Search Results (4,466)

Rollpave technology offers an efficient and low-disruption solution for pavement rehabilitation but has not yet been widely implemented in practice. This review aims to provide a comprehensive overview of rollpave technology by examining performance evaluation methods, material design strategies, and construction workflows, and identifying its advantages and limitations to support practical application. Recent advances in rollpave pavement technology are reviewed, including flexural performance testing methods and evaluation criteria for rollable pavement materials, as well as the design of flexible asphalt mixtures and interlayer bonding materials. Construction techniques across different stages of rollpave implementation are summarized, and existing engineering case studies are reviewed. The advantages and limitations of rollpave technology are evaluated in comparison with other pavement construction and rehabilitation approaches, and current research focuses are discussed. The review indicates that pavement performance requirements can be achieved through the development of specialized modified asphalt binders and optimized mixture designs. On-site installation relies on coordinated operation of multiple devices to ensure adequate interfacial bonding between new and existing layers; however, current practices are largely experience-based and lack standardized guidelines. It is believed that rollpave technology demonstrates unique advantages for rapid pavement repair and emergency rehabilitation, but there are still challenges related to material and structural design, on-site installation, and cost-effectiveness that remain, limiting large-scale adoption. Future research could focus on establishing technical standards, developing specialized equipment, and enhancing multifunctional integration. Full article

Reactive powder concrete (RPC) delivers outstanding mechanical performance and durability; however, it is commonly hindered by high cement consumption, elevated embodied carbon emissions, and high material costs. To mitigate these drawbacks, this study develops a low-carbon, cost-effective RPC incorporating high-volume class-F fly ash, a reduced silica fume dosage, conventional river sand, and an optimized steel fiber system. A systematic mix design framework, combining particle packing density with paste rheology optimization, was employed to balance workability, strength, and durability. The optimized mixtures were evaluated for compressive, splitting tensile, and flexural strength, as well as durability-related metrics, including water absorption rate and resistance to chloride penetration. Environmental impact and cost-effectiveness were further quantified via embodied carbon accounting and strength-normalized performance indices. The results show that well-designed high-volume fly ash RPC can achieve compressive strengths above 130 MPa while maintaining excellent impermeability, alongside substantial reductions in both material cost and carbon footprint relative to conventional RPC. In addition, mixed-size steel fibers further enhance mechanical performance through multi-scale crack bridging. Overall, this work provides a practical route to decouple ultra-high performance from high environmental burden, supporting the sustainable deployment of RPC in infrastructure engineering. Full article

High reclaimed asphalt pavement (RAP) half-warm mix asphalt (HWMA) mixtures provide a low-energy alternative for pavement repair but often suffer from insufficient binder activation and reduced mechanical performance at low production temperatures. This study develops a high-RAP (73.8%) half-warm repair mixture using a dual-additive system comprising a rejuvenator and a low-temperature composite additive. The mixture was designed to enable effective mixing and compaction at temperatures as low as 60 °C. The optimized formulation achieved a 5.84 kN Marshall stability, 7.0% voids in total mixture, 80% retained Marshall stability after moisture conditioning, and approximately 1100 passes/mm dynamic stability. Temperature sensitivity analysis showed that stability increased from 4.50 kN at 50 °C to 9.20 kN at 90 °C with corresponding VTM reduction from 15.2% to 4.8%. The results demonstrate that a high-RAP HWMA repair mixture can satisfy mechanical and durability requirements while being produced at substantially reduced temperatures, supporting practical and sustainable pavement maintenance applications. The study further provides mixture-scale evidence that a dual-additive strategy can stabilize high-RAP mixtures under very low half-warm production temperatures (≈60–70 °C), which are representative of rapid repair conditions and remain insufficiently investigated in existing WMA–RAP research. Full article

Diet is a major, modifiable determinant of cardiometabolic, cancer, and inflammatory disease risk, yet individuals frequently exhibit substantial heterogeneity in metabolic and clinical responses to similar dietary exposures. Genetic susceptibility and its interplay with diet plausibly contribute to this variability, motivating gene–diet (G×D) interaction research and the broader ambition of precision nutrition. Translation has lagged, however, because interaction effects are typically modest, context-dependent, and difficult to reproduce, particularly in the presence of pervasive dietary measurement error, heterogeneous exposure definitions, and stringent multiplicity correction. A methodologically oriented synthesis is presented across eight domains of contemporary G×D epidemiology: classical regression interaction models; efficient study designs; dietary assessment and measurement error; dietary patterns, mixtures, and non-linear modeling; genome-wide and polygenic approaches; causal inference frameworks; multi-omics integration; and machine learning. Central concepts include the recognition that “interaction” is a scale-dependent estimand and that transparent reporting of coding choices and effect-modification metrics—including additive interaction when relevant for public health interpretation—is essential. Credible inference further depends on high-quality, harmonized dietary phenotyping with explicit energy adjustment and, where feasible, biomarker calibration, alongside robust control of population structure and gene–diet correlation using ancestry adjustment, mixed models, and family-based designs. Genome-wide and polygenic risk-based approaches expand discovery potential but require disciplined multiplicity strategies, discovery-replication workflows, and explicit evaluation of portability and equity across ancestries. Causal inference methods can strengthen etiologic interpretation when assumptions are defensible and sensitivity analyses are routinely implemented. Multi-omics and machine learning may enhance mechanistic and predictive insight, but only under rigorous quality control, validation, and reproducible pipelines. Overall, harmonized measurement, clear estimands, multi-ancestry replication, and integrated evidence pipelines are pivotal for producing robust and actionable G×D evidence. Full article

Performance deterioration and unstable operation are common when multistage centrifugal pumps handle gas–liquid mixtures. Here, we investigate a two-stage centrifugal pump over a wide speed range and inlet gas volume fractions (IGVFs) using experiments and CFD. The two-phase flow is simulated with a Eulerian–Eulerian two-fluid approach (liquid as the continuous phase; gas as a dispersed bubbly phase with a representative bubble diameter of 0.3 mm). Turbulence is closed using the SST k–ω model for the liquid phase and the built-in dispersed-phase turbulence treatment in ANSYS CFX. Transient pressure signals are analyzed in the time and frequency domains (FFT) to assess how rotational speed affects void-fraction distribution, overall performance, and the dominant unsteady components within the adopted modeling framework. The results show that IGVF primarily controls gas accumulation in the impeller passages: as IGVF increases, the gas phase evolves from dispersed bubbles to a central core, whereas speed mainly alters the detailed morphology via centrifugal effects. Similarity-law scaling is strongly speed-dependent in this pump: agreement is better at higher speeds and deteriorates at lower speeds where viscous effects become more influential. The dominant unsteady content also changes with speed, shifting from low-speed broadband features associated with gas redistribution to high-speed periodic components linked to blade–vane rotor–stator interaction (RSI). In addition, the downstream stage exhibits more uniform void fraction and more regular periodic signatures, consistent with an inter-stage flow-rectification effect. These observations provide practical guidance for hydraulic design and variable-speed operation of multistage pumps under gas entrainment. Full article

This study investigates the application of artificial intelligence for predicting the compressive strength of a high-performance, eco-efficient engineered cementitious composite (ECC), designated mix S8-1, A. The composite incorporates supplementary cementitious materials and alternative aggregates derived from recycled glass waste. The binder system combines waste glass powder and silica fume, while the aggregate fraction includes recycled cobalt glass. An extensive experimental program involving 14 mixtures tested at 7, 28, 56, 90, and 120 days was performed to establish the reference mechanical and rheological properties. Mix S8-1, A achieved strength class C60/75 and workability corresponding to consistency class S4. To substantiate long-term performance, microstructural and chemical analyses were conducted on specimens preserved since 2011, using scanning electron microscopy (SEM) and X-ray fluorescence (XRF). The results confirmed a stable, densified microstructure, evidencing the long-term durability of the patented ECC formulation. For predictive modeling, a shallow feedforward artificial neural network with three hidden layers was developed and trained on 70 dataset entries representing mixture proportions and curing ages. Model performance was evaluated using cross-validation, achieving a coefficient of determination (R²) of 0.968, a mean absolute error of 1.96 MPa, and a root mean square error of 2.52 MPa. The results demonstrate that AI-based approaches can accurately predict the compressive strength of high-performance, environmentally sustainable ECCs incorporating recycled glass constituents, supporting both performance optimization and resource-efficient material design. Full article

The buildings and construction sector is a major contributor to global environmental impact, accounting for 34% of global energy demand and 37% of energy- and process-related CO₂ emissions in 2022. This context motivates the development of alternative construction materials with lower embodied energy and reduced environmental impact. In this study, vibrocompressed calcium sulfate prefabricated elements were developed and experimentally evaluated as an alternative to conventional concrete-based units. Unlike traditional gypsum molding processes, the proposed vibrocompression route enables the production of semi-dry mixtures with reduced water content, allowing rapid demolding and palletization within 10–20 min. The study was designed as a process-validation campaign under real industrial production conditions (LOREV 1010/A), combined with an initial technical characterization of the manufactured units. The experimental program focused on manufacturing feasibility and on the initial physical and mechanical characterization of the prefabricated elements, including aggregate granulometric control, dry density, normalized compressive strength, and microstructural observations. Under the selected process conditions, the units reached normalized compressive strength values of up to 2.90 N/mm² and dry density values of approximately 1228 kg/m³, indicating technical suitability for non-load-bearing applications. From a process-route perspective, the cement-free formulation and the use of gypsum-based aggregates support the technical plausibility of a more circular construction system. The environmental and economic implications of the proposed system are discussed from a preliminary process perspective and should be quantified in future life cycle and techno-economic assessments. Full article

This study investigates the properties of concrete incorporating recycled aggregates (RAs) for rigid pavement applications. A 15-point three-level experimental design was used to vary three composition factors: Portland cement substitution with fly ash (FA), and dosages of a superplasticizer (SP) and polypropylene fibers (PFs). A set of experimental–statistical models (ES models) was developed to predict the concrete strength, abrasion and frost resistance (FR), water absorption (WA), and global warming potential (GWP). This study aimed to develop a material that achieves both adequate mechanical performance for pavement applications and enhanced environmental sustainability by incorporating RAs and FA. The results demonstrate that replacing up to 13% of cement with FA does not compromise the splitting tensile strength or FR. For non-fibrous concrete, this substitution increases FR by approximately 50 freeze–thaw cycles. Application of PFs (2.4–3 kg/m³) enhances splitting tensile strength by 14–16% and improves FR by about 50 cycles. Using response surface methodology (RSM), optimal concrete compositions were identified that meet all target criteria: compressive strength ≥ 40 MPa, flexural strength ≥ 5 MPa, FR ≥ F200 (cycles), and abrasion resistance (AR) ≤ 0.5 g/cm², while simultaneously minimizing GWP. An additional optimum composition was determined by imposing a constraint on splitting tensile strength of ≥4.5 MPa. This graphical optimization approach, utilizing two-factor interaction diagrams, provides an effective and visual methodology for practical concrete mixture design. The novelty of the method lies in the discretization of the factor space, which enables efficient identification of optimal concrete mixture compositions. Full article

Isobutane is a key feedstock for alkylate production. For separating an equimolar isobutane/n-butane mixture with 2 mol% ethane, two conventional designs are reported in the literature: a single water-cooled condenser (SC) and a dual condenser system with refrigeration (DC). This study proposes two vapor recompression retrofit configurations, SC-VR and SC-PHVR (with preheating), to improve energy efficiency and enable electrification. Economic and environmental performance were evaluated using total annualized cost (TAC) and CO₂ emissions. Compared with SC and DC schemes, SC-VR reduces CO₂ emissions by 49 and 52%, while SC-PHVR delivers higher reductions of 64 and 66%. A sensitivity analysis of electricity prices across 3-, 5-, and 10-year payback periods indicates the most favorable performance at 10 years. At 16.67 USD/GJ, SC-PHVR lowers TAC by 22 and 25%; in contrast, SC-VR provides marginal savings. At 24.03 USD/GJ, SC-VR is not economically competitive, whereas SC-PHVR continues to outperform the conventional cases, with TAC reductions of 8% and 4%. Both retrofit options significantly reduce emissions, with SC-PHVR offering the best economic performance. Finally, the proposed configurations enable the complete electrification of the de-isobutanizer system, eliminating reliance on fossil-based thermal utilities, which allows the use of renewable sources in line with the decarbonization efforts. Full article

The separation of xenon (Xe) and krypton (Kr) is very important for industrial applications and environmental protection. However, the lack of permanent dipoles, low polarizabilities arising from their spherical nature, and similar kinetic diameters make their efficient separation by porous adsorbents exceptionally challenging. This study explored the effects of pore geometry and surface polarity of a series of aluminum-based metal–organic frameworks (CAU-10-H, MIL-160, KMF-1, CAU-23) on Xe/Kr separation performance using a heteroatom engineering strategy. These MOFs are composed of AlO₆ clusters and bent dicarboxylic acid linkers, enabling us to systematically investigate the effects of pore size and heteroatom types on Xe/Kr separation performance. Among them, MIL-160 has a polar linker based on furan, showing the best balance performance. At 298 K and 1.0 bar, the uptake of Xe is 4.12 mmol g⁻¹ and the IAST selectivity is 7.63 for a Xe/Kr (20/80) mixture. The practical performance was verified by dynamic breakthrough experiments, which yielded a long Xe breakthrough time of 42.9 min g⁻¹. Grand Canonical Monte Carlo (GCMC) simulations and first-principles density functional theory (DFT) calculations revealed that the enhanced performance originates from cooperative confinement and polarization effects, with the furanyl oxygen atoms providing optimal Xe-binding sites. This work clarifies the structure–property relationships governing Xe/Kr separation in aluminum-based MOFs (Al-MOFs), highlighting the potential of heteroatom engineering for designing efficient noble gas adsorbents. Full article

Concrete compressive strength is traditionally modeled as a function of mixture composition, with cement dosage often assumed to produce proportional strength gains. However, such interpretations are typically correlational and do not quantify the causal effectiveness of cement additions under varying mixture conditions. This study introduces an interpretable causal machine learning (ICML) framework to estimate the marginal causal effect of cement dosage on compressive strength using an R-learner-based approach. Cement content is treated as a continuous intervention variable, and heterogeneous treatment effects are estimated conditionally on mixture composition and curing age. The estimated average marginal effect of cement dosage is 0.136 MPa per kg/m³ (95% bootstrap confidence interval: [0.1055, 0.1433]). However, substantial heterogeneity is observed, with individual marginal effects ranging from −0.027 to 0.370 MPa (5th–95th percentile). Near-zero and, in limited regimes, negative marginal effects emerge under high water content and unfavorable mixture conditions, indicating inefficient cement utilization. Robustness checks across alternative cross-fitting schemes and trimming procedures confirm the stability of the estimated causal effects. Unlike conventional machine learning models that explain predicted strength values, the proposed framework applies explainability directly to the estimated causal effect function. Local SHAP-based explanations reveal the mixture configurations under which cement additions are effective or inefficient. By explicitly identifying mixture conditions under which cement additions are effective or inefficient, the proposed framework supports more rational cement use, reducing unnecessary material consumption, lowering construction costs, and easing the decision-making burden on designers in practical concrete mix design. Full article

Stone Mastic Asphalt (SMA) mixtures are widely used in high-capacity road pavements due to their durability and resistance to permanent deformation. However, although electric arc furnace (EAF) steel slag and recycled crumb rubber have been individually investigated as alternative materials in asphalt mixtures, evidence regarding their simultaneous incorporation in SMA mixtures under full-scale construction and real traffic conditions remains limited. Moreover, quantitative environmental assessments are often restricted to simplified or qualitative approaches, with limited reporting of carbon footprint results. This study investigates the combined use of electric arc furnace (EAF) steel slag aggregates and recycled crumb rubber in SMA mixtures, integrating laboratory evaluation with full-scale field application on a high-traffic motorway. Two SMA 11 mixtures were designed and assessed: one incorporating steel slag aggregates as a replacement for natural coarse aggregates, and another combining steel slag aggregates with recycled crumb rubber added through the dry process (0.8% by mixture mass). Laboratory testing included volumetric characterization, moisture sensitivity and rutting resistance, while field validation covered surface macrotexture, skid resistance, executed thickness and interlayer bonding. Both mixtures fully complied with the applicable technical specifications, achieving indirect tensile strength ratios (ITSR) above 90% and wheel-tracking slopes below 0.07 mm/10³ cycles. A simplified comparative life-cycle assessment (LCA), limited to modules A1–A3, showed a reduction in CO₂-equivalent emissions of approximately 2% for the mixture containing steel slag and up to 27% for the mixture combining steel slag and recycled crumb rubber, mainly due to the valorization of industrial by-products and end-of-life tyres. Overall, the results demonstrate the technical feasibility and potential environmental benefits of these SMA mixtures within the defined scope of laboratory verification, short-term field performance and screening LCA. The contribution of this study lies in providing applied evidence from a full-scale motorway intervention, complementing predominantly laboratory-based studies and offering a quantified environmental comparison under consistent methodological assumptions. Full article

The use of a multi-component binder (MCB), consisting of Ordinary Portland Cement (OPC) combined with one or more supplementary cementitious materials (SCMs), has gained prominence for enhancing sustainability and improving the performance of cementitious systems. This study provides an integrated approach to optimize both binder composition and aggregate gradation through advanced mixture design and particle packing techniques. The MCB system consists of OPC partially replaced with SCMs such as fly ash (FA), Ground Granulated Blast Furnace Slag (GGBFS), metakaolin (MK), and silica fume (SF), with particle sizes ranging from micron to sub-micron scale. The D-optimal mixture design (DOD) method is used to determine the optimal material proportions by evaluating the relation between binder composition and wet packing density measured through the wet packing method (WPM). To further enhance packing efficiency, the Modified Toufar Model (MTM) is employed to optimize fine aggregate gradation. The maximum packing density is considered the primary criterion for identifying the optimal mix design, as it reflects the minimum void ratio and the most efficient particle size distribution. The optimized mortar mixes are evaluated for mechanical strength, pozzolanic reactivity, capillary water sorptivity, and drying shrinkage. Results indicate that the optimized MCB and optimized fine aggregate gradation improve the packing density and pozzolanic activity, significantly enhancing strength and durability performance. The incorporation of SCMs offers an effective strategy to improve performance while mitigating carbon emissions. Compared with C100, CFGMS-based systems achieved energy reductions of 35–40% and CO₂ emission reductions of 34–48%. Full article

The demand for concrete has led to increased use of raw materials and significant waste generation. Recycled aggregate concrete (RAC) offers a viable approach to sustainable concrete; however, the use of weakly bonded mortar on aggregate leads to low strength and crack formation. Fiber reinforcement, specifically hybrid fiber reinforcement combining steel, glass, basalt, and polypropylene fibers, can increase the tensile and flexural properties of RAC. This study developed machine learning models to enable the prediction of hybrid fiber-reinforced RAC’s compressive, splitting tensile, and flexural strength performance; these new models overcome the limitations of previous research, which relied on only one fiber type and regular methods of optimization. Two models (a deep neural network (DNN) and an XGBoost model) were trained and optimized using bald eagle search (BES), particle swarm optimization (PSO), and the Bayesian optimization (BO) algorithm to improve performance. Among the three optimization analyses, PSO-XGBoost achieved the highest accuracy for compressive strength and splitting tensile strength, while BES-XGBoost achieved the highest accuracy for flexural strength. The most significant influences on the compressive strength were curing age and silica fume, while the main drivers of splitting tensile strength and flexural strength were fiber volume and fiber characteristics. The use of SHAP-based methodology with a user-friendly interface further improved the design of RAC mixtures, reducing waste from raw materials, enhancing the structural performance of RAC, and enabling data-driven decision-making in the manufacturing of eco-friendly concrete products. Full article

With global plastic production creating immense environmental pressure and conventional recycling methods facing limitations, advanced chemical recycling techniques are crucial. This paper presents details of the design, construction, and operation of two fluidized reactors: a laboratory-scale (LS) reactor and a large-scale laboratory reactor (LSLR) for the catalytic pyrolysis of mixed plastic waste. A waste stream simulating municipal collection, consisting of polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and polystyrene (PS), was processed using a custom Ni/γ-Al₂O₃ catalyst and an industrial G-0110 catalyst in a two-stage system. The large-scale reactor demonstrated high efficiency, achieving a 90% yield of valuable pyrolysis oil and waxes, a 2% yield of syngas, and an 8% yield of solid residue containing mainly carbon at operating temperatures between 400 and 453 °C. The resulting liquid and wax fractions contained a rich mixture of aliphatic and aromatic hydrocarbons (such as styrene, indene, benzoic acid, toluene, and cumene), confirming their potential as a feedstock for the chemical industry. These results establish that two-stage catalytic pyrolysis in a fluidized bed reactor is a highly effective and promising technology for upcycling mixed plastic waste into valuable resources. Full article