Alkali-activated materials (AAMs) are a kind of hardened slurry produced by an alkali activation reaction between a silicate precursor and an alkali activator that is treated as an environmentally ...friendly cementitious material that can be used in place of ordinary Portland cement (OPC). However, some studies point out that the AAMs with a single precursor had some defects. To realize the high value-added utilization of phosphorus slag (PS), this paper mixed PS with granulated blast furnace slag (GBFS) to prepare alkali-activated composite cementitious materials. The workability, mechanical properties, and hydration of alkali-activated phosphorus slag—granulated blast furnace slag (AAPG) were characterized using fluidity, setting time, compressive strength, flexural strength, hydration heat, XRD, FTIR, TG-DSC, and SEM + EDS. The results show that GBFS can improve the fluidity of AAPG, but the slurry will flash set after exceeding 20% GBFS content. GBFS can rapidly hydrate to generate C-S–H to improve its early strength, but the later stage results in larger pores due to the uneven distribution of matrix products. The hydration generation products of AAPG are C-S–H and C-(N)-A-S–H dominated by the Q
2
unit, with some hydrotalcite by-products generated.
Electric arc furnace slag (EAFS) and ladle furnace slag (LFS) are by-products of the electric steelmaking sector with suitable properties for use in bituminous mixtures as both coarse and fine ...aggregates, respectively. In this research, the production of a porous asphalt mixture with an aggregate skeleton consisting exclusively of electric steelmaking slags (using neither natural aggregates nor fillers) is explored. The test program examines the asphalt mixtures in terms of their mechanical performance (abrasion loss and indirect tensile strength), durability (cold abrasion loss, aging, and long-term behavior), water sensitivity, skid and rutting resistance, and permeability. The results of the slag-mixes are compared with a standard mix, manufactured with siliceous aggregates and cement as filler. The porous mixes manufactured with the slags provided similar results to the conventional standard mixtures. Some issues were noted in relation to compaction difficulties and the higher void contents of the slag mixtures, which reduced their resistance to raveling. Other features linked to permeability and skid resistance were largely improved, suggesting that these mixtures are especially suitable for permeable pavements in rainy regions. In conclusion, a porous asphalt mixture was produced with 100% slag aggregates that met current standards for long-lasting and environmentally friendly mixtures.
A proper and detailed understanding of the thermal stability of Fe-rich fayalite slag-based alkali-activated materials (AAMs) is important due to their potential use in refractory and fire-resistant ...applications. Here, fayalite slag (FS) was used as the main precursor for AAMs. The effects of incorporating ladle slag (LS) or blast furnace slag (BFS) and different temperature exposures up to 1000 °C were investigated through visual observation, compressive strength, ultrasonic pulse velocity (UPV), thermal conductivity, x-ray diffraction (XRD), thermogravimetry and differential scanning calorimetry (TG/DSC), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope coupled with electron probe microanalyzer (SEM-EPMA). The experimental results indicated that the incorporation of LS or BFS as additional calcium and aluminum sources positively affected the high-temperature behavior of blended mortars, which exhibited a reduction in voids, cracks, and thermal shrinkage while having higher residual strength and thermal stability than solely FS-based AAMs. This was mainly due to the differences in mineralogical transformation and the phases formed. Interestingly, the joint effect of elevated temperature exposure and the addition of LS or BFS enhanced the formation of more stable crystalline phases and densified the structure of blended mortars at 1000 °C.
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•Upcycling of Fe-rich fayalite slag as refractory and fire-resistant alkali-activated materials (AAMs) was elucidated.•Ladle slag (LS) or blast furnace slag (BFS) addition improved AAMs properties during ambient and high temperature exposure.•AAMs containing LS or BFS have better mechanical, thermal, and microstructural properties.•Joint effect of elevated temperature and LS or BFS addition favored more stable crystalline phase formation and densification.•The results provided an insight for designing eco-friendly refractory materials for building and construction industry.
Modern industrialization leads to an increasing demand for steel around the world, the production of one ton of crude steel generates a substantial amount of steel slag (SS11SS: steel slag), ranging ...from 130–200 kg. The accumulation of SS poses economic and environmental challenges, particularly in developing countries with low utilization rates. Therefore, enhancing the utilization ratio of steel slag has become an urgent priority. To address this issue, this paper examines the effect of incorporating steel slag as a supplementary cementitious material (SCM22SCM: supplementary cementitious material) and aggregate in concrete on various properties of concrete, aiming to promote the reuse of steel slag. The analysis results indicate that the incorporation of steel slag powder (SSP33SSP:steel slag powder) may have adverse effects on the initial setting time, volume stability, compressive strength, and durability of concrete. However, these issues can be mitigated through aging processes and high-reactivity SCMs. As for the steel slag aggregate (SSA44SSA:steel slag aggregate), it can effectively enhance the compressive strength of concrete. However, it may negatively impact workability, volume stability, and the residual strength of concrete after exposure to high temperatures. Furthermore, the effect mechanism of SSA on the durability performance of concrete is complex, making it difficult to draw reliable conclusions.
•Two types of SS were analyzed for the chemical composition and physical properties.•Effect of SSP as SCM on various properties of concrete was analyzed.•Effect of SSA on the performance of concrete was analyzed.•Effect of w/b ratio, curing age and replacement ratio on SSA concrete was analyzed.•Suggested research directions for future research on steel slag concrete.
•SP in FS contribute to the formation of new pores with RC.•SP could block the micropores of HTC.•The composites exhibited the CO2 uptake of 10.3 mg/g (HTC) and fast adsorption kinetics.
The ...value-added utilization coal gasification fine slag (FS) is extremely vital for minimizing the environmental problems. In this study, coal gasification FS was successfully used to prepared hierarchical porous composites (HTC) for CO2 adsorption. Furthermore, the role of slag particles (SP) in the composites was also studied through orthogonal experiments designed by acid washing conditions. Orthogonal experiments showed that the surface area of the HTCs was varied from 852 to 1295 m2/g except the samples treated by HF. The changes were primarily contributed to the SP content and the existing forms in the HTCs. There had no micropores in the HTCs treated by acid at low temperature and acid concentration because those pores were blocked by the SP. While increasing the treatment temperature and acid concentration, the acid could diffuse into the micropores to remove embedded SP and the micropores were exposed. The HTCs also proved to be attractive for CO2 capture. The highest CO2 adsorption capacity of 2.64 mmol/g at 25 °C was achieved with 1- FSHTC-AT sample. The sample not only exhibited good selectivity of CO2 over N2 of 10.8, but also had fast adsorption kinetics that it reached adsorption equilibrium in less than 2 min. Besides, there were no apparent decrease in the CO2 adsorption capacity after ten cycles. All these results suggest that fine slag has a great potential to produce HTCs for practical CO2 adsorption applications. Furthermore, it also provides a sight into the role of SP in HTC which could realize pore structure control by changing acid treatment conditions.
•Ground granulated blast furnace slag (GGBFS) and silica fume (SF) were replaced as 20% and 10% by weight of total binder.•GGBFS and SF positively affected the workability of HPC.•High Performance ...Concrete (HPC) containing steel slag and GGBFS has a good mechanical performance and durability.•The Algerian steel and crystalized slags have good physical and mechanical properties.
The present research study was conducted in order to compare the mechanical properties and durability indicators of High Performance Concrete (HPC) using artificial aggregates such as steel slag and crystallized slag as coarse aggregate with HPC using natural limestone aggregates. Properties of fresh and hardened HPC were evaluated for three concrete mixtures using steel slag, crystallized slag and limestone aggregates. Ground granulated blast furnace slag (GGBFS) and silica fume (SF) were added as supplementary cementing materials. Water to binder ratio equal to 0.27 was maintained for all mixtures. Different mixtures were tested for mechanical strength at different ages, while durability indicators such as capillary absorption, water porosity, gas permeability and chloride ion diffusion tests were also carried out. The analysis of tests results showed that the mineralogy, morphology and strength of aggregates are significant factors affecting the compressive strength and durability of HPC. Rough surface texture of artificial aggregates, improved the bond between aggregates and hardened cement paste and better increased the strength of concrete.
A lot of slag was produced by ancient production processes such as smelting, melting, and refining. Iron slag has information that can be used to determine the characteristics of the site, the ...iron-making process and manufacturing date, but there is a limit to reading information through visual observation and nondestructive analysis. Various slag terms have been used depending on the location and characteristics, but it is necessary to use terms that have exact meaning and unity. Although many scientific analyses have been supplemented by archaeological theses, the iron-making trends of each period have not yet been systematically proven. This study reviewed the type of iron-making process used for 100 ancient slags. The slags were analyzed by XRF, revealing when it was formed and some of the detailed processes. XRD analysis was used to define and classify Tap slag, Bloom slag, and Ceramic-rich slag as relative concepts. From the Three Kingdoms Period to the Joseon Dynasty, the amount of temperature variation in the iron-making furnace decreased and the GAS reaction became uniform. It was observed that the amount of iron oxide remaining decreased and the proportion of ceramic-rich slag increased. The change in iron oxide content kept decreasing while the levels of refining, smelting, and melting were maintained, in that order. The results confirmed that advances in ancient iron-making technology can be interpreted based on a comparative review of the relative changes in iron oxide and silicon oxide content in slag.
(Received 23 August, 2022; Accepted 28 December, 2022)
•Three slags, electric arc furnace, blast furnace, and copper, were used as asphalt modifiers.•The performance of the slag-modified asphalts was characterized via physical and rheological tests.•The ...addition of the slags improved the short-term asphalt aging properties.•Rheological test results showed an enhancement in permanent deformation resistance of slag-modified asphalts.
Metallurgical slags are residues that are obtained in the manufacturing and smelting processes of metals, such as steel and copper. However, their use is limited because they may cause environmental problems at their disposal sites. This study aims to evaluate the effects of the addition of slag on the properties of slag-modified asphalts using three different slag proportions (3, 6, and 10% by weight of asphalt). Electric arc furnace slag, blast furnace slag, and copper slag were used to evaluate the effects of the addition of slag on their performance properties via physical and rheological tests. The results showed an improvement in the consistency of the slag-modified asphalts, decreasing the penetration rate and increasing the softening point. An enhancement in the short-term asphalt aging characteristics was also observed with the addition of slag. Finally, the rheological test results revealed an improvement in the resistance to permanent deformation with the addition of slag in neat asphalt, whereas no statistically significant results were observed when the slag content was increased.
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•Recycling environmentally hazardous SPW into industry raw material.•Removing the oxide layer of SPW by economically-attractive vacuum sintering.•Na3AlF6-enhanced slag refining ...exhibited a larger reaction interface.•A smoother remove pathway of BO33- was created.•The removal rate of impurity boron has increased by 40.92%.
Recycling of environmentally hazardous silicon powder waste (SPW) is conducive to achieving “carbon neutrality”. However, the high-cost and low-efficiency impurity removal limit the industrial recovery of SPW. Herein, a combination strategy of vacuum sintering and Na3AlF6-enhanced slag refining is demonstrated to upgrade the traditional recycling process. The cost-effective vacuum sintering can remove 89.44% of oxygen in silicon waste, indicating that the oxide layer of SPW is removed effectively. In the Na3AlF6-enhanced CaO–SiO2 slag, the optimal Na3AlF6 content and CaO/SiO2 mass ratio are set to 20 wt% and 1.6 based on thermodynamic simulation. Na3AlF6 reduces the liquidus temperature and increases the interfacial tension of the slag system. Moreover, in Na3AlF6-containing slag, the diffusion pathway of BO33- is dredged. As a result, the silicon-slag interface is adjusted from a half-spherical to a cylindrical surface, and the interface area has increased by 14.69%. The boron removal rate by Na3AlF6-strengthened slag refining is 40.92% faster than that of traditional slag. This work improves the removal efficiency of key impurity boron, reducing the cost of SPW recovery. Based on economic evaluation, this strategy offers a commercially available way to achieve the high-value recycling of silicon waste.
•High performance alkali activated slag concrete mixes were developed more effectively using the industrial wastes.•Higher rheological and mechanical properties were achieved for all the HPAASC mixes ...developed here in.•The statistical analysed results showed a very good predictive capabilities for all the mechanical properties tested herein.•Microstructural studies also showed a densified morphology for all the HPAASC mixes.
In the present study, development of a class of High Performance Alkali Activated Slag Concrete mixes (hereafter referred to as HPAASC mixes) is discussed. These mixes are developed using three industrial wastes from Iron and Steel industry. While Ground granulated blast furnace slag (GGBFS) was used as the main binder, in the development of these HPAASC mixes, steel slag sand and Electric Arc Furnace slag (EAF slag) have been employed in the fine aggregate and coarse aggregate fractions of them. Higher flow characteristics, as those of self-compacting concrete mixes, as well as enhanced mechanical strength properties of these mixes are discussed in detail. The alkaline solutions used consist mixtures of sodium hydroxide and sodium silicate solutions, with a constant activator modulus (ratio of SiO2/Na2O) of one maintained in them. Taguchi’ design of experiments methodology was used to reduce the experimental efforts.
The formulation of all the mixes developed herein was based on Taguchi’s L-9 orthogonal array. Flow and strength properties of a set of nine mixes were used for performance evaluation purposes in an initial, calibration phase. Strength prediction equations were derived based on such results, the predictive capability of which were then assessed and ascertained with actual results of experiments on the next six new mixes, in the prediction phase. Test results indicated a higher flowability values for all the mixes (with slump flows greater than 700 mm), good filling and passing abilities, all satisfying the EFNARC (European Federation of Specialist Construction Chemicals and Concrete Systems) recommendations for SCC mixes. Higher compressive strengths (65–90 MPa), split-tensile strengths (4.8–5.3 MPa), flexural strengths (6.5–7 MPa), and Modulus of Elasticity (30.4–36.2 GPa) were observed along with lower water absorption values (2.1–2.7%) for all the HPAASC mixes tested herein. Microstructure studies were conducted on samples from the fractured surfaces of test specimens from different mixes, using advanced SEM, EDX and XRD analyses and the results are discussed.
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