Abstract State agencies require rigorous testing to ensure the quality and durability of asphalt mixtures used in pavement construction. Standard protocols mandate frequent evaluation of key mixture properties, including gradation, binder content, volumetrics, and performance metrics to ensure pavement durability. However, time-consuming laboratory tests often delay corrective actions, creating a need for efficient predictive tools to streamline quality control. This study developed a data-driven framework to estimate the cracking resistance of asphalt mixtures, as quantified by the cracking tolerance (CT) index from the indirect tensile cracking test (IDT-CT). Variable selection and model robustness were guided by rigorous statistical methods, including correlation analysis, variance inflation factors, and principal component analysis. Three diverse data sets spanning laboratory- and plant-produced mixtures were compiled for model development. Key predictors included asphalt content, aggregate specific gravity, the Glover–Rowe parameter, and gradation (as measured by the No. 30 sieve). A comprehensive suite of statistical diagnostics, combined with forward feature selection (FFS), was employed to establish a practical, statistically robust modeling framework. Multiple linear regression was selected for its interpretability, target-oriented optimization, and compatibility with regulatory design practices. The proposed model demonstrated reliable predictive performance across training, validation, testing, and independent verification stages. A case study further demonstrated the practical application of the proposed framework in proactively identifying, addressing, and minimizing risks associated with current and potential upgrades to acceptance specifications. To further support the use of the model, future work should incorporate additional data to enhance its ability to estimate the cracking potential of asphalt mixtures and improve operational efficiency.
Abstract The complex and variable service environment of bituminous pavements makes the aging behavior of bitumen difficult to predict. This study aims to reveal the aging mechanisms and kinetics of bitumen in the field. Kinetic aging models were developed for different aging modes. To achieve these objectives, the effects of environmental factors on bitumen were systematically characterized at multiple scales. Performance changes during aging were quantified using the complex modulus and carbonyl index. Aging models for bitumen were developed based on chemical reaction kinetics equations. The results indicated that field aging of bitumen was significantly more severe than laboratory-simulated aging. Thermal-oxidative (TO) aging and all-weather (AW) aging followed a two-stage chemical reaction, starting with a rapid initial aging rate and followed by stabilization. In photo-oxidative (PO) aging, the ultraviolet (UV) radiation maintained the aging process in the rapid-reaction stage, with no constant-rate stage observed. The AW aging results indicated that wind, rainfall, and dust attenuated UV exposure, yielding an aging rate intermediate between those of TO and PO aging. The findings provide theoretical support for durability optimization in design and for life-cycle maintenance decision-making.
Abstract Traditional foaming agents and foam concrete rely on synthetic chemicals and ordinary portland cement (OPC) with a high carbon footprint. This paper presents the formulation of novel anacardate-based green foaming agents derived from cashew industry waste to address the environmental concerns associated with synthetic surfactants. Unsaturated and saturated anacardic acids were extracted and modified using sodium and potassium-based alkalis to synthesize anionic surfactants. The salts of unsaturated anacardic acid-ene mixture demonstrated superior foaming capabilities over their saturated counterparts, which exhibited unfavorable gelling behavior in an aqueous solution. This is beneficial considering the economy and sustainability; as an intermediate, extracting unsaturated anacardic acid is straightforward, less energy-intensive, and more cost-efficient than extracting saturated anacardic acid. Disodium anacardate (unsaturated) yielded foam with favorable density and stability but required further stabilization for use in foam concrete. Thus, three polymer admixtures, namely, xanthan gum, guar gum, and sodium carboxymethyl cellulose (Na-CMC), were investigated. Xanthan gum showed maximum viscosity enhancement of foaming solution and foam stabilization, followed by Na-CMC and guar gum. The compatibility of the stabilized disodium anacardate (unsaturated) foaming agents with both OPC and geopolymer binders was evaluated in terms of reaction kinetics, fresh-state stability, compressive strength, and water absorption. Isothermal calorimetry results confirmed that the anacardate-based foaming agent did not retard binder reactions, irrespective of the admixture used. Further, geopolymer foam concrete exhibited higher compressive strength and lower water absorption than OPC-based mixes at comparable densities, indicating a better synergy. Thus, anacardate-based foams offer a viable, sustainable alternative to synthetic surfactants in foam concrete.
Abstract This study investigates the development of sustainable geopolymer-based pelletized aggregates using fly ash (FA) and spent catalyst (SC) waste. Taguchi experimental design was employed to optimize key parameters influencing aggregate production, including Na 2 O content (6%–8%), water content (20%–22%), and SC proportion (20%–30%). Pelletized FA-SC aggregates were produced through disc pelletization and cured under ambient conditions. Their physical and mechanical properties—including aggregate impact value (AIV), aggregate crushing value (ACV), individual pellet strength (IPS), and water absorption (WA)—were evaluated along with microstructural and thermal analyses using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). Among the nine mixes investigated, the FASC-9 mix (8% Na 2 O , 22% water, and 20% SC) exhibited the best overall performance, showing improved mechanical strength and reduced water absorption. Microstructural results confirmed the formation of dense geopolymeric gel networks contributing to enhanced thermal stability up to 700°C. Life-cycle impact assessment further indicated lower environmental impacts, particularly reduced global warming potential, compared with conventional natural aggregates. The results demonstrate the feasibility of valorizing spent catalyst waste into sustainable geopolymer aggregates for construction applications.
Abstract This paper aims to analyze the chemical and mechanical effects of the interaction between recycled plastics, derived from food packaging and bitumen, in order to assess the potential use of the plastics as a component of bituminous mixtures. The growing difficulty in recycling multilayer food-packaging residues, typically composed of polyethylene, polypropylene, polyethylene terephthalate, cellulose, and aluminum, motivates the investigation of alternative high-volume reuse pathways such as asphalt applications. Chemical properties of plastics were assessed by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Fourier-transform infrared (FTIR) spectroscopy. The interaction between bitumen and plastics was induced by mixing them at 150°C with different mixing speeds, durations, and proportions. Bitumen was then separated by sieving. The chemical and thermomechanical properties of bitumen before and after interaction with plastics were compared, considering the short-term aging effects caused by the mixing procedure. Chemical characterization was conducted by means of FTIR spectroscopy, while thermomechanical characterization was performed using a dynamic shear rheometer (DSR). TGA and DSC data suggest that the plastic is composed by a blend of different polymers and a residue of cardboard. From spectroscopic analysis, moderate variations in specific absorption bands were observed after mixing at 20% plastic content; however, these changes may be associated either with partial interaction phenomena or with finely dispersed inclusions passing through the sieve. The interaction between the two materials has effects on the thermomechanical properties of the bitumen, which presented similar characteristics as those observed in modified binders. In particular, at 20% plastic content and prolonged mixing, a reduction of the purely viscous (Newtonian flow) asymptote at high temperature was observed, together with variations in oxidation-related functional groups. The results indicate the potential use of the plastic as a material for asphalt mixtures.
