Synthetic Aggregates Research Articles

Geopolymer-Based Artificial Aggregates: A Review on Methods of Producing, Properties, and Improving Techniques.

The depletion of aggregate-related natural resources is the primary concern of all researchers globally. Recent studies emphasize the significance of recycling and reusing various types of natural or by-product material waste from industry as a result of the building industry’s rising demand for aggregate as the primary component in concrete production. It has been demonstrated that the geopolymer system has exceptional features, such as high strength, superior durability, and greater resistance to fire exposure, making it a viable alternative to ordinary Portland Cement (OPC) concrete. This study will examine the present method utilized to generate artificial aggregate-based geopolymers, including their physical and mechanical properties, as well as their characterization. The production process of geopolymer derived from synthetic aggregates will be highlighted. In conjunction with the bonding of aggregates and the cement matrix, the interfacial transition zone (ITZ) is highlighted in this work as an additional important property to be researched in the future. It will be discussed how to improve the properties of geopolymers based on artificial aggregates. It has been demonstrated that cold bonding provides superior qualities for artificial aggregate while conserving energy during production. The creation of ITZ has a significant impact on the bonding strength between artificial aggregates and the cement matrix. Additionally, improvement strategies demonstrate viable methods for enhancing the quality of manufactured aggregates. In addition, other recommendations are discussed in this study for future work.

Paving roads with recycled plastics: Microplastic pollution or eco-friendly solution?

Although plastic-modified roads are a promising approach to reducing the amount of landfilled and incinerated plastic and improving asphalt pavement performance, the contribution of plastic-modified roads to microplastic pollution is unknown. This study aimed to develop a new abrasion procedure to quantify the release of microplastics from recycled plastic-modified asphalt depending on environmental factors, the type and content of plastic used, and the incorporation method in bitumen/asphalt. A Wet Track Abrasion machine was used to simulate road traffic abrasion on a plastic-modified asphalt sample, and a novel microplastic extraction procedure was designed to extract the generated microplastics. Incorporating recycled plastic as a polymer modifier in the bitumen matrix resulted in an early release of microplastics compared to its addition as a synthetic aggregate substitute in the asphalt mix. Cold temperatures and low pH values favoured the generation of microplastics from plastic-modified asphalt. Due to the lack of universal thresholds for the release of microplastics into the environment, environmental agencies and local authorities could benefit from this novel laboratory-based microplastic assessment procedure to foster the sustainable use of recycled plastic in roads.

Recycled plastics as synthetic coarse and fine asphalt aggregate

ABSTRACT This study investigates the performance of asphalt concrete containing recycled plastics as synthetic aggregates in the dry mixing process. Two types of recycled plastics were used, namely, acrylonitrile butadiene styrene (RABS) and Polyethylene Terephthalate (RPET), based on the high-temperature properties of the plastics that make them suitable to be treated as synthetic aggregates (i.e. do not melt during the asphalt mixing phase). The proportions of recycled plastics were chosen at 0.5%, 1%, 2% and 4% of the mix mass. The laboratory testing programme includes the evaluation of compactability properties, moisture resistance, cracking resistance via IDEAL-CT test, fatigue resistance via four-point bending beam test and rutting resistance via Hamburg wheel tracking (wet) test. It was found that the inclusion of recycled plastics did affect the compactability of the mixes depending on their relative size and shape. On the other hand, the inclusion of recycled plastics did not significantly vary the moisture resistance of asphalt mixes. The cracking and rutting behaviour of asphalt mixes that incorporated recycled plastics were also modified and some benefits were observed depending on the plastic content and size.

Production and Evaluation of Synthetic Lightweight Aggregates Based on Mixture of Fluidized Bed Fly Ash and Post-Mining Residues.

This paper presents an attempt to obtain technically valuable lightweight aggregate produced from a mixture of fluidized bed fly ash and post-mining residues. The motivation to take up this study is a problem with the reasonable utilization of huge amounts of ashes produced by power plants in Poland. The ashes still produced and those stored in heaps amount to a tonnage of millions, and new ways to utilize them are desired. A real lack of mineral aggregates (non-renewable resources) demands the search for alternative materials. Using the industrial ashes as aggregates is a possible solution to the two above-mentioned problems. The aim of the study was to produce the lightweight aggregate components and to assess them in terms of their physical and mechanical properties. The components were prepared by mixing, granulation, and sintering at the temperature of over 1170 °C. Evaluation of physical parameters was based on parameters such as bulk density and water absorption. The study of mechanical properties was carried out on the basis of aggregates’ resistance to crushing. The obtained results revealed that using a mixture of the combustion and post-mining residues in the production of a lightweight aggregate is beneficial and results in the formation of a porous and durable structure. The measured resistance to the crushing of the produced aggregates varied from 5.9 MPa to 7.5 MPa. They also showed a high freeze-thaw resistance and good resistance to aggressive environments (bases, acids, salt). The registered properties indicate that the aggregates meet the basic requirements for materials used in construction and road-building. This study has a scientific and didactic value in that it describes the step-by-step process of planning and implementing the production of synthetic mineral aggregates.

Preparation and Characterization of the Functional Properties of Synthetic Aggregates from Silico-Manganese Slag.

A large number of natural aggregates are used in the field of construction materials, resulting in the exhaustion of natural aggregates. Therefore, looking for an alternative will slow down the consumption of natural aggregates. The sintering method not only consumes a lot of energy to prepare aggregates but also produces a lot of pollutants. In this study, silico-manganese (SM) slag was dried, ground into powder, and used as raw material. Solid and liquid alkaline activator methods were used to prepare SM slag non-burning aggregate (SMNA) by the cold bonding method. The effects of grinding time, amounts of solid and liquid alkaline activators, curing temperature, and the amount of added fly ash on aggregate properties were investigated. The aggregate microstructure was characterized by XRD, SEM, and FTIR methods, and the toxic leaching analysis of aggregate was performed. The results showed that with a fixed amount of liquid activator (16.2% wt.) and solid activator (15% wt.) and fly ash (20% wt.), respectively, and curing was performed at room temperature, the aggregate properties were optimal: the bulk density of 1236.6–1476.9 kg/m3 and the water absorption lower than 4.9–5.5%. The apparent density was 1973.1–2281.6 kg/m3, and the bulk crushing strength was 24.7–27.9 MPa. The XRD, SEM, and FTIR results indicated that amorphous gel could be formed from SM under an alkaline activator, improving the aggregate strength. The results of toxic leaching showed that the aggregate prepared from SM exhibited environmentally friendly characteristics. The SMNA was obtained via the simple and low-energy consumption production process, paving the new way toward large-scale utilization of SM.

Utilization of construction and demolition waste and synthetic aggregates

Construction and demolition (C&D) waste are generated during the creation of structure or building or when renewing or demolishing a current structure. C&D waste exhibits many environmental problems including diminishing landfill, increasing wastage areas, landfill contamination, and increasing energy required for waste disposal and transportation. The re-using C&D waste as an aggregate in concrete making have reduced extraction demanding and landfill pressure. The utilization of C&D as recycled concrete aggregate (RCA) alternative to natural one not only decreases environmental problems but also leads to the conservation of naturally occurring resources. On the other hand, the synthesis of an aggregate from powdered industrial solid waste was also found to have a good alternative to natural aggregate with lower specific gravity and high thermal insulation . This work have reviewed the application of C&D and synthetic aggregates for making structural and non-structural concrete. Owing to the contaminants attached on the surface of RCA, the replacement of natural aggregate with this aggregate has resulted in a significant reduction in the performance of cement concrete . Therefore, many approaches have been done to enhance the quality of RCA. Among these different methods, the carbonation and pozzolan slurry are regarded as the best methods for enhancing the properties of RCA. Synthetic aggregate could be prepared by different methods including sintering, cold bonding, and autoclaving. Lightweight aggregate synthesized by the cold-bonding method could be successfully applied to fabricate a moderate strength lightweight concrete. More research is required to evaluate the resistivity of lightweight concrete containing autoclaved lightweight aggregate. • The construction and demolition waste aggregate could be reused in concrete mixes. • Different methods were used to improve the performance of recycled aggregate. • Carbonation is the best method for improving the performance of this aggregate. • The synthetic aggregate could be also used in some types of concrete pastes.

Equation of state and sound wave velocities of fayalite at high pressures and temperatures: implications for the seismic properties of the martian mantle

Abstract. The elastic properties of a pure, synthetic fayalite aggregate were studied by coupled synchrotron X-ray diffraction and ultrasonic interferometry in a DIA-type multi-anvil press. Measurements at pressures up to about 7 GPa and temperatures up to 873 K yielded an adiabatic bulk modulus, KS0=127.2±0.3 GPa with (∂KS/∂P)T0=6.5±0.1, and a shear modulus, G0=53.3±0.4 GPa with (∂G/∂P)T0=1.25±0.05. When fixing (∂KS/∂P)T0=5.3 (after (∂KT/∂P)T0 from Nestola et al., 2011), KS0 increases to about 130 GPa. These estimates of (KS0,(∂KS/∂P)T0) follow a general linear trend, K=f(dK/dP), for fayalite. We define limited ranges for both bulk and shear moduli from previous studies, and we discuss how these variations affect seismic velocities and the determination of a mineralogical model in the context of the Mars InSight SEIS (Seismic Experiment for Interior Structure) experiment.

Characterization of physical & mechanical properties of asphalt concrete containing low- & high-density polyethylene waste as aggregates

Coarse aggregate is one of the main ingredients of asphalt concrete as it plays a vital role in the serviceability and durability of a flexible pavement. This study aimed at evaluating the effect of partially adding waste plastic aggregates in asphalt mix and studying its influence on different physical and mechanical properties. For this purpose, plastic waste was collected from landfill sites and classified into low density polyethylene (LDPE) and high-density polyethylene (HDPE), and, shredded into aggregates of desired size. Natural aggregates were replaced with these synthetic aggregates in different proportions such as 5%, 15% and 25%. Results showed that the incorporation of both types of plastic wastes reduced the density of asphalt mixture due to increase in air voids. The stability and flow values increased up to 15% partial replacement of natural aggregates with LDPE and HDPE. Similarly, LDPE-25 samples had lowest rut depth followed by HDPE-25. HDPE-15 sample showed the highest value of resilient modulus with a percentage increase of about 168.5% as compared to control sample. The dynamic modulus of asphalt also improved with plastic aggregates. However, the dynamic modulus values reduced with the increase in frequency for all study samples.

Production of Green Synthetic Lightweight Aggregate and its Utilisation in Green Concrete

Environmental sustainability faces many challenges, including the increase in the amount of plastic compared to its low recycling rate. Therefore, it is important to increase its recycling rate by using plastic waste in other applications such as aggregate and/or concrete production, its recycling rate can be increased, while reducing its negative effects and saving natural resources. A green synthetic lightweight aggregate (GSLA) containing plastic waste and additives was produced, and its physical and mechanical properties were compared with those of control aggregates. A green lightweight concrete comprising GSLAs was then developed, and their fresh, hardened and microscopic properties were investigated and compared to those of reference mixes. Findings showed that the GSLAs were light in weight, with an average specific gravity of 1.7 and less water absorption at around 0.8%; it was stiff with an average impact value of 16%. Green lightweight concrete mixes with average slump of 170 mm and density of 1900 kg/m3 were feasibly produced. Additionally, average of 28-day compressive and flexural strengths of the produced concrete was only 16% and 40% less, respectively, compared to the normal weight control mix. The SEM analysis indicated strong interlocking between the cement paste and the developed aggregates.

Generalizability Improvement of Deep Learning-Based Non-Intrusive Load Monitoring System Using Data Augmentation

Practical application of deep learning based non-intrusive load monitoring (NILM) system requires the deep neural network model to generalize on new unseen data. Existing NILM solutions are not suitable for real-world application due to their poor disaggregation accuracy on new unseen data. In order to address this problem, this paper presents a NILM algorithm that uses data augmentation to generate synthetic data for training deep convolutional neural network models for each target appliance. Proposed data augmentation technique works by combining on and off-durations of a target appliance from various datasets, and forms a unified and comprehensive synthetic aggregate and sub-meter profiles. Apart from proposed algorithm, this paper also proposes an evaluation approach that relies on total predicted energy and ground-truth energy of an appliance to provide detailed insights about total overlapping energy, missing energy and extra energy predicted by the algorithm. Comparison results on our proposed evaluation approach showed that proposed disaggregation algorithm was able to predict energy that was 60% overlapping with ground truth energy and 36% energy was extra. Overall results showed that overlapping energy was 2.5 times more, and extra-predicted energy was 60% less than state-of-the-art algorithms in unseen test cases.

Experimental & computational study on fly ash and kaolin based synthetic lightweight aggregate

The objective of this study is to manufacture environmentally-friendly synthetic lightweight aggregates that may be used in the structural lightweight concrete production. The cold-bonding pelletization process has been used in the agglomeration of the pozzolanic materials to achieve these synthetic lightweight aggregates. In this context, it was aimed to recycle the waste fly ash by employing it in the manufacturing process as the major cementitious component. According to the well-known facts reported in the literature, it is stated that the main disadvantage of the synthetic lightweight aggregate produced by applying the cold-bonding pelletization technique to the pozzolanic materials is that it has a lower strength in comparison with the natural aggregate. Therefore, in this study, the metakaolin made of high purity kaolin and calcined kaolin obtained from impure kaolin have been employed at particular contents in the synthetic lightweight aggregate manufacturing as a cementitious material to enhance the particle crushing strength. Additionally, to propose a curing condition for practical attempts, different curing conditions were designated and their influences on the characteristics of the synthetic lightweight aggregates were investigated. Three substantial features of the aggregates, specific gravity, water absorption capacity, and particle crushing strength, were measured at the end of 28-day adopted curing conditions. Observed that the incorporation of thermally treated kaolin significantly influenced the crushing strength and water absorption of the aggregates. The statistical evaluation indicated that the investigated properties of the synthetic lightweight aggregate were affected by the thermally treated kaolin content more than the kaoline type and curing regime. Utilizing the thermally treated kaolin in the synthetic aggregate manufacturing lead to a more than 40% increase in the crushing strength of the pellets in all curing regimes. Moreover, two numerical formulations having high estimation capacity have been developed to predict the crushing strength of such types of aggregates by using softcomputing techniques: gene expression programming and artificial neural networks. The R-squared values, indicating the estimation performance of the models, of approximately 0.97 and 0.98 were achieved for the numerical formulations generated by using gene expression programming and artificial neural networks techniques, respectively.

Recycling waste plastics in roads: A life-cycle assessment study using primary data

The present study investigates – from an environmental perspective – the processes that lead to the conversion of waste plastics into recycled plastic pellets to be used either as an additive (wet method) or as a replacement of natural aggregate (dry method) in the production of asphalt mixes. Data from recycling facilities in Victoria, Australia, were collected and used as the basis for a comparative life cycle assessment (LCA) study. Analyses were conducted by considering several replacement ratios of virgin material by its recycled counterpart in the so-called wet and dry method. A case study considering the production of recycled-plastic asphalt to be applied in the construction of a typical surface layer of a road in Victoria was evaluated. In general, the results show that recycling plastics as a polymer for bitumen modification and as a synthetic aggregate replacement in asphalt mixes has the potential to be environmentally advantageous compared to their virgin counterpart (i.e. virgin polymers and natural quarry aggregates).

Recycling sand-wash fines as synthetic lightweight aggregates

Local aggregate sources in Kuwait are scarce and quarrying for coarse aggregates has been completely stopped. The construction industry is now entirely dependent on imported aggregates. Research has been carried out at the Kuwait Institute for Scientific Research to explore suitable indigenous raw materials as alternative sources for the production of synthetic lightweight aggregates (LWAs). This paper presents the outcome of the investigation on LWAs made using sand-wash fines from a sand-washing plant in Kuwait, in addition to other waste materials acting as gas generating and fuelling agents such as used lube oil and municipal sewage sludge. The physical and mechanical properties of the sand-wash fines and other ingredients, and synthetic LWA products were assessed. The investigation revealed that the sand-wash fines contain all the necessary elements to enable the bloating and sintering processes. The engineering properties of concrete made with the LWAs were also tested.

Assessment of Sustainability in Agriculture of the European Union Countries

This paper aimed at evaluating the level of sustainability in agriculture in 28 member states of the European Union. The surveys were carried out based on a synthetic technique for order preference by similarity to an ideal solution (TOPSIS)-based measure. This method synthesizes factors of various nature and assigns them a synthetic aggregate measure. The analysis made it possible to develop a ranking of EU member states according to a differentiated level of measures and assign them to one of four groups characterized by different levels of sustainability in agriculture. The group of member states representing the highest level of sustainability in agriculture included two countries from Central and Eastern Europe, i.e., Slovakia and the Czech Republic. The group of countries with a greater than average level of sustainability comprised 14 member states of the European Union, including seven countries admitted to the community after 2004. The group with a low level of sustainability consisted of eight EU member states, six of them from the group of old EU member states, i.e., Ireland, Portugal, Greece, Italy, Denmark and the United Kingdom, and two new members, i.e., Romania and Slovenia. On the other hand, the lowest level of sustainability was characteristic of two “old EU” member states, i.e., The Netherlands and Belgium, and two “new EU” member states, i.e., Cyprus and Malta. The differentiated synthetic measure values showed disparities in the level of sustainability in agriculture among the member states of the European Union. They are a result of the varied level of development of this sector, production intensity and the resulting environmental impact.

Fabricación de Componentes Constructivos con la Fracción Plástica de Residuos Provenientes del Reciclado de RAEE

Los residuos de aparatos eléctricos y electrónicos (RAEE), han crecido notablemente en cantidad en los últimos años y se espera que esta tendencia continúe. La fracción plástica del desecho (FPR), constituye aproximadamente el 30% del total en peso, y no ha podido ser insertada en el circuito del reciclado, debido a la heterogeneidad de plásticos constitutivos y a la presencia de contaminantes, principalmente retardantes de llama y metales pesados, ambos tóxicos para la salud humana.Existen numerosos estudios sobre el agregado de plásticos a morteros, actuando como material de carga o fibras de refuerzo, logrando materiales con aptitud para este uso. El estudio de estos antecedentes llevó a considerar el uso de la FPR como agregado en morteros, en reemplazo total y parcial del agregado tradicional.Se desarrolló un agregado sintético (AS) mediante la estrategia del core -shell, en el cual el núcleo de plástico es recubierto con sucesivas capas de cemento y se estudió su desempeño como componente constructivo mediante ensayos de resistencia mecánica y determinación de propiedades físicas. El AS puede ser utilizado en morteros en reemplazo total y parcial de agregado fino, sin disminuir significativamente la resistencia mecánica. A pesar de los buenos resultados que se obtuvieron, con el paso del tiempo aparecen exudados amarillos en la superficie resultado de la desestabilización de los retardantes de llama en el medio básico del cemento, lo cual lo hace potencialmente peligroso para el uso en construcciones civiles. Para revertir este efecto se agregó al proceso carbón activado (CA) como aditivo estabilizante. El análisis químico mostró una muy buena estabilización de los contaminantes cuando se usa CA al 3% en peso. Para evaluar el efecto del CA con el fraguado de cemento, este trabajo presenta los resultados del uso de diferentes tipos y dosificaciones de CA.

Metamaterial Analogues of Molecular Aggregates.

Molecular aggregates are a fascinating and important class of materials, particularly in the context of optical (pigmented) materials. In nature, molecular aggregates are employed in photosynthetic light harvesting structures, while synthetic aggregates are employed in new generation molecular sensors and magnets. The roles of disorder and symmetry are vital in determining the photophysical properties of molecular aggregates, but have been hard to investigate experimentally, owing to a lack of sufficient structural control at the molecular level and the challenge of probing their optical response with molecular spatial resolution. We present a new approach using microwave analogues of molecular aggregates to study the properties of both individual meta-molecules and 1D molecular chains. We successfully replicate J- and H-aggregate behavior and demonstrate the power of our approach through the controlled introduction of structural symmetry breaking. Our results open a new area of study, combining concepts from molecular science and metamaterials.

Hydrophobic Modification of Copper Nanospheres for Incorporation into Poloxamer Micelles, Aggregated Micellar Nanocages and Supramolecular Assemblies

Background: Polymer nanogels are increasingly used for the encapsulation of nano-solids and quantum dots such as in advanced forms of drug and therapeutic isotope delivery. Objective: Unlike ex vivo application of systems in vivo application and internalization are likely to suffer from aspects of failure to ensure safety and biocompatibility. Biocompatible hydrophilic poloxamer (Pluronic F108 and F68) micelles were studied by light scattering and tensiometry. Methods: The micelles of nano-gels are synthetic heteropolymer aggregates, which are used to encapsulate drugs but in this study chemically-modified (hydrophobized) copper nano-spheres, for the purposes of demonstration for further application and medical use. Copper benzoate nano-particles (CuBzNPs) were produced by maceration and subsequently stabilized in Pluronic F108 solution was added at different concentrations. Results: The resulting particle size increase was studied by dynamic light scattering. Moderate size increase was observed at low Pluronic F108 concentrations, which indicated successful coating, but at higher F108 concentrations large size agglomerates formed. Coated copper benzoate nano-particles (CuBzNPs) were fabricated as a proof-of-principle and as a substitute for bare metal nano-particles (MNs), which were not successfully entrained in the poloxamer nano-gel. As part of the synthesis copper benzoate (CuBz) beads and their characterization through contact angle measurements were performed. Conclusion: Micelles sizes of 4 nm for F68 Pluronic at equilibrium surface tensions of 36 mNm-1 were captured in weak, 1.25 to 2.0 Pas pseudoplastic gels fabricated from hydroxypropylmethylcellulose (HPMC).

Synthetic Aggregates for the Production of Innovative Low Impact Porous Layers for Urban Pavements

According to the latest estimates, 40% of urban areas are covered by pavements. One of the most remarkable effects on the urban environment is the increase in impermeable surfaces which leads to problems related to water infiltration into the ground and the increase in wash-off volumes. The use of permeable and porous layers in urban applications for cycle lanes, footpaths and parking areas is growing in interest, increasing the potential for control and management of urban runoff. In this paper, a physical and mechanical characterization is proposed of an innovative mixture, prepared with a polymeric transparent binder for semi-porous layers with reduced contribution to the urban heat island effect. Two versions of this mixture are compared, one with just virgin and the one with artificial synthetic aggregates, produced through the alkali-activation of waste basalt powder. Results show suitable properties for both materials if compared to porous asphalt concretes in traditional pavements. Furthermore, the application of synthetic aggregates seems to be a viable solution for the production of innovative and eco-friendly mixtures, allowing the recycling of waste materials.

Rapid, Refined, and Robust Method for Expression, Purification, and Characterization of Recombinant Human Amyloid beta 1-42.

Amyloid plaques found in the brains of Alzheimer’s disease patients primarily consists of amyloid beta 1-42 (Aβ42). Commercially, Aβ42 is synthesized using high-throughput peptide synthesizers resulting in the presence of impurities and the racemization of amino acids that affects its aggregation properties. Furthermore, the repeated purchase of even a small quantity (~1 mg) of commercial Aβ42 can be expensive for academic researchers. Here, we describe a detailed methodology for robust expression of recombinant human Aβ(M1-42) in Rosetta(DE3)pLysS and BL21(DE3)pLysS competent E. coli using standard molecular biology techniques with refined and rapid one-step analytical purification techniques. The peptide is isolated and purified from transformed cells using an optimized reverse-phase high-performance liquid chromatography (HPLC) protocol with commonly available C18 columns, yielding high amounts of peptide (~15–20 mg per 1 L culture) within a short period of time. The recombinant human Aβ(M1-42) forms characteristic aggregates similar to synthetic Aβ42 aggregates as verified by western blotting and atomic force microscopy to warrant future biological use. Our rapid, refined, and robust technique produces pure recombinant human Aβ(M1-42) that may be used to synthesize chemical probes and in several downstream in vitro and in vivo assays to facilitate Alzheimer’s disease research.

Synthetic Aggregates: Their Role in the Production of Smart Infrastructures

Synthetic Aggregates: Their Role in the Production of Smart Infrastructures