Slag Concrete Research Articles

Mechanical properties and microstructure of slag and fly ash alkali-activated lightweight concrete containing miscanthus particles

To improve the early age strength of miscanthus-based composites, alkali-activated binders (ground granulated blast furnace slag and fly ash: AASF) were investigated against Portland cement. The impact of miscanthus content on strength development was assessed at three levels of aggregate to precursor binder mass ratio (0.27, 0.43 and 0.76). For the same aggregate to binder ratio, AASF mixes developed compressive strengths exceeding 1.3 MPa at 5% strain, seven times higher than those obtained with Portland cement, with the bulk density values measured in the range of 910–1070 kg/m3. However, these values for vegetal concretes remain lower than non-vegetal concretes of similar apparent densities such as those made with polystyrene aggregates. The analysis of the microstructure of AASF composites indicates a strong interfacial transition zone, showing microstructural features that suggest the achievement of a complete reaction.

Compressive Strength Prediction of Alkali‐Activated Slag Concretes by Using Artificial Neural Network (ANN) and Alternating Conditional Expectation (ACE)

Compressive strength of alkali‐activated slag (AAS) concrete is influenced by multi‐factors in a nonlinear way. Both artificial neural network (ANN) and alternating conditional expectation (ACE) models of 3‐day (3 d) and 28‐day (28 d) compressive strength of AAS were established in this study by using the data reported in related literature, where alkali concentration of activator (Na2O%), modulus of activator (Ms), water/binder ratio (W/B), surface area of slag (SA), and basicity index of slag (Kb) were taken as input parameters. The models were employed later to predict 3 d and 28 d compressive strength of AAS concretes, respectively, and the results were validated by experimental work. The results show that both the ANN and the ACE models had adequate accuracy, no matter 3 d or 28 d compressive strength was considered. Compared to the 3 d compressive strength, due to data scattering that increased with the increase of data size, both the models did not yield a higher accuracy in the case of 28 d strength. However, also due to the increase in data size, both the models were more feasible to implement 28 d strength prediction as a result of sufficient learning and training during modeling. In addition, based on ACE analysis, the weight‐influencing compressive strength of AAS decreased in a sequence of Na2O% > Ms > W/B > Kb > SA. If data size was sufficiently large, it was more suitable to establish an ANN model for compressive strength prediction of AAS concretes. Otherwise, ACE could be considered as an alternative to yield an acceptable result.

Experimental studies on partial replacement of E-waste and Blast Furnace Slag in concrete

The purpose of this project is to delay the corrosion of concrete structure in marine environment. Here the PCB E-waste is used as the material for the purpose of replacement without reducing the properties of the concrete and its durability and strength. The curing process of cubes, cylinders and flexural beams are done in the artificially prepared marine environment. The maximum compressive strength was attained at 15% partial replacement of GGBS and E –Waste within 28 days. The flexural and split tensile strength also reaches their maximum level by replacing 15% of GGBS and E – Waste in concrete. At the same time the chloride and sulphate attack of the partially replaced concrete is gradually reduced the weight and compressive strength within 30 days in the marine environment. From the above studies, it was concluded that the GGBS and E –Waste can be used up to 30% for getting the maximum strength.

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.

Effect of High-Range Water-Reducing Admixtures on Alkali-Activated Slag Concrete

Effect of High-Range Water-Reducing Admixtures on Alkali-Activated Slag Concrete

A study on the mechanical properties of alkali activated ground granulated blast furnace slag and fly ash concrete

Alkali activated concrete (AAC) is one concrete which is made without cement. As sustainable construction is gaining interest, this alkali activated concrete is a better option for conventional cement concrete. Concrete is the most used commodity second only to water with a global Carbon emission of 5%. The evaluation of strength under compression of alkali activated fly ash and ground granulated blast furnace slag concrete, was carried out in this study. The evaluation of compressive strength depending on the method of curing is also studied. In this study Ground Granulated Blast Furnace Slag (GGBFS) and fly ash are used as the pre-cursor materials. These two materials are used in varying proportions and are activated using sodium hydroxide and sodium silicate solutions of varying proportions, after which the strength properties of alkali activated concrete are studied under two methods of curing i.e., water curing and ambient temperature curing. When the results obtained for water curing and curing at ambient temperature were compared the later yields good results. So, the curing at ambient temperature can be preferred over water curing. When GGBFS alone was used as a pre-cursor material the results show higher compressive strength can be achieved in comparison to the specimens having both GGBFS and Fly ash as pre-cursor materials. With increasing proportions of fly ash and decreased GGBFS content, the decrease in compressive strength was witnessed. Also, the specimens kept under water curing and the specimens cured under ambient temperature are compared and found that the later yields higher compressive strength.

Mechanical and Durability Properties of Cementless Concretes Made Using Three Types of CaO-Activated GGBFS Binders.

This study examined the mechanical and durability properties of CaO-activated ground-granulated blast-furnace slag (GGBFS) concretes made with three different additives (CaCl2, Ca(HCOO)2, and Ca(NO3)2) and compared their properties to the concrete made with 100% Ordinary Portland Cement (OPC). All concrete mixtures satisfied targeted air content and slump ranges but exhibited significantly different mechanical and durability properties. The CaO-activated GGBFS concretes showed different strength levels, depending on the type of additive. The added CaCl2 was the most effective, but Ca(NO3)2 was the least effective at increasing mechanical strength in the CaO-activated GGBFS system. The OPC concrete showed the most excellent freezing–thawing resistance in the durability test, but only the CaO-activated GGBFS concrete with CaCl2 exhibited relatively similar resistance. In addition, the chemical resistance was significantly dependent on the type of acid solution and the type of binder. The OPC concrete had the best resistance in the HCl solution, while all CaO-activated GGBFS concretes had relatively low resistances. However, in the H2SO4 solution, all CaO-activated GGBFS concretes had better resistance than the OPC concrete. All concrete with sulfate ions had ettringite before immersion. However, when they were immersed in HCl solution, ettringite tended to decrease, and gypsum was generated. Meanwhile, the CaO-activated GGBFS concrete with CaCl2 did not change the type of reaction product, possibly due to the absence of ettringite and Ca(OH)2. When immersed in an H2SO4 solution, ettringite decreased, and gypsum increased in all concrete. In addition, the CaO-activated concrete with CaCl2 had a considerable amount of gypsum; it seemed that the dissolved C-S-H and calcite, due to the low pH, likely produced Ca2+ ions, and gypsum formed from the reaction between Ca2+ and H2SO4.

Mechanical and durability performance of concretes produced with steel slag aggregate and mineral admixtures

The steel slag is a residue for the steel industry that is already applied in many cement-based composites, although there is a lack of studies on the durability of this material in aggressive environments. This work evaluated the durability against chloride attack of concrete produced using steel slag as aggregate and mineral admixture, called steel slag powder. For comparison purposes, reference concretes using conventional aggregates and commercial mineral admixtures (silica fume and metakaolin) were produced. The concretes produced with steel slag aggregates and steel slag powder had lower chloride penetration depths compared to conventional ones. The steel slag powder presented an ability similar to silica fume of forming Friedel salt. The concrete produced with steel slag aggregates also presented a smaller water absorption and a higher compressive/tensile strength compared to the reference one. In general, this research observed that steel slag concretes are technically feasible options for the construction sector.

Effect of fiber content and stress–strength ratio on the creep of basalt fiber–reinforced alkali‐activated slag concrete

AbstractAlkali‐activated materials are increasingly being used in practical applications as potential alternatives to Portland cement. If alkali‐activated slag (AAS) is to be applied to prestressed engineering and large‐size structures, it is necessary to study the creep performance of AAS. Existing studies have found that the creep of AAS concrete is larger than that of ordinary Portland cement (OPC) concrete, and adding fiber is an effective way to overcome this defect. In this study, we investigated the creep of basalt fiber–reinforced AAS (FRAAS) concrete for fiber contents ranging from 0% to 0.9% (by volume) at a stress–strength ratio of 0–0.6. After analyzing the experimental results, it was found that the basalt FRAAS concrete had no obvious linear creep range. It was observed that with an increase in the fiber content, the inhibition effect of fiber on creep became stronger initially and then weaker. The inhibitory effect of fiber on creep was strengthened by the increase in the stress–strength ratio. The creep coefficient showed no obvious change when the fiber content was in the range of 0%–0.9%. Based on the existing OPC concrete creep models, a method for predicting the creep of basalt FRAAS concrete was proposed.

Study on Road Performance of Cement Fly Ash Stabilized Steel Slag-Concrete Recycled Macadam.

In order to promote the application of steel slag in road engineering, improve its utilization rate and solve the environmental problems caused by its large accumulation, unconfined compressive strength (UCS) test, indirect tensile strength (ITS) test, freeze-thaw cycle test, dry shrinkage and temperature shrinkage test tests with different steel slag contents were carried out. And the strength formation mechanism of steel slag in base material was revealed by SEM. The results show that the strength of the mixture initially increased and then decreased with increasing steel slag content. The frost resistance increased with increasing steel slag content, which should be limited to no more than 75%. Increasing the steel slag content improved the drying shrinkage resistance but was not conducive to the temperature shrinkage resistance. Microscopic analysis shows that adding a suitable amount of steel slag generated a gel material that was distributed inside the pores. This increased the density of the hardened slurry structure, which improved the strength. The research can provide scientific basis for the application and promotion of steel slag in road base.

The impact of alkali activator dosage on the compressive strength and water absorption of steel slag concrete

Steel Slag (SS) is an alternative for cement replacement in concrete. However, high replacement rate of SS increases the workability of concrete at the same time reduces the early strength of concrete. The aim of this study is to investigate the effect of different dosage of alkali activator in concrete with 40% SS as cement replacement on its workability, compressive strength, and water absorption. In this study, different dosage of Na2SO4 were added into SS based concrete with fixed cement replacement rate at 40%. Result shows that the workability of SS based concrete decreased with the increase of Na2SO4 dosage. The early strength increases with the addition of Na2SO4 from 1 to 3% and decreased over 3%. The 28-day and 90-day strength increase with the addition of Na2SO4 from 1 to 4% and decrease over 4%. The rate of water absorption of SS based concrete reduced significantly with the increase of Na2SO4. From the experimental result, it is observed that the addition of 4% Na2SO4 gives the highest strength of 35.12 MPa at 28-day.

Effect of Ground Slag on Mechanical Properties of Concrete under Low Temperature

Through using cube resisting compression test, fracture properties and micro-structure, the mechanical properties of high volume ground slag concrete under low temperature are studied in this paper. The results show that low temperature can improve the compressive strength of high volume ground slag concrete. And strength increased with the decreased of temperature. Low temperature can also improve the fracture energy and fracture toughness. Not only can ground slag reduce the content of calcium hydroxide in hardened cement paste, but ground slag can improve the compactness of hardened cement paste, reduce porosity and improve the strength of the interface.

Flexural performance of reinforced beams made with composite ferronickel slag concrete

Concrete containing ferronickel slag with blast furnace slag, namely composite ferronickel slag concrete or F-S concrete, is featured by low bond strength with horizontally-placed rebar compared with normal concrete of equal strength. This feature may affect the flexural capacity and deformational characteristic of F-S concrete beams, which needs to be investigated. Four under-reinforced beams were prepared and tested, including one normal concrete beam and three F-S concrete beams. The variable was the percentages of F-S powder content, i.e., 0%, 20%, 30%, and 40%. The experimental results showed that as F-S powder content increased, both the flexural capacity and ductility of RC beams decreased. For the flexural capacity analysis, directly increasing F-S powder content lowers concrete strength, thus reducing the flexural capacity. Regarding the deformational characteristic analysis, the RC beam is ideally simplified to the combination of the compressive concrete column model plus the tie bar model, and the influence of tensile rigidity effect with different bond level on the tie bar deformation is mainly studied. It is found that the lower bond stress just increases the flexural crack spacing, and changes the stress and strain distribution of rebar and concrete, but does not change the stress-mean strain relation of the rebar in the tie bar per unit length. The incorporation of F-S powder has no effect on the deformation of RC beams. Unexpectedly, the concrete strength is another important factor affecting the plastic rotation ability of RC beams. Whether increasing/decreasing the concrete strength will increase or decrease the ductility of RC beams, it is much determined by the given ratio of the longitudinal tensile reinforcement. In other words, while F-S concrete strength equals that of normal concrete, the ductility of the F-S concrete beam resembles that of normal concrete beam. F-S concrete can be applied in engineering structures, as long as it meets the design strength requirement as normal concrete does, irrespective of any F-S powder content.

Effect of fibre dosage and stress-strength ratio on creep of polypropylene fibre-reinforced alkali-activated slag concrete

Effect of fibre dosage and stress-strength ratio on creep of polypropylene fibre-reinforced alkali-activated slag concrete

Mechanical Properties of Coarse Aggregate Electric Arc Furnace Slag in Cement Concrete

The feasibility of using EAF slag aggregate, fly ash, and silica fume in pavement Electric Arc Furnace Slag Concrete (CEAFS) is the focus of this research. EAF slag aggregate is volume stable and suitable for use in concrete, according to the findings of the testing. EAF slag was utilized to replace natural coarse aggregates in the CEAFS mixes. CEAFS was created by blending 50% crushed stone with 50% EAF slag in coarse aggregates, with fly ash (FA) and silica fume (SF) partially replacing cement at content levels (i.e. FA: 0, 20, 30, and 40%; SF: 0, 5, and 10%). The soil compaction approach was used to evaluate the optimal moisture level for CEAFS mixes containing EAF slag aggregate fly ash and silica fume. A testing program was used to investigate the weight of CEAFS units and their mechanical qualities (compressive strength, flexural strength, and elastic modulus). As a result, the fresh and hardened unit weights in the CEAFS are comparable. Moreover, variations in the concentration of mineral additives FA and SF in adhesives, as well as the CEAFS mixed aggregate ratio, have an impact on compressive strength, flexural strength, and elastic modulus at all ages. However, combining EAF slag aggregate with (FA0% +SF10%; FA10% +SF0%; FA10% +SF10%; and FA20% +SF10%) the CEAFS mixtures have improved mechanical characteristics over time. According to this study, CEAFS pavements can be made with EAF slag aggregate fly ash and silica fume. In addition, a formula correlation was suggested to compute CEAFS (i.e. compressive strength with elastic modulus and compressive strength with flexural strength). Doi: 10.28991/cej-2021-03091755 Full Text: PDF

Effect of slag nickel (FeNi3) as coarse aggregate on properties of no-fine concrete

One of the industrial wastes of the B3 category is nickel slag. PT. Antam Pomalaa produces nickel slag annually of 1 million tons. It has been widely used as an embankment material or reclamation. This waste is hazardous for the environment if not used. An attempt to utilize it is to use it as an aggregate for no-fine concrete. In this research, no-fine concrete is designed by variations of cement ratio to slag. Unit weight and specific gravity test of slag aggregate were performed to calculate the use of nickel slag in a no-fine concrete mixture. The design of no-fine concrete was 1: 2, 1: 4, 1: 6, 1: 8, and 1; 10 by a water-cement ratio of 0.4. The samples of no-fine concrete were made in a 15x15x15 cm cube, with 3 samples of each variation. All the samples were cured for 28 days in the water. Compression tests were performed to analyze the compressive strength of no-fine concrete. The results showed slag nickel (FeNi3) increase unit weight and compressive strength of no-fine concrete. For practical uses no-fine concrete slag (NFC-S) of 1:6 qualifies as a material for city parks, while ratio 1:4 qualifies pavements for pedestrians.

Cyclic compressive behavior of limestone and silicomanganese slag concrete subjected to sulphate attack and wetting-drying action in marine environment

Concrete in maritime structure is vulnerable to deterioration owing to external sulphate attack, which can be exacerbated by wetting-drying action (WDA), jeopardizing its resistance to cyclic loads such as wind, wave and earthquake actions. This study aims to investigate the compressive fatigue behavior of concrete exposed to sulphate attack and WDA in marine environment. Cyclic compressive loading test was conducted on concrete after 150 days of deterioration. The effects of sulphate attack and WDA, upper stress loading level and loading frequency on fatigue life, residual strain, variation of elastic modulus and post-cyclic compressive strength were investigated. The sulphate penetration profiles, volume change and mass change of concrete during the exposure time were also measured. In addition, the performance of limestone concrete and silicomanganese (SiMn) slag concrete was compared in the study. The sulphate ion was found to penetrate concrete up to a depth of 20 mm, with a maximum content of 1.72%–2.58% near the surface. The cyclic loading test showed that degraded concrete had 38.2% higher residual displacement and 1.4% lower modulus of elasticity than normal concrete. The sulphate attack and WDA weakened the concrete, reducing its fatigue resistance. SiMn slag concrete had a lower fatigue life, larger residual displacement and greater stiffness degradation than limestone concrete.

Engineering Characteristics and Environmental Risks of Utilizing Recycled Aluminum Salt Slag and Recycled Concrete as a Sustainable Geomaterial

Recycled aluminum salt slag (RASS) is an industrial by-product generated from the melting of white dross and aluminum scraps during the secondary smelter process. Insufficient knowledge in the aspects of engineering characteristics, and the environmental risks associated with RASS, is the primary barrier to the utilization of RASS as a substitute material for natural quarry materials in the field of geotechnical construction. In this research, comprehensive geotechnical and environmental engineering tests were conducted to evaluate the feasibility of utilizing RASS as a sustainable geomaterial. This was undertaken by comparing the laboratory testing results for RASS with a well-known recycled material, namely recycled concrete aggregate (RCA), and the relevant specifications set forth by the local road authority. The geotechnical engineering assessment included particle size distribution, flakiness index, organic content, pH, particle density, water absorption, modified Proctor compaction, aggregate impact value, Los Angeles (LA) abrasion, hydraulic conductivity, and California bearing ratio (CBR). The CBR results of the RASS samples satisfied the minimum CBR value (>80%) for usage as pavement subbase material in road construction. In addition, the repeated load triaxial (RLT) tests were carried out on the RASS samples to assess the response of the RASS under cyclic loading conditions. Furthermore, a range of chemical tests, consisting of leaching and polycyclic aromatic hydrocarbon tests, were also performed on the RASS to address the environmental concerns. Comparing the chemical test results with the environmental protection authorities’ guidelines provided satisfactory evidence that RASS will not pose any environmental and health issues throughout its service life as a geotechnical construction material.

Neural network model for predicting the carbonation depth of slag concrete

Neural network model for predicting the carbonation depth of slag concrete

Characterization of quarry dusts and industrial by-products as potential substitutes for traditional fillers and their impact on water susceptibility of asphalt concrete

Mixing, paving, and compaction of hot asphalt mixtures results in the formation of a three-phase system in which aggregates are represented in different fractions including subsieve particles (<0.063 mm), referred to as filler material. Larger particles interlock and form a skeleton, while the bituminous binder bonds individual grains together. Two filler types are commonly used for the production of asphalt mixtures: (i) lime, hydrated lime, or portland cement and (ii) fine particles retained in the separation units of a mixing plant (known as back/back-house filler) or those separated during aggregate production in quarries (quarry dust). We investigated the impact of several quarry dusts or back fillers as well as of selected treated by-products such as blast furnace slag, finely ground waste gypsum boards, or recycled concrete, all potentially applicable as alternative fillers. Different approaches were adopted to characterize these fillers and assess their impact on the adhesion between bitumen and aggregate in the presence of water, stripping resistance, and effect on the stiffness of the asphalt mixture. The results indicate that the effect of blast furnace slag or recycled concrete is superior to some conventional fillers and that mixing quarry dusts with portland cement or talc is beneficial for rendering the originally hydrophilic dusts more hydrophobic.