Addition Of Slag Research Articles

Mineralogy at early age of alkali activated mortar based on binary additions of limestone quarry dust and electric arc furnace slag

Aggregates, produced by quarrying, are used in the construction industry and are considered vital for the development of the construction sector. In limestone quarries, considerable amounts of limestone quarry dust (LQD) are produced as a by-product of stone crushers. These quantities of powders are intended for use as an addition to building materials. Electric arc furnace slag (EAFS) consist of metal oxides trapped in fluxes such as lime and dolomite, this industrial by-product comes from the Moroccan steelworks SONASID-Jorf, and is used in this study. The main concern is to find a cement/sand substitute by replacing normal cement/sand by LQD/ESAFS that will reduce the amounts of cement/sand used in mortars and concretes and at the same time reduce the produced amounts of these industrial solid wastes. This article reports a preliminary study of the early age mineralogy of a mortar based on the partial replacement of cement/sand by LQD/ESAFS and co-grinding mixtures, the proportions used in the mortar mixtures are 20%, 25%, 30% LQD and 15% EAFS.

Phase Composition and Properties of Ceramic Matrix Composites with the Addition of Ferrovanadium Slag

Phase Composition and Properties of Ceramic Matrix Composites with the Addition of Ferrovanadium Slag

Experimental study of strength behavior of soft soil stabilised with alkali activated copper slag

In this work, Unconfined compression test (UCS) were used to study the effects of an industrial by-product copper slag (CS) on the geotechnical properties of soil in treated and untreated condition. Soil specimens were created with five different percentages of CS (i.e., 0 %, 10%, 20%, 30%, and 40%) by weight to that of dry soil mass. The samples were compressed into a cylindrical specimen and then kept for processing for 7, 14, and 28 days of curing. The presence of CS with alkali activator had a substantial effect on the unconfined compressive strength (UCS) of the given soft soil according to the test results. The effects of the CS on the UCS were more noticeable in 10 M alkali activated specimens as compared to unstabilized specimens. Furthermore, in the alkali activated specimen, the UCS value was increased by more than 5times as the CS content raised by up to 30%. Addition of copper slag reduces the optimum moisture content (OMC) and also increases the maximum dry density (MDD) of the soil because of its higher specific gravity. In addition, an artificial neural network (ANN) model created with eight input parameters: CS content, Alkakli Activator (AA) content, dry density, moisture content, plastic limit, liquid limit, clay content, and curing age. The optimum design for predicting the compressive strength of mixes was determined by a neural network consisted of 10 neurons in the ANN hidden layer, with good similarity between the observed or predicted data and test results. The results of this study showed that the suggested model may be used to estimate the unconfined compressive strength of the CS-stabilized soft soil.

Self-healing capacity of asphalt mixtures with steel fiber, steel slag and graphite powder, evaluated with microwave induction and fatigue test

Self-healing in asphalt mixtures can be induced by adding particles that are susceptible to heating by electromagnetic microwaves. This process allows the closure of microcracks caused by the fatigue phenomenon and can extend the service life of the asphalt pavement. In this article, the self-healing index of asphalt mixtures without and with the addition of steel slag (15% and 65.7%), steel fibers, (0.2% and 0.4%), and graphite powder (15% and 65.7%) was evaluated. The index was determined after subjecting the mixtures to fatigue damage, microwave heating, rest, and fatigue damage again. Results showed that all additions led to mixtures susceptible to microwave heating and with healing capacity. A higher self-healing index was observed when the mixture was produced with slag than with graphite powder. It was found that the use of a higher content of steel fibers was more effective for healing, and for successful healing, the mixtures must be heated to temperatures ranging between 50°C and 75°C. The results also showed that it is possible to achieve high healing values without having to subject the mixtures to microwave heating.

Studies on hardened properties of concrete incorporated with copper slag

The present study aims to develop sustainable construction aggregates using industrial solid waste material like copper slag which is produced from smelting and refining process of copper. Copper slag contains Fe2O3 [35–60%] and SiO2 [25–40%] apart from small amounts of CaO, Al2O3 and CuO which makes it a potential solid waste material to be used as replacement to conventional fine aggregates. In this study, an attempt has been made to utilize copper slag as alternative to conventional fine aggregates in engineered way by conducting mix proportioning for M20, M25, M30, M35 and M40 grade of concrete. Initially the dosage of super plasticizer i.e., 0.75% is fixed to get the required workability of 75–100 mm by performing various trials. The water to cement ratio for each grade of concrete was found by trial and error method using the ratios 0.4, 0.42 and 0.44. This paper also studies the corrosion behaviour of steel reinforcement embedded in copper slag concrete. Corrosion of steel reinforcement is one of the major causes affecting the long-term performance of reinforced-concrete structures. Hence, the corrosion test was conducted by using thermo mechanical treatment (TMT) steel of 150 mm length and 8 mm diameter which are embedded in concrete cube of size 150 mm × 150 mm × 150 mm. On completion of accelerated corrosion, all the concrete samples were removed from all the connections and taken out of tank. Further for reinforced concrete with 40% replacement of copper slag, the percent of decrease in compressive strength is on lower side for nominal concrete as compared to concrete with copper slag. All the concrete specimens were subjected to wetting and drying in alternate way by placing in 3.5% NaCl solution. The findings in the study demonstrate that copper slag addition contributes to less resistance to corrosion attack.

Iron-rich slag addition in ternary binders of Portland cement, aluminate cement and calcium sulfate

The growing demand for sustainability in the recent decades has driven the exploration for new supplementary cementitious materials (SCM) such as the non-ferrous metallurgy (NFM) slags. In this study, the hydration of an iron-rich NFM slag incorporated in CAC-PC‑calcium sulfate ternary binders was investigated. The dimensional stability of mortars demonstrated the contribution of the slag addition in mitigating excessive expansion while maintaining an acceptable mechanical strength over 180 days. The degree of slag hydration estimated with X-ray Computed Tomography (XCT) support the activating effect of the PC, while isothermal calorimetry, XRD, TGA and ATR-FTIR were used to delineate the evolution of the phase assemblage. Finally, TEM-EDS revealed the incorporation of Fe in hydrate gels grouped into two clusters according to a Ca-Al-Si ternary diagram: (1) Al-rich gels in the formulation with no PC; and (2) intermixed hydrate gels associated with Ca, Al and Si in the formulations with PC.

Interfacial reactions between impurities and slag onset of Si purification by slag addition

The interfacial reactions between impurities (Al and Ti) and slag onset of Si purification by 51 mol% SiO2–34 mol% CaO–15 mol% MgO slag addition were studied to enhance impurity removal efficiency from Si. The Al distribution behavior at the Si/Slag interface was investigated; a short reaction time (10 s) resulted in the formation of successive SiO2–CaO–MgO–Al2O3 layers in the slag with a thickness of 10 µm; increasing the reaction time (60 s) resulted in the entire ternary slag being changed into SiO2–CaO–MgO–Al2O3 quaternary slag due to the diffusion of Al2O3. It was shown that the highest impurity removal rate of Al could be achieved at the onset of the slag refining process. Based on the Ti distribution at the Si/slag interface, the slag refinement with 51 mol% SiO2–34 mol% CaO–15 mol% MgO had no effect on Ti removal.

Application of calorimetry and other thermal methods in the studies of granulated blast furnace slag from the old storage yards as supplementary cementitious material

The calorimetric and DTA/TG measurements were applied in testing the effect of granulated blast furnace slag originated from the storage yards of different age, added as a supplementary cementing material to the Portland cement clinker. The studies were performed with aim to evaluate the kinetics of cement hydration and the modification of hydrated paste composition in the presence of additive. The material after 20-year storage, the crushed slag after approximately 2-years storage and the new slag from the current production in the metallurgical plant were used. The slag percentage was 5 ÷ 50%. The addition of granulated blast furnace slag stored for a long time affects the standard properties of cement reducing the compressive strength at longer maturing and with the percentage of additive. This is related mainly to the reduction in the vitreous component. However, at the additive content up to 50% the binder complying with the requirements of the relevant European standards for common cements could be produced. Basing on the results of TG measurements the role of calcium carbonate, being the product resulting from the slag weathering process, acting as a grindability and setting/hardening modifying agent, was highlighted.

Highly targeted solidification behavior of hazardous components in phosphogypsum

In this study, an effective approach has developed to solidify phosphorus, fluorine and heavy metals in phosphogypsum by using carbide slag(CS) and polymer, and the effect of carbide slag and polymer addition on the pH and the speciations of phosphorus, fluorine in phosphogypsum has discussed in detail. The experimental results showed that in the carbide slag modified phosphogypsum system, soluble phosphorus and fluoride were significant fixed and converted into Ca3(PO4)2, CaF2 and other stable precipitates. The pH-related leaching test results indicated that there was little significant relationship between the total phosphorus leaching concentration and pH under neutral and alkaline conditions. Fluorapatite is the control phase of phosphorus in the phosphogypsum system, and the fluorite and fluorapatite are the main control phases of fluorine leaching. After long-term leaching, the proportion of the control phase of fluorite was reduced. In the polymer modified phosphogypsum system, large amount of soluble phosphorus and fluorine were solidified, which achieve high effective solidification of phosphorus and fluorine. The pH-related leaching test showed that the polymer has a significant effect on phosphorus and fluorine under different pH conditions. Besides, the curing effect has a significant relationship with pH. At the same time, carbide slag and polymer have a certain effect on the conversion between the speciations of heavy metals in the system. The experimental results showed that the pH, phosphorus, fluorine and heavy metals in the carbide slag-phosphogypsum (CS-PG) system meet the requirements of the "Integrated Wastewater Discharge Standard (GB 8978–1996)" of China.

Long-term application of fused magnesium phosphate and calcium silicate change soil chemical properties, C decomposition and N mineralization in a single rice paddy field of Northeastern Japan

ABSTRACT This study investigated the long-term (31 years) effects of mineral slag fertilizer (fused magnesium phosphate [FMgP] and calcium silicate [CaSi]) application on changes in the main soil chemical properties, including pH, electrical conductivity (EC), available phosphorus (P), soil organic carbon (SOC), and total nitrogen (TN) contents in paddy soils. Soil samples were obtained from six fertilizer treatments [(1) Nitrogen, phosphorus, and potassium chemical fertilizer only (CF); (2) CF + mineral slag fertilizer (CF+); (3) CF + rice straw (RS); (4) CF + rice straw + mineral slag fertilizer (RS+); (5) CF + rice straw compost (CM); and (6) NPK + rice straw compost + mineral slag fertilizer (CM+)] at five depth soils (0–5, 5–10, 10–15, 15–20, and 20–25 cm). An anaerobic incubation experiment was performed at 30°C to determine carbon (C) decomposition and nitrogen (N) mineralization potentials at every 2-week interval (0, 2, 4, 6, and 8 weeks). The results indicated that compared to non-mineral slag additions, both EC and available P increased by 36.6–136.6% in mineral slag addition treatments. Still, only compost addition mostly influenced pH values; meanwhile, SOC and TN exhibited an increase (~23.8%) in compost addition treatments but a reduction (~12.7%) in rice straw treatments by applying mineral slag fertilizer. Mineral slag addition reduced the C decomposition potential but enhanced N mineralization potential observed by the first-order reaction kinetic models. Our study suggested that mineral slag fertilizers affected the soil organic matter and its mineralization potentials.

Influence of the Addition of Blast Furnace Slag to Alkali-Activated Mixtures Based on Natural Zeolites

This study focuses on a comparison of alkali-activated materials based on natural zeolites without and with the addition of blast furnace slag and their subsequent modification by acid leaching. The addition of slag to alkali-activated mixtures is generally used to increase the strength. The subsequent modification of its chemical, textural and mechanical properties by acid leaching makes this material usable in other industries, especially in the chemical industry. This study aimed to examine the influence of the addition of blast furnace slag to alkali-activated mixtures based on natural zeolites and observe the effect of subsequent acid leaching on the chemical, textural and mechanical properties and CO2 adsorption capacity of these materials. The modification of alkali-activated materials was carried out by acid leaching using 0.1 M HCl and then using 3 M HCl. The properties of these materials were determined using N2 physisorption, Hg porosimetry, XRF, XRD, DRIFT, TGA and strength measurements. The results showed that the addition of blast furnace slag significantly increased the cutting-edge strength of the obtained materials and affected the textural properties, especially in leached samples. The presence of blast furnace slag generated a higher proportion of mesopores, which are attributed to the presence of the calcium silicate hydrate (C–S–H) phase and are easily removed by leaching, as shown by the XRF results. The obtained data showed an improvement in properties and extension of the potential applicability of these materials in the chemical industry, especially for catalytic and adsorption applications.

Properties of Concrete Made from Cupola Furnace Slag and Recycled Construction Aggregates

The replacement of traditional constituents of concrete with waste has garnered a lot of interest due to the increasing demand for natural resources used in concrete production. Hence, this study presents the outcome of an experimental investigation on the effect of partial replacement of Ordinary Portland Cement (OPC) at percentage levels of 0% to 25% in steps of 5%, partial and complete replacement of sand and granite in the percentage of 0 to 50 in steps of 10% with cupola slag and recycled construction aggregates. The fresh and hardened properties of concrete such as workability, compressive strength, and microstructural characteristics were assessed. The test results showed a decrease in workability as the percentage replacement of cupola furnace slag (CFS) and recycled construction aggregates (RCA) increases. Concrete produced at 28 days from the partial replacement of cement and sand with cupola slag has an optimum compressive strength of 20.37 N/mm2 at 10% and 22.81 N/mm2 at 20%, resulting in improved strength of 29.4% and 56.82%, respectively when compared with the control. In contrast, granite’s partial replacement with coarse cupola slag and complete replacement of sand and granite gave a lesser compressive strength when compared with the control samples at 7, 14, 28, and 56 days. The porosity of the concrete with optimum compressive strength from each mix was studied using microscopic and image analysis. The result showed that the addition of cupola slag in granulated and fine forms decreases the porosity, hence leading to higher compressive strength.

Research on Curing Water Demand of Cementing Material System Based on Hydration Characteristics.

The performance of cover concrete is acknowledged as a major factor governing the degradation of concrete structures. Curing plays a vital role in the development of concrete durability. The effects of different water-binder ratios and mineral admixtures on the curing water demand of concrete were studied by the surface water absorption test. Combined with the characteristics of the hydration heat and chemically bound water of the composition cementing material system, the law of variation for curing water demand was analyzed. The results show that the addition of mineral admixtures can reduce the early hydration rate and hydration exothermic characteristics, and the hydration degree decreases with the increase of mineral admixtures. Due to the filling effect and active effect, the addition of fly ash (FA) and ground granulated blast slag (GGBS) reduces the curing water demand. The curing water demand of cover concrete decreases with the increase of mineral admixture content, and the curing water demand of pure water is the maximum and that of mix FA and GGBS is the minimum. Moreover, there is a strong correlation between the cumulative curing water demand and the chemically bound water content, indicating that the power of water migration mainly comes from the hydration activity of the cementing material system. The results provide a theoretical basis for the fine control of a concrete curing system.

Properties of Concrete Made from Cupola Furnace Slag and Recycled Construction Aggregates

The replacement of traditional constituents of concrete with waste has garnered a lot of interest due to the increasing demand for natural resources used in concrete production. Hence, this study presents the outcome of an experimental investigation on the effect of partial replacement of Ordinary Portland Cement (OPC) at percentage levels of 0% to 25% in steps of 5%, partial and complete replacement of sand and granite in the percentage of 0 to 50 in steps of 10% with cupola slag and recycled construction aggregates. The fresh and hardened properties of concrete such as workability, compressive strength, and microstructural characteristics were assessed. The test results showed a decrease in workability as the percentage replacement of cupola furnace slag (CFS) and recycled construction aggregates (RCA) increases. Concrete produced at 28 days from the partial replacement of cement and sand with cupola slag has an optimum compressive strength of 20.37 N/mm2 at 10% and 22.81 N/mm2 at 20%, resulting in improved strength of 29.4% and 56.82%, respectively when compared with the control. In contrast, granite’s partial replacement with coarse cupola slag and complete replacement of sand and granite gave a lesser compressive strength when compared with the control samples at 7, 14, 28, and 56 days. The porosity of the concrete with optimum compressive strength from each mix was studied using microscopic and image analysis. The result showed that the addition of cupola slag in granulated and fine forms decreases the porosity, hence leading to higher compressive strength.

Mechanical Properties of Furnace Slag and Coal Gangue Mixtures Stabilized by Cement and Fly Ash.

The mechanical properties and strength formation mechanism of cement–fly-ash-stabilized slag–coal gangue mixture were examined using an unconfined compressive strength test, splitting strength test, triaxial test, and scanning electron microscopy to solve the limitations of land occupation and environmental pollution that is caused by fly ash from the Xixia District thermal power plant in Yinchuan, slag from the Ningdong slag yard, and washed coal gangue. Its performance as a pavement base mixture on the road was investigated. The results demonstrated that as the slag replacement rate increased, the maximum water content increased while the maximum dry density decreased. The addition of slag reduced the unconfined compressive strength and splitting strength of the specimens; furthermore, the higher the slag substitution rate, the lower the unconfined compressive strength and splitting strength of the specimens. As the cement content increased, the specimen’s unconfined compressive strength increased. Based on the principle of considering the mechanical properties and economic concerns, the slag replacement rate in the actual construction should be ~50% and should not exceed 75%. Based on the relationship between the compressive strength and splitting strength of ordinary concrete, the relationship model between the unconfined compressive strength and splitting strength of cement–fly-ash-stabilized slag–coal gangue was established. The failure mode, stress–strain curve, peak stress, and failure criterion of these specimens were analyzed based on the triaxial test results, and the relationship formulas between the slag substitution rate, cement content, peak stress, and confining pressure were fitted. As per the SEM results, the mixture’s hydration products primarily included amorphous colloidal C-S-H, needle rod ettringite AFt, unhydrated cement clinker particles, and fly ash particles. The analysis of the mixture’s strength formation mechanism showed that the mixture’s strength was the comprehensive embodiment of all factors, such as the microaggregate effect, secondary hydration reaction, and material characteristics.

Chloride-related steel corrosion initiation in cement paste prepared with the incorporation of blast-furnace slag

Steel corrosion caused by chloride penetration is an important problem in construction practices threatening the long-term durability of reinforced concrete structures. In this study, the effects of blast-furnace slag on the passivation and corrosion processes of carbon steel embedded in cement pastes were investigated by electrochemical measurements, and equivalent circuit models were proposed for analysis of the passivation and corrosion processes. The spatial chloride distributions in the cement paste after corrosion initiation were determined distinguishing between amounts of total, free and bound chloride. The values of the open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) measurements indicated that the carbon steel embedded in cement pastes was passivated due to the presence of an alkaline pore solution. However, the formation of passive layers on the surface of carbon steel in the slag-blended cement paste was weakened by the more negative OCP value due to a lower pH value and higher sulphide concentration in the pore solution. Upon initiation of corrosion during the electrical acceleration test, the OCP value dropped to a significantly more negative value whereas the Warburg impedance in the equivalent circuit model sharply decreased. Moreover, the addition of slag decreased the threshold chloride concentration at the steel surface to initiate steel corrosion. On the other hand, the enhanced resistance against chloride penetration and the higher chloride binding capacity resulted in an overall increase of the corrosion resistance of carbon steel in slag-blended cement paste.

Reducing detrimental sulfate-based phase formation in concrete exposed to sodium chloride using supplementary cementitious materials

The sodium chloride (NaCl) can chemically interact with the monosulfate (AFm) within the concrete matrix, leading to a detrimental sulfate-based phase formation during thermal cycling. This paper studies the potential of reducing the sulfate-based phase in the cementitious pastes made using different types of supplementary cementitious materials (SCMs) used as a partial replacement of ordinary portland cement (OPC). A low-temperature differential scanning calorimetry was used to quantify the amount of the sulfate-based phase. The results indicated that the addition of SCMs as a partial replacement of OPC revealed different effects on forming the sulfate-based phase through pozzolanic activities and/or dilution effects. The addition of slag or class F fly ash can lower the formation of the sulfate-based phase through the dilution effect, while the addition of silica fume can substantially lower the formation of the sulfate-based phase by both dilution and pozzolanic activities. The use of class C fly ash, however, showed negative effects through increasing the formation of the sulfate-based phase. Thermodynamic modeling was used to predict the phase equilibrium of hydrated cementitious systems. Results from thermodynamic predictions were in agreement with the experimental results, indicating that the formation of the sulfate-based phase was associated with the amount of AFm present in the cementitious systems.

Toxicity assessment of the utilization of AOD slag as a mineral fertilizer for pakchoi (Brassica chinensis L.) planting

The application of argon oxygen decarburization (AOD) slag as a mineral fertilizer can be employed as an effective and environment-friendly approach. In this study, batch leaching tests and pot experiments were performed to assess the toxicity exhibited by AOD slag fertilization for pakchoi (Brassica chinensis L.) planting. pH, Eh and element leaching concentration were measured to examine the effect exerted by AOD slag addition on physicochemical properties exhibited by soil. The effect of AOD slag fertilization on pakchoi growth was determined by measuring its physiological and biochemical parameters. Moreover, the heavy metal accumulation, biological accumulation coefficient (BAC), estimated daily intake (EDI) and target hazard quotient (THQ) were identified to assess the health risks. As indicated from the result, adding AOD slag could increase pH and the leaching concentrations of Ca, Si, Cr and Ti, while decreasing the leaching concentrations of Fe, Ni, Cd, Hg and Pb in soil. With the increase in the addition rate, the concentrations of Mg, Al and Mn were elevated and then started to decrease at the rates of 2%, 8% and 2%, respectively. Low rates (≤1%) of AOD slag fertilization positively impacted pakchoi growth, whereas high rates exerted an opposed effect. The calculated EDI and THQ values were all less than 1. The consumption of the pakchoi grown on the AOD slag fertilized soil was at low risk. For plant growth perspective, the utilization amount of AOD slag as a mineral fertilizer for pakchoi planting should not exceed 1%.

Analysis of the Possibility of Using Slags from the Thermal Treatment of Municipal Waste as Potential Component of Cement-Case Study.

In Europe there are nearly 500 incinerators. There are over 2000 of them in the world. It is estimated that the combustion of 1 ton (Mg) of waste produces about 250–300 kg of slag. Due to the large amounts of this waste, the construction industry’s demand for raw materials and the reduction of CO2 emissions, research was undertaken to use slags as a cement component. The problem was complex because slags generated in the thermal treatment of municipal waste have different chemical compositions and physical properties and contain variable amounts of impurities. The choice of chemical analyses of slag was dictated by the potential influence on the properties of cement mortars. The total moisture of raw slag (4–10%), the bulk density (600–1267 kg/m3) and the specific surface after grinding (over 3000 cm2/g) were determined. The pH (11.9) and the content of sulphates (3.5% by weight), chlorides (0.3% by weight) and selected heavy metals (Cd, Cu, Fe, Mn, Zn, Pb) were measured in the aqueous extract. The obtained results of the washing test were compared with the values resulting from the currently binding legal regulations. In the next step, cement mortars with 30% addition of tested slags were designed and made. The article presents the results of compressive strength tests, which were compared with the results of samples without the addition of slag. The addition of slag to the cement mortar decreased S_MSWI 1 by 64% and S_MSWI 2 by 31%. The high loss of strength and the swelling of the S_MSWI 1 test led to the activation of the NaOH slag. In the endurance test, an increase from 16 to 32 MPa was recorded. Preliminary studies show that the addition of slag in the cement mortar allows obtaining the strength at the level of 30–32 MPa.

Degradation mechanism of hybrid fly ash/slag based geopolymers exposed to elevated temperatures

As a promising alternative to alkali-activated fly ash (AAF) for high temperature application, the degradation mechanism of alkali-activated fly ash/GGBS (AAFS) under high temperature is not clear. This work investigates physicochemical properties of AAFS up to 800 °C and presents their synergetic influence on the thermal behavior. A quantitative assessment of the crack is developed to learn the cracking behavior. Results reveal that the crack density exhibits a linear relationship with ultrasonic pulse velocity. The crack density and compressive strength exhibit a positive correlation before 100 °C, but a negative relationship beyond 100 °C. The addition of slag into geopolymers lessons the geopolymeric behaviors such as further geopolymerization and viscous sintering, but further aggravates the thermal damage owing to the compact structure and unstable hybrid gel. The conceptual models of AAF and AAFS are proposed to explain the degradation mechanism of low slag contained geopolymers under elevated temperatures.