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26 pages, 10877 KiB  
Article
Analysis of Mechanical Properties of Crumb Rubber Tires Mixed with Silty Sand of Various Sizes and Percentages
by Sindambiwe Theogene, Jianxiu Sun, Yanzi Wang, Run Xu, Jie Sun, Yuchen Tao, Changyong Zhang, Qingshuo Sun, Jiandong Wu, Hongya Yue and Hongbo Zhang
Polymers 2025, 17(15), 2144; https://doi.org/10.3390/polym17152144 - 5 Aug 2025
Abstract
Every year, a billion tires are discarded worldwide, with only a small percentage being recycled. This leads to significant environmental hazards, such as fire risks and improper disposal. Silty sand also presents technical challenges due to its poor shear strength, susceptibility to erosion, [...] Read more.
Every year, a billion tires are discarded worldwide, with only a small percentage being recycled. This leads to significant environmental hazards, such as fire risks and improper disposal. Silty sand also presents technical challenges due to its poor shear strength, susceptibility to erosion, and low permeability. This study explores the incorporation of crumb rubber derived from waste tires into silty sand to enhance its mechanical properties. Crumb rubber particles of varying sizes (3–6 mm, 5–10 mm, and 10–20 mm) were mixed with silty sand at 0%, 3%, 6%, and 9% percentages, respectively. Triaxial compression tests of unconsolidated and consolidated undrained tests with cell pressures of 100, 300, and 500 kPa were conducted. The deviatoric stress, shear stress, and stiffness modulus were investigated. The results revealed that the addition of crumb rubber significantly increased the deviatoric and shear stresses, especially at particle sizes of 5–10 mm, with contents of 3%, 6%, and 9%. Additionally, the stiffness modulus was notably reduced in the mixture containing 6% crumb rubber tire. These findings suggest that incorporating crumb rubber tires into silty sand not only improves silty sand performance but also offers an environmentally sustainable approach to tire waste recycling, making it a viable strategy for silty sand stabilization in construction and geotechnical engineering performance. Full article
(This article belongs to the Section Polymer Analysis and Characterization)
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22 pages, 3743 KiB  
Article
Mechanical and Performance Characteristics of Warm Mix Asphalt Modified with Phase Change Materials and Recycled Cigarette Filters
by Zahraa Ahmed al-Mammori, Israa Mohsin Kadhim Al-Janabi, Ghadeer H. Abbas, Doaa Hazim Aziz, Fatin H. Alaaraji, Elaf Salam Abbas, Beshaer M. AL-shimmery, Tameem Mohammed Hashim, Ghanim Q. Al-Jameel, Ali Shubbar and Mohammed Salah Nasr
CivilEng 2025, 6(3), 41; https://doi.org/10.3390/civileng6030041 - 5 Aug 2025
Abstract
With rising global temperatures and increasing sustainability demands, the need for advanced pavement solutions has never been greater. This study breaks new ground by integrating phase change materials (PCMs), including paraffin-based wax (Rubitherm RT55), hydrated salt (Climator Salt S10), and fatty acid (lauric [...] Read more.
With rising global temperatures and increasing sustainability demands, the need for advanced pavement solutions has never been greater. This study breaks new ground by integrating phase change materials (PCMs), including paraffin-based wax (Rubitherm RT55), hydrated salt (Climator Salt S10), and fatty acid (lauric acid), as binder modifiers within warm mix asphalt (WMA) mixtures. Moving beyond the traditional focus on binder-only modifications, this research utilizes recycled cigarette filters (CFs) as a dual-purpose fiber additive, directly reinforcing the asphalt mixture while simultaneously transforming a major urban waste stream into valuable infrastructure. The performance of the developed WMA mixture has been evaluated in terms of stiffness behavior using an Indirect Tensile Strength Modulus (ITSM) test, permanent deformation using a static creep strain test, and rutting resistance using the Hamburg wheel-track test. Laboratory tests demonstrated that the incorporation of PCMs and recycled CFs into WMA mixtures led to remarkable improvements in stiffness, deformation resistance, and rutting performance. Modified mixes consistently outperformed the control, achieving up to 15% higher stiffness after 7 days of curing, 36% lower creep strain after 4000 s, and 64% reduction in rut depth at 20,000 passes. Cost–benefit analysis and service life prediction show that, despite costing USD 0.71 more per square meter with 5 cm thickness, the modified WMA mixture delivers much greater durability and rutting resistance, extending service life to 19–29 years compared to 10–15 years for the control. This highlights the value of these modifications for durable, sustainable pavements. Full article
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38 pages, 15791 KiB  
Article
Experimental and Statistical Evaluations of Recycled Waste Materials and Polyester Fibers in Enhancing Asphalt Concrete Performance
by Sara Laib, Zahreddine Nafa, Abdelghani Merdas, Yazid Chetbani, Bassam A. Tayeh and Yunchao Tang
Buildings 2025, 15(15), 2747; https://doi.org/10.3390/buildings15152747 - 4 Aug 2025
Abstract
This research aimed to evaluate the impact of using brick waste powder (BWP) and varying lengths of polyester fibers (PFs) on the performance properties of asphalt concrete (AC) mixtures. BWP was utilized as a replacement for traditional limestone powder (LS) filler, while PFs [...] Read more.
This research aimed to evaluate the impact of using brick waste powder (BWP) and varying lengths of polyester fibers (PFs) on the performance properties of asphalt concrete (AC) mixtures. BWP was utilized as a replacement for traditional limestone powder (LS) filler, while PFs of three lengths (3 mm, 8 mm, and 15 mm) were introduced. The study employed the response surface methodology (RSM) for experimental design and analysis of variance (ANOVA) to identify the influence of BWP and PF on the selected performance indicators. These indicators included bulk density, air voids, voids in the mineral aggregate, voids filled with asphalt, Marshall stability, Marshall flow, Marshall quotient, indirect tensile strength, wet tensile strength, and the tensile strength ratio. The findings demonstrated that BWP improved moisture resistance and the mechanical performance of AC mixes. Moreover, incorporating PF alongside BWP further enhanced these properties, resulting in superior overall performance. Using multi-objective optimization through RSM-based empirical models, the study identified the optimal PF length of 5 mm in combination with BWP for achieving the best AC properties. Validation experiments confirmed the accuracy of the predicted results, with an error margin of less than 8%. The study emphasizes the intriguing prospect of BWP and PF as sustainable alternatives for improving the durability, mechanical characteristics, and cost-efficiency of asphalt pavements. Full article
(This article belongs to the Special Issue Advanced Studies in Asphalt Mixtures)
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13 pages, 1635 KiB  
Article
Mechanical Performance of Sustainable Asphalt Mixtures Incorporating RAP and Panasqueira Mine Waste
by Hernan Patricio Moyano Ayala and Marisa Sofia Fernandes Dinis de Almeida
Constr. Mater. 2025, 5(3), 52; https://doi.org/10.3390/constrmater5030052 - 4 Aug 2025
Abstract
The increasing demand for sustainable practices in road construction has prompted the search for environmentally friendly and cost-effective materials. This study explores the incorporation of reclaimed asphalt pavement (RAP) and Panasqueira mine waste (greywacke aggregates) as full replacements for virgin aggregates in hot [...] Read more.
The increasing demand for sustainable practices in road construction has prompted the search for environmentally friendly and cost-effective materials. This study explores the incorporation of reclaimed asphalt pavement (RAP) and Panasqueira mine waste (greywacke aggregates) as full replacements for virgin aggregates in hot mix asphalt (HMA), aligning with the objectives of UN Sustainable Development Goal 9. Three asphalt mixtures were prepared: a reference mixture (MR) with granite aggregates, and two modified mixtures (M15 and M20) with 15% and 20% RAP, respectively. All mixtures were evaluated through Marshall stability, stiffness modulus, water sensitivity, and wheel tracking tests. The results demonstrated that mixtures containing RAP and mine waste met Portuguese specifications for surface courses. Specifically, the M20 mixture showed the highest stiffness modulus, improved moisture resistance, and the best performance against permanent deformation. These improvements are attributed to the presence of stiff aged binder in RAP and the mechanical characteristics of the greywacke aggregates. Overall, the findings confirm that the combined use of RAP and mining waste provides a technically viable and sustainable alternative for asphalt pavement construction, contributing to resource efficiency and circular economy goals. Full article
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25 pages, 4247 KiB  
Article
Mechanical Behavior of Self-Compacting Concrete Incorporating Rubber and Recycled Aggregates for Non-Structural Applications: Optimization Using Response Surface Methodology
by Yaqoob Saif, Jihen Mallek, Bilel Hadrich and Atef Daoud
Buildings 2025, 15(15), 2736; https://doi.org/10.3390/buildings15152736 - 3 Aug 2025
Viewed by 78
Abstract
The accumulation of end-of-life tires and the rapid increase in demolition activities pose significant environmental and waste-management challenges. The redevelopment of construction materials incorporating this waste is a potentially promising strategy for minimizing environmental impact while promoting the principles of a circular economy. [...] Read more.
The accumulation of end-of-life tires and the rapid increase in demolition activities pose significant environmental and waste-management challenges. The redevelopment of construction materials incorporating this waste is a potentially promising strategy for minimizing environmental impact while promoting the principles of a circular economy. This study investigates the performance of self-compacting concrete (SCC) incorporating up to 20% rubber aggregates (sand and gravel) and 40% recycled concrete aggregate (RCA) for non-structural applications. A series of tests was conducted to assess fresh and hardened properties, including flowability, compressive strength, tensile strength, flexural strength, water absorption, and density. The results indicated that increasing RCA content reduced density and compressive strength, while tensile and flexural strengths were only moderately affected. Response surface methodology (RSM), utilizing a Box–Behnken design, was employed to optimize compressive, tensile, and flexural strength responses. Statistical analysis was used to identify the optimal mix proportions, which balance the mechanical performance and sustainability of SCC with recycled components. Mixtures incorporating moderate rubber content—specifically, 5–5.5% sand rubber and 0–6% coarse rubber—and 40% recycled-concrete aggregate (RCA) achieved the highest predicted performance, with compressive strength ranging from 20.00 to 28.26 MPa, tensile strength from 2.16 to 2.85 MPa, and flexural strength reaching 5.81 MPa, making them suitable for sidewalks and walkways. Conversely, mixtures containing higher rubber proportions (5.5–20% sand rubber and 20% coarse rubber) combined with the same RCA level (40%) showed the lowest mechanical performance, with compressive strength between 5.2 and 10.08 MPa, tensile strength of 1.05–1.41 MPa, and flexural strength from 2.18 to 3.54 MPa. These findings underscore the broad performance range achievable through targeted optimization. They confirm the viability of recycled materials for producing environmentally friendly SCC in non-structural applications. Full article
(This article belongs to the Section Building Materials, and Repair & Renovation)
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24 pages, 913 KiB  
Article
Fermentation Efficiency and Profile of Volatile Compounds in Rye Grain Mashes from Crops Fertilised with Agrifood Waste Ashes
by Łukasz Ściubak, Andrzej Baryga, Maria Balcerek, Katarzyna Pielech-Przybylska, Urszula Dziekońska-Kubczak and Stanisław Brzeziński
Molecules 2025, 30(15), 3251; https://doi.org/10.3390/molecules30153251 (registering DOI) - 2 Aug 2025
Viewed by 162
Abstract
The utilisation of agrifood waste ashes has the potential to enhance the nutrient content of cereal crops, thereby optimising both yield and grain quality. This study investigated rye grain composition, the fermentation efficiency, and volatile compounds in mashes made from crops fertilised with [...] Read more.
The utilisation of agrifood waste ashes has the potential to enhance the nutrient content of cereal crops, thereby optimising both yield and grain quality. This study investigated rye grain composition, the fermentation efficiency, and volatile compounds in mashes made from crops fertilised with agrifood waste ashes derived from the combustion of corn cob, wood chips, and biomass with defecation lime. The ashes were applied at 2, 4, and 8 t/ha, separately and as mixtures of corn cob (25%) with wood chips (75%) and corn cob (50%) with biomass and defecation lime (50%). Rye mashes were prepared using the pressureless starch liberation method. The starch content in the majority of the rye grains was comparable to the control sample (57.12 g/100 g). The range of ethanol concentrations observed in the fermented mashes was from 55.55 to 68.12 g/L, which corresponded to fermentation yields of 67.25–76.59% of theoretical. The lowest fermentation yield was exhibited by the mash derived from rye cultivated on soil fertilised with a 50:50 mixture of ashes from corn cob and biomass with defecation lime at 8 t/ha. This mash contained more than double the acetaldehyde concentration and total aldehyde content compared to the other samples. These findings demonstrate the potential of using waste biomass ash as a source of macro- and microelements for rye cultivation, enabling the production of agricultural distillates. To ensure high fermentation efficiency and low aldehyde levels, ash dosage and composition need to be established based on experimental optimisation. Full article
(This article belongs to the Section Food Chemistry)
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31 pages, 1741 KiB  
Review
Recycled Concrete Aggregate in Asphalt Mixtures: A Review
by Juan Gabriel Bastidas-Martínez, Hugo Alexander Rondón-Quintana and Luis Ángel Moreno-Anselmi
Recycling 2025, 10(4), 155; https://doi.org/10.3390/recycling10040155 - 2 Aug 2025
Viewed by 66
Abstract
Effective management and handling of construction and demolition waste (CDW) can yield significant technical and environmental benefits for road pavement construction. This article aims to provide a comprehensive and up-to-date chronological review of studies on the mechanical performance of asphalt mixtures—primarily hot mix [...] Read more.
Effective management and handling of construction and demolition waste (CDW) can yield significant technical and environmental benefits for road pavement construction. This article aims to provide a comprehensive and up-to-date chronological review of studies on the mechanical performance of asphalt mixtures—primarily hot mix asphalt (HMA)—incorporating recycled concrete aggregate (RCA). Since the main limitation of RCA is the presence of residual adhered mortar, the review also includes studies that applied various surface treatments (mechanical, chemical, and thermal, among others) to enhance mixture performance. The article summarizes the experimental procedures used and highlights the key findings and conclusions of the reviewed research. Although the results are varied and sometimes contradictory—mainly due to the source variability and heterogeneity of RCA—the use of these materials is technically viable. Moreover, their application can provide environmental, social, and economic advantages, particularly in the construction of low-traffic roadways. Finally, the article identifies research gaps and offers recommendations for future researches. Full article
(This article belongs to the Special Issue Recycled Materials in Sustainable Pavement Innovation)
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16 pages, 1176 KiB  
Article
Evaluating the Use of Rice Husk Ash for Soil Stabilisation to Enhance Sustainable Rural Transport Systems in Low-Income Countries
by Ada Farai Shaba, Esdras Ngezahayo, Goodson Masheka and Kajila Samuel Sakuhuka
Sustainability 2025, 17(15), 7022; https://doi.org/10.3390/su17157022 - 2 Aug 2025
Viewed by 214
Abstract
Rural roads are critical for connecting isolated communities to essential services such as education and health and administrative services, as well as production and market opportunities in low-income countries. More than 70% of movements of people and goods in Sub-Saharan Africa are heavily [...] Read more.
Rural roads are critical for connecting isolated communities to essential services such as education and health and administrative services, as well as production and market opportunities in low-income countries. More than 70% of movements of people and goods in Sub-Saharan Africa are heavily reliant on rural transport systems, using both motorised but mainly alternative means of transport. However, rural roads often suffer from poor construction due to the use of low-strength, in situ soils and limited financial resources, leading to premature failures and subsequent traffic disruptions with significant economic losses. This study investigates the use of rice husk ash (RHA), a waste byproduct from rice production, as a sustainable supplement to Ordinary Portland Cement (OPC) for soil stabilisation in order to increase durability and sustainability of rural roads, hence limit recurrent maintenance needs and associated transport costs and challenges. To conduct this study, soil samples collected from Mulungushi, Zambia, were treated with combinations of 6–10% OPC and 10–15% RHA by weight. Laboratory tests measured maximum dry density (MDD), optimum moisture content (OMC), and California Bearing Ratio (CBR) values; the main parameters assessed to ensure the quality of road construction soils. Results showed that while the MDD did not change significantly and varied between 1505 kg/m3 and 1519 kg/m3, the OMC increased hugely from 19.6% to as high as 26.2% after treatment with RHA. The CBR value improved significantly, with the 8% OPC + 10% RHA mixture achieving the highest resistance to deformation. These results suggest that RHA can enhance the durability and sustainability of rural roads and hence improve transport systems and subsequently improve socioeconomic factors in rural areas. Full article
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18 pages, 273 KiB  
Review
Incorporation of E-Waste Plastics into Asphalt: A Review of the Materials, Methods, and Impacts
by Sepehr Mohammadi, Dongzhao Jin, Zhongda Liu and Zhanping You
Encyclopedia 2025, 5(3), 112; https://doi.org/10.3390/encyclopedia5030112 - 1 Aug 2025
Viewed by 115
Abstract
This paper presents a comprehensive review of the environmentally friendly management and reutilization of electronic waste (e-waste) plastics in flexible pavement construction. The discussion begins with an overview of e-waste management challenges and outlines key recycling approaches for converting plastic waste into asphalt-compatible [...] Read more.
This paper presents a comprehensive review of the environmentally friendly management and reutilization of electronic waste (e-waste) plastics in flexible pavement construction. The discussion begins with an overview of e-waste management challenges and outlines key recycling approaches for converting plastic waste into asphalt-compatible materials. This review then discusses the types of e-waste plastics used for asphalt modification, their incorporation methods, and compatibility challenges. Physical and chemical treatment techniques, including the use of free radical initiators, are then explored for improving dispersion and performance. Additionally, in situations where advanced pretreatment methods are not applicable due to cost, safety, or technical constraints, the application of alternative approaches, such as the use of low-cost complementary additives, is discussed as a practical solution to enhance compatibility and performance. Finally, the influence of e-waste plastics on the conventional and rheological properties of asphalt binders, as well as the performance of asphalt mixtures, is also evaluated. Findings indicate that e-waste plastics, when combined with appropriate pretreatment methods and complementary additives, can enhance workability, cold-weather cracking resistance, high-temperature anti-rutting performance, and resistance against moisture-induced damage while also offering environmental and economic benefits. This review highlights the potential of e-waste plastics as sustainable asphalt modifiers and provides insights across the full utilization pathway, from recovery to in-field performance. Full article
(This article belongs to the Collection Sustainable Ground and Air Transportation)
37 pages, 1664 KiB  
Review
Mining Waste in Asphalt Pavements: A Critical Review of Waste Rock and Tailings Applications
by Adeel Iqbal, Nuha S. Mashaan and Themelina Paraskeva
J. Compos. Sci. 2025, 9(8), 402; https://doi.org/10.3390/jcs9080402 - 1 Aug 2025
Viewed by 175
Abstract
This paper presents a critical and comprehensive review of the application of mining waste, specifically waste rock and tailings, in asphalt pavements, with the aim of synthesizing performance outcomes and identifying key research gaps. A systematic literature search yielded a final dataset of [...] Read more.
This paper presents a critical and comprehensive review of the application of mining waste, specifically waste rock and tailings, in asphalt pavements, with the aim of synthesizing performance outcomes and identifying key research gaps. A systematic literature search yielded a final dataset of 41 peer-reviewed articles for detailed analysis. Bibliometric analysis indicates a notable upward trend in annual publications, reflecting growing academic and practical interest in this field. Performance-based evaluations demonstrate that mining wastes, particularly iron and copper tailings, have the potential to enhance the high-temperature performance (i.e., rutting resistance) of asphalt binders and mixtures when utilized as fillers or aggregates. However, their effects on fatigue life, low-temperature cracking, and moisture susceptibility are inconsistent, largely influenced by the physicochemical properties and dosage of the specific waste material. Despite promising results, critical knowledge gaps remain, particularly in relation to long-term durability, comprehensive environmental and economic Life-Cycle Assessments (LCA), and the inherent variability of waste materials. This review underscores the substantial potential of mining wastes as sustainable alternatives to conventional pavement materials, while emphasizing the need for further multidisciplinary research to support their broader implementation. Full article
(This article belongs to the Special Issue Advanced Asphalt Composite Materials)
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27 pages, 565 KiB  
Review
Review of the Use of Waste Materials in Rigid Airport Pavements: Opportunities, Benefits and Implementation
by Loretta Newton-Hoare, Sean Jamieson and Greg White
Sustainability 2025, 17(15), 6959; https://doi.org/10.3390/su17156959 - 31 Jul 2025
Viewed by 152
Abstract
The aviation industry is under increasing pressure to reduce its environmental impact while maintaining safety and performance standards. One promising area for improvement lies in the use of sustainable materials in airport infrastructure. One of the issues preventing uptake of emerging sustainable technologies [...] Read more.
The aviation industry is under increasing pressure to reduce its environmental impact while maintaining safety and performance standards. One promising area for improvement lies in the use of sustainable materials in airport infrastructure. One of the issues preventing uptake of emerging sustainable technologies is the lack of guidance relating to the opportunities, potential benefits, associated risks and an implementation plan specific to airport pavements. This research reviewed opportunities to incorporate waste materials into rigid airport pavements, focusing on concrete base slabs. Commonly used supplementary cementitious materials (SCMs), such as fly ash and ground granulated blast furnace slag (GGBFS) were considered, as well as recycled aggregates, including recycled concrete aggregate (RCA), recycled crushed glass (RCG), and blast furnace slag (BFS). Environmental Product Declarations (EPDs) were also used to quantify the potential for environmental benefit associated with various concrete mixtures, with findings showing 23% to 50% reductions in embodied carbon are possible for selected theoretical concrete mixtures that incorporate waste materials. With considered evaluation and structured implementation, the integration of waste materials into rigid airport pavements offers a practical and effective route to improve environmental outcomes in aviation infrastructure. It was concluded that a Triple Bottom Line (TBL) framework—assessing financial, environmental, and social factors—guides material selection and can support sustainable decision-making, as does performance-based specifications that enable sustainable technologies to be incorporated into airport pavement. The study also proposed a consequence-based implementation hierarchy to facilitate responsible adoption of waste materials in airside pavements. The outcomes of this review will assist airport managers and pavement designers to implement practical changes to achieve more sustainable rigid airport pavements in the future. Full article
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15 pages, 3566 KiB  
Article
The Influence of Coal Gangue on the Mechanical Properties of Ground-Granulated Blast Furnace Slag-Based Geopolymers
by Xiaoping Wang, Feng Liu, Weizhi Chen, Kaifeng Xing, Kexian Zhuo and Lijuan Li
Buildings 2025, 15(15), 2695; https://doi.org/10.3390/buildings15152695 - 30 Jul 2025
Viewed by 249
Abstract
The reuse of coal gangue (CG) and ground-granulated blast furnace slag (GGBFS) to synthesize geopolymers presents a sustainable strategy for industrial waste recycling. This study investigates the influences of various GGBFS/CG mixtures on the mechanical behavior and microstructure of the synthesized geopolymers. Results [...] Read more.
The reuse of coal gangue (CG) and ground-granulated blast furnace slag (GGBFS) to synthesize geopolymers presents a sustainable strategy for industrial waste recycling. This study investigates the influences of various GGBFS/CG mixtures on the mechanical behavior and microstructure of the synthesized geopolymers. Results show that the geopolymer matrix is composed of calcium aluminosilicate (C-(A)-S-H) and sodium aluminosilicate (N-A-S-H) hydrates, which is essential for enhancing the compressive strength of the specimens. With 100% GGBFS, the geopolymer matrix sets in 17 min, reaching a compressive strength of 107.55 MPa after 28 days. As the CG content increases, both compressive strength and compactness decrease gradually, while the setting time prolongs. When the GGBFS/CG mass ratio is 1:1, the specimens’ setting time increases by 64.7% (from 17 to 28 min). The corresponding compressive strengths at 3 days, 7 days, and 28 days are recorded to be 46.73 MPa, 53.25 MPa, and 54.59 MPa, respectively. Specimens with 100% CG exhibit a prolonged setting time (122 min), but the compressive strength is just 21.80 MPa. Microscopic analysis reveals that specimens with 50% CG have smaller average pore diameters (22.84 nm) and a compact microstructure. These findings indicate that the GGBFS content significantly influences geopolymer performance, highlighting the effective utilization of GGBFS/CG wastes. Full article
(This article belongs to the Special Issue Next-Gen Cementitious Composites for Sustainable Construction)
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26 pages, 4775 KiB  
Article
Effects of Partial Replacement of Cement with Fly Ash on the Mechanical Properties of Fiber-Reinforced Rubberized Concrete Containing Waste Tyre Rubber and Macro-Synthetic Fibers
by Mizan Ahmed, Nusrat Jahan Mim, Wahidul Biswas, Faiz Shaikh, Xihong Zhang and Vipulkumar Ishvarbhai Patel
Buildings 2025, 15(15), 2685; https://doi.org/10.3390/buildings15152685 - 30 Jul 2025
Viewed by 197
Abstract
This study investigates the impact of partially replacing cement with fly ash (FA) on the mechanical performance of fiber-reinforced rubberized concrete (FRRC) incorporating waste tyre rubber and recycled macro-synthetic fibers (MSF). FRRC mixtures were prepared with varying fly ash replacement levels (0%, 25%, [...] Read more.
This study investigates the impact of partially replacing cement with fly ash (FA) on the mechanical performance of fiber-reinforced rubberized concrete (FRRC) incorporating waste tyre rubber and recycled macro-synthetic fibers (MSF). FRRC mixtures were prepared with varying fly ash replacement levels (0%, 25%, and 50%), rubber aggregate contents (0%, 10%, and 20% by volume of fine aggregate), and macro-synthetic fiber dosages (0% to 1% by total volume). The fresh properties were evaluated through slump tests, while hardened properties including compressive strength, splitting tensile strength, and flexural strength were systematically assessed. Results demonstrated that fly ash substitution up to 25% improved the interfacial bonding between rubber particles, fibers, and the cementitious matrix, leading to enhanced tensile and flexural performance without significantly compromising compressive strength. However, at 50% replacement, strength reductions were more pronounced due to slower pozzolanic reactions and reduced cement content. The inclusion of MSF effectively mitigated strength loss induced by rubber aggregates, improving post-cracking behavior and toughness. Overall, an optimal balance was achieved at 25% fly ash replacement combined with 10% rubber and 0.5% fiber content, producing a more sustainable composite with favorable mechanical properties while reducing carbon and ecological footprints. These findings highlight the potential of integrating industrial by-products and waste materials to develop eco-friendly, high-performance FRRC for structural applications, supporting circular economy principles and reducing the carbon footprint of concrete infrastructure. Full article
(This article belongs to the Topic Sustainable Building Development and Promotion)
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26 pages, 2467 KiB  
Article
Antioxidant and Nutrient Profile of Tomato Processing Waste from the Mixture of Indigenous Croatian Varieties: Influence of Drying and Milling
by Tea Petković, Emerik Galić, Kristina Radić, Nikolina Golub, Jasna Jablan, Maja Bival Štefan, Tihomir Moslavac, Karla Grudenić, Ivana Rumora Samarin, Tomislav Vinković and Dubravka Vitali Čepo
Appl. Sci. 2025, 15(15), 8447; https://doi.org/10.3390/app15158447 - 30 Jul 2025
Viewed by 155
Abstract
Tomato processing waste (TPW) represents a valuable but underutilized by-product of the food industry with potential for valorization within bioeconomy models. This study investigated the chemical composition, antioxidant profile, and sanitary safety of TPW, analyzing the whole TPW; its fractions (peels and seeds) [...] Read more.
Tomato processing waste (TPW) represents a valuable but underutilized by-product of the food industry with potential for valorization within bioeconomy models. This study investigated the chemical composition, antioxidant profile, and sanitary safety of TPW, analyzing the whole TPW; its fractions (peels and seeds) and oil are obtained from TPW seeds. All samples showed contaminant levels within regulatory limits, confirming their safety for further applications. Various drying methods (air-drying at 70 °C and at 50 °C, lyophilization and vacuum drying) and grinding intensities were evaluated to determine their impact on TPW bioactive compounds retention and organoleptic characteristics. TPW exhibited valuable nutritional properties, particularly high protein and dietary fiber content while TPW oil was characterized with high monounsaturated fatty acid content. Results demonstrated that drying method and particle size significantly influenced the yield of bioactive compound and organoleptic properties, with either lyophilization or vacuum drying and finer milling generally enhancing the recovery of polyphenols, β-carotene, and lycopene and improving color intensity. This research provides the first characterization of the TPW obtained from Croatian indigenous tomato varieties, establishing a scientific foundation for its sustainable valorization and, in broader terms, supporting circular economy objectives and contributing to more resource-efficient food systems. Full article
(This article belongs to the Special Issue Food Chemistry, Analysis and Innovative Production Technologies)
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25 pages, 4297 KiB  
Article
Application of Carbon–Silicon Hybrid Fillers Derived from Carbonised Rice Production Waste in Industrial Tread Rubber Compounds
by Valeryia V. Bobrova, Sergey V. Nechipurenko, Bayana B. Yermukhambetova, Andrei V. Kasperovich, Sergey A. Yefremov, Aigerim K. Kaiaidarova, Danelya N. Makhayeva, Galiya S. Irmukhametova, Gulzhakhan Zh. Yeligbayeva and Grigoriy A. Mun
Polymers 2025, 17(15), 2070; https://doi.org/10.3390/polym17152070 - 29 Jul 2025
Viewed by 301
Abstract
The disposal of agro-industrial waste is a pressing environmental issue. At the same time, due to the high silica content in specific agricultural residues, their processed products can be utilised in various industrial sectors as substitutes for commercial materials. This study investigates the [...] Read more.
The disposal of agro-industrial waste is a pressing environmental issue. At the same time, due to the high silica content in specific agricultural residues, their processed products can be utilised in various industrial sectors as substitutes for commercial materials. This study investigates the key technological, physico-mechanical, and viscoelastic properties of industrial elastomeric compounds based on synthetic styrene–butadiene rubber, intended for the tread of summer passenger car tyres, when replacing the commercially used highly reinforcing silica filler (SF), Extrasil 150VD brand (white carbon black), with a carbon–silica filler (CSF). The CSF is produced by carbonising a finely ground mixture of rice production waste (rice husks and stems) in a pyrolysis furnace at 550–600 °C without oxygen. It was found that replacing 20 wt.pts. of silica filler with CSF in industrial tread formulations improves processing parameters (Mooney viscosity increases by up to 5.3%, optimal vulcanisation time by up to 9.2%), resistance to plastic deformation (by up to 7.7%), and tackiness of the rubber compounds (by 31.3–34.4%). Viscoelastic properties also improved: the loss modulus and mechanical loss tangent decreased by up to 24.0% and 14.3%, respectively; the rebound elasticity increased by up to 6.3% and fatigue resistance by up to 2.7 thousand cycles; and the internal temperature of samples decreased by 7 °C. However, a decrease in tensile strength (by 10.7–27.0%) and an increase in wear rate (up to 43.3% before and up to 22.5% after thermal ageing) were observed. Nevertheless, the overall results of this study indicate that the CSF derived from the carbonisation of rice production waste—containing both silica and carbon components—can effectively be used as a partial replacement for the commercially utilised reinforcing silica filler in the production of tread rubber for summer passenger car tyres. Full article
(This article belongs to the Special Issue Polymeric Composites: Manufacturing, Processing and Applications)
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