Steel Slag Research Articles

Recycling steel slag as fertiliser proxy in agriculture is good circular economy but disrupts plant microbial symbioses in the soil

Modern agriculture depends on synthetic fertilisers to ensure food security but their manufacture and use accounts for ~5 % of the global greenhouse gas emissions. Achieving climate change targets therefore requires alternatives, that while maintaining crop productivity, reduce emissions across the lifecycle of fertiliser utilisation. Steel slag, a nutrient-rich by-product of steel manufacture, offers a viable alternative. Being substantially cheaper than fertilisers, it is economically attractive for farmers, particularly in low-middle income countries of the Global South. However, slag application in agriculture poses risk of pollutant transfer to the human food chain and disruption of key plant-microbe symbioses like the arbuscular mycorrhizal fungi (AMF). Here, using barley as a model crop, we tested the suitability of slag as a fertiliser proxy. Mycorrhizal and non-mycorrhizal barley were grown in soils ameliorated with slag in concentrations of 0, 2, 5 and 10 t ha−1. We analysed slag-mycorrhiza interaction and their combined effects on crop yield and risks to human nourishment. Slag increased grain yield by respective 32 and 21 % in mycorrhizal and non-mycorrhizal barley. Grain concentration of metal pollutants in mycorrhizal and non-mycorrhizal barley fertilised with slag were within the WHO recommended limits. But slag reduced mycorrhizal colonisation in barley roots and extraradical hyphal spread in the soil. The consequent decline in symbiont function lowered AMF-mediated plant nutrient uptake and increased mineral losses in leachates. AMF are keystone species of the soil microbiome. Loss of AMF function presents long-term ecological consequences for agriculture and necessitates a careful evaluation of slag application to soil.

Passivation behavior of reinforcement in simulated pore solutions of composite cement incorporating ultrafine steel slag and blast furnace slag

The steel slag and ground granulated blast furnace slag with high fineness exhibit synergistic effects on hydration progress and can be introduced into concrete in high volume. In this paper, the simulated pore solution (SPS) of ternary cement incorporating ultrafine steel slag (US) and ultrafine ground granulated blast furnace slag (UG) was prepared to examine the passivation behavior of the HRB400 reinforcing steel under SPS. It is found that the rapid growth of passive films occurs primarily within the initial 2–3 days after immersion in the SPS, while the compaction of passive films takes place mainly at the later stages. The open circuit potential and charge transfer resistance of the passive films initially increase and then decrease with the continuous rise in the US content. The Fe2O3 constitutes a significant portion of the passive films above the steels treated with the SPS irrespective of US dosages, whereas the content of FeO is highly influenced by US dosages. The UG-US-C pore solution could enhance the passivation behavior because of lower Ca2+ and higher Na+. In case of UG/US ratio at 2:3, the passive film exhibits the greatest thickness at 7.5 nm and meanwhile with the highest compaction and the least roughness.

Radiation shielding properties of sustainable concrete with novel plastering techniques

In concrete applications. Major/critical applications of such concrete are radiation-shielding facilities. Both steel slag and silica fume are examples of common by-product materials that can be used as a replacer of aggregates and cement. Thus, in this research work, steel slag was utilized as heavy aggregate in concrete production besides silica fume to present sustainable concrete mixtures probably with better radiation-shielding properties. Different cementitious plasters were applied on the conducted sustainable concrete mixture using different powdery materials; hematite, magnetite, barite, bentonite, and steel slag powders in addition to nano-titanium dioxide as full replacers for sand. The proposed plasters were presented to determine the optimum plaster technique in terms of static performance and attenuation capability against gamma and neutron radiations. The results exhibited that utilizing steel slag and silica fume in concrete mixtures enhanced compressive strength by up to 9.09 % compared to conventional concrete, while the addition of nano-titanium to conventional plaster led to superior enhancement in the compressive strength by up to 38.65 % relative to traditional plaster. Conversely, fully replacing conventional silica sand with the abovementioned powdery materials generally reduced the compressive strength of cementitious plasters by up to 30.83 %. However, the radiation shielding properties against Cs-137, and Co-60 energies have been enhanced by up to 20 % and 26 %, respectively.

Noise-reducing double-layer porous pavement with steel slag as aggregate in the top layer

This paper presents results of a trial replacing the natural aggregate in the top layer of a double-layer porous asphalt pavement with steel slag. A 200 m long motorway section was paved with this material and performance in terms of macrotexture and noise properties (made annually with the CPX method) were monitored for an entire life-cycle of 7 years. The results in terms of noise reduction compared to the common Swedish reference pavement (SMA16) indicated an initial noise reduction of about 7 dB; only marginally lower than the same pavement with normal natural aggregate. By time, this marginal loss in noise reduction was turned into a somewhat higher noise reduction after 5-6 years of service. This was surprising since the steel slag pavement appeared to clog a little more than the conventional double-layer asphalt pavement. Probably, there are (uncertain) properties in the slag material which balances out the clogging effect. At the present time this pavement has reached an age of 7 years, which is similar as the conventional porous pavement has served on the same road over two lifecycles so far. With its lower noise-reducing deterioration versus time, steel slag is a promising material for recycling in this way.

Study on use of recycled waste materials on the performance of asphalt binder and mixes: A comprehensive review

All aspects of daily living frequently involve the use of plastics. Due to the lack of effective waste treatment methods, massive global environmental problems will be caused by the accumulation of waste plastics. The use of waste materials in road building is of tremendous interest since it has the potential to reduce hazards and pollution while conserving natural resources. High-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), ethyl vinyl acetate (EVA), and polyvinyl chloride are the most appropriate and relevant of waste plastics. There are other types of waste materials used in the asphalt such as reclaimed asphalt pavement (RAP), crumb rubber (CR), steel slag, glass powder etc. These all-waste materials have been briefly discussed. In this review article several concerns have been raised about the physical and chemical qualities, of asphalt pavements that have been mixed with waste materials. Using waste materials in asphalt pavements can raise several concerns regarding the physical and chemical qualities of the resulting mixtures. These concerns typically revolve around factors such as durability, performance, environmental impact, and overall sustainability. This research article provides a thorough analysis of the wet and dry procedures used to mix different types of waste plastics. Overall, including waste plastics into asphalt mix improved rutting, fatigue, and moisture resistance. Additionally, recycling waste plastics in this manner helps in reducing environmental pollution and conserving natural resources. Overall, the inclusion of waste plastics in asphalt mixtures can contribute to the development of more sustainable and durable pavements with improved performance in terms of rutting, fatigue, and moisture resistance. There are still certain issues like compatibility and low temperature performances that need to be addressed. To overcome the aforementioned issues, many strategies are used, including the use of nanomaterials, chemical additives, and polymer additives. Additional research should be conducted to investigate the ageing effect, pavement performance monitoring, polymer stability, and the economic and environmental considerations associated with the usage of plastics in asphalt pavements.

Predictive Modelling and Functional Group of Clay Soil Treated with Steel Slag and Calcium Carbide Residue

Swell-shrink subgrade soils like clay are rich in sulphate and exhibit a high rate of volume change by swelling and shrinking during wet and dry cycles, respectively, leading to heaves, cracks, and differential settlement of pavement layers. The aim of this study was to establish predictive simulation models and functional group of clay soil treated with steel slag and calcium carbide residue. Physical and geotechnical tests (such as California bearing ratio (CBR), compaction characteristics, and consistency parameters) were carried out on the unstabilised and stabilised clay soil. Using SPSS statistical software (version 23), multiple linear regression analysis was applied to the experimental data that relate CBR to compaction parameters and additive contents (steel slag and calcium carbide residues). The generated models gave a reliable coefficient of determination, R2 , of 0.990, and 0.998, which can be used to successfully predict both unsoaked and soaked CBR of the stabilised clay soil, respectively. Fourier transform infrared spectroscopy (FTIR) analysis was examined on the clay soil, the additives, and the stabilised clay soils. The FTIR analysis showed weak peaks at 1115 and 1103 cm-1 for all the stabilised clay soils, and this revealed that both additives drastically reduced the sulphate content in the clay soil, which consequently reduced the expansion, cracking, and disintegration rates. As a result, the clay soil's chemical bonding was enhanced through physico- chemical mechanisms.

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.

Quality Assurance of Steel Slag Asphalt Mixtures for Sustainable Pavement Surface Courses

The present study investigates the use of electric arc furnace (EAF) steel slag, a by-product of the steel industry, in asphalt pavement surface courses instead of virgin aggregates (VAs). Therefore, a general performance evaluation of such mixtures compared to conventional mixtures is carried out through laboratory and in situ tests, while both mixtures are environmentally assessed using the life cycle assessment (LCA) tool. The results of the laboratory and in situ tests show that asphalt mixtures containing granulated EAF slag aggregates perform as well as mixtures containing only VA. In addition, the LCA results show that the use of EAF slag aggregates in the asphalt surface course has a lower environmental impact than the exclusive use of VA when it comes to the impact categories of acidification, climate change, marine and terrestrial eutrophication, energy consumption and photochemical pollution. In summary, these results show that replacing virgin aggregates with a proportion of EAF slag aggregate is a viable and sustainable method for road pavement construction.

Steel slag aggregate property improvement in cold mixed asphalt mixtures through surface modification treatment

Expanding the resource utilization of solid waste steel slag (SS) is necessary to reduce the environmental impact of stockpiling and disposal. However, SS has the shortcomings of poor volume stability and poor water damage resistance, which limits its application in pavement engineering, especially in cold mixed asphalt mixtures. In this work, hexamethylene diisocyanate biuret (containing -NCO) and hydroxyl acrylic resin (containing -OH) were utilized as raw materials to prepare NCO-OH composite modifier (NOCM) by regulating NCO/OH (0.75, 1.00, 1.25, and 1.50) for SS surface modification. Surface morphology, adhesion properties, aggregate properties, and prepared mixture properties of SS before and after modification were investigated, respectively, and the curing mechanism of NOCM and action mechanism were analyzed. Results show that the cured NOCM forms a dense modified film on the SS surface, and the rough surface and large pores of SS were blocked, which effectively hindered the free oxides in SS from coming into contact with water. NOCM reduced the apparent relative density, water absorption, and wear loss of SS. NOCM with NCO/OH=1.25 was recommended to modify SS to obtain the most balanced properties, at which time MSS has a roughest surface to mechanically interlock with asphalt, and there are excess -NCO groups to chemically bond with polar components in asphalt. Mixtures prepared at the optimum NCO/OH had good water damage resistance, freeze-thaw cycle resistance, and volume stability. Applying NOCM-modified SS in environment-friendly cold mixed asphalt mixtures can effectively improve pavement durability and bring good environmental benefits.

Development of a sustainable stabilized macadam road base using steel slag as supplementary cementitious material

As the main waste product of iron and steel industry, steel slag possesses considerable cementitious activity, making it a promising alternative to cement in Cement Stabilized Macadam (CSM). However, CSM was inevitably exposed to groundwater and rainwater when served as the pavement base course, leading to concerns over poor early strength and potential pollutant leakage, which are the main factors that may hinder the widespread utilization of steel slag in CSM base. To address these issues, this study investigated the feasibility of using steel slag powder to produce CSM. Steel Slag Powder-Cement Stabilized Macadam (SSCSM) samples were prepared and the hydration products, microstructure, mechanical properties, water damage resistance and heavy metal ions leaching behavior were investigated. The results show that the nucleation effect of steel slag powder accelerates the early hydration, but the C-S-H produced by hydration is not sufficient to form a stable hydration product network, so the microstructure of SSCSM is looser than that of CSM. The addition of steel slag powder improved the shrinkage performance of SSCSM, and the mechanical properties and heavy metal ion leaching concentration of SSCSM meet the engineering application requirements when the steel slag powder replacement level does not exceed 30 %. It was also found that the addition of steel slag powder promoted the development of pores in SSCSM samples after dry-wet cycles, resulting in the reduction of water damage resistance. Compared with conventional CSM, the use of SSCSM can not only reduce 4 % of raw material cost and 23.5 % of equivalent CO2 emission, but also mitigate the heavy metal ions leaching risk associated with steel slag, making it an effective and sustainable solution for steel slag recycling.

Concurrent removal of Fe(II), Cu(II), and Zn(II) cations from acid mine drainage by an industrial solid waste - steel slag: Behaviors and mechanisms

Acid mine drainage (AMD) contamination poses a severe environmental threat and is a significant risk to human health. There is an urgent need to develop environmentally sustainable and technically viable solutions for water contamination caused by heavy metals. In this study, steel slag (SS) was used as a secondary resource to concurrently remove Fe(II), Cu(II), and Zn(II) from AMD. Because of the loose and porous structure, abundant functional groups, fast sedimentation velocity, and excellent solid-liquid separation, SS showed exceptional removal performance for heavy metal ions. The adsorption kinetic data of Fe(II), Cu(II), and Zn(II) showed good regression with the pseudo-second-order model. Besides, the adsorption of Fe(II) by SS conformed to the Freundlich model, whereas the adsorption of Cu(II) and Zn(II) followed the Langmuir model, with the maximum adsorption amounts of Cu(II) and Zn(II) being 170.69 and 155.98 mg/g. Furthermore, competitive adsorption was observed among Fe (II), Cu (II), and Zn (II) in a multi-component system, with the adsorption priority being Fe (II) > Cu (II) > Zn (II). The removal mechanism of Fe(II), Cu(II), and Zn(II) in AMD by SS mainly includes electrostatic attraction, chemical precipitation, and surface complexation. Interestingly, the leached concentrations of Fe(II), Cu(II), and Zn(II) from the spent slag after calcination were all within the detection limit of the Chinese emission standard, demonstrating excellent environmental stability. Theoretically, this renders it a viable candidate for use as an additive in construction materials. Meaningfully, the work offers a practical approach for energy-efficient and eco-friendly heavy metal ions adsorption, and the secondary utilization of SS also contributes to the sustainable development of the steel industry. It is beneficial to implement the development concepts of clean production and efficient utilization of industrial solid waste.

Evaluation method for uniformity of steel slag concrete aggregate based on improved YOLOv8

The use of steel slag as a replacement for natural aggregates in concrete effectively alleviates the issue of natural resource scarcity. The uniformity of aggregates in steel slag concrete directly affects its performance and durability. Therefore, precise segmentation of aggregates in sedimentation images is crucial for evaluating their uniformity. This paper not only proposes an improved instance segmentation model for accurate segmentation of steel slag concrete aggregates but also introduces a new method for assessing the uniformity of aggregates when steel slag replaces natural aggregates. This method quantitatively analyses the area, replacement rate, and spatial distribution of the aggregates and conducts a comprehensive quantitative analysis using the comprehensive uniformity evaluation coefficient, K. This approach allows for the evaluation of the uniformity of aggregates in sedimentation images of steel slag concrete. Experimental results show that the proposed improved model achieved an mAP50 of 98.3 %. Furthermore, the aggregate uniformity assessment method based on the improved model can objectively and accurately evaluate the uniformity of steel slag concrete aggregates.

Development and properties of cost-effective self-sensing Ultra-High Performance Fiber-Reinforced Concrete (UHPFRC) incorporating steel slags

This study examined the electrical and self-sensing capacities of ultra-high performance fiber-reinforced concrete （UHPFRC） with and without steel slag powder. The inclusion of steel slags provides a reliable way to enhance the electrically conductive and self-sensing capabilities of UHPFRC, which is composed of cement, silica fume, and steel fiber. The conductibility of UHPFRC and its response to external loading were investigated. Additionally, through 3D analysis of fiber structure and pore distribution, the conductive mechanisms were revealed. The results show that the addition of steel slags powder (SSP) can improve both mechanical properties and flowability. The maximum fractional change in electrical resistivity under compressive and flexural loads reached 37.6 % and 54.1 %, respectively. However, the conductive model under compressive loading differs from that under flexural loading. Furthermore, an analysis of carbon emissions and material costs revealed that using SSP reduced carbon emissions by 45.2–96.4 % and lowered costs by 41.8–88.8 %, making this approach both economically and environmentally advantageous.

Synthesis of novel composite material with spent coffee ground biochar and steel slag zeolite for enhanced dye and phosphate removal.

Rising concerns over water scarcity, driven by industrialization and urbanization, necessitate the need for innovative solutions for wastewater treatment. This study focuses on developing an eco-friendly and cost-effective biochar-zeolite composite (BZC) adsorbent using waste materials-spent coffee ground biochar (CGB) and steel slag zeolite (SSZ). Initially, the biochar was prepared from spent coffee ground, and zeolite was prepared from steel slag; their co-pyrolysis resulted in novel adsorbent material. Later, the physicochemical characteristics of the BZC were examined, which showed irregular structure and well-defined pores. Dye removal studies were conducted, which indicate that BZC adsorption reach equilibrium in 2h, exhibiting 95% removal efficiency compared to biochar (43.33%) and zeolite (74.58%). Moreover, the removal efficiencies of the novel BZC composite toward dyes methyl orange (MO) and crystal violet (CV) were found to be 97% and 99.53%, respectively. The kinetic studies performed with the dyes and phosphate with an adsorbent dosage of 0.5g L-1 suggest a pseudo-second-order model. Additionally, the reusability study of BZC proves to be effective through multiple adsorption and regeneration cycles. Initially, the phosphate removal remains high but eventually decreases from 92% to 70% in the third regeneration cycle, highlighting the robustness of the BZC. In conclusion, this study introduces a promising, cost-effective novel BZC adsorbent derived from waste materials as a sustainable solution for wastewater treatment. Emphasizing efficiency, reusability, and potential contributions to environmentally conscious water treatment, the findings highlight the composite's significance in addressing key challenges for the removal of toxic pollutants from the aqueous solutions. PRACTITIONER POINTS: A novel biochar-zeolite composite (BZC) material has been synthesized. Excellent removal of dyes by BZC (~95%) was achieved as compared to their counterparts The kinetic studies performed suggest a pseudo-second-order model. BZC proves to be highly effective for multiple adsorption studies. Excellent reusability showed potential as a robust adsorbent.

Performance assessment of sustainable asphalt concrete using steel slag, with an artificial neural network prediction of asphalt concrete behavior

This research evaluated the possibility of using Moroccan steelworks slag as a substitute for natural aggregates in asphalt mixtures, using chemical and mechanical analyses to demonstrate its compatibility with this application. Two granular mixtures, M1 and M2, were developed, incorporating respectively 15% and 25% natural sand (0/1.25) with slag aggregates to obtain granular mixtures complying with local standards. These mixtures were then tested with three different asphalt contents (4.7%, 5.2%, and 5.7%). Mechanical tests, including a gyratory compactor, Marshall stability, and Duriez strength, were carried out. In particular, the M1:5.2 and M2:5.2 mixtures met compaction criteria and showed remarkable Marshall Stability values, reaching 23.49 kN and 21.81 kN respectively. In comparison, the control mixtures only achieved a maximum stability of 11 kN. Thermal properties were also assessed, showing that the maximum thermal conductivity was achieved at an asphalt content of 5.2%. The slag-based mixtures, M1 and M2, showed higher thermal conductivity than the control mix M0, with maximum values of 0.74W/mK for M1 and 0.86W/mK for M2, compared with 0.56W/mK for M0. The overall results show that the M1 and M2 mixtures had improved thermal and mechanical properties compared with the M0 control mix. Artificial neural network (ANN) modelling was carried out using Marshall Test data. It showed excellent performance in predicting the stability and flow properties of asphalt mixtures. These results suggest that incorporating steelmaking slag into asphalt concrete mixtures was an effective strategy for simultaneously improving their thermal and mechanical properties.

Recycling steel slag as aggregate in developing an ultra-thin friction course with high comprehensive road performance

The demand for skid-resistant and wear-resistant alternative aggregates in the preparation of ultra-thin friction course (UTFC) asphalt mixtures is a key direction for achieving high durability and low-carbon development in pavement maintenance. As a typical industrial waste, steel slag with high alkalinity and strong adhesion can facilitate the mechanical property of asphalt mixtures. However, few researches focused on the impact of steel slag on the comprehensive road performance of UTFC mixtures. Hence, the issue merits systematic exploration. In this study, the chemical components, microstructure and morphological characteristics of three steel slags (GXSS, HBSS and IMSS) obtained from different sources were surveyed. Then the stone matrix asphalt (SMA)-5 and open-grade friction courses (OGFC)-5 mixtures with different steel slags were fabricated. And their comprehensive road performances were quantitatively explored via the improved radar chart. The results indicate that steel slag with approximately 40 % Ca content, about 20 % Fe content, irregular shapes and tiny pores endows its wear resistance and strong adhesion. IMSS demonstrates the largest average angularity and form 2D values of 3850 and 7.28, respectively, representing its significant crowding function and interlocking structure. Incorporating steel slag remarkably reinforces the rutting resistance, skid resistance and anti-interlayer shear performance of UTFC. While the effect of water stability and crack resistance of UTFC depend on the category of steel slag. All three steel slags manifest the improvement function on the comprehensive assessment indexes (CAI) of OGFC-UTFC. IMSS-OGFC reveals the optimal comprehensive road performance, achieving the highest CAI of 0.9909. It is inferred that steel slag is more suitable for OGFC-UTFC than SMA-UTFC due to its relatively high CAI and consistent performance regardless of the steel slag type.

Evaluation of carbon nanotube (CNT) cement-based traffic sensor incorporating steel slag based on Accelerated Pavement Test (APT)

ABSTRACT In this study, a carbon nanotube (CNT) cement composite containing CNT and steel slag was developed and its application in traffic information sensing was studied. The mix ratio of steel slag cement mortar matrix and CNT cement composite was determined by mechanical properties and electrical conductivity tests. Then the CNT cement composite intelligent sensing device was prepared and an Accelerated Pavement Test equipment was used to test its piezoresistive response curve. The test results show that steel slag and CNT enhance mechanical properties and electrical conductivity. The vehicle speed and wheelbase were calculated based on the piezoresistive response results, and the calculation errors of the wheel speed (0.375 and 0.844 km/h) were less than 10% and 20%, respectively. The wheelbase estimate has a maximum error of approximately 12% and 15% for wheel speeds of 0.375 and 0.844 km/h, respectively. Therefore, the CNT cement composite containing steel slag developed in this study has the potential to serve as a traffic sensor.

Replacement of conventional aggregates and fillers with steel slag and palm kernel shell ash in dense-graded asphalt mixtures

Large quantities of steel slag and palm kernel shell ash (PKSA) – waste products from steel production and palm oil milling, respectively – are generated annually in several countries, and their disposal is challenging. Meanwhile, the over-reliance on conventional rock aggregates for asphalt mixture production poses increasing sustainability challenges. This study investigated the potential of entirely replacing granite aggregates with steel slag and PKSA in a dense-graded asphalt mixture. Two sets of asphalt mixtures were prepared; the control mixture contained crushed granite aggregate and hydrated lime, while the other set incorporated steel slag as coarse aggregate and PKSA as fine aggregate and filler. Both mixture types utilized AC-30 viscosity-graded asphalt binder. The properties of the waste materials met the quality standards required for aggregates in asphalt mixture production. Both mixture types were designed according to the Marshall design procedure and were evaluated for durability (Cantabro abrasion loss), fatigue cracking Resistance, rutting Resistance, and moisture damage susceptibility. The Cantabro abrasion loss test indicated that the waste-based mixture was 3% less durable than the control. However, the cracking Resistance of the waste-based mixture was approximately twice that of the control. Even though the rapid rutting test indicated that the control mixture was slightly superior in rutting Resistance, the Marshall quotient suggested otherwise. Both mixture types exhibited similar moisture damage resistance. Overall, the steel slag and PKSA samples have shown high potential to replace virgin granite aggregates and lime in asphalt mixtures fully and are, thus, recommended for field performance evaluation and possible adoption.

Evaluation of geotechnical, mineralogical and environmental properties of clayey soil stabilized with different industrial by-products: A comparative study

The utilisation of soil stabilization techniques employing binders like lime or cement enables the use of soils that are classified as disposable, thereby reducing the need for landfills and the consumption of natural resources. However, the production of lime and cement results in significant CO2 emissions. Therefore, the application of industrial by-products (IBP) for stabilizing expansive soils presents an opportunity to minimise the use of traditional binders. This study investigates the geotechnical, mechanical, mineralogical, and environmental properties of four IBP (biomass bottom ash, biomass fly ash, steel slag, and mixed recycled aggregate) combined with a silica-based nanomaterial for road layer applications. The technical feasibility of the use of IBP was demonstrated, especially in combination with nanomaterials, allowing a 66 % reduction in the percentage of added lime, obtaining significant improvements with minimal plasticity and swelling index and bearing capacity CBR values higher than 25 %, applying BBA, BFA and SS. An environmental assessment of leachate analysis was performance, showing an immobilization of heavy metals that makes the application of IBP feasible. In addition, a life cycle analysis study showed the environmental benefits of applying IBP, such as a 50 % reduction in CO2 emissions due to the reduction of lime, resulting from the use of these materials, thus promoting more sustainable economic models.

EFFECT OF ALTERNATIVE RAW MATERIALS OVER CLINCKER QUALITY AND CO2 EMISSIONS

In the cement industry, the actual challenges are the preservation of the raw materials and energy resources, as well as reduction of pollutant emissions. In this context, the cement producers demand studies to reduce of the production costs and atmospheric emissions. One way to achieve these objectives, is to use alternative fuels or by-product raw materials. Any reduction in the required energy has a beneficial influence both on the viability of the cement plant and on the environment. One of the approaches aimed at reducing thermal energy consumption is the partial substitution of traditional raw materials (limestone, clay, gypsum) with other alternative materials, with a melting effect, among which stand out byproducts of the steel industry such as furnace and steel slag. Another way for preservation of energy resources is using alternative fuels instead of traditional fuels like coal, petroleum coke or gas. The clinkering process and clinker quality can be influenced by any additions, in this study was determined these influences.