Addition Of Steel Slag Research Articles

Effects of Steel Slag Used as Substrate on the Growth of Hydrangea macrophylla Cuttings

Steel slag is an industrial solid waste produced during the steelmaking process. To explore the application of steel slag in the agricultural field, the present experiment was carried out to study the effect of substrates with different contents of steel slag on the growth of Hydrangea macrophylla cuttings. The conventional substrate (perlite: vermiculite: peat = 1:1:1) was used as the control (CK), and the treatments were designed as T1 (steel slag: perlite: vermiculite: peat = 1:3:3:3, v/v/v/v), T2 (steel slag: perlite: vermiculite: peat = 1:2:2:2, v/v/v/v), T3 (steel slag: perlite: vermiculite: peat = 1:1:1:1, v/v/v/v), and T4 (steel slag: perlite: vermiculite: peat = 1:0:0:0, v/v/v/v). The results showed that the addition of steel slag significantly increased the substrate’s bulk density, EC, and pH and improved its water retention capacity to a certain extent. There were significant differences among different treatments in morphological indicators, root growth and development, and physiological and biochemical characteristics of cutting seedlings. All traits, including plant height, fresh weight, dry weight, root length, root surface area, root volume, the number of root tips, root activity, and soluble protein content of seedlings grown in T3 were significantly higher than those in other substrates. The results indicated that the appropriate addition of steel slag is helpful to hydrangea cuttings’ growth, and the optimal mixing ratio is steel slag: perlite: vermiculite: peat = 1:1:1:1 (v/v/v/v). This is a significant innovation in applying steel slag in agricultural production.

Synergistic effect of CO2-mixing and steel slag addition on performance and microstructure of concrete

This study systematically investigated the influence of varying carbon dioxide (CO2) dosages and steel slag (SS) replacement rates on the fresh and hardened properties of concrete through the injection of CO2 gas during the mixing process. The composition of hydration products, degree of hydration, and the evolution of microstructural characteristics within the CO2-SS-cement system were analyzed. The results showed that CO2 addition during the mixing process enhanced early strength in SS concrete. For concrete with a 10 wt% SS replacement rate, the incorporation of CO2 ranging from 0.4 wt% to 1.2 wt% of the total mass of cementitious materials resulted in notable compressive strength increases of 1.26%–12.47%, 0.64%–6.14%, and 11.79%–18.24% at ages of 1 d, 3 d, and 7 d, respectively. CO2 rapidly reacted with SS to form calcite-type CaCO3 and promoted the generation of C-S-H through synergistic hydration with cement. However, a high CO2 dosage (1.2 wt%) led to issues such as microcrack propagation and interface loosening due to CaCO3 deposition, which could be mitigated to some extent by appropriately increasing the SS content.

Analysis of Wear-Coated Asphalt Concrete (AC-WC) Modified With Addition of Steel Slag and Resin for Road Conditions Inlowed In Tide

Causes of damage to road construction, among others due to the influence of excessive vehicle traffic loads, temperature, water (puddles), and pavement construction that does not meet technical requirements. Water (puddle) is one of the causes of damage or reduces durability for road construction with asphalt pavement. This study aims to examine the effect of asphalt mixture (AC-WC) with the addition of resin and steel slag aggregate on asphalt stability (AC-WC), Obtain Job Mix Design (JMD) for road conditions that are inundated by high tide and Assess the effect of immersion rob water against asphalt resistance (AC-WC) with the addition of resin and steel slag.In this research, it can be said that we play a role and participate in building prosperity in the advancement of transportation and the development of technological civilization, through continuous research that is adjusted to continuous research. We carry out research with the aim of developing science and technology and applying the reconstruction of science and technology to provide solutions to be able to solve environmental and societal problems, where local wisdom forms the basis of research.The research method used as a mix tester is the Marshall method, where from the Marshall test the results are obtained in the form of Marshall components, namely the volume weight of the test object, the value of stability, flow, voids in the mix (VIM), voids in mineral aggregate (VMA), void filled with asphalt (VFA), the thickness value of asphalt blanket or film and then can be calculated Marshall quotient. The last test was in the form of a Marshall immersion test. In the comparison of VIM, VMA and VFA above that for aggregate slag 25%, 50% and resin addition 5%, 7%, 10%, for resin content 5% and 10% did not meet specifications, however for 7% resin content meets the 2018 Revised Highways Technical Specifications. Based on the marshal test, there was only one that met the specifications of the binamarga, namely a test object with a resin composition of 7% by soaking for 7 days. The results of this study based on the Marshall test, the strength/stability value of the AC-WC asphalt mixture using a pen 60/70 asphalt mixture with steel slag and resin mining met the specifications. The stability value of asphalt AC-WC decreased with increasing variations in the resin content used in the mixture.

Enhanced ammonia removal in tidal flow constructed wetland by incorporating steel slag: Performance, microbial community, and heavy metal release

Utilizing alkaline solid wastes, such as steel slag, as substrates in tidal flow constructed wetlands (TFCWs) can effectively neutralize the acidity generated by nitrification. However, the impacts of steel slag on microbial communities and the potential risk of heavy metal release remain poorly understood. To address these knowledge gaps, this study compared the performance and microbial community structure of TFCWs filled with a mixture of steel slag and zeolite (TFCW-S) to those filled with zeolite alone (TFCW-Z). TFCW-S exhibited a much higher NH4+-N removal efficiency (98.35 %) than TFCW-Z (55.26 %). Additionally, TFCW-S also achieved better TN and TP removal. The steel slag addition helped maintain the TFCW-S effluent pH at around 7.5, while the TFCW-Z effluent pH varied from 3.74 to 6.25. The nitrification and denitrification intensities in TFCW-S substrates were significantly higher than those in TFCW-Z, consistent with the observed removal performance. Moreover, steel slag did not cause excessive heavy metal release, as the effluent concentrations were below the standard limits. Microbial community analysis revealed that ammonia-oxidizing bacteria, ammonia-oxidizing archaea, and complete ammonia-oxidizing bacteria coexisted in both TFCWs, albeit with different compositions. Furthermore, the enrichment of heterotrophic nitrification-aerobic denitrification bacteria in TFCW-S likely contributed to the high NH4+-N removal. In summary, these findings demonstrate that the combined use of steel slag and zeolite in TFCWs creates favorable pH conditions for ammonia-oxidizing microorganisms, leading to efficient ammonia removal in an environmentally friendly manner.

The enhanced weathering potential of a range of silicate and carbonate additions in a UK agricultural soil

Enhanced weathering (EW) is a carbon dioxide removal (CDR) technology which aims to accelerate silicate and/or carbonate weathering in agricultural land. At present, the rate and magnitude of CDR from EW remains uncertain. In this study, soil cores extracted from a typical UK agricultural site in Oxfordshire were used to geochemically assess the efficacy of EW while simulating field conditions. Six material “treatments” were applied to soil cores at a rate equivalent to 50 t ha−1: agricultural lime (aglime), basalt, cement kiln dust (CKD), olivine, steel slag, and volcanic ash. A range of chemical measurements were used to constrain the rate of dissolution, fate of dissolution products, and the CDR potential and environmental impact of treatment.After a single application, the CDR rates were, in decreasing order: steel slag (20 ± 4 kgCO2 ha−1 yr−1) > CKD (16 ± 4 kgCO2 ha−1 yr−1) > basalt (5 ± 3 kgCO2 ha−1 yr−1) > volcanic ash (3 ± 3 kgCO2 ha−1 yr−1) > aglime (2 ± 1 kgCO2 ha−1 yr−1) > olivine (0 ± 2 kgCO2 ha−1 yr−1). Despite its drawdown potential, steel slag addition is not advised because application raised the dissolved concentration of heavy metals in the soil. CKD application will be limited due to availability of this material. Liming of agricultural soil is normally considered a source of CO2, but this study indicates liming could cause CDR in some UK soil conditions.Extrapolating from this site to a wider scale supports the conclusions of recently published research which suggests 10 years of basalt application over UK cropland could remove 1.8 ± 0.9 MtCO2 yr−1. Given the low rates of CDR observed in this study, EW is only likely to be worthwhile, at least in soil and climate conditions common to SE England, where there are co-benefits beyond carbon uptake.

Thermal and mechanical properties of bio-cemented quartz sand mixed with steel slag

The aim of this study is to disclose the feasibility of improving the thermal conductivity and mechanical strength of quartz sand steel slag mixtures treated by enzyme-induced carbonate precipitation (EICP). In this work, the effects of steel slag content (SSC) and number of treatment cycle (N) on the thermal conductivity and mechanical strength of EICP-treated specimens were investigated. The immersion method was adopted for specimen preparation. The thermal conductivity was measured by transient plane source method (TPS) and the unconfined compressive strength (UCS) was obtained through a uniaxial compression test. Moreover, the SEM test was conducted to obtain the morphology and deposition characteristics of calcium carbonate crystals. The result shows that the thermal conductivity and UCS of EICP-treated sands increase before decreasing as the SSC increases. Consequently, the maximum values of thermal conductivity and UCS are 1.28 W/(m⊡K) and 6.31 MPa, respectively, corresponding to the optimal parameter of 20% SSC at 12 N. The optimal thermal conductivity and UCS increase by 367% and 137%, respectively, compared to that of EICP-treated sand with no addition of steel slag. The SEM analysis indicates that the spherical calcium carbonate exists in the range of 0–20% SSC, whereas there is mainly amorphous calcium carbonate when the SSC varies from 40% to 80%. It also demonstrates that the UCS is more sensitive to the variation of calcium carbonate content than that of thermal conductivity.

Modification of phases evolution and heavy metal immobilization in alkali-activated MSWI FA by the incorporation of converter steel slag

Municipal solid waste incineration fly ash (MSWI FA) poses serious environmental concerns due to its high content of hazardous organics, heavy metals, and soluble salts. This study aimed to solidify the harmful components in MSWI FA by alkali activation and explore the influence of converter steel slag on the phase evolution. With the increase of curing time, the amount of C-(A)-S-H gel increased and its microstructure shifted to a high crystalline and crosslinked state, accompanied by the increase of Ca/Si ratio. The addition of steel slag was beneficial to the formation of C-(A)-S-H gel and enhanced its crystallinity and crosslinking degree. Compared with alkali-activated MSWI FA, NaCl and KCl content decreased more significantly with curing time and Friedel ’salts were found in the matrix modified by steel slag. The leaching toxicity of heavy metals in alkali-activated matrix was reduced as curing time increased. The increase of C-(A)-S-H gel content and changes of its microstructure were conducive to the stabilization of heavy metals and chlorides. The refinement of pore size and improvement of compressive strength contributed to the physical encapsulation of heavy metals and chlorides.

Pyrite coupled with steel slag to enhance simultaneous nitrogen and phosphorus removal in constructed wetlands

FeS2-based constructed wetland has garnered increasing interest as an efficient and eco-friendly method for nitrogen and phosphorus removal from carbon limitation wastewater. However, large-scale application is limited due to low nitrogen and phosphorus simultaneous removal performance, slow growth rate of autotrophic denitrifiers and high effluent acidity. This study proposes a novel constructed wetland by coupling with pyrite and steel slag (PSCW) as substrates. The results showed that steel slag addition in PSCW increased total nitrogen removal by 40% ∼ 54%. The higher removal of total phosphorus was mainly attributed to the strong substrate adsorption and metal ions precipitation, which was removed at the pyrite and steel slag layer. The genes involved in denitrification, glycolysis, oxidative phosphorylation and sulfur oxidation were notably enriched in PSCW, indicating the increasing contribution of FeS2-based autotrophic denitrification coupled with steel slag to NO3− removal. The XPS analysis identified the formation of SO42−, S2−, S0, and Fe(III) on the pyrite surface in PSCW. S0 formation and sulfate reducing bacteria enrichment in PSCW were all promoted due to the coupling of pyrite and steel slag, which also maintained higher NO3− removal efficiency. Thiobacillus was specifically enriched in PSCW due to steel slag addition. The toxicity effect of pyrite on root tip can be alleviated by steel slag, which was conducive to nutrients assimilation by roots. The findings of this study provide new insights into the molecular mechanism of carbon, nitrogen, and sulfur metabolism in the pyrite-steel slag based constructed wetland.

Engineering Properties and Environmental Impact of Soil Mixing with Steel Slag Applied in Subgrade

The purpose of this study was to evaluate the feasibility of the large-scale application of steel slag (SL) in subgrade. Subgrade materials with three kinds of SL proportions were first prepared. Then, a compaction test, liquid-plastic limit combined-measurement test, and a California bearing ratio (CBR) test were applied to determine the best proportion between SL and intact soil (S), i.e., SL/S. Subsequently, static and dynamic tests and a volume stability test were carried out for soil mixed with SL at the optimum proportion (SSL). In addition, a composition analysis of infiltration fluid and a permeability test of SSL were performed. The test results showed that compared to S, the physical properties of SSL were significantly improved, especially the liquid-plastic limit, as well as the soil water stability. The optimum proportion of SL was determined as 50% of soil by mass. At the optimum proportion, SSL had the highest CBR value of 60%, which had both economic and engineering compaction performance, leading to a large-scale utilization rate of SL. The static and dynamic characteristics showed that the addition of SL would greatly improve the shear strength and dynamic modulus of soil, mainly expressed as the increase of internal friction angle. The volume stability of SSL could also meet the requirements of the Chinese specification. After adding 2% cement, the strength and stability of SSL was further improved. In addition, the environmental impact test proved that the infiltration liquid did not pollute surface water nor underground secondary water. Although the permeability coefficient of SSL with the optimum proportion of 50% was higher than that of pure soil, it still belonged to the normal value of clay and silty clay, and good impermeability would ensure the controllability of potential trace elements. Based on the test results of mechanical properties and environmental impact, SSL proved to have the potential for green road material engineering properties. This study proposes a reliable and practical method to promote the utilization of steel slag.

Evaluation of airborne particulates and associated metals originating from steel slag applied to rural unpaved roads.

Various metals have toxic effects by the inhalation route, and electric arc furnace (EAF) steel slag is known to contain metals with a potential for toxicity to humans. In some states, EAF slag is applied to unpaved (gravel) roads as a low-cost supplement to limestone and other crushed stone, where it may be a public health concern for the local population. This study compared the mass of selected metals in the PM10 size fraction of fugitive dust from roads where slag was applied to metals in fugitive dust where slag was not applied. Manganese, designated by the EPA as a hazardous air pollutant (HAP) and one of the primary metals of concern in the slag, was 1.3 times more concentrated in the PM10 fraction from the slag-covered roads as compared to the PM10 fraction from the non-slag-covered roads, but that increase was not significant (p = 0.26). Other metals detected in the airborne dust from both slag-covered and non-slag-covered roads that are also designated as HAPs are antimony, arsenic, chromium, cobalt, lead, nickel, and selenium. In addition, hourly sampling of PM10 and metals in the PM10 fraction was conducted at one of the sample locations where slag had been applied to the road. Manganese mass in the PM10 was positively correlated (Spearman r = 0.86) with the particulate mass in the PM10. Wind direction and the interaction of traffic and wind direction were found to be statistically significant factors affecting manganese concentrations in the fugitive emissions from the road to which EAF slag had been applied. This research demonstrated that application of steel slag can result in elevated levels of manganese in the airborne dust generated by vehicular traffic on the unpaved roadway.

Suppression of arsenic leaching from excavated soil and the contribution of soluble and insoluble components in steel slag on arsenic immobilization.

A huge amount of soil is excavated by tunnel and road construction projects in urban, coastal, and mountainous regions. These projects enable the effective use of underground spaces, and generally, the excavated soil is expected to be reused after treatment, which is required due to the potential release of geogenic arsenic from the soil. The present study investigated the level of water-soluble arsenic and arsenic phases in excavated soil in order to identify how arsenic is immobilized by soluble calcium and insoluble components in steel slag. The soluble calcium was found to suppress the level of water-soluble arsenic as well as arsenic in fraction 1 (nonspecifically bound) identified by sequential extraction from the soil but increased the level of fraction 2: specifically bound arsenic. The insoluble component did not suppress the level of water-soluble arsenic, but decreased and increased the arsenic levels in fractions 2 and 3 (amorphous iron/aluminum oxide bound), respectively. A column percolation test demonstrated that the arsenic that was inhibited from leaching by the addition of steel slag was the fractions 1 and 2 arsenic. The amounts of arsenic released in the serial batch leaching test were comparable with levels leached regardless of the addition of steel slag. These results indicate that both soluble calcium and insoluble components of steel slag have different roles in suppressing arsenic leaching from excavated soil. Based on these results, it is suggested that steel slag could be utilized to suppress arsenic release, thus enabling the reuse of excavated soil.

Effect of steel slag on ammonia removal and ammonia-oxidizing microorganisms in zeolite-based tidal flow constructed wetlands

The ammonia removal performance of tidal flow constructed wetlands (TFCWs) requires to be improved under high hydraulic loading rates (HLRs). The pH decrease caused by nitrification may adversely affect the NH4+–N removal and ammonia-oxidizing microorganisms (AOMs) of TFCWs. Herein, TFCWs with zeolite (TFCW_Z) and a mixture of zeolite and steel slag (TFCW_S) were built to investigate the influence of steel slag on NH4+-N removal and AOMs. Both TFCWs were operated under short flooding/drying (F/D) cycles and high HLRs (3.13 and 4.69 m3/(m2 d)). The results revealed that a neutral effluent pH (6.98–7.82) was achieved in TFCW_S owing to the CaO dissolution of steel slag. The NH4+-N removal efficiencies in TFCW_S (91.2 ± 5.1%) were much higher than those in TFCW_Z (73.2 ± 7.1%). Total nitrogen (TN) removal was poor in both TFCWs mainly due to the low influent COD/TN. Phosphorus removal in TFCW_S was unsatisfactory because of the short hydraulic retention time. The addition of steel slag stimulated the flourishing AOMs, including Nitrosomonas (ammonia-oxidizing bacteria, AOB), Candidatus_Nitrocosmicus (ammonia-oxidizing archaea, AOA), and comammox Nitrospira, which may be responsible for the better ammonia removal performance in TFCW_S. PICRUSt2 showed that steel slag also enriched the relative abundance of functional genes involved in nitrification (amoCAB, hao, and nxrAB) but inhibited genes related to denitrification (nirK, norB, and nosZ). Quantitative polymerase chain reaction (qPCR) revealed that complete AOB (CAOB) and AOB contributed more to the amoA genes in TFCW_S and TFCW_Z, respectively. Therefore, this study revealed that the dominant AOMs could be significantly changed in zeolite-based TFCW by adding steel slag to regulate the pH in situ, resulting in a more efficient NH4+–N removal performance.

The mechanism of pristine steel slag for boosted performance of fly ash-based geopolymers

The high autogenous shrinkage of geopolymers hampers their application as building materials. In this study, pristine steel slag was used as an expansion material to mitigate shrinkage in geopolymers. The influence of pristine steel slag on the chemical deformation of alkali-activated fly ash-based geopolymers is investigated. The microstructure of the expanded system was studied by X-ray diffraction (XRD), FTIR measurement, thermogravimetric measurement (TGA), scanning electron microscopy with energy dispersive X-ray (SEM/EDS) and mercury intrusion porosimetry (MIP). Finally, the mechanisms of expansion were elucidated. The experimental results show that the shrinkage of the geopolymer is eliminated with the addition of steel slag. Fly ash was replaced by 0, 5, 10, and 15% of steel slag, and the expansion rate ranged from −0.29% to 20.24%. Increased steel slag content reduced the bulk density of geopolymer. The incorporation of steel slag not only provided calcium for the information of C-A-S-H but also filled the pores. Steel slag produces different expansion effects in different porous media and thus refines the pore structure. Therefore, expansion by means of steel slag is an efficient approach for mitigating shrinkage in fly ash-based geopolymers.

Performance evaluation and lifetime prediction of steel slag coarse aggregate concrete under sulfate attack

The durability of steel slag coarse aggregate concrete limits the application of steel slag in construction engineering. This study carried out the erosion test, material mechanics test, and microscopic test of steel slag coarse aggregate concrete under the action of different mass fractions of sulfate solution to investigate the effect law and mechanism of steel slag coarse aggregate on sulfate erosion resistance of concrete. The deterioration laws of performance indexes such as compressive strength, mass change, and relative dynamic elastic modulus of steel slag coarse aggregate concrete under sulfate erosion were investigated. X-ray diffraction (XRD) and Scanning electron microscope (SEM) were used to examine the erosion products and microstructure changes of samples before and after sulfate erosion, and the GM (1, 1) model of grey theory was used to forecast the service life of steel slag coarse aggregate concrete under various conditions. The results demonstrate that utilizing steel slag instead of coarse aggregate to prepare concrete may significantly alleviate the damage caused by the attack of sulfate solutions. And in 15% sulfate erosion environment, the maximum compressive strength increase rate of 20.7% was obtained when the steel slag substitution rate was 60%. Microscopic study reveals that the active components (such as dicalcium silicate (C2S) and tricalcium silicate (C3S)) in steel slag can promote the production of hydrated calcium silicate gel in concrete, improving the strength and durability of the material. To a certain extent, the addition of steel slag can improve the sulfate resistance of concrete. The prediction results of the GM (1, 1) model show that the service lifetime of concrete with 60% steel slag coarse aggregate substitution rate under sulfate solution erosion is better than that of the other three groups, and the predicted results are compatible with the experimental results.

Influence of Steel Slag Addition on Strength Characteristics of Clayey Soil

Abstract: The disposal of industrial waste or by-products has become more difficult and expensive as a result of the increasing environmental regulations and shortages of suitable disposal sites. When molten steel is separated from impurities in steel making furnaces, steel slag is produced as a by-product of the process. In the construction industry, steel slag has long been used in various applications in the construction industry such as aggregates in road construction, railway ballast and hydraulic protection structures. Using steel slag for soil stabilization is a modern application of steel slag. In this study the main approach is to investigate the effect of steel slag on the strength characteristics of clayey soil. Steel slag is blended with clayey soil in amounts of 10%, 15%, 20%, 25%, and 30% of dry weight. In our study, the optimum content of steel slag was determined by considering the maximum unconfined compressive strength. A series of further laboratory tests have been performed on this optimum mix to evaluate its suitability as a stabilizer material. The test was also conducted with conventional stabilizing material such as l0% fly ash and 5%cement with clayey soil and the obtained optimum mix was determined. Then the results are compared accordingly. In the above study, it has been observed that the addition of steel slag results in significant improvement in strength parameter as compared to fly ash but less strength in case of cement. Also from the cost comparison, it has been observed that cost of optimum mix of steel slag is less as compared to cement. It is therefore used to stabilize clayey soil.

Influence of Five Additives on No Loading Swelling Potential of Red Clay

In this study, cement, zeolite powder and three industrial by-products (blast furnace slag, steel slag, and fly ash) were selected as additives to study their effects on the swelling potential of red clay with different curing ages and dosages. At the same time, the mechanism of additives reducing the swelling potential of red clay was analyzed by scanning electron microscope (SEM) and X-ray fluorescence (XRF) tests. The X-ray diffraction (XRD) test was used to detect the clay mineral content of the red clay specimens before and after the modification to determine the change in the clay mineral content of the specimens. The direct shear test was used to explore the influence of additives on the strength of red clay. The results show that with 9% cement content, the no loading swelling potential of specimens can be reduced by 82.5% under 28 days of curing, and the cohesion of the specimens can be greatly increased by 82%. However, the specimens with cement have an increase in no loading swelling potential under the condition of no curing. In contrast, when steel slag is used as an additive to modify the swelling properties of red clay, the swelling potential can be reduced without curing, but the addition of steel slag will reduce the cohesive strength of specimens. XRD testing shows that the clay mineral composition in cement-modified specimens and steel slag-modified specimens experienced a relative change, the relative content of montmorillonite and illite decreased, and the relative content of kaolinite increased. Combined with SEM and XRF test results, it is concluded that cement’s reduction in the swelling potential of red clay depends on pozzolanic reaction products filling the pores in specimens and bonding clay particles, so as to reduce the permeability of red clay and increase the resistance during swelling. The addition of cement can also convert hydrophilic clay minerals into nonhydrophilic clay minerals. Compared with cement, the reduction in swelling potential caused by steel slag mainly depends on the adsorption of ions to reduce the adsorption of water molecules on the surface of clay slices.

Geotechnical Beneficiation of the Strength Indices of Lateritic Soil Using Steel Slag and Cement

The impact of admixture of both Ordinary Portland Cement (OPC) and steel slag was examined on the geotechnical properties of the lateritic soil, by conducting basic geotechnical tests: Particle size analysis, Consistency limits, Compaction, California Bearing Ratio (CBR) and Unconfined Compressive Strength (UCS) on both the natural and stabilized soil samples and results were subjected to statistical analysis using 2-way ANOVA (Analysis of Variance) at 5% level of significance. The natural soil was classified as s A-7-6 and MH under standard soil classification systems. Addition of steel slag lowered the liquid limit (LL) and plasticity index (PI), while cement increased the LL and decreased PI of the lateritic soil, respectively. With increasing content of slag and cement, maximum dry density increased with the corresponding decrease in optimum moisture content. CBR and UCS of the stabilized soil increased substantially with increasing contents of slag and cement. Both steel slag and cement have statistically significant effects on the geotechnical properties of the lateritic soil. Hence, this soil can be stabilized with addition of 12% steel slag and 6% cement contents for its application as an improved subgrade material for light trafficked pavement. Keywords: Lateritic soil, steel slag, cement, stabilization, Index properties, strength indices.

High-Volume Upcycling of Waste Sediment and Enhancement Mechanisms in Blended Grouting Material

Waste sediment (WS) is a solid waste produced from subway construction. In the present work, high-volume WS was upcycled to prepare grouting material.The results showed that the working performances (consistency, fluidity, setting time, bleeding ratio, and stone ratio)of WS-based grouting material were significantly affected by the mass concentration of solid components, binder to WS ratio, and steel slag addition. This material can meet the engineering requirement by adjusting these parameters. The WS-based grouting material exhibited superior performance compared to traditional grouting materials. It achieved self-leveling (160 mm fluidity) and wassuitable for grouting (consistency within 100-130 mm, 95.0% stone ratio). Amorphous phases were formed in the hardened sample. The addition of a suitable amount of steel slag (10%) can reduce the total porosity, and also promote the hydration degree and increase the mechanical properties of cement matrix.The strength development can be attributed to the formation of hydration products and the cementation between hydrates and sediment particles.

Preparation of Adsorbents by Pyrolysis of Sludge Mixed With Steel Slag and Study on Adsorption of Chromium Ions in Water

In this study, the dewatered sludge from the sewage plant and the open-hearth steel slag of the steel plant are used as raw materials. As two wastes, they were mixed and pyrolyzed to prepare a composite absorbent. Further, the adsorption mechanism of the adsorbent to chromium ions in the sewage is explored. The pyrolysis reaction behavior of sludge mixed with steel slag was studied by the thermogravimetric analysis technology. SEM, BET, and XPS were used to analyze the specific surface area, pore size distribution, and pore structure characteristics of pyrolysis products, respectively. Moreover, a comprehensive analysis of the adsorbent was carried out for the adsorption mechanism of hexavalent chromium ions. The results show that the addition of steel slag promotes the pyrolysis of the sludge in each stage. When the content of steel slag is 80%, the increases of reaction rate are the most obvious with the largest increase of weight loss rate in each stage. The SEM results show that the enrichment of sludge on metal oxides is enhanced in the high-temperature range (600–700°C). Besides, when the content of steel slag is 40–60%, the mixture’s growth rate of the specific surface area can reach 600% and the growth rate of total pore volume can reach 350% (the situations of sludge as the baseline). Regarding the measurement of Cr(VI), the adsorption rate of the steel-slag solution is 50.93% and that of the sludge solution is 69%. However, the adsorption rate can be increased to 95% when the steel slag and sludge were mixed as an adsorption solution. In conclusion, the adsorption mechanism of Cr(VI) by additives is controlled by both physical and chemical processes. The present study provides a theoretical basis and technical support for the scientific and reasonable utilization of sludge and steel slag.

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.