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Asphalt pavements inevitably deteriorate over time, requiring frequent maintenance work to ensure the proper serviceability of the road network. Small interventions, such as resurfacing for pavement preservation, are preferable to reconstruction at the end of roads' in-service lives as they limit environmental- and economic-related impacts. Thin asphalt overlay (TAO) mixture represents a suitable maintenance solution to restore the functional properties of road surfaces. Due to the increasing awareness of the depletion of non-renewable resources and the importance of promoting the circular economy, this study evaluated the possibility of using fully recycled TAO mixes by investigating their volumetric and mechanical properties. Two eco-friendly TAO mixes were designed using recycled aggregates from reclaimed asphalt pavements, a municipal solid waste incinerator, and steel slags in order to meet EN 13108-2 requirements. The TAO mixes differed in regard to the type of bituminous binder (neat/SBS-modified bitumens) and fibres (natural/synthetic) employed. The preliminary results demonstrated that the presence of recycled aggregates did not negatively affect the workability and the mechanical performances of the two sustainable mixtures in terms of stiffness, tensile resistance, rutting and moisture susceptibility. Of these, the TAO mix with neat bitumen and synthetic fibres showed enhanced mechanical performance highlighting the structural effects of the used fibres. [ABSTRACT FROM AUTHOR]

This research effort is geared towards revealing the latent potential of discarded shoe polish that might be repurposed as an asphalt fluxing agent for the construction of durable and sustainable road surfaces. To drive this creative invention, the effect of various proportions of waste shoe polish (e.g., 5, 10 and 15 wt. % WSP) on the performance of base AP-5 bitumen was inspected in great detail. A meticulous investigation of the chemical, physical, and rheological properties of the resultant combinations was carried out using a variety of state-of-the-art laboratory techniques, specifically: thin-layer chromatography-flame ionization detection (TLC-FID), Fourier transform-infrared spectroscopy (FT-IR), needle penetration, ring-and-ball softening point, Brookfield viscometer, ductility, flash/fire points, dynamic shear rheometer (DSR), multiple stress-creep recovery (MSCR), and bending beam rheometer (BBR) tests. The Iatroscan data disclosed that the continuous feeding of binder with WSP had a minor impact on SARA fractional distribution, regardless of aging. According to the FT-IR scan, the stepwise addition of WSP to the binder did not result in any significant chemical alterations in the blends. The combined outcomes of the DSR/BBR/empirical test methods forecasted that the partly bio-sourced additive would greatly improve the mixing–compaction temperatures, workability, and coating–adhesion properties of bituminous mixtures while imparting them with outstanding anti-aging/cracking attributes. In short, the utilization of waste shoe polish as a fluxing agent for hot asphalt mix production and application is not only safe, feasible, and affordable, but it has the potential to abate the pollution caused by the shoe-care market while simultaneously enhancing the overall performance of the pavement and extending its service lifespan. [ABSTRACT FROM AUTHOR]

(i) Recycled and renewable materials in asphalt pavements may be employed for the modification of asphalt binders and/or for the full or partial replacement of natural aggregates and mineral filler in asphalt mixtures [[1]]. A sustainable approach in asphalt pavement engineering should focus on materials, design methods, and technologies that can contribute to minimizing environmental impacts through a reduction in energy consumption and natural resources, while ensuring that all performance standards and requirements are met. By comparing the performance of various binders based on Zero Shear Viscosity (ZSV), grey relational analysis showed the highest correlation with an anti-rutting indicator for a high-viscosity-modified asphalt binder, thus indicating its pronounced anti-rutting potential. [Extracted from the article]

The research presented by Gaudenzi et al. [[30]] involved rheological measurements aimed at evaluating the fatigue behaviour and comparing the self-healing capability of two plain bitumen and a bio-binder obtained by partially replacing one of the plain bitumen with a renewable bio-oil. The mineral composition, the physical and mechanical properties, the morphology and the texture of the aggregates, as well as the affinity between aggregate and bitumen were investigated. The results showed that both temperatures improved the properties of the base bitumen, although the bitumen modified at 190 °C contained more non-degraded rubber. Moreover, the complex modulus values confirmed that cold recycled asphalt mixtures provide an intermediate behaviour between asphalt concrete mixtures and cement-treated mixtures. [Extracted from the article]

Over the years, the need for the synthesis of biodegradable materials has facilitated the drift of the asphalt industry towards eco-sustainable and cost-effective production of road pavements. The principal additives in the asphalt industry to improve the performance of road pavements and increase its lifespan are majorly rheological modifiers, adhesion promoters and anti-oxidant agents. Rheological modifiers increase physico-chemical properties such as transition temperature of asphalt binder (bitumen), adhesion promoters increase the affinity between binder and stone aggregates while anti-oxidant agents reduce the effects of oxidation caused by exposure to air, water and other natural elements during the production of asphalt pavements. In this study, we tested the effectiveness of a food grade bio-additive on these three aforementioned properties. We also sought to hypothesize the mechanisms by which the additive confers these desired features on bitumen. We present this study to evaluate the effects of turmeric, a food-based additive, on bitumen. The study was conducted through dynamic shear rheology (DSR), atomic force microscopy, scanning electron microscopy (SEM) and boiling test analysis. [ABSTRACT FROM AUTHOR]

The compactability of an asphalt mixture is related to the heating temperature of the materials, but the heating temperature of reclaimed asphalt pavement (RAP) is limited by the production process of hot-in-plant recycled mixtures. To choose a reasonable heating temperature for RAP according to the compactability, the compaction energy ratio (CER) obtained from the Superpave gyratory compactor compaction curve was developed. The CERs of fourteen kinds of asphalt mixtures made with different RAPs were compared, all of which were different in type, content, and heating temperature. The results indicated that CER is an effective energy index to evaluate the workability of a bituminous mixture, and it considers both the accumulated energy after each gyration and the number of gyrations. It was also found that increasing the heating temperature of the RAP cannot always improve the workability of the recycled mixture, because the higher heating temperature caused more hard-aged bitumen to be blended with soft virgin bitumen during the mixing process. At the same RAP heating temperature, increasing the RAP content made it more difficult to compact the mixture, especially for RAPs with styrene–butadiene–styrene (SBS) modified bitumen, and the recycled mixtures with SBS-modified bitumen were more difficult to compact than those with nonmodified bitumen. [ABSTRACT FROM AUTHOR]

Strength is an important parameter for the design of asphalt pavement materials and structures. To study the influence of various factors on the three-dimensional strength of asphalt mixtures, three aggregate gradations (dense-graded bituminous mixture AC-13, stone mastic asphalt SMA-13 and bituminous stabilization aggregate paving mixture OGFC-13) and two binders (SBS modified bitumen and 70# base bitumen) were used to prepare the asphalt mixture specimens. Among them, SBS+SMA-13 asphalt mixture has the best performance. On this basis, the uniaxial compressive test, uniaxial tensile test and confining triaxial test were conducted on the SBS+SMA-13 asphalt mixture under six oil-stone ratios conditions (5.5%, 5.7%, 5.9%, 6.1%, 6.3%, and 6.5%), six temperatures conditions (5 °C, 10 °C, 15 °C, 20 °C, 25 °C, and 30 °C), and five loading rates conditions (1 mm/min, 2 mm/min, 3 mm/min, 4 mm/min, and 5 mm/min). In addition, a unified three-dimensional strength calculation model considering the influence of temperature, loading rate, and oil-stone ratio was proposed, and the change law of the three-dimensional strength with these above factors was revealed. Furthermore, two sets of three-factor three-level orthogonal tests were carried out on the SMA-13 asphalt mixture. The sensitivity analysis and strength regulation research between three-dimensional strength and each factor were carried out. The results show that the type of asphalt has the greatest influence on the strength of the mixture, the temperature has the second most influence, the loading rate has less influence, and the oil-stone ratio has the least influence. The strength regulations proposed to improve the strength of the asphalt mixture include the use of modified asphalt, high-temperature stability high-quality asphalt, and the lower oil-stone ratio than the Marshall optimal oil-stone ratio. The strength control measures proposed from the perspective of the three-dimensional stress state, the joint failure of each stress components and real stress states are taken into consideration. [ABSTRACT FROM AUTHOR]

Compaction of Hot Mix Asphalt (HMA) is a process aimed at obtaining the desired performance properties. Attainment of the required compaction can be hampered by external factors, which includes the presence of water. Water is known to cause quick lowering of the HMA temperature. The bottom face of the asphalt layers of a pavement is a sensitive point from the fatigue life point of view. In the site conditions, it is often difficult to obtain the required air void content at the bottom of an asphalt layer and excessive moisture content in the base course lying beneath the asphalt layer can be one of the causes. This article presents the results of tests carried out on a test section on which HMA was placed on an unbound aggregate base layer of varying moisture content. The material used for the binder course was asphalt concrete mixture composed of aggregate of minus 16 mm grading and 35/50 bitumen. Being relatively hard it is the most often specified bitumen for binder courses and also base courses. One of its characteristics is a considerable increase of viscosity with decreasing temperature, which hampers the process of compaction. The bulk specific gravity was measured to determine the variations in the air void content through the specimens. The complex modulus of elasticity and fatigue life were the other parameters which were determined on the specimens with different air void contents. The test results show worsening of the properties which have a decisive bearing on the service life of pavement. [ABSTRACT FROM AUTHOR]

Asphalt self-healing by encapsulated rejuvenating agents is considered a revolutionary technology for the autonomic crack-healing of aged asphalt pavements. This paper aims to explore the use of Bio-Oil (BO) obtained from liquefied agricultural biomass waste as a bio-based encapsulated rejuvenating agent for self-healing of bituminous materials. Novel BO capsules were synthesized using two simple dripping methods through dropping funnel and syringe pump devices, where the BO agent was microencapsulated by external ionic gelation in a biopolymer matrix of sodium alginate. Size, surface aspect, and elemental composition of the BO capsules were characterized by optical and scanning electron microscopy and energy-dispersive X-ray spectroscopy. Thermal stability and chemical properties of BO capsules and their components were assessed through thermogravimetric analysis (TGA-DTG) and Fourier-Transform Infrared spectroscopy (FTIR-ATR). The mechanical behavior of the capsules was evaluated by compressive and low-load micro-indentation tests. The self-healing efficiency over time of BO as a rejuvenating agent in cracked bitumen samples was quantified by fluorescence microscopy. Main results showed that the BO capsules presented an adequate morphology for the asphalt self-healing application, with good thermal stability and physical-chemical properties. It was also proven that the BO can diffuse in the bitumen reducing the viscosity and consequently self-healing the open microcracks. [ABSTRACT FROM AUTHOR]

The feasibility and effectivity of recycling waste rubber and waste plastic (WRP) into asphalt binder as a waste treatment approach has been documented. However, directly blending WRP with asphalt binder brings secondary environmental pollution. Recent research has shown that the addition of WRP into asphalt binder may potentially improve the workability of asphalt binder without significantly compromising its mechanical properties. This study evaluates the feasibility of using the additives derived from WRP as a multifunctional additive which improves both the workability and mechanical properties of asphalt binder. For this purpose, WRP-derived additives were prepared in laboratory. Then, three empirical characteristics—viscosity, rutting factor, fatigue life were analyzed. Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were employed to evaluate the effect of WRP-derived additive on the workability and chemical and mechanical properties of base binder. The dispersity of WRP-derived additive inside asphalt binder was also characterized using fluorescence microscope (FM). Results from this study showed that adding WRP-derived additive increases the workability of base binder. The WRP-derived additive appears positive on the high- and low- temperature performance as well as the fatigue life of base binder. The distribution of the WRP-derived additive inside base binder was uniform. In addition, the modification mechanism of WRP-derived additive was also proposed in this paper. [ABSTRACT FROM AUTHOR]

Cold recycled asphalt mixtures (CRAM) are a cost-effective and environmentally-friendly way to reuse reclaimed asphalt pavement (RAP). This paper evaluates the rheological properties and microstructure of mineral filler-asphalt mastic, mineral filler-residue mastic, and cement-residue mastic. Then, based on the premise of using 100% RAP with a gradation that was determined experimentally, the effects of emulsified asphalt and cement on the porosity, indirect tensile strength, tensile strength ratio, dynamic stability, and mechanical properties of CRAM were evaluated. It was found that the rheological properties and cohesive coefficient of the cement-residue mastic varied differently to those of the first two types of mastic and the results show that the addition of cement can greatly improve the interfacial bonding between binders and fillers in the mastic, thereby improving the water damage resistance and high-temperature stability of CRAM. The relationships between cement content and the dynamic modulus and phase angle of CRAM are different to that for emulsified asphalt obviously. In addition, under certain conditions, the properties of CRAM can meet the requirements of relevant technical specifications for its application to subsurface layer of pavement. Hence, the use of 100% RAP in CRAM may be feasible. [ABSTRACT FROM AUTHOR]