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Reusing reclaimed asphalt pavements (RAPs) provides economic, social, and environmental benefits. To improve the performance of these materials, rejuvenating agents such as waste cooking oil (WCO) have been implemented. The annual amounts of RAP and WCO available in the Área Metropolitana de Bucaramanga (AMB) were calculated to be 32 thousand and 22 thousand tons per year, respectively. Subsequently, international standards were reviewed and compared with Colombian regulations to establish a methodology to determine the appropriate percentage of WCO to add to RAP for hot asphalt mix preparation. The authors suggest investigating WCO levels from 3% to 6% and selecting the percentage that reestablishes the penetration grade (INV-E-706-13), softening point (INV-E-712-13), and viscosity (INV-E-717 -13) of asphalt binder. For hot asphalt mix preparation, the authors propose using the Marshall method and determining the appropriate percentage of asphalt according to stability and flow tests (INV-E-748-13), percent air voids (INV-E-736-13), and bulk density (INV-E-733-13).3).

Ultraviolet radiation, oxidation, temperature, moisture, and traffic loads produce degradation and brittleness in the asphalt pavement. Microcracks develop into macrocracks, which eventually lead to pavement failure. Although asphalt has an inherent capacity for self-healing, it is constricted. As a result, damages build beyond the ability of asphalt to repair themselves. This research employs the in-situ crack healing method of encapsulated rejuvenator technology to enhance the insufficient self-healing capability of roads. This allows the extrinsically induced healing in asphalt to assist it in recovering from damage sustained during service life. Optical microscopy, thermogravimetric analysis, and the compressive load test of capsules were done to characterise their properties. We measured the self-healing behaviour of encapsulated rejuvenator-induced asphalt utilising the three-point bending beam tests on unaged, short-term aged and long-term aged asphalt beams. The rate of oil release before and after healing was quantified using Fourier transform infrared spectroscopy. The results of these tests were utilised to explain the link between healing time, temperature, asphalt ageing, and healing level. Overall, it was determined that the encapsulated rejuvenator was acceptable for mending asphalt mixes because it increased healing temperature and duration, resulting in an up to 80% healing index.

This paper presents the synthesis and characterisation of biopolymeric capsules for asphalt self-healing. A sodium alginate biopolymer extracted from the cell wall of brown algae was used as the encapsulating material to contain Waste Cooking Oil (WCO) as a potential encapsulated rejuvenating agent for aged bitumen. Polynuclear capsules were synthesised by ionic gelation. The size, surface aspect and internal structure of the WCO capsules were evaluated using Optical and Scanning Electron Microscopy. The physical-chemical properties and thermal stability of the WCO capsules and their components were also evaluated. Moreover, the diffusion process and self-healing capability of the released WCO on cracked bitumen test samples were determined by image analysis through fluorescence microscopy. The main results of this study showed that the WCO capsules presented a suitable morphology to be mixed in asphalt mixtures. WCO capsules and their components presented mechanical and thermal stability and physical-chemical properties which suggest their feasibility for self-healing applications. It was proven that the encapsulated WCO can diffuse in the aged bitumen, reducing its viscosity and promoting the self-healing of microcracks.

Fatigue cracking of asphalt mixtures is highly dependent on ageing. Using larger amounts of reclaimed asphalt pavement (RAP) presents a concern that the resultant mixtures may be prone to fatigue cracking because of the aged binder in the RAP. Several studies have indicated that asphalt rejuvenators can allow more aged binder to be incorporated into asphalt mixtures. The four-point flexural beam fatigue test, HMA (hot-mix asphalt) fracture mechanics model, simplified viscoelastic continuum damage model, and the semi-circular bending test were used to evaluate the effect of ageing on the fatigue characteristics of high RAP mixtures modified with rejuvenators. The results from these tests were compared to see if they provided similar performance trends. The results indicated that the long-term ageing used in this study did not have a significant effect on the fatigue characteristics of the high RAP mixture with and without rejuvenators. Comparison of the fatigue tests did not show universal agreement.

Recycle and reuse of waste asphalt materials in the pavement industry has brought tremendous contributions to the infrastructure sustainability and environmental preservation. The recent literature has suggested a great potential of plasticizers to be used for rejuvenating the oxidated paving asphalts. This study was aimed at assessing the rejuvenating effectiveness by rheological characterizations of two typical plasticizers, dibutyl phthalate (DBP) and tributyl citrate (TBC), selected based on the molecular structural differences. The underlying rejuvenating mechanisms were approached using molecular dynamics (MD) simulation, for probing the interactions between the plasticizers and oxidized asphaltenes and examining the outcomes in terms of deagglomeration. The results indicated that both plasticizers were highly effective in restoring the stiffness and elasticity properties as well as fatigue resistance of the aged asphalt. According to the simulations, the two plasticizers were able to deagglomerate the asphaltene associations. Owing to the high polarity and hydroxyl group, TBC appeared to be slightly more efficient in dissociating the asphaltenes, which explained its higher effectiveness in restoring the rheological properties as compared to DBP. Both the rheology and simulation results suggested that the plasticizers were rejuvenating instead of simply softening the aged asphalt.

In this paper, the possibility of using different amounts of re-recycled (repeated recycled) Reclaimed Asphalt Pavement (RAP) in the asphalt mixture was experimentally investigated. First, a single virgin mixture was prepared and artificially aged to simulate the first generation of RAP to be used for designing the first generation of recycled mixtures. Next, the recycled mixtures were further aged to obtain a second generation of RAP to be mixed for preparing the second generation of recycled mixtures with and without the contribution of a rejuvenator. The fatigue behavior and low-temperature properties of all asphalt mixtures were experimentally investigated based on the cylindrical indirect tensile test (CIDT), Bending Beam Rheometer (BBR) mixture creep stiffness tests, and Semi-Circular Bending (SCB) fracture tests, respectively. Results indicate that re-recycled materials designed with and without rejuvenator show inferior fatigue behavior with respect to the first generation of recycled mixtures while exhibiting better performance than the virgin material. Meanwhile, poorer low-temperature creep properties were observed for the mixture prepared with recycled and re-recycled RAP. Fracture properties comparable with those of the virgin material were obtained only for re-recycled mixtures designed with rejuvenator. The present experimental work provides evidence on the possibility of using re-recycled RAP up to 40% when rejuvenators are included in the mix design.

Up to date, no extravagant attempts have been made to use the vegetable oil-based polyols as rejuvenator agents for aged asphalts. In this context, the nature and composition of these biodegradable products need to be identified and physicochemical properties of different nature of compounds need to be measured. Three different vegetable oil-based polyols designed as castor oil polyol, soybean flexible polyol, and soybean rigid polyol were characterized by FT-IR, TLC-FID, 1H-NMR, and 13C-NMR and by the determination of some usual characteristics such as acid value, hydroxyl value, iodine value, and viscosity. It is speculated that the soybean flexible polyol may serve as a potential rejuvenator for aged asphalts.

The U.S. Army Engineer Research and Development Center conducted a study to provide recommendations for evaluating asphalt surface treatments for airfield pavements. The evaluation included an analysis of laboratory testing procedures to provide quantitative predictive performance capabilities. This paper contains testing results and provides guidance on selecting appropriate surface treatments based on laboratory testing procedures. Results indicate that ASTM D 2939 is appropriate for determining a product's fuel resistance. Calculations of the International Friction Index (ASTM E 1960) provided an effective quantitative procedure for predicting a product's impact on pavement friction. Tests performed to predict a product's ability to prevent oxidation and to predict delamination were inconclusive. [PUBLICATION ABSTRACT]

Reclaimed asphalt pavement (RAP) has received much attention recently due to its increased use in hot mix asphalt (HMA) pavements to enhance pavement sustainability. The use of aged asphalt in RAP, which is highly oxidised and has lost its properties due to exposure to traffic loads and climatic conditions throughout its lifespan, can cause asphalt mixtures to stiffen and embrittle, thus negatively affecting the behaviour of asphalt mixtures. This issue may be resolved by including rejuvenating agents that can restore both physical and rheological properties of aged asphalt by increasing maltene fractions and decreasing asphaltene. However, the high restoration capacity of any kind of rejuvenating agent does not assure the durability of restored aged asphalt. This study explored the performance and durability of rejuvenated asphalt mixtures embedded with several types of rejuvenators identified from the extensive literature review. The study serves as a significant reference to predict future challenges in rejuvenating aged asphalt.

Encapsulated rejuvenators embedded in asphalt mixtures are a promising technology to extend the service life of asphalt pavements. However, their effects on the asphalt mixture’s performance still need to be properly understood. A recently developed three-dimensional discrete element method framework enables the evaluation of non-homogeneous distributions of the rejuvenator, closely resembling real conditions. This includes different scenarios involving capsule content and release efficiency. The presented numerical results show that the rejuvenator-to-mastic ratio and the number of rejuvenator-modified contacts influence the stiffness properties of asphalt mixtures. In cases where a homogeneous rejuvenator distribution is assumed, the three-dimensional DEM model predicts a significant reduction in the asphalt mixture’s stiffness that compromises the pavement’s performance. Simulations show that the diffusion effect needs to be considered for predicting the post-healed behavior of asphalt mixtures. For cases considering more suitable modified mastic amounts (less than 1.20 wt%), the effect on the asphalt mixture’s stiffness modulus is less pronounced, and the phase angle is not significantly affected. Additionally, the presented simulations suggest that the capsule content can be increased up to 0.75 wt%, and capsules with a release rate higher than 48% can be used without compromising the rheological performance of asphalt mixtures, possibly improving their self-healing properties. These numerical insights should be considered in future designs to achieve optimal post-healed behavior.