Production Of Artificial Aggregates Research Articles

Review on Advancements in the Production of Artificial Aggregates from Industrial Byproducts: A Sustainable Solution for Infrastructure Development

This review paper explores the burgeoning interest in artificial aggregates as sustainable alternatives to traditional construction materials, driven by concerns over resource depletion and environmental degradation. It comprehensively examines recent advancements, challenges, and future prospects in this field. Beginning with an overview of the imperative for alternative aggregates in construction, the paper discusses various types of artificial aggregates sourced from industrial by-products, recycled materials, and innovative manufacturing processes. It delves into their mechanical, physical, and environmental properties, contrasting them with natural aggregates, and evaluates the impact of production techniques like sintering, foaming, and chemical activation on their performance. Environmental sustainability aspects, including carbon footprint reduction and waste management, are rigorously analyzed, underscoring the potential of artificial aggregates to mitigate ecological impacts associated with conventional extraction and processing methods. Addressing hurdles to widespread adoption, such as technological barriers and economic viability, the review proposes strategies for overcoming these challenges and outlines future research directions to optimize artificial aggregates' properties and applications. In conclusion, this review offers valuable insights into the state-of-the-art developments in artificial aggregate technology, highlighting their pivotal role in advancing sustainability and resilience within the construction sector. Key Word: Artificial aggregates, Sustainable construction materials, Environmental impact, Recycling, Waste utilization.

The production of artificial aggregates with flue gas desulfurization ash: Development of a novel carbonation route

Using solid waste to absorb CO2 in the production of aggregates is an efficient approach, which can reduce CO2 emissions and improve the recycling of solid waste. However, a challenge lies in addressing the cracking issues of aggregates prepared by the calcium oxide (CaO) system, particularly those containing flue gas desulfurizati ash (FGDA), during the direct carbonation process. This study presents a novel carbonation route combining air curing (AC) and CO2 curing (CC) under industrial flue gas conditions that effectively resolves the cracking problem of FGDA. The results show that under the optimized conditions (6 % CaO, 2 % Na2SO4, 3 days of AC, and 12 h of CC), the FGDA can be used to produce the flue gas desulfurization ash artificial aggregate (FGDAA), with pellet strength and water absorption of 3.11 MPa and 16.87 %, respectively. The CaCO3 forms during the carbonation, which improves pellet strength and decreases water absorption, except for the high CaO content (8 %) or AC age over 3 days. This shows that this method has clear requirements for the CaO content in solid waste. By developing a low-cost and energy-efficient carbonation process, FGDAA offers significant advantages in the construction field. With a production cost of only $5.14 per ton and a shorter curing time, it is environmentally sustainable and has a low global warming potential of 52.68 kg CO2-Eq. Although its compressive strength of 32.52 MPa is slightly lower than some conventional aggregates, FGDAA is still suited for applications such as road construction and mine backfill.

Producing of alkali-activated artificial aggregates by pelletization of fly ash, slag, and seashell powder

In the construction sector, the material supply chain of aggregates is frequently disturbed due to seasonal unavailability, quarrying issues, and environmental norms. The production of artificial aggregates has gained prominence to conserve natural resources and promote green construction practices. The current study encompasses the production of alkali-activated artificial aggregates through cold-bonding pelletization technique using three different raw materials, including fly ash, ground granulated blast furnace slag, and seashell powder in binary and ternary blending combinations. The cold bonding was achieved by alkali activation of binders with the aid of a sodium-based alkaline solution, which acts as an activator and hydrating liquid. The fresh artificial aggregates were subjected to surface treatment using the same alkaline solution to enhance their characteristics. The mechanical properties of artificial aggregates confirmed their potential as a substitute for conventional aggregates by exhibiting crushing and impact values of 18.19–27.53% and 12.06–18.85%, respectively. The microstructural and mineralogical characteristics depicted dense microstructure and compact matrix. The study concludes that artificial aggregates can effectively replace natural coarse aggregate in making structural concrete with many economic, environmental, and technical advantages.

Upcycling of demolition material from concrete and brick for the production of cold-bound, alkali-activated lightweight aggregates

This paper deals with the production of artificial aggregates based on the recycled fine fraction (≤ 4 mm) from construction demolition waste. Concrete powder, brick powder and their combination were used to produce aggregates through pelletisation using sodium silicate solution as an activator. For all aggregates, efficiency, bulk crushing resistance, particle density, water absorption and loose bulk density were evaluated. The bulk crushing resistance was evaluated for samples cured with different methods. A higher proportion of concrete powder increased the strength and density. The aggregates were successfully formed with bulk crushing resistance and particle densities in the range of lightweight aggregates.Graphical abstract

Municipal woody biomass waste ash-based cold-bonded artificial lightweight aggregate produced by one-part alkali-activation method

The rapid industrialization process has resulted in the overconsumption of natural aggregates, leading to significant environmental concerns. Additionally, the disposal of municipal woody biomass ash (MWBA) has caused the depletion of land and further environmental pollution. Hence, production of artificial aggregate using MWBA is of great interest, as it reduces the consumption of natural aggregates and landfill area while recycling the MWBA. The main objective of this study is to determine the optimal mix design that can produce artificial aggregates with satisfactory strength and lightweight properties while maximizing the utilization of MWBA. Following that, the effects of different alkaline contents (9%, 12%, 15%) and ground granulated blast-furnace slag (GGBS) contents (0%, 10%, 20%, 30%) on the physical properties of the MWBA-based AAAs were investigated. Additionally, the pore distribution, phase and elemental compositions of the aggregates were examined to ascertain the mechanism of alkali-activation and strength development of the MWBA-based AAAs. The main result showed that at 15% Na2SiO3·5H2O content, increasing the GGBS content from 0% to 30% resulted in an increase in the loose bulk density and crushing strength of MWBA-based AAAs from 817 kg/m3 to 950 kg/m3 and from 0.84 MPa to 2.25 MPa, respectively, while decreasing the water absorption from 24.0% to 12.5%. This is due to the denser matrix observed, attributed to the GGBS addition, which enhances the effect of alkali-activation. Additionally, a new amorphous phase, namely C-A-S-H, was identified. The Si/Al ratio decreased with the GGBS content, resulting in more C-A-S-H gel formation and a denser microstructure with better performance for the AAAs. The novelty of this study is to demonstrate the feasibility of using MWBA in producing AAAs through a cold-bonded one-part alkali activation method. This method presents an alternative to natural aggregates that can be utilized in concrete.

Mechanical Properties of Concrete Produced by Light Cement-Based Aggregates

There is great growing concern regarding the environmental impact of the building and construction industry. Aggregate, one of the most crucial ingredients of concrete, is among the concerns in this regard. There will be a steady increase in demand for aggregates in the near future, but limited natural reserves will not be able to respond to this demand due to the risk of depletion. This current situation is forcing researchers to conduct new and artificial material production techniques that keep the resources within the allowed boundaries. Artificial aggregate production is one of the new methods for sustainable, environmentally friendly material production. The mechanical and environmental properties of lightweight concrete produced via artificial aggregates in different ratios were investigated in this study. Fly ash (FA), ground granulated blast-furnace slag (GGBFS), and quartz powder (QP) were utilized in the production of artificial lightweight aggregate (LWA) by using a special technique known as cold-bonding pelletization. The prepared concrete samples with the artificial aggregates were subjected to compressive, tensile, flexural, and bonding tests. The test results demonstrated that the bonding, tensile, and compressive strength values of lightweight concrete with a 20% GGBFS coarse aggregate replacement ratio of lightweight aggregates increased by 11%, 12%, and 30%, respectively. Moreover, it has been observed that a 41% increase in compressive strength is possible with a 40% QP coarse aggregate replacement ratio of lightweight aggregates. Finally, in addition to significantly impacting the mechanical properties of the lightweight concrete produced via artificial lightweight aggregates, we demonstrated that it is possible to control and reduce the harmful environmental effects of waste materials, such as FA, GGBFS, and QP in the present study.

Cold Bonded and Low Temperature Sintered Artificial Aggregate Production by Using Waste Materials

The paper presented the possibility of manufacturing aggregates from industrial waste materials and their ecological benefits. The cold bonding process to create aggregates uses substantially less energy than the sintering technique. This study deals with the outcomes of an experimental assessment of the physical and strength properties of environment-friendly cold-bonded and sintered fly ash (FA), ground granulated blast furnace slag (GGBFS), and quartz (Q) lightweight aggregates. The waste materials were mixed with Portland cement at 20–50 percent by weight to make artificial lightweight aggregates. To investigate the impacts of temperature on the physical properties, such as crushing strength, density, and water absorption, the pellets were sintered at 300, 600, and 900 °C for an hour. The results show that all the produced aggregates might be categorized as lightweight aggregates due to the combinations' average densities being less than 2,000 kg/m3. The fly ash lightweight aggregates had higher density and crushing strength, as well as decreased water absorption. The density and crushing strength improved somewhat by raising the temperature, while the water absorption decreased with increased temperature. In this research, the most efficient mineral admixture concentration has been evaluated as 50 percent for both fly ash and ground granulated blast furnace slag and 30 percent for quartz for cold-bonded pellets. Furthermore, superior physical qualities have been reported at the 900 °C sintering temperature.

Production of artificial aggregates by granulation and carbonation of recycled concrete fines

There is a growing need to find ways to reuse fine concrete waste from the construction industry. In this study, recycled concrete fines were granulated and used as lightweight aggregates. Ladle slag, a steel industry residue, was used as a co-binder in different ratios (0, 10, 20, and 30%). The materials were blended and granulated, and then the granules were cured in three conditions: ambient condition, humidity chamber, and carbonation chamber. The results showed that the ladle slag content of 30% cured in a humidity chamber produced the strongest granules, with a crushing strength of 127 N, which was 135% greater than a commercial lightweight aggregate. The granules generally had satisfactory density and water absorption with a higher ladle slag content. Carbonation increased the granule strength with a low ladle slag content and decreased the granules’ water absorption. The improved physical and mechanical properties of carbonated granules are attributed to the formation of calcium carbonate during the carbonation process. The granules produced in this study show good potential for use as lightweight aggregates in the construction industry.Graphical abstract

Artificial Lightweight Aggregates Made from Pozzolanic Material: A Review on the Method, Physical and Mechanical Properties, Thermal and Microstructure.

As the demand for nonrenewable natural resources, such as aggregate, is increasing worldwide, new production of artificial aggregate should be developed. Artificial lightweight aggregate can bring advantages to the construction field due to its lower density, thus reducing the dead load applied to the structural elements. In addition, application of artificial lightweight aggregate in lightweight concrete will produce lower thermal conductivity. However, the production of artificial lightweight aggregate is still limited. Production of artificial lightweight aggregate incorporating waste materials or pozzolanic materials is advantageous and beneficial in terms of being environmentally friendly, as well as lowering carbon dioxide emissions. Moreover, additives, such as geopolymer, have been introduced as one of the alternative construction materials that have been proven to have excellent properties. Thus, this paper will review the production of artificial lightweight aggregate through various methods, including sintering, cold bonding, and autoclaving. The significant properties of artificial lightweight aggregate, including physical and mechanical properties, such as water absorption, crushing strength, and impact value, are reviewed. The properties of concrete, including thermal properties, that utilized artificial lightweight aggregate were also briefly reviewed to highlight the advantages of artificial lightweight aggregate.

Use of CO2-active BOFS binder in the production of artificial aggregates with waste concrete powder

This study investigated the possibility of using CO2-active basic oxygen furnace slag (BOFS) as binder for the production of AAs with low-value waste concrete powder (WCP). The effects of curing methods (CO2 and natural air curing) and BOFS dosages on the AAs properties were analyzed. The results showed that BOFS could be successfully used as binder to produce WCP granulated AAs, with attained loose bulk density, crushing strength and water absorption of 1220 kg/m3, 3.6 MPa and 8.6%, respectively. Increasing the BOFS dosage enhanced the crushing strength and decreased the water absorption of AAs. CO2 curing resulted in C-S-H and CaCO3 formation, which contributed to further improving the crushing strength by 30%-109% and decreasing the water absorption by 12–22%. From an environmental perspective, the produced BOFS-WCP granulated AAs activated with CO2 were able to reduce global warming potential by 25% compared with conventional AAs containing 20 wt.% cement as binder.

COMPARISON OF PHYSICAL AND MECHANICAL PROPERTIES OF COLD BONDED AND SINTERED LIGHTWEIGHT ARTIFICIAL AGGREGATES

Artificial aggregate production which has the highest volume ingredient in concrete has gained great importance in recent years. The fundemental cause for this is to reduce harmful environmental impacts. In addition, artificial aggregates are tried to be used to improve some important features of concrete. In the present study, the physical and mechanical properties of two types of artificial aggregates produced by cold bonding and sintering methods were compared. For this purpose, artificial aggregates pelletized and sintered at different temperatures were produced by using fly ash at different percentages. Dry density, specific density, water absorption and crushing strength tests were carried out to investigate the physical and mechanical properties of the produced artificial aggregates. The results showed that the bulk density and density values of sintered Fly ash artificial aggregates have a trend of rising but the water absorption values have a decreasing trend. Moreover the highest crushed strength value was observed in samples sintered at 900 oC.

The Effects of Various Concentrations of NaOH on the Inter-Particle Gelation of a Fly Ash Geopolymer Aggregate.

Aggregates can be categorized into natural and artificial aggregates. Preserving natural resources is crucial to ensuring the constant supply of natural aggregates. In order to preserve these natural resources, the production of artificial aggregates is beginning to gain the attention of researchers worldwide. One of the methods involves using geopolymer technology. On this basis, this current research focuses on the inter-particle effect on the properties of fly ash geopolymer aggregates with different molarities of sodium hydroxide (NaOH). The effects of synthesis parameters (6, 8, 10, 12, and 14 M) on the mechanical and microstructural properties of the fly ash geopolymer aggregate were studied. The fly ash geopolymer aggregate was palletized manually by using a hand to form a sphere-shaped aggregate where the ratio of NaOH/Na2SiO3 used was constant at 2.5. The results indicated that the NaOH molarity has a significant effect on the impact strength of a fly ash geopolymer aggregate. The highest aggregate impact value (AIV) was obtained for samples with 6 M NaOH molarity (26.95%), indicating the lowest strength among other molarities studied and the lowest density of 2150 kg/m3. The low concentration of sodium hydroxide in the alkali activator solution resulted in the dissolution of fly ash being limited; thus, the inter-particle volume cannot be fully filled by the precipitated gels.

Recycling Fly Ash from MSWI for Artificial Aggregate Production for Concrete

This study focusses on the development of new lightweight aggregate (LWA) that eventually will have comparable properties with existing natural aggregate which is granite. The main objectives of this study is to examine potential use of recycled municipal solid waste incineration (MSWI) ash as raw material in LWA production with a method of cold-bonded palletization process. The ashes are collected from Cameron Highland Incineration Plant, Malaysia that can be divided into bottom ash (BA) and fly ash (FA). This study uses FA as partial raw material to substitute the Ordinary Portland Cement (OPC). The properties FA are studied by means of X-Ray Fluorescence (XRF). The LWA is fly ash lightweight aggregate (FALA). The production of LWA is based on cold-bonded palletization technique. FALA have experienced two different curing process for 28 days namely room-room (RR) and room-water (RW) curing conditions. The percentage of FA used in this study is 10%, 20%, 30%, 40% and 50% of cement replacement and the size is fixed between 10 mm to 20 mm with circular shape. The properties of FALA produced in this study is examined including loose bulk density, and aggregate impact value (AIV). Other physical properties including colour and texture are also being investigated. From the results of LWA it is clearly seen that 20% FA were the best percentage of ash used to produce good quality LWA. Loose bulk density of FALA selected is 716.72 kg/m3 and AIV 13.80%.

Recent advances in artificial aggregate production

Artificial aggregates (AAs) are man-made construction material, and the properties greatly depend on its manufacturing process (e.g. granulation and hardening) and the raw materials (usually different source of wastes) used. This paper reviews the granulation process and suitable raw materials for each hardening method. Hardening methods including sintering, cold-bonding, accelerated carbonation and alkaline activation can significantly impact the final properties of the produced AAs. In general, finer material fractions are required for granulation to increase the pelletization efficiency and strength of AAs. Among the hardening methods, sintering usually gives a better physical and mechanical properties of AAs with a condition that SiO 2 /∑flux ratio of raw materials used should exceed 2, and (SiO 2 +Al 2 O 3 )/∑flux ratio of between 3.5 and 10. The cold-bonded method requires hydraulic raw materials and is restricted by a longer curing time, but this can be solved by introducing autoclaving or alkaline activation approaches to accelerate the strength gain. Post curing of AAs under a strongly alkaline solution can also effectively reduce the water absorption of aggregate by nearly 90%. The accelerated carbonation technique seems to be a green and more sustainable hardening method, as it can turn less valuable waste into strength bearing calcite and permanently store the waste CO 2 through mineral carbonation. In terms of leachability, sintering can stabilize most heavy metals, while other hardening methods such as cold bonding and carbonation are only effective for stabilizing certain heavy metals. • Recent advances in manufacturing technology of artificial aggregate were reviewed. • Sintered aggregates usually show low density and good physical properties. • Accelerated carbonation is a green and carbon negative approach with excellent CO 2 uptake. • Most artificial aggregates are classified as lightweight aggregate and their strength is below 10 MPa. • Sintering technology is the most effective method to limit the leaching of heavy metals.

Strength enhancement of artificial aggregate prepared with waste concrete powder and its impact on concrete properties

Waste concrete powder (WCP), a byproduct generated in the production of recycled concrete aggregates, is proposed as the main material for manufacturing artificial aggregate (WCPA) through cold-bonding pelletization. The addition of cement, ground granulated blast furnace slag and calcium hydroxide as well as the application of CO2 curing are integrated with the purpose of strength enhancement. Experimental results indicate that aggregate strength increases in proportion with cement and slag dosages while calcium hydroxide content reaches the optimum at 3%. By optimizing mix proportion, the aggregate obtains the highest strength of 3.0 MPa and the lowest water absorption of 6.3%. In addition, when it is incorporated in concrete, WCPA shows stronger interactions with cement matrix as compared with natural aggregate and ceramsite since the width of interfacial transition zone is only 30 μm as compared to 60 μm in the reference groups. The compressive strength of WCPA concrete reaches over 30 MPa, suggesting the viability of WCPA in many civil engineering applications; however, it is found that the drying shrinkage tends to increase by up to 47%. Overall, this study contributes to the establishment of waste to resources chain with regards to the concrete industry through the green production of artificial aggregate with WCP.

Production of artificial aggregates from steel-making slag: Influences of accelerated carbonation during granulation and/or post-curing

Accelerated carbonation is envisaged to be a significant curing method for the development of cement-free artificial aggregates. In this paper, two accelerated carbonation approaches, applied during granulation and post-curing respectively, are investigated for their influences on the properties of the aggregates made by 100 % basic oxygen furnace slag (BOFS). The result shows that carbonation during post-curing significantly enhances the overall properties of the granulated BOFS, such as increasing the strength by 220 %. In contrast, synchronized carbonation applied simultaneously during the granulation process yields considerable property degradation, though a CO2 uptake of ∼16 % can be achieved. It contradicts with the common understanding that carbonation is beneficial to the strength enhancement. This is because synchronized carbonation of BOFS is found to release extensive heat and vaporize a great amount of bridging water for agglomeration, thus causing a very loose structure. In general, synchronized and post-granulation carbonation result in two notably different influences on the properties of BOFS aggregates. The integrated approach of granulation and post-granulation carbonation creates a promising cement-free alternative to the local natural aggregates; while the synchronized carbonation shows significant potential for the production of lightweight aggregates.

Experimental Study on Manufacturing Artificial Aggregate from Various Industrial Waste and Its Applications in Concrete – A Critical Review

The aim of this paper is to examine the production of artificial aggregate and its potential applications in concrete. The waste materials from industrial are one of the concern issues in sustainable development. Recycle and reuse these waste materials is one of the strategies to produce the better sustainable system. One of the methods is by using the waste materials to produce artificial aggregate by palatalization. There are wide applications of artificial aggregate, for instance construction, agriculture, geotechnical fill, waste water, drainage and many more. Physical properties such as bulk density, specific gravity, unit weight, porosity and water absorption are important criteria. The performance of the artificial aggregate varies, depending on the application.

Obtaining an Artificial Aggregate from Cement-Asbestos Waste by the Melting Technique in an Arc-Resistance Furnace

Nowadays, asbestos waste still remains a serious problem. Due to the carcinogenic properties of asbestos, which are related to its fibrous structure, the exposure to asbestos mineral and asbestos-containing materials (ACM) causes dangerous health effects. This problem can be solved by recycling techniques, which allow the re-use of neutralized asbestos waste, instead of disposing it in special landfills. The article presents the results of research aimed at investigating the possibility of obtaining aggregates from asbestos waste by the fusion process in the electric arc-resistance process. A mixture of ACM with selected fluxes was were melted and then cast to form a grain of aggregates. The chemical composition of the material was determined before and after the melting process. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were applied to evaluate the effects of the fusion process. The main properties of the obtained aggregate were also measured. The results confirmed that the fibrous structure of asbestos was destroyed in the obtained material, which can be successfully used for the production of artificial aggregates.

Evaluation of the influence of aggregate type on selected properties of epoxy mortars

Aggregates, or granular materials, are currently one of the most sought-after construction materials. Natural aggregate deposits are quite common in the world, but their widespread consumption and progressive environmental degradation forces many countries to take measures to reduce the depletion of natural resources. One of the solutions is the use of alternative aggregates. The use of this type of aggregates enables further minimization of the volume of wastes and their adverse impact on the environment and the neutralisation of the remaining waste by, among others, production of artificial aggregates. Forecasts for the future assume a reduction in the production of artificial aggregates, brought about by the production of alternative aggregates from recycling. Many research centres around the world conduct research on the assessment of the effect of various aggregates on the properties of concrete and mortar. This article compares selected properties, i.e. the flexural and compressive strength and bulk density of epoxy mortars, in which the natural aggregate has been partially replaced by perlite, expanded clay and rubber waste pellets. The type of filler used differentiates the mortar characteristics recorded. The tested properties of composites indicate the possibility of their use in construction industry.

Properties of cold-bonded lightweight artificial aggregate containing bottom ash with different curing regime

Cold-bonded pelletizing technique is frequently used in aggregate manufacturing process as it can minimise the energy consumption. It has contributed to both economical and environmental advantages because it helps to reduce the gas emissions problems. Bottom ash collected from municipal solid waste incineration (MSWI) plant was selected as raw material in this study and was utilised as a partial replacement for cement for artificial aggregate production. Several percentage of ash replacement was selected ranged from 10 to 50%. Aggregate pellets were subjected to different types of curing condition which is room-water (RW), room-room (RR), oven-room (OR) and oven-water (OW) condition. Properties of aggregate pellets were examined to obtain its density, water absorption, aggregate impact value (AIV) and specific gravity (SG). The results indicated that the most efficient curing regime is by exposing the aggregate in RW condition. The optimum aggregate was selected at 20% where it has satisfied the required density of 739.5kg/m3, and classified as strong aggregate with AIV 14. However, the water absorption of aggregate increased proportionately with the increment of ash content.