Percentage Of Slag Research Articles

Performance of Concrete Containing Granulated Blast Furnace Slag as a Fine Aggregate

The present challenge in front of Civil Engineers is to find alternative materials for fine aggregates in concrete. Since, most of the State Govt. banned the dredging of river sand. The Granulated blast furnace slag is considered as a fine aggregate in concrete. At present, in India Steel Industry produces about 40 Million Tonnes by 2020 it is estimated to 60 million tonnes. The Author has investigated the effect of compressive strength of concrete, when Granulated blast furnace slag is used (GBFS) as a fine aggregate in concrete. The work includes the partially and fully replacement of river sand by granulated slag in M25 Grade of concrete with a constant 0.45 W/C ratio. Slag replacement of 50, 80, 100% are used. It has been observed that concrete made with 50% of river sand and 50% (GBFS) is nearer to Zero percent replacement. Objectives: To determine the optimum percentage slag replacement as a fine aggregate in concrete which helps in maintaining sustainability of concrete and balancing between the environmental problems due to construction industry as it is necessary to find out the alternative materials for use as fine aggregates because of restrictions by the local authorities. Methods: The experiments are planned to find out the optimum replacement percentage of GBFS against river sand as a fine aggregate in concrete. Mix design for M25 grade of concrete is made with OPC (Ordinary Portland Cement) and PPC (Port land Pozzolana Cement) is considered with a constant 0.45 W/C ratio and slag replacement of 50, 80, 100% are used. 30 Cubes for each cement category of 150 mm size are casted, cured by immersion and tested by CTM. Findings: In both the cement category, the compressive strength and slump of concrete is found reducing with the increase in the percentage of slag as a replacement to fine aggregate. In concrete made with OPC when compared with 50%, 80% and 100% replacement with GBFS reduction upto 96.50%, 87% and 77.5% in strength and 84.6%, 53.84% and 34.6% in slump respectively is observed. In concrete made with PPC when compared with 50%, 80% and 100% replacement with GBFS reduction upto 95.30%, 80% and 63% in strength and 82.7%, 51.7% and 34.0% in slump respectively is observed. Application/Improvements: This study using alternatives to fine aggregate in concrete will help in making concrete economical, reduction in environmental problems and saving the natural resources. The study may be extended to determine the concrete sustainability in saline conditions also.

Utilization of Steel Slag in Concrete as a Partial Replacement to Fine Aggregate

Concrete is largest produced material in the construction industry and as per WHO concrete is the largest consumed material by human beings after food and water. About 75% of the concrete is composed of aggregates and because of huge demand of concrete all over the world, availability of natural aggregates is becoming scarce. Civil engineers have always been looking for an alternative for the use of more eco-friendly and easily available materials as a replacement to conventional constituents in concrete. Concrete industry has always welcomed the use of various industrial waste materials as a replacement to these constituents since, otherwise such industrial waste need to be disposed in the form of landfills causing enormous amount of land pollution. This project presents the experimental investigation carried out to evaluate the effect of partial replacement of fine aggregate in concrete by steel slag which is waste product generated during the production of steel. The use of steel slag reduces the need of natural rock as constructional material, hence preserving our natural rock resources besides provides an environmental friendly option of concrete production. Steel slag mainly consists of calcium carbonate and is produced as a by-product of oxidation process in steel industry. The primary aim of this study is to evaluate the various properties of a concrete, obtained by partial replacement of fine aggregate by steel slag. In this research, apart from cement, fly ash and metakoalin (as a partial replacement to cement) were used as binding material. Five sample mixes were taken whose compression tests, tensile tests, sorptivity and water absorption tests were conducted. The mixes were obtained with 0, 30 and 40 percent replacement of fine aggregate by steel slag besides using different percentage replacements (25% of cement by fly ash in three trials, 15% and 10% cement by fly ash and metakoalin respectively in other two trials) of cement by pozzalonas. The experimental results were plotted and compared. It was observed that compressive and tensile strength increased with the increase in steel slag percentage upto to certain limit (30%). Increasing the percentage to 40% there was a sharp decline in magnitude of strength parameters and furthermore increasing metakoalin content had an effect of increasing strength. Capillary rise and water absorption increased with addition of steel slag and decreased with increase in metaloalin content.

Investigation on shear strength of stabilised clay using cement, sodium silicate and slag

A total number of 84 direct shear tests (DST) were performed on slag, sodium silicate, and cemented clay compositions to determine how these materials affect the engineering properties of cemented clay. A constant 2% percentage (by weight) of cement in clay with three different ratios of sodium silicate (1%, 1.5% and 2.5% by weight of dry soil) were mixed with three different percentages of slag (3%, 4% and 5% by weight of dry soil) and tested based on curing times of 7, 14 and 28days under three types of vertical load, being 50kPa, 150kPa and 250kPa respectively. The results indicated that the shear resistance of cured cemented clay soil was improved by adding percentages of slag and sodium silicate, and this improvement was almost three times stronger for the third sample (1% sodium silicate and 5% slag) under a 250kPa normal load compared with untreated soil, however sodium silicate generally showed a reverse effect on the improvement of soil shear resistance properties. Observing the visual characteristics using micrographs and X-ray diffraction patterns from the ultimate composition and each component by SEM/EDS and XRD phase analysis techniques, confirmed this improvement in shear resistance.

English

Literature shows increase in slag percentage in place of NCA enhances the compressive strength while increase in tensile strength is not substantial. As use of slag has increased the compressive strength to a substantial amount, the civil engineers are in a need to pace their research for enhancement of tensile strength. In normal strength and high strength concrete use of steel fiber with natural coarse aggregate has increased tensile strength to a higher amount. So, the same can be used for enhancement of tensile strength for concrete with slag. Till now no such work is carried out for improvement of tensile strength as well as compressive strength with addition of glass fiber with slag as coarse aggregate. In this study an attempt has been taken to measure fresh properties of concrete as well as the effect of addition of glass fiber on mechanical properties of slag concrete.

Utilization of high volume of industrial slag in self compacting concrete

This paper presents the results of an experimental investigation carried out to study the influence of industrial slag on the rheological, self-compactability and strength properties of self-compacting concrete (SCC) incorporating high volume replacements of industrial slag up to 90%. The rheological properties such as plastic viscosity and yield stress were evaluated using ICAR rheometer. The effect of high range water reducing admixture (HRWR) dosage, and the self-compactability properties such as T50, slump flow, V-funnel flow times and L-box blocking ratio were also investigated. The results illustrated that plastic viscosity decreased with the increase of the percentage of slag and the yield stress was nearly zero for all the replacements studied. The compressive strengths determined for the SCCs demonstrated that high strength SCC of more than 100 MPa at 30% and low strength SCC of 20 MPa at 90% replacement can be realized by utilizing slag appropriately.

Physico-mechanical, thermal, and coating properties of composite materials prepared with epoxy resin/steel slag

The interest in using different solid waste as reinforcement in polymer composite preparation has increased considerably in recent years. Slag is one of the inorganic waste materials obtained from ore processing. In this work, epoxy composites filled with different percentages of slag were prepared. Physico-mechanical, thermal, and coating properties of these composites were determined depending on the amount of filler, type of hardener, and polyethylene glycol (PEG) addition. X-ray diffraction (XRD) studies were carried out to examine the compatibility of the filler and epoxy resin and XRD results showed good compatibility between two materials. The results of mechanical testing illustrated that hardness of the epoxy composites containing anhydride was partially higher than with Epamine PC17 in contrast to elongation at break. The tensile strength and Young modulus decreased with increasing filler amount. When compared to neat epoxy resin, corrosion, and adhesion properties of the composites with filler addition did not change significantly. The highest water sorption values were obtained for the epoxy composites with PEG addition. The composites hardened by anhydride had better thermal stability than the composites including Epamine PC17. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

Compressive strength development and shrinkage of alkali-activated fly ash–slag blends associated with efflorescence

This study reports the changes in the compressive strength and shrinkage property of alkali-activated fly ash and slag (AAFS) blends associated with efflorescence. The AAFS specimens cured in air for different periods were further aged under the following three conditions: bottom-contact with water, fully immersed in water and in air. The second condition, i.e., bottom in contact with water, was used to accelerate efflorescence of AAFS. The efflorescence of the AAFS binders was dependent on the reaction extent of the solid precursors. A higher reaction extent present in the binder by extending initial-curing age can reduce efflorescence rate. The incorporation of low percentage of slag (lower than 50 wt%) in the AAFS binders has little influence on the efflorescence potential, while with the increased contents of slag higher than 50 %, the binders exhibit more rapid efflorescence than the 100 % fly ash binders. The efflorescence led to the strength loss because of the formation of carbonate crystals in the binder and the damage of the microstructure. The linear shrinkage of the binders was also related to efflorescence and alkali leaching. The slag addition can reduce the negative effects of efflorescence and alkali leaching on the absolute compressive strength and shrinkage of the binders.

Blended Cement Containing High Volume Ground Dune Sand and Ground Granulated Blast Furnace Slag for Autoclave Concrete Industry

This paper presents the results of using ground dune sand (GDS) and ground granulated blast furnace slag (slag) as high volume cement replacement materials. In this study, plain and four blended mixtures were fabricated and cured under normal and autoclave conditions. For the blended mixtures, 40% GDS by weight of the total binder materials and different percentages of slag (15%, 30% and 45%) were incorporated as partial cement replacement materials. The effect of curing conditions (normal and autoclave) on the compressive strength of prepared mixtures was studied. The results showed that, for the autoclave cured mixture, up to 85% of cement can be replaced by GDS and slag without significant drop in the compressive strength. Microstructure analyses using scanning electron microscope (SEM) and X-ray diffraction analysis (XRD) were carried out to examine the microscale changes of the hydrated mixtures. The SEM revealed the formation of thin plate-like calcium silicate hydrate and compacted microstructure of autoclave cured mixture. XRD showed the elimination of calcium hydroxide and existence of residual crystalline silica of all blended mixtures.

Application of Wood to Sand-slag and its Effect on Soil Strength

In certain situations, sand is required to have extra shear strength to provide more safety, stability and support for structures. Shear strength in sand arises from friction and resistance between particles. The most common means of increasing the shear strength of sand is the cementation method. Another practice is using an additive such as slag. Some studies show that wood has also been used to improve soil strength, mostly for soft and expansive soil. However, there is limited information available on sand. Therefore, the purpose of this research is to determine whether the shear strength of a sand-slag mixture is affected by the addition of wood. Baldivis sand, a locally sourced material, was used in the experiment because it has been widely used in construction and geotechnical projects in Western Australia. The shear strength of the sand-slag-wood material was determined using an automated direct shear testing machine. There were a number of variations in test conditions, including as the amount of wood introduced into the sand-slag, the percentage of slag in the sand, the gaps between the wood, and wood orientation. The results showed that the shear strength of the sand-slag mixture tended to be enhanced by the presence of wood. The sand-slag mixture containing wood seemed to be stronger than the sand-slag without wood or the pure sand. The position of the wood also contributed to the improvement in shear strength. Placing the wood vertical to the shear direction resulted in greater strength than when the wood was positioned horizontally. From these results, it can be concluded that wood is another potential means of enhancing the shear strength of sand-slag mixture. The quantity of wood and the way it is arranged, such as distance and direction, may result in different levels of improvement to the shear strength of the sand-slag.

Effect of Slag on the Rheological and Strength Properties of Self-Compacting Concrete

This study deals mainly deals with the rheological and strength properties of self-compacting concrete (SCC) incorporating high volume replacements of slag. Plastic viscosity and yield stress were evaluated using ICAR rheometer. The effect of high range water reducing admixture (HRWR) dosage, the time to reach 500 mm diameter (T50), the final slump flow, V-funnel flow times and L-box blocking ratio were also investigated and studied in this research program. The results show that the plastic viscosity decreases with the increase of the percentage of slag and the yield stress was nearly zero for all the replacements studied. The compressive strengths determined for the SCCs demonstrate that high strength SCC of more than 100 MPa can be realized by using slag appropriately.

Ferronickel slag toxicity tests on Chlorella vulgaris and Artemia sp.

Acute effects of ferronickel slag toxicity on Chlorella vulgaris and Artemia sp. were studied. Tests were conducted on ferronickel slag to determine the concentration of heavy metals leached out to the environment. Toxicity tests were also carried out on the organisms with minimum exposure duration of 4 days or until the occurrence of a negative effect. About 400 cells mL-1 of C. vulgaris and 20 individuals of Artemia sp. were used in each of the reactors with media containing slag concentration ranged from 0 to 50%. Results showed that the IC50 (inhibition concentration) value of the percentage of slag (w/v) for C. vulgaris was 5-10%. Slag toxicity test on Artemia showed that LC50 (lethal concentration) for the percentage of slag was also between 5-10%. The study proved beyond doubt the acute effects of the slag at low concentration (10% w/v) as indicated by the inhibition of growth of 60% of the C. vulgaris population and deaths of more than 50% of the Artemia in the reactors. Hence the study suggests wise use of the slag to avoid disturbances to environment and society at large.

Effect of blast furnace slag on self-healing of microcracks in cementitious materials

The physico-chemical process of self-healing in blast furnace slag cement paste was investigated in this paper. With a high slag content i.e., 66% in cement paste and saturated Ca(OH)2 solution as activator, it was found that the reaction products formed in cracks are composed of CSH, ettringite, hydrogarnet and OH–hydrotalcite. The fraction of CSH in the reaction products is much larger than the other minerals. Large amount of ettringite formed in cracks indicates the leaching of SO42− ions from the bulk paste and consequently the recrystallization. Self-healing proceeds fast within 50h and then slows down. According to thermodynamic modeling, when the newly formed reaction products are carbonated, the filling fraction of crack increases first and then decreases. Low soluble minerals such as silica gel, gibbsite and calcite are formed. Compared to Portland cement paste, the potential of self-healing in slag cement paste is higher when the percentage of slag is high.

Compressive strength and electrical properties of concrete with white Portland cement and blast-furnace slag

Abstract Electrical resistivity is an important characteristic of concrete because it allows evaluation of the accessibility of aggressive agents prior to the beginning of the corrosive process and estimation of the corrosion propagation. This study investigated the apparent electrical resistivity of concrete mixes with white Portland cement and with and without blast-furnace slag using Wenner’s four-electrode method. The compressive strength of concrete cylinders and the electrical conductivity of the pore solution were tested. Examined slag contents were 50% and 70% by mass and the results were compared to reference mixtures of 100% white Portland cement and 100% grey Portland cement, as well as to mixtures with equal percentages of slag and grey Portland cement. Larger amounts of slag resulted in increased electrical resistivity and decreases in the electrical conductivity of the pore solution, when compared to the reference concretes. The mixture made of 50% slag and 50% white Portland cement showed, on average, compressive resistance levels between 35 MPa and 60 MPa, electrical resistivity values that were approximately five times greater, costs that were 14.6% less per m3, and whiteness similar to the reference concrete. These results indicate that white Portland cement can be partially substituted by blast-furnace slag.

The influence of small particle on the fluidity of blast furnace slag cement paste containing superplasticizers

This paper presents research results of superplasticizers effect on rheological properties of cement pastes containing blast furnace slag. The percentage of slag was from 20% to 80% by mass of cement. The specific surface of slag was similar to cement according to Blaine’a but the slag contained smaller percentage of fine fraction than cement. It was found that superplasticizer addition lowers rheological parameters of cement pastes. The decrease of rheological parameters depends on fine fraction contents in cement. Various degree of fluidity of cement pastes (C3 and CEM III/A 32.5) with similar contents of slag (about 60%) results from different amount of fine fraction below 20 μm.

Behaviour of slag cement concrete under restraint conditions

Some constructions built with slag cement concrete exhibit cracking at early age due to restrained shrinkage. To determine the slag effect on cracking, this study focuses on the autogenous deformation evolution of concretes characterized by different percentages of slag (0 and 42% of the binder mass) under free and restraint conditions by means of the TSTM device (Temperature Stress Testing Machine). Despite the fast kinetics of its autogenous deformation, the cracking appears later for the slag cement concrete than for the Portland cement concrete. This behaviour is related to the swelling of its cementitious matrix at early age and its large capacity for relaxing the stresses.

Behaviour of slag cement concrete under restraint conditions

ABSTRACT Some constructions built with slag cement concrete exhibit cracking at early age due to restrained shrinkage. To determine the slag effect on cracking, this study focuses on the autogenous deformation evolution of concretes characterized by different percentages of slag (0 and 42% of the binder mass) under free and restraint conditions by means of the TSTM device (Temperature Stress Testing Machine). Despite the fast kinetics of its autogenous deformation, the cracking appears later for the slag cement concrete than for the Portland cement concrete. This behaviour is related to the swelling of its cementitious matrix at early age and its large capacity for relaxing the stresses.

Effect of copper slag as a fine aggregate on the properties of cement mortars and concrete

An experimental investigation was conducted to study the effect of using copper slag as a fine aggregate on the properties of cement mortars and concrete. Various mortar and concrete mixtures were prepared with different proportions of copper slag ranging from 0% (for the control mixture) to 100% as fine aggregates replacement. Cement mortar mixtures were evaluated for compressive strength, whereas concrete mixtures were evaluated for workability, density, compressive strength, tensile strength, flexural strength and durability. The results obtained for cement mortars revealed that all mixtures with different copper slag proportions yielded comparable or higher compressive strength than that of the control mixture. Also, there was more than 70% improvement in the compressive strength of mortars with 50% copper slag substitution in comparison with the control mixture. The results obtained for concrete indicated that there is a slight increase in density of nearly 5% as copper slag content increases, whereas the workability increased significantly as copper slag percentage increased compared with the control mixture. A substitution of up to 40–50% copper slag as a sand replacement yielded comparable strength to that of the control mixture. However, addition of more copper slag resulted in strength reduction due to the increase in the free water content in the mix. Also, the results demonstrated that surface water absorption decreased as copper slag content increases up to 50% replacement. Beyond that, the absorption rate increased rapidly and the percentage volume of the permeable voids was comparable to the control mixture. Therefore, it is recommended that up to 40–50% (by weight of sand) of copper slag can be used as a replacement for fine aggregates in order to obtain a concrete with good strength and durability requirements.

Copper slag as sand replacement for high performance concrete

This paper reports on an experimental program to investigate the effect of using copper slag as a replacement of sand on the properties of high performance concrete (HPC). Eight concrete mixtures were prepared with different proportions of copper slag ranging from 0% (for the control mix) to 100%. Concrete mixes were evaluated for workability, density, compressive strength, tensile strength, flexural strength and durability. The results indicate that there is a slight increase in the HPC density of nearly 5% with the increase of copper slag content, whereas the workability increased rapidly with increases in copper slag percentage. Addition of up to 50% of copper slag as sand replacement yielded comparable strength with that of the control mix. However, further additions of copper slag caused reduction in the strength due to an increase of the free water content in the mix. Mixes with 80% and 100% copper slag replacement gave the lowest compressive strength value of approximately 80 MPa, which is almost 16% lower than the strength of the control mix. The results also demonstrated that the surface water absorption decreased as copper slag quantity increases up to 40% replacement; beyond that level of replacement, the absorption rate increases rapidly. Therefore, it is recommended that 40 wt% of copper slag can used as replacement of sand in order to obtain HPC with good strength and durability properties.

Viscosity predictions of the slag composition of gasified coal, utilizing FactSage equilibrium modelling

Agglomeration of ash particles provides the desired porosity of the ash bed for adequate agent (steam and oxygen) flow and distribution, whereas excessive slagging inside the gasifier can cause channel burning, pressure drop problems or unstable operation, resulting in cut backs on gasifier load, which implies a direct loss in gas production. The ash flow temperature (AFT) is one property that specifically gives more information on the suitability of a coal source for combustion or gasification purposes. However, normal AFT analyses give an average flow property and do not indicate exactly at what temperature the first melt/slag is occurring or what the properties of the slag is at a specific temperature. Operating experience indicates that even when the gasifiers are operated at temperatures above the flow temperature as given by AFT analysis, a low percentage of slag is formed. In this study, the focus will be on the application of viscosity determinations together with FactSage modelling. Conventional AFT analyses take the bulk chemical composition of the mineral phase into account, and does not differentiate between the composition in the slag–liquid phase and the composition of the crystalline phase. It is therefore important to describe the viscosity of not only the completely molten phase, but also the partly crystallised slag and liquid portion. The combination of viscosity predictions together with FactSage modelling will result in viscosity predictions of the actual liquid component, rather than just an average or pseudo-viscosity prediction of the total mineral system at a specific temperature. Based on the fact that the Urbain model assumes the composition as 100% liquid or molten, which is not the case for example during fixed bed gasification where the mineral structure is of a heterogeneous nature with partial melting and crystalline material, viscosity predictions of the slag or molten portion can be more accurately determined by using the FactSage results. The viscosities, as determined from specific slag compositions at specific temperatures between 1000 °C and 1250 °C, differ from the average viscosity prediction and is highly likely to be a more accurate prediction of the slag viscosity than just based on the average mineral composition. The viscosity of the actual slag composition also remains fairly constant up to temperatures >1200 °C. This can also be related back to the initial deformation temperature onset of the coal, where the slag properties are cumulative enough for the onset of deformation to start. The specific decrease of the viscosity at the temperature between 1200 °C and 1250 °C correlates with the slag formation trend as obtained with FactSage modelling. During the gasification process the viscosity of the slag portion decreases to ±3.5 cp, which is on the border between a weak deposit and strong deposit. With increasing temperature above 1250 °C, for this specific coal source the viscosity moved into the strong deposit region. After the gasification zone, the viscosity increased again as the material crystallised in the combustion process. For a specific coal source, the viscosity of the slag portion can thus be calculated. The major source of glass is derived from included minerals in carbon rich particles. It is clear that a focus on the modification of the unclassified/amorphous phase, to increase the viscosity (decrease slag formation or have a higher concentration of crystalline phases) at a certain temperature, is important. An AFT analyses only supplies information on the temperature where a mass of material, enough to deform the structure of the cone, starts to slag and does not give information on the properties of the slag below that point. The use of viscosity predictions together with FactSage modelling supplies a better understanding of slag and ash properties at specific temperatures.

Application of Taguchi philosophy for parametric optimization of bead geometry and HAZ width in submerged arc welding using a mixture of fresh flux and fused flux

Taguchi philosophy has been applied for obtaining optimal parametric combinations to achieve desired weld bead geometry and dimensions related to the heat-affected zone (HAZ), such as HAZ width in the present case, in submerged arc welding. The philosophy and methodology proposed by Dr. Genichi Taguchi can be used for continuous improvement in products that are produced by submerged arc welding. This approach highlights the causes of poor quality, which can be eliminated by self-adjustment among the values of the process variables if they tend to change during the process. Depending on functional requirements of the welded joint, an acceptable weldment should confirm maximum penetration, minimum reinforcement, minimum bead width, minimum HAZ width, minimum bead volume, etc. to suit its area of application. Hence, there exists an increasing demand to evaluate an optimal parameter setting that would fetch the desired yield. This could be achieved by optimization of welding variables. Based on Taguchi’s approach, the present study has been aimed at integrating statistical techniques into the engineering process. Taguchi’s L9 (3**3) orthogonal array design has been adopted and experiments have been accordingly conducted with three different levels of conventional process parameters using welding current and flux basicity index to obtain bead-on-plate weld on mild steel plates. Features of bead geometry and HAZ in terms of bead width, reinforcement, depth of penetration and HAZ width have been measured for each experimental run. The slag, generated during welding, has been consumed in further runs by mixing it with fresh unmelted flux. The percentage of slag in the mixture of fused flux (slag) and fresh flux has been defined as slag-mix%. Welding has been performed by using varying slag-mix%, treated as another process variable, in order to obtain the optimum amount of slag-mix that can be used without any alarming adverse effect on features of bead geometry and HAZ. This would lead to ‘waste to wealth’.