fly ash) are low cost, the prohibitive costs of laboratory grade activators (such as sodium hydroxide and sodium silicate) greatly limit the widespread application of GPC. Therefore, there is a need to develop low-cost geopolymer concrete. Meanwhile, a few other challenges should also be overcome, such as difficulties to achieve consistent properties and to control efflorescence of GPC. Further research is required at both material and structural levels to address these issues. Particularly, there is a need to develop relevant building codes to promote the use of GPC in practice. [ABSTRACT FROM AUTHOR]

The paper shows the results of an experimental tests campaign carried out on concretes with recycled aggregates added in substitution of sand. Sand, in fact, has been totally replaced once by blast-furnace slag and fly ashes, once by blast-furnace slag and microsilica. The aim is both to utilize industrial by-products and to reduce the use of artificial aggregates, which impose the opening of pits with high environmental damage. The results show that in the concretes so made the water absorption capacity has reduced and durability has improved. The test campaign and the results described in the present article are certainly useful and can be especially utilized for research on a larger scale in this field. [ABSTRACT FROM AUTHOR]