Air-cooled Slag Research Articles

Sustainable composite cement prepared by two different types of iron slag

The utilization of two kinds of iron slag in the production of pozzolanic cement is introduced. A series was created with a fixed percentage of OPC (30%) and varying amounts of imported granulated blast-furnace slag (IGBFS) and air-cooled slag (ACS) at which imported IGBFS was substituted by ACS with the mass ratios of 10, 20, and 30%. Physico-mechanical properties and hydration parameters of the hardened pastes were examined at different time intervals. Furthermore, the aggressive attack of seawater on chosen specimens was studied for up to one year of immersion. The hardened composite cement pastes were tested in terms of weight loss, compressive strength, bulk density, total porosity, and free lime at different thermally treated temperatures starting at 105 °C and ending at 800 °C for 2 h of a socking period to investigate its thermal characteristics. XRD, IR, and DTA/TGA techniques were used to examine some chosen samples. The results revealed that the incorporation of ACS reduces the water consistency and prolongs setting times. Compressive strengths are higher in samples containing 10% ACS than those specimens containing 20–30 wt% and without ACS. A 7% reduction in the compressive strength was achieved by A1 (30%OPC and 70% IGBFS), which is the lowest one over 1 year of exposure to seawater. The incorporation of ACS at the expense of IGBFS tends to lower the strength but tends to enhance the bulk density.

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

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

The effect of Basic Oxygen Furnace, Blast Furnace, and Kanbara Reactor Slag as Reinforcement to Cement Based Mortar

Slag is a waste from steelmaking industries that was released into the environment. Slag was used as reinforced material in mortar. Different types of slag, including Air Cooled Slag (ACS), Granulated Blast Furnace Slag (GBFS), Basic Oxygen Furnace Slag (BOFS), and Kanbara Reactor Slag (KRS), were used as a reinforcing material in this study. The composition of slag in the mixture on mortar was 10%, 20%, 30%, 40%, and 50%. The sample was made with a water-cement ratio (w/c) of 0.35, with the ratio of sand and cement being 1:1.5, respectively. Treatment of mortar sample at ambient temperature was applied. The mortar samples were left to cure until 3, 7, and 28 days, which performed a compression test. The results show that adding slag to the mortar enhanced the compressive strength of the pristine mortar. The highest strength was obtained by adding 10% slag at 28 days. The compressive strength of GBFS, BOFS, KRS, and ACS was 23.76 MPa, 23.28 MPa, 19.68 MPa and 17.48 MPa, respectively. Based on the XRD result, it was discovered that the mixture has more Calcium Silicate Hydrate Peak than Pristine mortar.

Thermodynamics analysis and experiments on Ti-bearing blast furnace slag leaching enhanced by sulfuric acid roasting.

The potential-pH diagrams of the main components of Ti-bearing blast furnace slag (air-cooled slag) at 298.15 K (25 °C) and an ion activity of 1.00 were drawn by thermodynamic calculation. Thermodynamic analysis showed that the main metal components, when the Ti-bearing blast furnace slag is roasted with concentrated sulfuric acid, could be converted to sulfate. From these analyses, it can be seen that under strong acid conditions, the major metal components could react to form sulfate, and the effective separation of Ti, Mg, and Al can be achieved from both Ca and Si. Further experiments were performed with a 5.0% dilute sulfuric acid solution used to leach a Ti-bearing blast furnace slag sample that had been calcined with concentrated sulfuric acid, at a liquid-solid ratio of 10, a reaction time of 60 min, and a reaction temperature of 338.15 K (65 °C). This led to a leaching ratio of Ti above 85.0%, leaching ratios of Mg and Al higher than 95.0%, and leaching ratios of Fe and Ca of 45.7% and 24.7%, respectively. All these values were higher than the leaching ratios of Ti-bearing blast furnace slag.

Value-added waste substitution using slag and rubber aggregates in the sustainable and eco-friendly compressed brick production

The current study aimed to analyse the viability of incorporating the post cryogenic discarded rubber and the air-cooled slag as an aggregate in partial replacement of stone dust in fly ash bricks production. A range of mechanical, non-destructive, and microstructural tests was performed on bricks thus produced by incorporating rubber and slag aggregates in various dosages (i.e., 5, 10, 15, 20 and 25% by stone dust weight). The result revealed that the compressive strength dropped from 71 to 43 % in the case of rubber aggregate replacement. Morphology study confirms that the rubber aggregates resulted in the porous microstructure of the bricks and leads to lesser unit weight and lighter structure. The rubber may be used as a lightweight aggregate in the brick possibly as it reduces the density of the final product. However, the use of rubber in bricks needs to be cautiously designed to get hold of productive solutions at the end. The findings demonstrate that the copper slag substitution of up to 15%, found to be enhanced the strength properties and it will be a better choice for low-cost construction as a promising alternative construction material.

The Influence of the Environment on the Properties of Hybrid Cement-Based Concrete with Steel and Air-Cooled Slags

This article presents the results of research that dealt with the development of non-traditional concrete using a hybrid alkali-activated cement. It is concrete based on by-products from a metallurgical plant that replaced 100% of the natural aggregates. Steel slag (CSS, fraction: 0/8 mm) was used as a filler in combination with air-cooled slag (ACBFS, fraction: 8/16 mm and 16/32 mm). Portland blended cement (CEM II/B-S 42.5N) and H-CEMENT were used as binding components in the development of the concrete mixture designs. Both of these cements were produced by Považská cementáreň, a.s., Ladce. Attention was focused on testing the physical and mechanical properties of the developed concretes in various environments. An aqueous environment was selected as the first environment for the placement of test specimens (cubes with 150 mm edges and prisms with dimensions of 100 × 100 × 400 mm3) according to the ČSN EN 206-1 standard and the outdoor environment (August to October). The determination of the cube strength was made after 7, 28, and 90 days, the determination of the flexural and compressive strength was made at the end of the prisms, and the determination of the dynamic modulus of elasticity was made after 28 days on the prisms. The test results of the test specimens, which were placed in two environments, were compared and it was found that, after 90 days, the outdoor environment caused a decrease in the concrete’s strength characteristics when using Portland blended cement (CEM II/ B-S 42.5N) of about 8%; in contrast, when using H-CEMENT, the concrete’s strength increased by about 14%. The use of H-CEMENT and the addition of PUZZOLANIT in the amount of 30% in combination with CEM II/B-S 42.5N in the amount of 70% reduced the decrease in the strength of the concrete after 90 days by about 3%. The research results confirm the suitability of using H-CEMENT and the addition of PUZZOLANIT for the production of concrete based on steel slag (CSS) and air-cooled slag (ACBFS).

Chloride Ion Diffusion and Durability Characteristics of Rural-Road Concrete Pavement of South Korea Using Air-Cooled Slag Aggregates

In the construction industry, the lack of supply and demand for high-quality natural aggregates is a problem. In the case of South Korea, according to data from the Ministry of Environment, it is predicted that the depletion of aggregate resources will occur in 20 years, considering the amount of aggregate used in construction every year and the amount of natural aggregate. Therefore, it is necessary to develop recycled aggregates that can replace natural aggregates for construction. The purpose of this study is to evaluate the applicability of recyclable air-cooled slag (ACS) aggregates as a substitute material for natural aggregates applied to rural-road pavement concrete. That is, the applicability of rural-road pavement concrete is evaluated by evaluating the strength and durability of rural-road pavement concrete to which an ACS aggregate is applied. Durability was assessed in terms of the chloride ion diffusion, repeated wetting-drying, abrasion resistance, impact resistance, and repeated freezing-thawing tests. The test result showed that the diffusion coefficient of the mixture to which the ACS aggregate was applied was slightly larger. In addition, the diffusion coefficient was slightly larger in the case of applying the air-cooled slag coarse aggregate (GG) than in the case of applying the air-cooled slag fine aggregate (GS). The results of abrasion and impact resistance tests of ACS-aggregate-incorporated rural-road concrete indicated that abrasion and impact resistance decreased as the aggregate content increased. The ACS retained some of the properties of the blast furnace slag. Thus, in repetitive wetting-drying tests, which can cause changes in chemical properties, the ACS aggregate increased the concrete’s long-term residual strength. In addition, the results showed that the relative dynamic elastic modulus targeting repeated freezing-thawing resistance satisfied the 80% target. The freeze-thaw resistance improved as the ACS aggregate content increased. In conclusion, the results of this study showed that the durability of rural-road pavement concrete can be improved experimentally by applying both GG and GS at the same time. Therefore, it is shown that ACS aggregates can be applied to rural-road pavement concrete as a substitute for natural aggregates.

Effect of Freeze–Thaw Cycles on the Performance of Concrete Containing Water-Cooled and Air-Cooled Slag

An experimental study on the resistance of concrete containing air-cooled slag (AS) and water-cooled slag (WS) against freeze–thaw cycles was conducted. For comparison, the durability of ASTM Type I ordinary Portland cement (OPC) concrete exposed to the same freeze–thaw environment was examined. To evaluate the durability of concrete exposed to the freeze–thaw environment, an experiment was conducted according to ASTM C 666 procedure A. Furthermore, the relative dynamic modulus of elasticity, surface electrical resistivity, and compressive strength of concrete specimens were measured after exposing them to freeze–thaw cycles for a predetermined period, and the results were compared with those of OPC concrete. The relationship between the freeze and thaw resistances of concrete and the air-void system (spacing factor and specific surface area) was identified. Furthermore, the microstructure of concrete exposed to freeze–thaw cycles was observed using scanning electron microscopy to identify the interfacial transition zone, cracks, and micropores. Experimental results showed that the resistance of blended cement concrete containing WS and AS against freeze–thaw cycles was significantly higher than that of OPC concrete. The concrete in which 10% of OPC was replaced by AS exhibited a similar durability as that of the concrete in which 40% of OPC was replaced only by WS. Therefore, it is expected that blended cement concrete containing WS and AS based on an appropriate mix proportion design will exhibit excellent durability in regions experiencing freezing temperatures.

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

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

Strength of Concrete with Recycled Manganese Slag

This paper studies the effect of replacing coarse aggregates with manganese slag on the mechanical properties of concrete. Air-cooled granulated manganese slag was used. The control sample was designed to achieve concrete strength of 30 MPa at 28 days. Tests were conducted on five different compositions of concrete having manganese slag to coarse aggregates ratios of 0, 0.2, 0.3, 0.4, and 1. The specimens were tested at 7, 14, and 28 days for their compressive and flexural strength. Test results revealed that all manganese slag concrete specimens had improved compressive and flexural strength. The maximum compressive strength achieved was 43.54 MPa, increased by 16% of the control specimen and the maximum flexural strength achieved was 4.50 MPa, increased by 22% of the control specimen. Both results were obtained in concrete with 0.4 manganese slag to coarse aggregate ratio. Besides, the study also showed that it might be possible to substitute all coarse aggregates in concrete with manganese slag without any loss in strength. However, it was observed that the concrete workability decreased when manganese slag was added. Nonetheless, this could be corrected using superplasticizer.

Behavior of Crack Generation of Slag in Continuous Solidification Process of Blast Furnace Slag

A continuous solidification process of blast furnace slag was developed to promote the use of air-cooled slag coarse aggregate for concrete. In this process, the molten slag can solidify in only 120 s and the slag thickness is about 25 mm. This process suppresses gas generation and greatly reduces water absorption. Most of the slag is crystalline, and part of the slag has a glass layer on its surface. Slag with a glass layer is brittle because it contains several cracks. Therefore, microscopic observation and thermal stress analysis of the solidified slag were carried out to clarify the mechanism of crack generation in the plate-like slag. In the microscopic observation, several cracks with a length of about 8 mm were found in the slag with the glass layer. From the analysis, in the cooling pattern of the slag on the piled slag a temperature difference of about 200 K exists between the center and the mold side in the slag pit, and keeping this difference results in tensile stress of more than 50 MPa. However, in the cooling pattern of the crystalline slag in the piled slag, the temperature gradient in the slag in the slag pit was very small because the slag was retained in the piled slag, and as a result, the thermal stress was almost 0 MPa.

Utilization of alkaline Aluminosilicate activation in heavy metals immobilization and producing dense hybrid composites

Recently geopolymer technology possesses not only great efficiency in immobilizing heavy metal wastes but also produces valuable materials that can be applied in building sectors. The aim of this study is to examine the capability of geopolymers in the immobilization and entrapping of heavy metals bearing materials. The study will focus on the evaluation of optimum ratio of heavy metal that can affect and densify the produced composite. The studied mortar’s binder was made from blast furnace slag, while the used fine aggregates were air-cooled slag < 1 mm. However, the used activator was 8% sodium hydroxide. The studied heavy metals’ bearing materials were barium sulfate, lead phosphate, lead slag and electric arc furnace dust used as partial replacement of blast furnace slag. The physico-mechanical characterization of each set of samples was conducted using XRD, FTIR, SEM, compressive strength and bulk density. Results demonstrated that barium sulfate can be efficiently used up to 2%, lead phosphate up to 1%, lead slag up to 5% and electric arc furnace dust up to 10%.

Experimental Study on Freeze–Thaw Resistance of Concrete Containing Air-Cooled and Water-Cooled Slag Binders

Experimental Study on Freeze–Thaw Resistance of Concrete Containing Air-Cooled and Water-Cooled Slag Binders

Utilization of Water-Cooled and Air-Cooled Slag Aggregate in Concrete: A Solution to the Secular Economy

Aggregates are generally thought of as inert filler within a concrete mix, and a typical concrete mix is comprised of as much as 70–80% of them. They play an essential role in the properties of both fresh and hardened concrete. Nowadays, scientists are aiming to use waste materials, thereby replacing natural aggregates for economic and environmental considerations. This study investigates the effect of the utilization of steel slag by-product aggregates (air- and water-cooled slag) as concrete aggregates on the behavior characteristics of concrete. Various concrete mixtures, with different levels of replacement of slag aggregate (50, 75, and 100%), were conducted in order to find the optimum percentages to improve the microstructure and different properties of concrete (fresh and hardened). The results showed that increasing the fine aggregate replacement percentage led to a decrease in compressive strength values, in contrast with coarse aggregate replaced with slag aggregate. The steel slag aggregates showed potential to be used as replacement for natural aggregate with comparable compressive strength and acceptable workability.

Simulation of the strain diagram of a slag-concrete element subject to bending

In the modern world of information technology personal computers considerably dominate our everyday life. All real, field experiments and tryouts replace computer-aided simulations as they often save a lot of time. It is much easier to make the multiple calculations related inter alia to reinforced concrete structures using strain diagrams for the concrete and rebars. This is the method ensuring the results similar to the field tests and the only challenge is that many equation parameters have to be reduced. Therefore, the objective of the work is to propose a simplified mathematical model for describing the strain diagram of a bended slag-concrete element based on air-cooled slag (ACS) and the aggregate made of sieves (0…5 mm fraction) from crashed ACS originating from NLMK’s Blast Furnace Operations, while implementation of the model helps to avoid complicated equilibrium experiments. As a result of the research and mathematical simulation of the bended element diagram a model capable of reflecting the sample behavior at any loading stage using maximum load and initial modulus of elasticity was proposed.

Acidolysis Performance of Titania Slag Treated at Different Cooling Conditions

The effect of cooling methods such as granulating, water cooling, and air cooling on the quality of Titania slag was investigated. The results show that the Ti2O3 content in Titania slag is decreased with three different cooling ways. For instance, Ti2O3 content in granulated slag decreased by 27.6%. Content of Fe2O3 in granulated slag was approximately 2.86% higher than both water-cooled slag and air-cooled slag. The main phases in the cooled slag consisted of TiO2 and (Fe, Mg)xTiyO5. Rutile phase in both water-cooled slag and air-cooled slag is not found; however, it is detected in the granulated slag. The acidolysis ratio was measured to be 90.61% and 92.46% in water-cooled slag and air-cooled slag, respectively. However, the acidolysis ratio of granulated slag was only 74.72% that is 20% less than that of original industry slag. It is found that the acidolysis ratio was dependent on the phases, composition of Titania slag, and cooling conditions. Rutile could reduce acidolysis ratio of Titania slag, and therefore, it should be controlled as low as possible. Prolonging the cooling time can increase acidolysis ratio of slag, and the optimum cooling time for this study is found to be about 18 h.

Utilisation perspective on water quenched and air-cooled blast furnace slags

Efficient utilisation and recycling of industrial waste along with minimum exploitation of natural resources are major challenge towards the circular economy and sustainability of the planet. Blast furnace slag is a by-product of the iron-making process while producing pig iron. The present research provides an understanding of the two different types of slags of water quenched granulated slag and air-cooled slag that are generated from iron making process through the blast furnace route. The chemical, mineralogical, physical, thermal and morphological properties of four different slags generated under different cooling condition are evaluated for recycling to cement and aggregate application. Results indicated that the cooling pattern of the slag significantly affects the particle morphology and phase formation, which determines their usage and utilisation. Air-cooled slag contains substantial quantity of crystalline phases (>50%) which prevents the slag to exhibit cementitious properties whereas water-quenched slag mainly contains amorphous phases (>90%). In addition, the applicability in cement and aggregate application of both mentioned types of slags were studied. It is concluded that water quenched slag is closely matching with the properties required to be utilised in Portland slag cement manufacturing process. On the other hand, air-cooled slag is suitable as an aggregate for application in the construction industry.

Minimizing Chromium Leaching from Low-Alloy Electric Arc Furnace (EAF) Slag by Adjusting the Basicity and Cooling Rate to Control Brownmillerite Formation

Brownmillerite is connected to chromium leaching when present in steel slags. To prevent chromium leaching, brownmillerite in slag should be prevented. Two methods for decreasing brownmillerite content in low-alloy electric arc furnace (EAF) slag were investigated: decreasing the basicity and increasing the cooling rate. The methods were tried on both laboratory scale and in full-scale production. In the laboratory scale experiments, chromium leaching decreased as the basicity decreased until brownmillerite was no longer present, slower cooling resulted in increased chromium leaching, and faster cooling decreased chromium leaching. In full-scale production, basicity modified single batches, with a basicity below 2.2, generally leached less chromium than slag batches with higher basicity, thus verifying the correlation between basicity and chromium leaching seen in laboratory scale experiments. The cooling process in the full-scale experiments was achieved either by letting the slag cool by itself in the air or by water spraying. The water-sprayed slag, which cooled faster, had less chromium leaching than the air-cooled slag. The full-scale production experiments confirmed that both decreasing basicity below 2.2 and increasing the rate of cooling could be used to decrease chromium leaching.

Behavior of Crystallization on a Continuous Solidification Process of Blast Furnace Slag

A continuous blast furnace slag solidification process was developed to promote the use of air-cooled slag coarse aggregate for concrete. In this process, molten slag can be solidified in only 120 seconds, and the thickness of the slag is about 25 mm. After crushing the slag, the water absorption ratio is much lower than that achieved in the past because gas generation is suppressed. With this apparatus, most of the slag is crystalline, but part of the slag has a glassy surface. Therefore, EPMA and XRD were used to study the glass transition phenomenon. It found that the thickness of the glass layer is about 2 mm. To discuss the glass transition and crystallization phenomena, the thermal history was simulated by heat transfer analysis. The results clarified the fact that all the slag on the mold has a glassy surface layer of about 2 mm, and good agreement between the calculation and experimental data concerning the layer was obtained. It was also shown that most of the slag crystallizes in the slag pit because the temperature inside the piled slags rises to more than 1173 K. The measured slag temperature and calculated temperature were also in good agreement.

Cupola Furnace Slag: Its Origin, Properties and Utilization

A cupola furnace is the most frequently used furnace aggregate for cast iron production. A by-product of the production of cast iron in cupola furnaces is cupola slag. Its amount is 40–80 kg per 1 tonne of the produced cast iron, and that is one of the reasons why this material is not as favoured as, for example, the blast-furnace slag. The purpose of this article is to provide the basic information on the formation of slag in a cupola furnace, and its chemical composition, structure and current potential applications. The greatest potential for the use of cupola slag is in the building industry; therefore, a section of the present article deals with the property that plays an important role particularly with regard to the use of slags in the building industry, i.e. the slag hydraulicity. The achieved results indicate that the hydraulicity of the cupola slag is incomparable with the hydraulicity of the blast-furnace slag; this may be associated with the problems that arise when the slag of this type is used in the building industry. The authors used the air-cooled as well as granulated slags from cupola furnaces in the production of concrete that was made from the slags alone. While the air-cooled slag may be used as a partial replacement for the blast-furnace slag in concrete mixtures, the use of granulated slag from cupola furnaces as a replacement for granulated blast-furnace slag in cement-free concrete has not proven to perform well.