Search Results (27)

This scoping review examines the distribution, sources, and characterization of atmospheric microplastics (AMPs) in Southeast Asia (SEA), following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidelines. A comprehensive search of Scopus and PubMed identified 58 relevant articles, with 16 meeting the inclusion criteria. Findings indicate high microplastic (MP) concentrations in urban centres, notably in Malaysia, Indonesia, and Thailand, a pattern driven by rapid urbanisation, industrial emissions, textile production, and insufficient waste management. Predominant polymer types include polyethylene (PE), polypropylene (PP), and polyester (PET), with fibres and black particles being the most common forms. Black particles, often linked to tire wear and vehicular emissions, underscore traffic pollution’s role in AMP distribution, while PET fibres reflect the influence of SEA’s textile industry. Geographic gaps were observed, with limited studies in countries such as Cambodia and Laos. The review highlights the need for standardised sampling and quantification methods to ensure data comparability and calls for expanded research into rural and coastal regions. Future studies should prioritise longitudinal investigations into the effects of chronic exposure on health; this is particularly relevant for nanoplastics (NPs) because of their greater potential for biological penetration. These insights form a crucial foundation for mitigating AMP pollution in SEA. Full article

Disposing of waste tyres in landfills poses significant environmental hazards, making recycling a crucial alternative. Rubberised concrete has been found to exhibit lower density and better thermal insulation performance than conventional concrete. In order to maximise the potential of thermal insulation of rubberised concrete, this study investigates the mechanical and thermal properties of foamed rubberised polypropylene fibre concrete (FRPFC). FRPFC was produced using a mix of crumb rubber (CR) granules, polypropylene fibres, and foam, targeting a density of 800 kg/m³, with CR substituting sand at varying levels. Compressive strength, flexural strength, splitting tensile strength, and thermal conductivity of FRPFC were evaluated. The results demonstrate that increasing CR granule content enhances compressive strength due to reduced porosity from lower foam usage. For instance, compressive strength improved by 55% (2.64 to 4.10 MPa) as CR granule content increased from 0% to 80%. Similarly, flexural strength and splitting tensile strength increased by 55% (1.61 MPa to 2.49 MPa) and 39% (0.41 MPa to 0.57 MPa), respectively, when CR content rose from 0% to 100% at a water-to-cement ratio of 0.50. Furthermore, thermal conductivity decreased by 34% (0.3608 W/mK to 0.2376 W/mK) when sand was fully replaced with CR granules, showcasing improved thermal insulation. Statistical analysis using ANOVA confirmed that the crumb rubber content significantly influences the mechanical and thermal properties of FRPFC, with higher CR content (80% and 100%) leading to superior performance. These findings highlight FRPFC’s potential as an environmentally sustainable and thermally efficient construction material, contributing to enhanced mechanical properties compared to conventional foamed polypropylene fibre concrete. Full article

One of the most significant challenges for 3D printing of construction elements from cementitious materials is the control of cracking caused by various contraction–shrinkage mechanisms, such as drying, chemical, plastic and autogenous shrinkage. This study addresses the effects of incorporating fine aggregates (maximum size ≤ 1.18 mm), both natural and recycled, as well as short (6 mm long) polypropylene (PP) fibres on the control of cracking in cementitious mixtures based on Portland cement. Admixtures and/or mineral additions (modifiers), such as metakaolin, micro-silica, calcium carbonate, and fine powders obtained from construction and demolition wastes were used in the mixtures. Mini-slump, flow rate and buildability tests were used to characterize the mixtures in their fresh state. Extrudability was evaluated using laboratory-scale 3D printing tests conducted with a plunger–piston extrusion system. It was demonstrated that the physical characteristics of the aggregates directly influence the extrusion capacity. Mixtures containing natural aggregates exhibited greater fluidity and lower water demand than those containing recycled aggregates. The results indicated that the maximum allowable volume of fibres was 0.75%. To evaluate the cracking susceptibility of the mixtures, both with and without reinforcement, hollow beams composed of seven layers were printed, and subsequently the elements were exposed to the outdoor natural environment and inspected for a period of 90 days. The inclusion of the PP fibres effectively prevented the occurrence of fissures and/or cracks associated with shrinkage phenomena throughout the inspection period, unlike in unreinforced mixtures, which cracked after 14 days of exposure to the environment. Full article

Modern construction is largely dependent on steel and concrete, with natural materials such as earth being significantly underutilised. Despite its sustainability and accessibility, earth is not being used to its full potential in developed countries. This study explores innovative building materials using Alhambra Formation soil (Granada, Spain) reinforced with difficult-to-recycle agricultural waste: polypropylene fibres contaminated with organic matter and leachates. Fibres were added at a ratio between 0.20 and 0.80% of the soil mass, leachates at a ratio between 4.25 and 8.50%, and lime was incorporated at 2.00% and 4.00% for specimens with higher residue content. Physico-mechanical properties, including uniaxial compressive strength and longitudinal strain, were analysed together with the microstructure. The results showed that polypropylene fibres, in comparison to the use of leachates, improved compressive strength and ductility, reaching a compressive strength of 1.76 MPa with a fibre content of 0.40%. On the other hand, this value is 7.4% lower than the reference sample without additives. The fibre-reinforced samples showed a higher porosity compared to the samples with leachates or without additives. This approach highlights the potential of agricultural waste for the development of sustainable construction materials, offering enhancements in the strength and ductility of reinforced soils. Full article

In order to limit the ever-increasing consumption of new resources for material formulations, regulations and legislation require us to move from a linear to a circular economy and to find efficient ways to recycle, reuse and recover materials. Taking into account the principles of material circularity and waste reuse, this research study aims to produce thermoplastic composites using two types of industrial waste from neighbouring companies, namely waste polypropylene (wPP) from household production and carbon-fibre-reinforced epoxy composite scrap from a pultrusion company. The industrial scrap of the carbon-fibre-reinforced epoxy composites was either machined/ground to powder (pCFRC) and used directly as a reinforcement agent or subjected to a chemical digestion process to recover the carbon fibres (rCFs). Both pCFRC and rCF, at different weight ratios, were melt-blended with wPP. Prior to melt blending, both pCFRC and rCF were analysed for morphology by scanning electron microscopy (SEM). The pCFRC powder contains epoxy resin fragments with spherical to ellipsoidal shape and carbon fibre fragments. The rCFs are clean from the matrix, but they are slightly thicker and corrugated after the matrix digestion. Further, the morphologies of wPP/pCFRC and wPP/rCF were also investigated by SEM, while the thermal behaviour, i.e., transitions and changes in crystallinity, and thermal resistance were evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. The strength of the interaction between the filler (i.e., pCFRC or rCF) and the wPP matrix and the processability of these composites were assessed by rheological studies. Finally, the mechanical properties of the systems were characterised by tensile tests, and as found, both pCFRC and rCF exert reinforcement effects, although better results were obtained using rCF. The wPP/pCFRC results are more heterogeneous than those of the wPP/rCF due to the presence of epoxy and carbon fibre fragments, and this heterogeneity could be considered responsible for the mechanical behaviour. Further, the presence of both pCFRC and rCF leads to a restriction of polymer chain mobility, which leads to an overall reduction in ductility. All the results obtained suggest that both pCFRC and rCF are good candidates as reinforcing fillers for wPP and that these complex systems could potentially be processed by injection or compression moulding. Full article

The paper presents a review of End-of-Life scenarios (EoL) (disposal, incineration, chemical, thermal and mechanical recycling) compared to the production stage of Fibre-Reinforced Polymers (FRPs) of composites regarding global warming potential. Innovative FRP manufacturing technologies (vacuum infusion, ultraviolet curved pultrusion, hot stamping, three-dimensional printing and automatic tape placement) commonly used in the shipbuilding industry were environmentally assessed. The materials, energy flows and waste discharged to the environment over the whole life cycle were collected, identified and quantified based on Life Cycle Assessment (LCA) analysis in the frame of the Fibre4Yards project. The results of LCA calculations show that waste management (the EoL scenario) contributes 5 to 39% of the total carbon footprint for FRP technologies. The highest contribution of the EoL scenario was found for technologies where polypropylene was applied, i.e., 33 and 38% of the total CO₂ emissions. Our analysis of the literature and information from industrial partners confirm that the standard and most common waste scenario for FRP materials and compounds is still incineration and landfilling. Full article

Agro-waste fibres for polymer composite reinforcement have gained increased interest in industry and academia as a more sustainable alternative to synthetic fibres. However, natural fibre composite (NFC) hygroscopicity is still an issue that needs to be solved. This work investigates how prolonged exposure to water affects the properties of the polypropylene (PP)-based injection-moulded composites reinforced with different contents of rice husk (rh) and olive pit (op) fibres. Both rh and op composites became more hydrophilic with increased fibre charge due to the affinity of cellulose and hemicellulose OH groups. Meanwhile, lignin contributes to the protection of the composites from thermo-oxidative degradation caused by water immersion. The PPrh composites had a higher saturation water content of 1.47% (20 wt.% rh) and 2.38% (30 wt.% rh) in comparison to PPop composites with an absorption of 1.13% (20 wt.% op) and 1.59% (30 wt.% op). The tensile elastic modulus has slightly increased, at the cost of the increased saturated composites’ rigidity, in composites with 30% rh and op fibre content (up to 13%) while marginally decreasing (down to 8%) in PP30%op compared to unsaturated counterparts. A similar trend was observed for the flexural modulus, enhanced up to 18%. However, rh and op composites with 30% fibre content ruptured in bending, highlighting their fragility after hydrolytic ageing. Full article

The advancement of agricultural mesh technology has contributed to its improved properties. As a result, agricultural nets are widely adopted in large-scale farming applications, for example, in cereal crop farming. However, a consequence of this increased use of agricultural nets is the accumulation of large amounts of waste. The current paper focuses on the recycling of agricultural nets used in wrapping straw bales to develop additives and fillers in cement composites. The research details an analysis of the use of waste agricultural meshes as an ingredient in cement composites. Six test series of different mixtures were conducted. In the first four series, agricultural waste was utilised as an additive in a composite comprising aggregate and cement slurry (the amounts of wasted nets were 20, 40, 60, and 80 kg/m³). In the last test series, the recyclate utilised comprised a mixture of cement slurry and waste only. The composites were subjected to standard tests and thermal resistance tests. The results showcased that that the addition of a net worsened the workability of the concrete mixture, and with increasing amounts of addition, the consistency of the mixture could change from liquid to dense plastic. The flexural strength of the composite decreased with increasing amounts of recyclate. In subsequent test series, the flexural strength value was lower than that of the control (3.93 MPa), from 7.38% (3.64 MPa) for the composite with 20 kg/m³ of recyclate to 37.66% (2.45 MPa) for the composite with of 80 kg/m³ recyclate. The flexural strength value of the net-filled composite without aggregate was very high (10.44 MPa), where the value obtained for the control composite was 62.36% lower. The results of the compressive strength test showed a decrease in this parameter with increasing amounts of additive. The value assessed for the control composite was 27.99 MPa. As expected, the composite that had no aggregate and consisted of only recycled filler had the lowest compressive strength. The value of this parameter was 13.07 MPa, and it was 53.31% lower than that of the control composite. The results of the tests of resistance to temperatures were similar to those recorded for the composites with polypropylene fibres. All composites demonstrated a significant decrease in their compressive and flexural strength after annealing. SEM imaging showed that the net fibres were closely bonded to the cement stone. Finally, it was concluded that recyclates performed best as fillers in lightweight composites with a low density, low absorption, high flexural strength, and satisfactory compressive strength. Full article

Incomplete data indicate that coal gangue is accumulated in China, with over 2000 gangue hills covering an area exceeding 200,000 mu and an annual growth rate surpassing 800 million tons. This accumulation not only signifies a substantial waste of resources but also poses a significant danger to the environment. Utilizing coal gangue as an aggregate in the production of coal-gangue concrete offers an effective avenue for coal-gangue recycling. However, compared with ordinary concrete, the strength and ductility of coal-gangue concrete require enhancement. Due to coal-gangue concrete having higher brittleness and lower deformation resistance than ordinary concrete, basalt fibre (BF) is a green, high-performance fibre that exhibits excellent bonding properties with cement-based materials, and polypropylene fibre (PF) is a flexible fibre with high deformability; thus, we determine if adding BF and PF to coal-gangue concrete can enhance its ductility and strength. In this paper, the stress–strain curve trends of different hybrid basalt–polypropylene fibre-reinforced coal-gangue concrete (HBPRGC) specimens under uniaxial compression are studied when the matrix strengths are C20 and C30. The effects of BF and PF on the mechanical and energy conversion behaviours of coal-gangue concrete are analysed. The results show that the ductile deformation of coal-gangue concrete can be markedly enhanced at a 0.1% hybrid-fibre volume content; HBPRGC-20-0.1 and HBPRGC-30-0.1 have elevations of 53.66% and 51.45% in total strain energy and 54.11% and 50% in dissipative energy, respectively. And HBPRGC-20-0.2 and HBPRGC-30-0.2 have elevations of 31.95% and 30.32% in total strain energy and −3.46% and 28.71% in dissipative energy, respectively. With hybrid-fibre volume content increased, the elastic modulus, the total strain energy, and the dissipative energy all show a downward trend. Therefore, 0.1% seems to be the optimum hybrid-fibre volume content for well-enhancing the ductility and strength of coal-gangue concrete. Finally, the damage evolution and deformation trends of coal-gangue concrete doped with fibre under uniaxial action are studied theoretically, and the constitutive model and damage evolution equation of HBPRGC are established based on Weibull theory The model and the equation are in good agreement with the experimental results. Full article

The purpose of this study was to evaluate the appropriateness of polypropylene fibres (PP) to decrease the brittleness of high-performance self-compacting concrete (HPSCC). The influence of PP fibre content on the fresh and mechanical assets of PP-fibre-reinforced HPSCC was investigated. PP fibres were applied with 0, 0.025, 0.05, 0.075, 0.125, 0.25% contents to the HPC blends with high cement replacement by ground granulated blast furnace slag (GGBS). The impact of PP fibre fraction on fresh properties of HPSCC, counting passing capability as well as filling parameters is discussed. In addition, the mechanical properties, i.e., compressive, splitting tensile, and flexural strengths, were evaluated after 7 and 28 days of specimens’ maturation in water. The higher content of PP fibres gradually reduced the HPSCC workability and improved the mechanical properties. The high performance of fresh and hardened ecological HPSCCs containing 46% GGBS instead of cement with 0.025–0.25% PP fibre content proves the great potential of using these composites in various applications in the construction industry. The advantages of the potential recycling of GGBS include, among others, the reduced use of cement in a durable material, reduced amount of waste in landfill and lower emission levels of greenhouse gases. Full article

The accelerated advancement of industrialization, urbanization, and technology produces an enormous amount of waste materials that are channelled into the environment, contaminating the soil, water and air. This exceedingly large volume of waste in the planet’s environment has made it challenging and difficult to handle; thus, it is urgent to facilitate alternative methods of waste disposal. Moreover, the consumption of concrete raw materials increases as a consequence of a sudden increase in concrete usage. In this study, printed circuit boards (PCB), cutting waste (e-waste) (0%, 5%, 10%, 15%, 20%) and recycled concrete aggregate (construction and demolition waste) (0%, 20%, 40%, 60%, 80%, 100%) replace the fine and coarse aggregate; this is utilised in the making of self-compacting concrete (SCC). To mitigate the impact of shrinkage and micro-cracks produced during loading, synthetic fibres (polypropylene fibres) (0%, 0.25%, 0.5%, 0.75%, 1%) are incorporated into the dense matrix of concrete. Based on the experiments conducted, it is concluded that the optimum percentages of e-waste, recycled aggregate and synthetic fibres are 10%, 60% and 0.5%, respectively. It is proposed to use response surface methodology for the statistical modelling of fibre-reinforced self-compacting concrete (FRSCC) ingredients, which will diminish the number of experiments conducted during optimisation. Experimental optimisation of ingredients was carried out by determining the workability properties (slump flow, L-Box, V-Funnel and Sieve test), strength properties (compressive, split tensile, flexural at 7, 14, 28 days of curing) and durability properties against chemical exposure (sulphuric and hydrochloric acid attack, sulphate attack at 29 and 90 days of immersion). In the statistical optimisation process, the central composite design (CCD) is utilised, and it is concluded that the optimum percentages of e-waste, recycled aggregate and synthetic fibres are 9.90%, 51.35% and 0.503%, respectively, as these produce a compressive strength (CS) of 47.02 MPa at the end of the 28th day of curing, whereas FRSCC created with experimentally optimised ingredients shows a strength of 46.79 MPa with the use of 60% of recycled aggregate, 10% of e-waste and 0.5% polypropylene fibre. Hence, it is observed that the CCD-optimised ingredients were the optimum dosage of ingredients based on the compressive strength values at 28 days. It is concluded that the FRSCC specimens created with CCD-optimised parameters show better resistance against loading and chemical exposure, as these show minimum weight and strength loss when compared to FRSCC with experimentally optimised parameters. Full article

This paper investigates the potential of recycling waste copper chromium and arsenic (CCA)-treated timber for use as a reinforcement material in wood–plastic composites (WPCs) produced for use in construction, including an assessment of mechanical properties and the leaching of heavy metals. Wood flour was obtained through mechanical grinding, and fibres were obtained through alkaline digestion followed by bleaching. Composites produced with 40 wt.% bleached fibres showed increased tensile strength from 18.5 MPa for the polypropylene used as the matrix to 27.6 MPa. Likewise, the Young’s modulus was increased from 0.84 to 2.33 GPa. The treatment of fibres was found to reduce arsenic concentration by up to 99.9%. Furthermore, the arsenic in the leachate from composites was found to decrease from 41.29 to 0.07 ppb when comparing CCA-treated wood flour composites to bleached fibre composites. The composites’ material properties indicate that the use of end-of-life CCA-treated timber could be used to produce a composite material that could be used in New Zealand’s building sector to meet the requirements of semi-structural applications. Full article

Paver blocks are manufactured from zero-slump plain concrete, which is small element used for outdoor applications and flexible road surfaces. IS:15658 (2006) permits the use of 33- grade ordinary Portland cement (OPC) as the minimum for manufacturing paver blocks, but the usage of this type of cement is restricted in India nowadays. In this context, we have studied OPC 43-grade cement replaced by 30% Class F-grade fly ash and the addition of 0.0% and 0.5% polypropylene fibre (PPF) to evaluate the suitability of paver blocks in terms of the climatic conditions, movement of vehicles and road surfaces in India. The synergistic effect of the mechanical properties of paver blocks revealed that a 30% replacement of OPC with fly ash and 0.3% PPF is more suitable for the manufacturing of paver blocks. The obtained results from the reference mixes indicated that the mechanical properties of paver blocks have increased with respect to the age of the blocks. The present study is important for paver block manufacturers as it fulfils the mix design, strength and durability requirements for Indian roads associated with the utilization of waste materials such as fly ash. Additionally, the study will help the national economy increase by 20% in the future, along with the sustainability of virgin materials. Full article

Currently, waste generation is a huge problem all over the world. The largest source of generated waste is plastics from plastic packaging made of polyethylene and polypropylene, including PET bottles. Modern ecology aims to reduce the carbon footprint by recycling plastics or by producing biodegradable plastics that are completely broken down by microorganisms into simple particles that occur naturally in nature. Polyethylene terephthalate (PET) has good mechanical properties but is resistant to microorganisms. As a result, it cannot be classified as a biodegradable plastic, but when it is reused for the production of utility products, it becomes a bioplastic. A good way to dispose of PET is to use it for the production of utility products, in which its good mechanical properties can be used. Concrete is a basic material, the consumption of which in the construction industry is enormous. One of the negative features of concrete is its low tensile strength, which can be improved with continuous or dispersed reinforcement. This paper presents the results of compressive and tensile-bending tests of concrete reinforced with dispersed “fibres” of a different length and width, which were produced by a prototype device from PET beverage bottles. The prototype device enables repeatable fibres with a width of 2 mm, and lengths of 38 mm, 62 mm, and 93 mm to be obtained. The highest flexural tensile strength of the concrete was achieved in the case of the PET fibres with a length of 62 mm. It turned out that concrete with such reinforcement has a higher bending tensile strength by 15 % in relation to the tensile bending strength of the concrete without the dispersed reinforcement. The PET fibres also improve compressive strength. PET fibres, in order not to deteriorate in the alkaline environment of concrete, must be secured with an appropriate chemical agent. The effect of concrete reinforcement with the recycled PET fibres was compared to the effect of dispersed reinforcement made of polypropylene and steel fibres. The highest bending tensile strength was obtained in the case of the concretes with the scattered PET reinforcement. However, the differences in the bending tensile strength of concrete are not big and are equal to 0.64 MPa for polypropylene fibres and only 0.09 MPa for steel fibres. Full article

White topping is a popular road rehabilitation technique that uses Portland cement concrete overlay on top of any existing bituminous pavement. However, this often results in additional cost and carbon emission escalations which complicates market useability of the product. The current study aims at comparing carbon emission and manufacturing cost of concrete topping mixes with three different fibre types. The study optimises the benefits and promotes the use of effective materials in sustainable road rehabilitation. Samples with polyolefin-twisted (F2) fibres indicated least carbon emission escalation while the sample with polypropylene (F3) exhibited least cost escalation with 0.75% and 7.17% from the control sample respectively. A multi-objective genetic optimisation study was conducted to identify the mix designs with least carbon emission and production cost escalations. Sensitivity analysis illustrated that transport distance is a critical contributing factor for production cost while carbon emission is highly sensitive to emission factors for transport and cement production. These results indicate the importance of considering locally available materials and clean energy for production processes. Future research can be focused on exploring the long-term environmental and economic benefits including the durability characteristics to benchmark the sustainable benefits of using waste fibre materials in the mix. Full article