Search Results (39)

Traditional blockchain consensus mechanisms, such as Proof of Work (PoW) and Proof of Stake (PoS), face significant challenges related to the centralisation of validators and miners, environmental impact, and trustworthiness. While PoW is highly secure, it is energy-intensive, and PoS tends to favour wealthy stakeholders, leading to validator centralisation. Existing mechanisms lack fairness, and the aspect of sustainability is not considered. Moreover, it fails to address social trust dynamics within validator selection. To bridge this research gap, this paper proposes Proof of Friendship (PoF)—a novel consensus mechanism that leverages social trust by improving decentralisation, enhancing fairness and sustainability among the validators. Unlike traditional methods that rely solely on computational power or financial stakes, PoF integrates friendship-based trust scores with geo-location diversity, transaction reliability, and sustainable energy adoption. By incorporating a trust graph, where validators are selected based on their verified relationships within the network, PoF mitigates the risks of Sybil attacks, promotes community-driven decentralisation, and enhances the resilience of the blockchain against adversarial manipulation. This research introduces the formal model of PoF, evaluates its security, decentralisation, and sustainability trade-offs, and demonstrates its effectiveness compared to existing consensus mechanisms. Our investigation and results indicate that PoF achieves higher decentralisation, improved trustworthiness, reduced validator monopolisation, and enhanced sustainability while maintaining strong network security. This study opens new avenues for socially aware blockchain governance, making consensus mechanisms more equitable, efficient, and environmentally responsible. This consensus mechanism demonstrates a holistic approach to modern blockchain design, addressing key challenges in trust, performance, and sustainability. The mechanism is tested theoretically and experimentally to validate its robustness and functionality. Processing latency (PL), network latency (NL) [transaction size/network speed], synchronisation delays (SDs), and cumulative delay per transaction are 85 ms, 172 ms, 1802 ms, [PL + NL + SD] 2059 ms, respectively. Full article

Oil palm kernel shell ash (POFA), a byproduct of the highly cultivated agro-industrial sector in Colombia, has been widely used for its pozzolanic properties, which enhance the mechanical and durability characteristics of concrete. Six POFA samples were analyzed after undergoing drying, cutting, grinding, crushing, and calcination at temperatures ranging from 500 °C to 1000 °C. SEM-EDS/EDX analysis, X-ray fluorescence (XRF), and loss on ignition (LOI) tests were conducted to characterize its pozzolanic potential. The results revealed that the SiO₂ content increased with the calcination temperature, reaching a peak of 76.8% at 1000 °C. However, calcination at 600 °C was identified as the optimal temperature, as it balances impurity removal without inducing the formation of crystalline silica, which would negatively affect the material’s reactivity. Considering the optimal calcination temperature and the high initial LOI values, which exceeded 70% in the first calcination stage, a second calcination was performed on the 500 °C sample by increasing the temperature to 600 °C. This resulted in an LOI of 3.33%, according to ASTM C311 standards for natural pozzolans used in Portland cement concretes. Full article

Geopolymers have emerged as promising materials for their superior thermal and mechanical properties, offering sustainable alternatives to conventional coatings. This study investigates the potential of Palm Oil Fuel Ash (POFA) as a raw material for fire-resistant geopolymer coatings. Through the optimization of POFA-to-alkaline activator (AA) ratios, NaOH concentrations, and curing temperatures, POFA-based coatings were synthesized and applied to mild steel substrates. Fire resistance testing revealed that the optimal formulation (0.35 POFA ratio, 8 M NaOH concentration, and curing at 65 °C) achieved a temperature at equilibrium (TAE) of 151.2 °C, significantly outperforming other compositions by reducing heat transfer during fire exposure. Thermal imaging and SEM analysis demonstrated that the optimized coating (GP-POFA8) exhibited a more uniform and stable intumescent layer, leading to lower peak temperatures (909 °C) compared to less optimized samples. Thermogravimetric Analysis (TGA) further confirmed that GP-POFA8 retained approximately 80% of its original mass at temperatures beyond 600 °C, highlighting its superior thermal stability. These findings underscore the potential of POFA-based geopolymers as effective, eco-friendly solutions for fire-resistant applications in construction and industrial sectors, contributing to sustainable waste management. Full article

Phosphorus (P) retention in soils in the presence of organic matter (OM) has been, for years, a topic with no clear conclusions. Considering the important ecological functions of peatlands, the objective of this study is to examine the role of OM transformation in relation to P status in Histosols in the Oder Valley (Poland). Basic physical and chemical properties and the following P forms were determined in the organic horizons of 5 soil profiles from two habitats (eutrophic and dystrophic): total (Pt) and organic P (P_o), available P (P_M3), easily soluble P (P_CaCl2), water-soluble P (P_W), and fraction of P_o in humic (P_o_HA) and fulvic (P_o_FA) acids after extraction with 0.5 mol L⁻¹ NaOH. The results were statistically verified in both examined habitat groups separately. The higher values of mobile P forms were found in the upper organic horizons released from OM constituents as a result of their decomposition. The role of OM in P retention was strongly related to the activity of humic substances (HS): a higher P_o percentage (6.9–99.4% of P_o) was observed in dystrophic, whereas a lower (9.3–28.6% of P_o) was observed in eutrophic Histosols. Humic acids played a dominant role in P retention compared to fulvic acids in most peat horizons, especially at pH < 5. The role of HA and FA in P retention was clearly dependent on forms found only in eutrophic Histosols. The important role of FA in P retention during OM transformation was confirmed by negative correlations between P_o_FA and macronutrient ratios in both soil groups. The results confirm the variable role of OM in P retention, depending on soil environmental conditions and OM type (peat and moorsh). This may have important applications not only in areas of natural importance, for which the release of mobile P forms may be a threat, but also in agricultural areas where, for a change, we struggle to increase P availability. Full article

Researchers have investigated the feasibility of using ultrafine palm oil fuel ash (u-POFA) as a cement replacement material because of its potential to reduce the environmental impact of concrete production. u-POFA, a by-product of palm oil fuel combustion, is a suitable replacement for Portland cement in concrete mixes because of its sustainability and cost-effectiveness. This study investigated the microstructural and compressive strengths of alkali-activated mortars (AAMs) based on fly ash (FA) and granulated blast-furnace slag (GBFS) being added with varying percentages of u-POFA. The mixture samples were prepared in eighteen mortars using sodium metasilicate (Na₂SiO₃) as the source material and sodium hydroxide (NaOH) as the alkaline activator. This study used field-emission scanning electron microscopy coupled with energy-dispersive X-ray spectrometry, X-ray diffraction, X-ray fluorescence, and Fourier-transform infrared spectroscopy to characterize the binary-blended mortars after 28 days of curing and determined the strength of the FA+GBFS (87.80 MPa), u-POFA+GBFS (88.87 MPa), and u-POFA+FA mortars (54.82 MPa). The mortars’ compressive strength was influenced by the CaO/SiO₂ and SiO₂/Al₂O₃ ratios in the mixture, which was directly due to the formation rate of geopolymer products of the calcium–alumina–silicate–hydrate (C–(A)–S–H), aluminosilicate (N–A–S–H), and calcium–silicate–hydrate (C–S–H) phases. Based on the contents of FA and GBFS, u-POFA significantly enhanced concrete strength; therefore, u-POFA used in a suitable proportion could enhance binary-blended AAMs’ microstructure. Full article

Supplementary cementitious materials (SCMs) are strongly advised as an alternative to cement to reduce its adverse environmental effects. One such SCMs is palm oil fuel ash (POFA), a waste material generated in large quantities in Southeast Asian countries, and there is insufficient data on its use in engineered cementitious composite (ECC). This study aims to optimize the properties of ECC using POFA as a cement replacement, by using 13 mixes developed by response surface methodology (RSM) with the POFA (at 20, 30, and 40% cement replacement levels) and PVA fiber (at 1, 1.5, and 2% volume fractions) as the input factors. The compressive, tensile, and flexural strengths, and tensile capacity (CS, TS, FS, and TC) were assessed. The microstructural properties were determined using Field-Emission Scanning Electron Microscopy (FESEM) and Mercury Intrusion Porosimetry (MIP). Results indicated that while the ductility and strain capacity increased with POFA, the strengths decreased by up to 51.5%. However, a structural POFA-ECC could be made with up to 30% POFA and 1–5% PVA fiber. The RSM optimization revealed 27.68% POFA and 2% PVA fiber as the optimal levels of the input factors, with the experimental validation correlating with the predicted values at less than 10% error. Full article

The repurposing of gold (Au) mine tailings from artisanal and small-scale mining (ASGM) operations via alkali activation technology is a promising strategy for waste reduction in developing countries. Direct activation of mine tailings, however, is challenging because these materials contain relatively low aluminum (Al)-bearing minerals. In this study, palm oil fuel ash (POFA) was elucidated as a high Al-bearing waste derived-admixture for the synthesis of an ASGM tailings-based geopolymer composite. Semi-quantitative XRD analysis showed that the tailings contained quartz (SiO₂) (~58%), pyrite (FeS₂) (~20%) and calcite (CaCO₃) (~15%) with minor to trace amounts of aluminosilicates (~7%). Substantial amounts of environmentally regulated pollutants such as mercury (Hg) (40 mg/kg), lead (Pb) (8430 mg/kg) and arsenic (As) (300 mg/kg) were also found in the tailings. SEM-EDS, XRD and ATR-FTIR results showed the successful formation of a hybrid geopolymer-CASH matrix, which improved the unconfined compressive strength (UCS) of geopolymer composites from ~5 MPa to ~7 MPa. Furthermore, POFA did not significantly affect the thermal resistivity of geopolymer composites based on thermal analysis. Finally, the TCLP results showed that the Pb leaching concentrations from ASGM tailings exceeded environmental standards (~15,000 µg/L), which was suppressed after alkali activation to 300–500 µg/L. This means that POFA addition to ASGM tailings-based geopolymer composite improved not only its applicability as backfill, pavements and bricks but also its ability to immobilize toxic elements. Full article

Given that rubber tires are almost immune to biological degradation, this vast amount of solid waste is a major environmental concern worldwide. Reuse of these waste tires in the construction industry is one of the strategies to minimize their environmental pollution and landfill problems, while contributing to more economical building design. Thus, we assessed the improved traits of rubberized concrete made by combining palm oil fuel ash (POFA) with tire rubber aggregates (TRAs). Studies on the effects of POFA inclusion on the durability properties of rubberized concrete with TRAs as the replacement agent for fine or coarse aggregates remain deficient. Herein, the rubberized concrete contained 20% POFA as ordinary Portland cement (OPC) substitute, and various amounts of TRAs (5, 10, 20 and 30%). The proposed mixes enclosing three types of TRAs (fiber, fine and coarse aggregates) were characterized to determine their durability and acoustic performance. The water absorption, fire endurance performance, chloride penetration, and acoustic properties of the proposed concrete were evaluated. The designed concrete showed a systematic increase in water absorption and chloride penetration with the increase in rubber amount and particle size. These POFA-modified rubberized concretes displayed a satisfactory performance up to 500 °C, and superior acoustic properties in terms of sound absorption. The presence of TRA as 30% coarse aggregate replacement was found to improve the sound absorption properties by as much as 42%. Full article

Emotional competence (EC) is a key component of children’s psychological, cognitive, and social development, and it is a central element of learning. The primary goal of this study was to evaluate the effectiveness of implementing a psycho-educational group intervention aimed at improving children’s emotional competence (EC), quality of integration and scholastic skills. A total of 229 children (123 females; M Age = 7.22 years; SD = 0.97 years) completed the Pictures of Facial Affect (POFA), the Drawn Stories Technique, the Classroom Drawing, and the Colored Progressive Matrices. The total sample was randomly divided into an intervention group (N = 116) who took part in psycho-educational activities and a control (no-intervention) group (N = 84). Both groups were tested at baseline, before the intervention started, and at the end of the intervention (4 months from baseline). Results from mixed-model ANOVA revealed a significant main effect for POFA score over time (F = 6.24, p = 0.01) and an interaction effect between POFA and group (F = 4.82, p = 0.03). No significant main effect was found for classroom drawing over time (F = 0.81, p > 0.05) or for quality of integration and group intervention. These findings support the importance of developing psycho-educational programmes in school for promotion of emotional health for preventing not only the onset of problematic behaviours at school such as bullying but also the development of clinical conditions linked to difficulties in emotional recognition, expression, and regulation such as alexithymia. Full article

Several researchers devoted considerable efforts to partially replace natural aggregates in concrete with recycled materials such as recycled tire rubber. However, this often led to a significant reduction in the compressive strength of rubberized concrete due to the weaker interfacial transition zone between the cementitious matrix and rubber particles and the softness of rubber granules. Thereafter, significant research has explored the effects of supplementary cementitious materials such as zeolite, fly ash, silica fume, and slag used as partial replacement for cement on rubberized concrete properties. In this study, systematic experimental work was carried out to assess the mechanical properties of palm oil fuel ash (POFA)-based concrete incorporating tire rubber aggregates (TRAs) using the response surface methodology (RSM). Based on the findings, reasonable compressive, flexure, and tensile strengths were recorded or up to 10% replacement of sand with recycled tire fibre and fine TRAs. In particular, the reduction in compressive, tensile, and flexural strengths of POFA concrete incorporating fibre rubber decreased by 16.3%, 9.8%, and 10.1% at 365 days compared to normal concrete without POFA and rubber. It can be concluded that utilization of a combination of POFA and fine or fibre rubber could act as a beneficial strategy to solve the weakness of current rubberized concrete’s strength as well as to tackle the environmental issues of the enormous stockpiles of waste tires worldwide. Full article

The search for new alternative materials for employment in the construction industry is necessary for more sustainable development. The construction demolition waste (CDW), as well as by-products generated by initiatives, such as slag, fly ash (FA), palm oil fuel ash (POFA), metakaolin (MK), silica fume (SF), and rice husk ash (RHA), are objects of studies in several segments of the civil construction sector. The addition of these wastes to the materials currently used to produce concrete and mortar can be one of the significant efforts to achieve more sustainable construction. The use of these wastes in the construction sector can bring considerable benefits in terms of costs, energy efficiency, and environmental and ecological benefits. Over the years, many types of research have been developed aiming at the possibility of a practical use of CDW as an aggregate and industrial by-product (FA, POFA, MK, SF, RHA) as pozzolans. Based on recent studies, this paper reviews the current state of knowledge about the production of concrete with partial replacement of natural aggregates by recycled aggregates from CDW and the use of fly ash (FA) as pozzolan in partial replacement with Portland cement. This work discussed the following concrete properties: compressive strength, water absorption, chloride penetration, carbonation, and modulus of elasticity. Full article

The utilization of waste materials in sustainable and green concrete manufacturing is particularly appealing because of the low cost of waste resources, the saving of landfill space, and the development and enhancement of concrete qualities. This paper investigates the strength and durability of green concrete composites made of waste metalized film food packaging (MFP) fibers and palm oil fuel ash (POFA). Compressive and tensile strengths, carbonation, drying shrinkage, electrical resistivity, and rapid chloride penetration tests in concrete mixtures are among the properties explored. With ordinary Portland cement (OPC), MFP fibers of 20 mm in length and six-volume fractions ranging from 0 to 1.25% were employed. Another six concrete mixes were made with 20% POFA in place of OPC. The results showed that adding MFP fibers to concrete mixes reduced their compressive strength. Despite a minor reduction in compressive strength, the inclusion of MFP fibers significantly increased tensile strength. The findings show that the combination of MFP fibers with POFA substantially impacts concrete durability. The addition of MFP fibers to concrete mixes resulted in a reduction in carbonation and drying shrinkage. The chloride penetration of specimens was also reduced, whereas the electrical resistivity of reinforced samples rose by nearly 80% compared to ordinary concrete. Full article

The fabrication of bricks commonly consumes relatively high natural resources. To reduce the carbon footprint in the brick production industry, repurposing industrial wastes in the making of sustainable bricks is a recent trend in research and application. Local wastes, such as oil palm shell (OPS), palm oil fuel ash (POFA), and quarry dust (QD), are massively produced annually in the palm oil-exporting countries. Moreover, QD from mining industries is hazardous to both water and air quality. For better waste management in marching towards sustainability, these wastes should be given their second life as construction materials. Therefore, this paper investigates the possibility of incorporating agro-industrial wastes into the brick mixture by examining their properties by means of several standardized tests. For the mix design, a 100% replacement of coarse aggregate with OPS, 20% replacement of cement with POFA, 20% cement weight of limestone as admixture, and 0 to 50% replacements of fine aggregate with QD are experimentally considered. The optimum mix of these wastes is preliminarily determined by focusing on high compressive strength as an indicator. Other examinations include splitting tensile, flexural strength, water absorption, and efflorescence tests. Although the agro-industrial waste cement brick is 18% lower in the strength to weight ratio compared to that of conventional, it is observed that it has better late strength development due to its POFA pozzolanic properties. Moreover, the proposed green cement brick is further checked for compliance with several standards for feasible use in the construction industry. Financially, the cost for the brick with the new mix design is almost equivalent to that of conventional. Hence, this green cement brick is reasonable to be employed in the construction industry to promote material sustainability for better waste management. Full article

Soft clay is categorized as problematic due to its weak and dispersive properties which requires stabilization. In Malaysia, there is another challenge, the increment of palm oil waste productions to meet the global demand for food oil. These two concerns motivate engineers to develop novel strategies for exploiting palm oil waste in soil stabilization. Utilizing POFA as a soil stabilizing agent is an economical and sustainable option due to that POFA contains high pozzolanic characteristics which make it more suitable and reliable to treat soft soil. This study uses the replacement portion of the soil with stabilizing agents -POFA and Gypsum; aiming to achieve Malaysia green technology goals by the balance of the economic expansion and environmental privilege. However, the aim of this study is to determine the effect of POFA-gypsum binary mixture replacement on the performance of mechanical and microstructural properties en-hancements of clays. Kaolin S300 is the control sample whereas POFA and gypsum are the used binders. The mechanical properties and shear strength with the curing period were tested. Results showed that treated clay marked increment of optimum water contents and reduction of maximum dry densities, a clear 200% of enhancement of treated clay’s compressive and shear strength with curing period as well as the amount of stabilizing agent to less than 15% of POFA and 6% of POFA. It is also found that as gypsum contains a high amount of lime (CaO), the results illustrate that strength raises significantly even with less curing time due to its high reactivity compared to silica and alu-mina. Overall, the results show an enhancement of mechanical and shear strength properties of treated kaolin supported by microstructural SEM imaging. Full article

Nowadays, an alkali-activated binder has become an emergent sustainable construction material as an alternative to traditional cement and geopolymer binders. However, high drying shrinkage and low durability performance in aggressive environments such as sulphuric acid and sulphate are the main problems of alkali-activated paste, mortar and concrete. Based on these factors, alkali-activated mortar (AAM) binders incorporating high-volume palm oil fuel ash (POFA), ground blast furnace slag (GBFS) and fly ash (FA) were designed to enhance their durability performance against aggressive environments. The compressive strength, drying shrinkage, loss in strength and weight, as well as the microstructures of these AAMs were evaluated after exposure to acid and sulphate solutions. Mortars made with a high volume of POFA showed an improved durability performance with reduced drying shrinkage compared to the control sample. Regarding the resistance against aggressive environments, AAMs with POFA content increasing from 0 to 70% showed a reduced loss in strength from 35 to 9% when subjected to an acid attack, respectively. Additionally, the results indicated that high-volume POFA binders with an increasing FA content as a GBFS replacement could improve the performance of the proposed mortars in terms of durability. It is asserted that POFA can significantly contribute to the cement-free industry, thus mitigating environmental problems such as carbon dioxide emission and landfill risks. Furthermore, the use of POFA can increase the lifespan of construction materials through a reduction in the deterioration resulting from shrinkage problems and aggressive environment attacks. Full article