Production Of Lightweight Aggregates Research Articles

Investigating effects of sintering mean residence time on engineering properties of coal ash‐based lightweight aggregate

AbstractThis study examines the effect of sintering mean residence time (MRT) on the engineering properties and morphological structure of lightweight aggregates (LWA) manufactured from waste coal combustion ash (W‐CCA). A thermodynamics‐based framework was used to tune LWA manufacturing processes. A minimum 35% liquid phase (by mass) and a lower bound viscosity of 100 Pa·s of molten material were found necessary to successfully produce LWA. Using W‐CCA's chemical composition and FactSage thermodynamic modeling, the sintering temperature for LWA was set to 1075°C. Green spherical pellets made using a pelletizer were sintered at MRT of 5.1, 14.8, and 25.9 min to test LWA physical‐mechanical properties including, unit weight, specific gravity, water absorption, and compressive strength. Results indicated that unit weight ranged from 752 to 800 kg/m3, providing desirable lightweight properties. Oven dry specific gravity ranged from 1.24 to 1.43, complying with ENI13055 specification for LWA. Water absorption capacity decreased as MRT extended from 5.1 to 14.8 min and then increased as MRT proceeded from 14.8 to 25.9 min, achieving an average absorption capacity of 26% ± 1.5%. The inverse effect was noticed for compressive strength as LWA sintered with an MRT of 14.8 min demonstrated the highest compressive strength of 14.7 ± 1.8 MPa. The initial decrease in water absorption and increase in compressive strength are attributed to the efficient sintering of the LWA's internal structure. The inverse effect observed as MRT proceeded from 14.8 to 25.9 min was believed to be a result of thermal cracking due to extensive heat exposure. MRT of 14.8 min is recommended for LWA production using the coal ash utilized in this study for its buoyancy characteristics, sufficient absorption capability, and higher compressive strength.

Properties of artificial lightweight aggregates prepared from coal and biomass co-fired fly ashes and sewage sludge fly ash

The use of solid waste such as coal and biomass co-fired fly ashes and sewage sludge fly ash instead of clay and other non-renewable resources to produce lightweight aggregates (LWAs) is conducive to sustainable development. In this study, the effects of co-fired fly ashes, sewage sludge fly ash and quartz sand proportion, sintering temperature and sintering time on the physical properties and microstructure of LWAs are studied by single factor experiment. Experimental results show that the optimal experiment conditions are the raw material ratio of co-fired fly ashes: sewage sludge fly ash: quartz sand = 9: 1: 4, 2 wt% SiC as an expansion agent, and sintering at 1060 °C for 10 min. The LWAs obtained under the above conditions have a bulk density of 0.85 g/cm3, an apparent density of 1.84 g/cm3, a 1-h water absorption of 2.71 %, and a compressive strength of 8.68 MPa, which are in accordance with the GB/T17431.1–2010 standard. Besides, the heavy metal immobilization effect of the LWAs is satisfying, where the heavy metal leaching concentrations meet the standard of GB5085.3–2007. In conclusion, it is feasible to use the raw materials to prepare the LWAs under the above sintering conditions, and the prepared LWAs have high strength and low water absorption.

Enhancing Structural Performance: Fiber Reinforcement in Sintered Flyash Lightweight Concrete for Impact Resistance and Toughness

Objectives: The goal of this project is to better understand the interaction between fibers and concrete in order to produce Light Weight Aggregate Concrete (LWAC) with improved structural performance that is made from recycled materials, such as sintered flyash aggregate, and LWAC structures that are more resistant to impact loads and other dynamic forces. Methods: The sintered flyash aggregates are added as coarse aggregate to the concrete and basalt fiber (0.25% of mix) is used as a secondary reinforcement to improve the energy absorption, impact resistance and toughness behaviour. M30 grade of concrete was arrived after laboratory trials after which the mechanical properties were evaluated. The effect of drop impact load on slabs of size 300mm x 300mm x 50mm reinforced with two layers of bundled wire mesh was studied. The flexural properties of concrete reinforced with fiber prism of size 500mm x 100mm x 100mm were evaluated. Findings: With the addition of fiber, flexural toughness index and post-cracking toughness were increased notably on the initial deflections and cracks. The conventional fiber reinforced concrete exhibited a superior peak load capacity compared to normal weight concrete, with a measured increase of 7.5%. Conversely, normal-weight concrete demonstrated a significantly higher deflection under load, exceeding that of fiber reinforced concrete by 47%. LWAC displayed a distinct increase in both peak load (18.7%) and deflection (39.13%) when compared to Normal Weight Aggregate Concrete (NWAC). The incorporation of basalt fiber enhanced the energy absorption by 150% in NWAC and 80% in LWAC. Novelty: The incorporation of fiber into lightweight concrete reduces the brittle nature of failure. The post-cracking toughness behaviour was enhanced because of the effect of crack-arresting by fibers. After the first break, it was discovered to retain residual strength, and removing the fibers from the matrix required more force. Keywords: Sintered flyash aggregate, Light weight concrete, Basalt fiber, Toughness, Impact load, Energy absorption

Synthesis of geopolymer composites using bauxite residue-based spheres as aggregate: Novel and eco-friendly strategy to produce lightweight building materials

In this study, and for the first time, highly porous red mud-based geopolymer spheres were produced, through a very simple and scalable procedure, and used as lightweight aggregate in the synthesis of geopolymer composites. To further demonstrate the potential of this unexplored route, a comparison with composites containing expanded perlite and expanded vermiculite was also performed. The sample produced with 85 vol% of spheres showed the lowest geometric density (0.84 g/cm3) amongst the studied composites, coupled with a suitable compressive strength (1.0 MPa), low thermal conductivity (175 mW/m K), and excellent thermal stability after exposure to 1000 °C for 2h. The much lower production temperature (80 °C), compared with the commercial expanded aggregates (above 650 °C), and the reuse of significant amounts of bauxite residue (strategy aligned with the circular economy) enables the production of eco-friendly lightweight aggregates for the building sector.

Optimization of the manufacturing process and properties of alkali-activated palm oil fuel ash-based cold-bonded aggregates

Tons of palm oil fuel ash (POFA) are currently being disposed of at landfills or left untreated in the environment, taking up valuable land space and posing significant hazard to the environment. To address this issue, this study investigates the production of artificial lightweight aggregates (LWAs) using POFA as a raw material through a cold-bonded one-part alkali-activation method. High-volume of weakly pozzolanic POFA and different combinations of GGBS (0%, 10%, 30%) as precursors, and Na2SiO3.5H2O (9% and 12%) as the activator were used to produce the artificial LWAs. The granulation process was systematically investigated, where the influence of granulation parameters (the ratio of POFA and GGBS, activator content, water content, rotation angle, and rotation speed) on granulation efficiency and granulation duration were evaluated. The physical properties including loose bulk density, water absorption, and crushing strength were also investigated. In addition, the phase change after alkali-activation was evaluated. Results showed that the water demand for the aggregates with different combination ranged from 0.3 to 0.46. Increasing the GGBS and Na2SiO3.5H2O content improved the granulation efficiency up to 87.4% and shortened the granulation duration to 7 min. Response surface methodology (RSM) modeling revealed that the optimum rotation angle and rotation speed were 55° and 50 rpm, respectively, resulting in a maximum granulation efficiency of 88.2%. The loose bulk density of POFA-based alkali-activated aggregates (PFAAs) was 595.4–730.3 kg/m3, meeting the requirement of LWAs in EN13055. After 28 days curing, the PFAAs with the GGBS replacement of 30% and 12% Na2SiO3.5H2O exhibited crushing strength and water absorption of 2.4 MPa and 22.4%, respectively. Moreover, a stronger alkali-activation was achieved with 30% GGBS replacement, which improved the performance of PFAAs, as evidenced by the phase analysis.

Comparative Environmental Evaluation of Sewage Sludge Treatment and Aggregate Production Process by Life Cycle Assessment

This study evaluated the environmental impact of landfill, incineration, and lightweight aggregate production for sewage sludge management techniques and compared the utilization of sewage-produced lightweight aggregates with natural aggregates in terms of building material production. Two scenarios were established for the life cycle assessment (LCA) of the sludge and associated product that was carried out after sludge generation. Sludge incineration and landfill deposition includes emissions from the drying, transportation, incineration of sludge, and landfill, and the production of lightweight aggregates and natural aggregates includes transportation to manufacturing facilities, the manufacturing processes themselves, and transportation of the produced aggregates to construction sites. We calculated the amount of pollutant emissions for each process in each scenario and analyzed the environmental impact index considering the environmental impact of each pollutant using the Open LCA program. The parameters used for the environmental impact index analysis for sludge management are potential acidification, climate change, eutrophication potential, human toxicity, photochemical oxidation, and stratospheric ozone depletion. The environmental impact values of lightweight aggregates (LWA) are GWP 100 441 kg CO2_Eq, AP 2.73 × 10−2 kg SO2_Eq, EP 4.46 × 10−3 kg PO4−_Eq, HTP 4.15 × 10−2 kg, 1,4-DCB_Eq, POCP 1.64 × 10−3 kg CH4_Eq, and ODP 3.41 × 10−7 kg CFC-11_Eq. We found that these values were low compared to landfill and incineration as a sewage sludge disposal method and compared to natural aggregate as a construction material production method. The environmental impact index analysis during LCA of lightweight aggregates produced from the sludge verified its positive environmental impact compared to the other potential methods of sludge management.

Fate of Cl and chlorination mechanism during municipal solid waste incineration fly ash reutilization using thermal treatment: a review.

Safe and sustainable treatment of municipal solid waste incineration fly ash (MSWI FA) is urgently needed worldwide because of its high heavy metals, dioxin, and chlorine (Cl) contents. Thermal treatment is widely considered as a promising method for treating MSWI FA owing to its high toxic content removal efficiency and resource recovery; however, residual Cl is a concurrent critical problem faced during reutilisation of thermal treatment products. This review summarises the innovative thermal treatment methods of MSWI FA, such as those employed in production of cement, lightweight aggregates, glass slag, and metal alloys. The characteristics of Cl in MSWI FA, removal rate, transformation of water-soluble Cl into water-insoluble Cl, and the effect of different influencing factors such as temperature, composition, superheated steam, and mechanical pressure were analysed. The volatilization and decomposition of NaCl, KCl and CaClOH dominates Cl removal; however, the degradation of organic Cl and heavy metal chlorination volatilization process that generate HCl and heavy metal chlorides, respectively, also contributed to Cl removal. To promote the reutilisation of MSWI FA-based products, the leaching behaviour of residual Cl in products obtained by different thermal treatments was investigated.

Mitigating heavy metal volatilization during thermal treatment of MSWI fly ash by using iron(III) sulfate as a chlorine depleting agent

In the thermal treatment of municipal solid waste incineration fly ash (FA), the presence of chlorides leads to the pronounced volatilization of heavy metals at high temperature, making heavy metals stabilization challenging. Conventional washing processes struggle to remove chlorides completely, and even minor residual chlorides can lead to significant heavy metal volatilization. This study innovatively applied iron(III) sulfate as a chlorine depleting agent, which can form FeCl3 (boiling point 316 °C) and volatilize to remove the residual chlorides at below 500 °C, thus preventing the chlorination and volatilization of heavy metals at 600–1000 °C. Using water-washed FA to produce lightweight aggregate (LWA) preparation, after adding iron(III) sulfate, the volatilization rates of Pb and Cd at 1140 °C decreased to 5.4% and 9.3%, respectively, a reduction of 82.8% and 84.1% compared to before its addition. The LWA met standard requirements in both performance and heavy metal leaching toxicity. The mechanism was further studied through thermodynamic equilibrium calculations and heating experiments of pure chemicals. This study presents novel approaches and insights for suppressing the volatilization of heavy metals in FA at high temperature, thereby promoting the advancement of thermal treatment techniques and the safe, resourceful disposal of FA.

The impact of slag on the process of geopolymerization and the mechanical performance of mine-tailings-based alkali-activated lightweight aggregates

Alkali-activated lightweight aggregates (LWAs) made of alkali-activated aluminosilicate-rich mine tailings (MTs) offer a promising alternative to natural lightweight aggregates. The comprehensive investigation of lightweight aggregate production using aluminosilicate-rich MTs in combination with commercial slag as a reactive aluminosilicate remains largely unexplored. In this study, mixtures of MTs and slag were pelletized through the application of a pan pelletizer machine. The study focused on examining the impact of different slag concentrations on the chemical, physical, mechanical, mineralogical, and morphological properties of the produced LWAs. Furthermore, a comparison was made between the physical and mechanical characteristics of the resulting LWAs and those of flay-ash (FA)-based LWAs. The results revealed that the inclusion of slag in LWAs, as compared to FA, led to the production of LWAs with superior physical and mechanical properties. Specifically, as the slag content increases, the water absorption, dissolution, and porosity of LWAs significantly decreased, while the bulk density and compressive strength increased. It is important to note that these changes occur without affecting the specific gravity of the LWAs. The scanning electron microscope (SEM) images clearly showed that the addition of slag, similar to FA, especially at concentrations of more than 20% and higher, promoted uniform geopolymerization within the specimens. Furthermore, the energy-dispersive X-ray spectroscopy (EDS) analysis revealed that all LWAs with concentrations of 20% slag and higher exhibited a Si:Al ratio exceeding three, indicating a higher likelihood of geopolymer backbone formation. The X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) analyses revealed that the alkali activation process led to the depletion of gypsum, originally present in the MTs, and the emergence of sodalite and zeolite in the LWAs. Thermogravimetric analysis (TGA) tests provided additional confirmation of the ongoing geopolymerization process in slag-based LWAs, particularly those containing 20% slag or higher.

Production, properties and life cycle assessment of artificial lightweight aggregates produced with corn straw ash (CSA) and concrete slurry waste (CSW)

Open burning of corn straw has been a long-standing environmental problem in developing agricultural countries. The development of the concrete material industry supplies a feasible consumption outlet for the bulk solid wastes from agriculture and construction fields. In this study, therefore, corn straw and concrete waste were turned into available cementitious materials: corn straw ash (CSA) and concrete slurry waste (CSW) powder. Then CSA and CSW were reused to be artificial lightweight aggregates (ALAs) by cold-bonding pelletization and carbonation curing. A multi-criteria decision-making model for ALAs was finally proposed to comprehensively evaluate the technical, environmental, and economic factors and select the most valuable candidate. The findings indicate that it is technically feasible to produce ALAs by using CSA and CSW. The optimal mechanical parameters of the disc granulator are 35 rpm and 45° inclination in the cold-bonding pelletization process of ALA production. From a technical point of view, with the increase of CSA content in ALAs, the strength of ALAs increased first and then decreased, reaching the optimum value of 14.2 MPa with the addition of 5% CSA. According to the sustainability score, the descending order of ALAs is C1, C4, C3, C2 and C0. Sustainability results show that the ALAs of the mixture of 5 wt% CSA and 95 wt% CSW is the optimal solution. The ALAs with dual-function in terms of reducing CO2 emissions and capturing CO2 is a promising candidate for low-carbon concrete production. The decision model could be suitable for the sustainable selection of artificial aggregates or recycling construction materials.

PH-controlled sulfuric acid washing enhancing heavy metal stabilization in lightweight aggregate production from municipal solid waste incineration fly ash

Municipal solid waste incineration fly ash (FA) is a pressing issue in urban development. In FA treatment, washing is a common dechlorination pre-treatment. During washing, considerable heavy metal would leach due to the abundant alkaline substances, posing challenges to the heavy metal stabilization. Also, with high alkalinity, FA has potential to co-dispose of waste sulfuric acid (hazardous waste). Addressing these, our study presented a novel pH-controlled sulfuric acid washing for FA dechlorination during the sintering preparation of lightweight aggregate (LWA). It was aimed at enhancing heavy metals stabilization and enabling the co-recycling of FA and waste sulfuric acid. By controlling a pH of 10.50 during sulfuric acid washing, the leaching rate of Pb, Cd, Zn, Cu, Ba, and Cr was below 2%, which was a marked improvement over conventional water washing. Sulfuric acid washed FA (SFA) can be used to produce standard-compliant LWA by sintering with bentonite and SiC. The SFA-based LWA stabilized heavy metals more effectively than LWA using FA and water-washed FA. At a 30 wt% addition rate, the stabilized rate of Pb and Cd increased from 11.7% (using FA) to 72.4% (using SFA), and from 6.3% (using FA) to 49.0% (using SFA), respectively. During washing and sintering, XPS analysis further investigated the transformation of Pb, Cu, and Zn into stable states (Pb-glass, Cu2O/CuO, and ZnAl2O4), enhancing their stabilization. Our study introduces a novel method for co-recycling FA and waste sulfuric acid, offering enhanced environmental sustainability and deeper insights into the mechanism of heavy metal stabilization.

Effect of microwave radiation temperature and content of different solid waste on the microstructure and physicomechanical properties of lightweight aggregates

Microwave radiation in the production of lightweight aggregates, it has not yet been thoroughly explored. Therefore, the main goal of the research is to analyze the possibility of using various types of waste, such as waste rock (0–30 %) and glass cullet (10 %), fly ash (50–80 %) and waste solution using different microwave temperature (1000, 1050, 1100 °C) in order to obtain lightweight aggregates. Above factors and, chemical and mineral composition of the waste materials, affect the microstructure and physico-mechanical parameters of the aggregates.). The thermophysical behavior (DTG/TG), grain composition, chemical composition (XRF), phase composition (XRD) and microstructure (SEM, μ-CT) were analyzed. The microstructure, as well as the related characteristics of aggregates, i.e. water absorption, density, and compressive strength, depend on the sintering temperature, chemical composition and mineral waste raw material. The best properties were obtained for a raw material mixture containing 80 % coal fly ash, 10 % glass cullet, 10 % clay and 48 g of the waste solution (per 100 g of raw mixture), sintered in the microwave at 1100 °C. The aggregates were characterized by water absorption of 6.96 %, bulk of 1.70 g/cm3, loose bulk density 0.60 g/cm3, and compressive strength 5.95 MPa. Closed porosity determined by micro-CT was 8.41 %, open - 0.24 %, sphericity 0.62. The total porosity depends on the loose bulk density and particle density of lightweight aggregates.Furthermore, washout tests meet environmental requirements. The proposed technology, moreover, enables a short time of thermal processing of raw materials, and thus energy savings and a sustainable approach to the production of green pellets. Thanks to the high strength, the obtained aggregates can replace commercial aggregates.

A REVIEW OF THE EFFECT OF ADDITIVES ON THE MECHANICAL PROPERTIES OF LIGHTWEIGHT CONCRETE

Many organizations around the world have recognized lightweight, long-lasting, cost and environmentally-friendly construction materials as a future necessity. The lightweight concrete is manufactured mainly either by replacing the original aggregate with lightweight aggregate or addition foam production materials to concrete mixtures. These additions lead to a decrease in the lightweight concrete density and change mechanical properties such as compressive strength. Therefore, there is much experimental research has been conducted to add different material types that can improve lightweight concrete compressive strength while maintaining low density. In this review, the effect of various additions such as steel fiber, product waste materials, and nano-materials on the lightweight concrete compressive strength and density have been explained. The various effects of these additive materials on lightweight concrete properties, some additives lead to improving the properties of lightweight concrete, while other materials lead to a decrease in those properties, and this depends on the type and amount of material additive, the method lightweight concrete manufacturing, and their mixture composition.

Immobilization enhancement of heavy metals in lightweight aggregate by component regulation of multi-source solid waste

Integrated recycling of solid waste containing heavy metals is a critical environmental challenge. In this study, a green solution to reduce heavy metal leaching from solid waste is demonstrated by combining contaminated soil, industrial sludge and lithium slag in pairs to produce lightweight aggregates (LWAs). The physical properties and heavy metal leaching behavior of LWA samples were systematically investigated and characterized. The results showed that industrial sludge reduced the density and water absorption of LWA, while the high content of lithium slag was detrimental to the physical properties. LWA containing 80% contaminated soil and 20% lithium slag had the lowest particle density of 1.47 g/cm3 due to the hollow structure caused by the low viscosity and violent generation of SO2. LWAs with lithium slag leached excessive Cu and Cr relatively, while heavy metals were immobilized well in LWAs with contaminated soil and industrial sludge as the main components. Because the flux components of industrial sludge could enhance the encapsulation of heavy metals by glass phase. In addition, the co-immobilization of multiple heavy metals was observed in the spinel phase. This study provides an efficient and safe method for the synergistic recycling of solid waste.

Influence of kiln type on the production of lightweight aggregates

Influence of kiln type on the production of lightweight aggregates

Seawater-Mixed Lightweight Aggregate Concretes with Dune Sand, Waste Glass and Nanosilica: Experimental and Life Cycle Analysis

The use of alternative and locally available materials is encouraged in the construction industry to improve its sustainability. Desert regions with shortages in freshwater and river sand as fine aggregates in concrete have to search for alternative materials such as seawater, dune sand, and waste glass powder to produce lightweight concretes. The potential negative effects of adding these alternative materials can be reduced by adding nanosilica to the cementitious system at very low quantities. This study evaluates the feasibility of using these alternative materials and nanosilica (NS) in producing lightweight aggregate concretes (LWACs). A systematic study was carried out to understand the synergistic effect of nanosilica and seawater in improving the hydration characteristics of the developed cementitious systems. Also, the effect of these alternative materials on the fresh properties of the cementitious system was assessed by slump flow tests. The evolution of compressive strength at early ages was investigated after 2, 7, and 28 days of moist curing and an improvement in the strength development in concretes with seawater was observed. Furthermore, the integrity of the developed LWACs was analyzed using oven-dry density, thermal conductivity, water porosity and shrinkage measurements. Moreover, the capillary porosity and sorptivity measurements revealed the denser microstructure in the nano-modified seawater lightweight concretes. In the end, the life-cycle assessment study calculated the benefit of alternative materials in terms of carbon footprint and water consumption. As an outcome, a sustainable solution for producing LWACs containing seawater, dune sand or glass powder was proposed.

A study of characteristics of man-made lightweight aggregate and lightweight concrete made from expanded polystyrene (eps) and cement mortar

Abstract This research investigated the feasibility of using waste-expanded polystyrene (EPS) and mortar to produce lightweight aggregate (LWA). The EPS extracted from the leftover backing waste was crushed into beads using an electric grinder and mixed in three different proportions with two types of mortars (with and without a superplasticizer). Physical property tests such as loose bulk density and water absorption were carried out for the LWA. Also, the compressive strength of the manufactured lightweight aggregate concrete (LWAC) was determined, and failure modes were discussed. The results indicate that using the EPS is effective for LWA. The loose bulk density is obtained at a range from 588 to 790 kg/m 3 790\hspace{0.33em}{\text{kg/m}}^{3} , which meets the requirements of the American society for testing and materials C330 specification of LWA. For water absorption, the value obtained ranges from 6.45 to 14.05%, slightly higher than the normal aggregate due to the voids in the LWA. When using LWA containing a superplasticizer to produce LWAC, the compressive strength was higher than the concrete with LWA without a superplasticizer. The highest compressive strength for LWAC was 21 MPa.

The effect of class F fly ash on the geopolymerization and compressive strength of lightweight aggregates made from alkali-activated mine tailings

Lightweight aggregates (LWAs) produced using alkaline activation of aluminosilicate-rich mine tailings (MTs) are viable substitutes for natural lightweight aggregates used in construction and building industry. However, most pure MTs do not contain adequate quantities of amorphous aluminosilicates to make geopolymerization feasible without adjusting the Si:Al ratio through the incorporation of amorphous aluminosilicates or other aluminum/silicon source materials. A comprehensive exploration of the production of LWAs using MTs in conjunction with reactive aluminosilicates has not yet been thoroughly investigated. In this study, class F fly ash (FA) was used as an amorphous supplement to adjust the Si:Al ratio, leading to improved geopolymerization of LWAs. The mixtures of MTs and FA were pelletized using a disk granulator machine by spraying 10 M NaOH with a liquid-to-solid ratio (L/S) of 0.25. The effects of different concentrations of FA (10%, 15%, 20%, 25%, and 30%) on the chemical, physical, mechanical, mineralogical, and morphological features of the resulting LWAs were examined. The results indicate that increasing the FA content of LWAs decreased their water absorption and porosity while increasing their bulk density and compressive strength without affecting their specific gravity. The scanning electron microscope (SEM-EDS) images show that by increasing the FA content, especially at 20% and upward, homogeneous geopolymerization was achieved in the specimens and the Si:Al ratio in LWAs with 20% or more FA was greater than three, indicating a greater likelihood of geopolymer backbone formation. The results of x-ray diffraction spectrometry (XRD) and Fourier-transform infrared spectroscopy (FTIR) showed that the alkali activation process resulted in the disappearance of the gypsum phase originally available in the MTs and the appearance of sodalite (sodium carbonate) in the LWAs. Future research should utilize the Life Cycle Assessment (LCA) methodology to evaluate environmental impact and should explore advanced additives/modifiers for improved mechanical characteristics and manufacturability to increase potential construction applications.

Potential of Waste Material as Coarse Aggregates for Lightweight Concrete Production: A Sustainable Approach

In recent times, there has been growing interest in utilizing waste materials as coarse lightweight aggregates in the production of lightweight aggregate concrete. This approach has been gaining momentum as it has the potential to address the environmental concerns that come with conventional construction practices. The objective of this review paper is to evaluate the viability and potential of waste materials as coarse lightweight aggregates for producing lightweight aggregate concrete. This paper reviews the current research on various types of waste materials, including waste plastic, recycled concrete aggregate, slag, fly ash, and expanded polystyrene, as potential candidates for coarse lightweight aggregates. The paper highlights the properties and characteristics of these waste materials and their suitability for use as coarse lightweight aggregates. Additionally, the evaluation explores the mechanical characteristics of lightweight aggregate concrete that is generated using waste materials as coarse lightweight aggregates. Specifically, it compares the compressive strength, splitting tensile strength, flexural strength, and modulus of elasticity of lightweight aggregate concrete that includes waste materials with those of typical concrete. Furthermore, the paper discusses the sustainability benefits of using waste materials as coarse lightweight aggregates. By using waste materials in construction, not only are resources conserved, but waste is also diverted from landfills, reducing the negative impact on the environment. In conclusion, this review paper demonstrates that the use of waste material as coarse lightweight aggregate for lightweight aggregate concrete production is a viable and sustainable approach. The application of waste materials as coarse lightweight aggregates in lightweight aggregate concrete demonstrates mechanical characteristics that are similar to traditional concrete. Moreover, utilizing waste materials in this manner provides environmental advantages. This study offers valuable insights into the implementation of waste materials in construction, and it emphasizes the possibility of further exploration and advancement in this domain. For this review, a total of 15 articles were analyzed, with publication dates ranging from 2005 to 2021. The study contributes to several Sustainable Development Goals (SDG 9/11/12/13) set by the United Nations such as providing insights into the role of industry, innovation, infrastructure, sustainable cities, responsible consumption, production practices, and climate action.

Efficient utilization of multi-source solid waste to prepare the novel core-shell structured lightweight aggregates and its immobilization for volatile heavy metals

Owing to the low utilization rate, the overall amount of solid waste has been increasing every year. However, some solid waste contains hazardous heavy metals, especially volatile ones. If being managed improperly, they will cause severe threats to the environment and the health of humans. This work aims to safely utilize solid waste (contaminated soil, lithium slag, sewage sludge, and waste glass powder) to prepare the novel core-shell structured lightweight aggregate (CSLWA). An optimized ratio of CSLWA materials was designed based on Riley's Ternary Diagram. The physico-mechanical properties, microstructures, and phase compositions of the prepared CSLWA were analyzed, and the immobilization ability of CSLWA to volatile heavy metals was evaluated. The experimental results showed that the CSLWA produced from multi-source solid waste, possessing a density of 1.44–1.67 g/cm3 and a compressive strength of 8.1–9.73 MPa, showed excellent properties. Moreover, the volatilization rate of volatile heavy metals was reduced by at least 87% because of the shell of CSLWA. The leaching test results further demonstrated that the Zn and Cd could be effectively solidified in the CSLWA. This work thus provides an eco-friendlier approach to converting hazardous and industrial solid waste into high value-added materials and contributes to a more sustainable technique for producing lightweight aggregates.