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The primary focus of this study is to assess the stripping resistance of bitumen when partially replaced with rice-straw biomass-based lignin from bio-ethanol industry residue. Moreover, the study examines the relationship between the chemical and physicochemical (surface free energy or SFE) properties of lignin-substituted bitumen blends and their stripping potential. Two distinct lignin materials were examined: fermentation residue (FRL), a by-product directly obtained from the bio-ethanol industry, and Isolated Lignin (IL), which was extracted from FRL through an alkali-acid precipitation process. These materials were partially substituted at dosages of 5%, 10%, and 15% by weight of bitumen. Test results indicated that the addition of lignin to bitumen led to a change in SFE, with an increase in the polar component and a reduction in the dispersive component. The rolling bottle test revealed that bitumen blends containing IL and FRL displayed superior stripping resistance compared to the base bitumen, retaining more coating after testing. This enhancement in performance was attributed to the increased heteroatom content [sum of nitrogen (N), oxygen (O), and sulfur (S)] and higher IS═O and IC═O indices upon adding the lignin materials. While the energy ratio obtained from the SFE alone did not entirely explain the stripping resistance of lignin-substituted bitumen, the presence of heteroatoms like N, O, and S, and the presence of silicon (Si) and associated functional groups played a substantial role in the chemical adhesion of these bitumen blends to aggregates. In conclusion, the incorporation of IL and FRL lignin materials holds promise for enhancing the stripping resistance of base bitumen. [ABSTRACT FROM AUTHOR]

The objective of this paper is to assess the impact of mineral grain size and grain size distribution of aggregates on the deterioration of pavement surface microtexture. For the study, aggregates were collected from nine different sources to cover a wide variation in mineralogical type. The grain size parameters were obtained by detecting mineral grain boundaries using scanning electron microscope electron back scattered diffraction (SEM EBSD) analysis on thin sections prepared from the aggregates. Scanning electron microscope (SEM) analysis was also carried out on thin sections of all aggregate types to determine their mineralogical composition. Microtexture deterioration was measured by collecting the British pendulum number (BPN) of the aggregate after every hour of polishing for six hours using an accelerated polishing machine. From the mineral composition analysis, it was observed that the aggregates in the study belonged to three rock types: granite, amphibolite, and basalt (three sources of each type). The BPN values of the polished stones indicated that aggregates with finer grains offer more resistance to polishing. Statistical analysis of the test results also suggests that a wide variation in grain sizes in aggregates positively contributes to resistance against polishing. The study confirmed that, for a given rock type, coarse aggregates with finer grains and greater variation in grain size can better withstand microtexture deterioration caused by mechanical polishing from vehicular loads when used in the surface course of pavements. [ABSTRACT FROM AUTHOR]

The current investigation presents a comparative study on the laboratory performance of dense graded emulsion mixes prepared with 100% virgin aggregates and 100% Recycled Asphalt Pavement (RAP) with and without a rejuvenator. Waste Engine Oil (WEO) was used as the rejuvenator in the current study. Cold mix design was carried out using a slow-setting type II (SS-2) emulsion. Further, the mechanical and performance properties of various cold emulsion mixes were evaluated. The mechanical properties of cold mixes such as the Indirect Tensile Strength and Resilient Modulus were determined. Rutting and cracking performance were evaluated in terms of the dynamic creep test and indirect tensile asphalt cracking test (IDEAL-CT) respectively. It was observed that the mix prepared with 100% RAP without rejuvenator exhibited a similar rutting performance, a much higher cracking tolerance and low moisture susceptibility compared to the mix with 100% fresh aggregates. The addition of the rejuvenator resulted in improved moisture resistance and cracking tolerance of the cold mix and decreased the rut resistance. [ABSTRACT FROM AUTHOR]

Improper curing of cold asphalt mixes can result in excessive moisture that can significantly impact the performance characteristics accompanied by premature failures. The present research investigated the impact of different curing temperatures and curing periods of 100% Cold Recycled (CR) mixes stabilised with foamed and emulsified asphalt. The results show that curing regime profoundly impacts the moisture loss and rate of evolution of the CR-Mix's stiffness properties. CR-Foam mixes resulted in a higher resilient modulus (Mr) than the CR-Emulsion mixes at most curing regime conditions. The study also confirmed that Mr of CR-Mixes with the same residual moisture content is dependent on curing temperature. Hence, it is concluded that retained moisture content may not be an appropriate criterion for curing of cold recycled (CR) layer because the stiffness achieved by the CR layer is different at different curing temperatures. It is recommended to adopt stiffness as the criterion to evaluate adequate curing. [ABSTRACT FROM AUTHOR]

The microtexture of the asphalt pavement, which is critical for the skid resistance, is dictated by the microtexture of the coarse aggregates used in the surface courses. The existing standard test methods can only capture the combined measure of coarse aggregate surface texture which can be influenced by other aggregate characteristics such as shape and angularity. Consequently, the surface texture of aggregates cannot be quantified explicitly using these tests, and therefore image analysis methods that can extract textural features are gaining more significance. In the present study, various image texture analysis methods are evaluated to identify a reliable texture indicator. Methods include traditional statistical approaches such as histogram method, Grey Level Co-occurrence Matrix (GLCM) methods, and transform-based wavelet texture analysis. The image analysis was carried out on the grey-scale scanning electron microscope (SEM) images before and after accelerated polishing. To compare the image texture parameters, the average surface roughness (Sa) measured from aggregate surface profile data obtained from a 3D Optical Surface Profilometer (3D OSP) was considered as a direct measure of surface texture. A detailed correlation analysis with Sa indicates that the surface texture index (STI) from the wavelet analysis quantifies the microtexture more accurately compared to statistical methods. [ABSTRACT FROM AUTHOR]