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The complicated viscoelastic characteristics of asphalt binders make it a challenging task to precisely predict their rheological behavior. This study aims to investigate and compare the suitability of response surface methodology (RSM) and machine learning (ML) modeling approaches in predicting the complex modulus (G*), phase angle (δ), and rutting parameter (G*/sinδ) of Nano Silica (NS) and/or waste denim fiber (WDF) modified asphalt binders before and after short-term aging. To achieve this, an experimental scheme was designed for RSM and ML modeling with three variables including NS contents (0–6%), WDF contents (0–6%), and testing temperature (40–76 °C) as the inputs, and provided the G*, δ and G*/sinδ before and after short-term aging as the outputs. A wide range of ML algorithms was evaluated to determine the optimum ML model that can be used to accurately predict the rheological properties of NS/WDF-modified asphalt binders. RSM analysis results indicated that the G*, δ, and G*/sinδ of NS/WDF composite asphalt are significantly affected by the %NS, %WDF, and test temperatures. The RSM-developed models showed coefficient of determination (R2) values exceeding 0.97 for all responses, indicating adequate agreement between experimental results and models developed by RSM. From ML algorithms optimization and among all evaluated ML models, it was found that Gaussian process regression (GPR) exhibited the highest R2 with a value of (0.99) and the lowest Root Mean Square Error (RMSE) with a value of approximately 1%. The performance evaluation of the GPR model for predicting all responses showed a very small difference between the predicted and experimental results, highlighting the prediction accuracy of the developed ML models.

Ultra-high performance concrete (UHPC), an advanced class of fiber-reinforced cementitious material with extraordinary mechanical properties, low permeability, shrinkage and creep, and high energy absorption capacity, has seen steady increase in use, with applications covering construction of new members and retrofit of existing ones. Fibers are added in the UHPC mix to bridge cracks, carry tensile stresses, and contribute greatly to member ductility and load capacity. Hybrid fibers comprising micro and macro types are beneficial where the first type resists microcracking and the second targets macrocracking. This study investigates the effects of blending three fiber types, namely, hooked-end steel (referred to as type 1, representing macro fibers class), straight-end steel (type 2, intermediate size fibers), and carbon (type 2, micro size fiber), on the mechanical properties of UHPC. Experimental tests were performed to characterize the following mechanical properties: flowability, compressive strength, tensile strength, flexural strength, modulus of elasticity, and dry shrinkage. The primary variable in the tests was the blending of different fiber types, using either a unary form of type 1, a binary form of type 1 and 3 or type 2 and 3, and a ternary mix of all three types, at 1.56% dosage by volume. The mix with ternary fibers yielded a compressive strength, tensile strength, flexural strength, and modulus of elasticity that is 14%–17%, 14%–16.8%, 43.66%–22.16%, and 12%–16%, larger than the same respective properties of the mix with unary fibers. In addition, ternary fibers increased the cohesiveness of the mix by 17% and 26% compared to unary fibers.

This investigation is centered around the application of warm mix asphalt (WMA) technologies to address workability concerns linked to rubberized asphalt binders. The primary aim of incorporating crumb rubber (CR) and WMA additives is to establish a robust paving method that fosters energy conservation, efficient waste management, noise reduction, and improved overall performance. The current study aims to comprehensively characterize and differentiate the physical attributes of rubberized asphalt binders by employing three distinct WMA additives: Sasobit, Cecabase RT and Rediset WMX. These additives are introduced into eight unique asphalt binders. Laboratory assessments are carried out to evaluate the workability and physical properties of these binders. The evaluation encompasses penetration, softening point, penetration index, penetration viscosity number, storage stability, ductility, viscosity, and stiffness modulus analyses. The findings indicate that the rubberized asphalt binder enhanced with Sasobit demonstrates the highest levels of both hardness and softening point in comparison to asphalt binders supplemented with alternative WMA additives. The evaluation of storage stability underscores the satisfactory stability across all modified asphalt binders. Both the unmodified and modified binders meet the requirements stipulated by the ductility test; the rubberized asphalt binder modified with Rediset falls short. The rubberized asphalt binder improved with Sasobit displays the most notable enhancement in workability. Furthermore, the blend of crumb rubber and Sasobit binder reveals the highest stiffness modulus values under conditions of intermediate and high temperatures with 1.88 and 0.46 MPa, respectively. In summation, the rubberized asphalt binder incorporating crumb rubber with Sasobit showcases superior improvements in both stiffness and workability compared to counterparts modified with Cecabase RT and Rediset WMX.

Researchers across the globe have explored several alternatives to recycling natural rubber and have identified several challenges. Therefore, this study evaluates the feasibility of recycling waste latex rubber gloves (WLRG) as a bitumen modifier to enhance the bitumen’s physical, thermal, and morphological characteristics. The study adds varying percentages of WLRG (3%, 5%, 7%, and 9%) to the 60/70 bitumen and analyzes them to determine the optimum WLRG percentage. The penetration, softening point, ductility, and viscosity tests of the modified binders show a consistent pattern. All WLRG-modified bitumens are stable storage blends at high temperatures. The thermal characteristics of the WLRG particles in the modified bitumen are examined through thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The ogive graph shows that the weight loss of the bitumen modified with 3%, 5%, 7%, and 9% WLRG occurred at 457.5, 464.3, 462.2, and 459.5°C. The maximum weight loss of the control sample occurred at 465.6°C when the environment switched from nitrogen (N2) to air. The DSC graph reveals the changes in the structure or physiochemical processes of the WLRG. The melting point for the binders modified with 3%, 5%, 7%, and 9% WLRG is 133.6, 132.1, 103.5, and 133.2°C. The morphological characteristics were determined using atomic force microscopy (AFM). The bee structure gives a scientific explanation of the microstructural characteristics. A contact angle test was performed to identify the wettability of the sessile drop device by using three types of solvent, namely distilled water, formamide, and glycerol. The contact angle of water showed a decreasing trend, where the binder containing 9% WLRG had the lowest contact angle. For the control sample, the contact angles of formamide and glycerol are 73.95° and 71.85°, respectively. In summary, WLRG is a suitable bitumen modifier and can enhance the physical, thermal, and morphological characteristics of the asphalt binder.

The compacting and mixing processes involving hot mix asphalt during asphalt production can lead to air pollution as a result of a high volatile organic compound. An alternative solution that can reduce greenhouse gas emissions is by using warm mix asphalt (WMA). A proper application of additives to the WMA can improve the asphalt mixture's strength, durability, and workability. In this study, a 60/70 grade asphalt binder was added with 5% of crumb rubber (CR) and three different WMA additives at the recommended dosages, namely Sasobit, Cecabase, and Rediset. The wet method was used to blend the additives with virgin asphalt binders. The mixing and compacting temperatures were set at 135°C and 125°C, respectively, to mix the asphalt mixture. Mechanical performance tests were performed to evaluate the impact of WAM additives with CR on asphalt mixture. Based on the results, all the modified asphalt mixtures showed a better mechanical performance than the virgin asphalt mixture in terms of indirect tensile strength, moisture resistance, permanent deformation, and stiffness. Among all the WMA additives, Sasobit with CR showed the most significant impact on the asphalt mixture's performance.

Machine learning (ML) models are excellent alternative solutions to model complex engineering issues with high reliability and accuracy. This paper presents two extensively explored ensemble models for predicting asphalt pavement temperature, the Markov chain Monte Carlo (MCMC) and random forest (RF). The RF and multiple MCMC (RF-MCMC) were used to hybridise the proposed algorithms for the optimal prediction of asphalt pavement temperature. This study used thermal instruments to measure the asphalt pavement temperature in Gaza Strip, Palestine. The temperature measurements were made at a two-hour interval from March 2012 to February 2013. The temperature data was used to model the pavement temperature. More than 7200 measured pavement temperatures were used to train and validate the proposed models. The validation showed that the ML models are satisfactory. The modelling results ensured the value of the proposed hybridisation models in predicting the asphalt pavement temperature levels. The developed hybrid algorithms regression model achieved acceptable and better prediction results with a coefficient of determination (R2) of 0.96. Generally, the results confirmed the significance of the proposed hybrid model as a reliable alternative computer-aided model for predicting asphalt pavement temperature.

The Sultanate of Oman has experienced rapid development over the last thirty years and has constructed environmentally friendly and sustainable infrastructure while it continues to find economical alternative resources to achieve the goals of the Oman 2040 vision. The primary concerns are preserving natural resources and reducing the impact of carbon dioxide (CO₂) emissions on the environment. This review aims to encourage the sustainable use of reclaimed asphalt pavement (RAP) materials in pavement construction and focuses primarily on employing RAP materials in new pavement projects. Currently, new construction projects utilise a significant percentage of demolished asphalt pavement to save costs and natural resources. The key issue that arises when mixing RAP into new asphalt mixtures is the effects on the mixtures’ resistance to permanent disfigurements, such as fatigue cracks, that influence asphalt mixture performance. Numerous studies have assessed the impact of using RAP in asphalt mixtures and found that RAP increases the stiffness of asphalt mixtures, and thus improves rutting resistance at high temperatures. Nevertheless, the findings for thermal and fatigue cracking were found to be contradictory. This review will address the primary concerns regarding the use of RAP in asphalt pavements, and aims to encourage highway agencies and academic researchers in the Gulf countries to develop frameworks for the practical usage of RAP in the construction of sustainable pavement systems.

This study was conducted to investigate the effect of ageing on bitumen, before and after modification. Nano-clay modified bitumen (NCMB) was produced by adding nano-clay (NC) to 60/70 penetration grade bitumen; then, the binder was tested using conventional tests for properties such as penetration, softening point and viscosity. These tests were carried out on the modified binder before and after ageing. A rolling thin film oven (RTFO) was used to simulate short-term ageing (STA), and a pressure ageing vessel (PAV) was used to simulate long-term ageing (LTA) for the modified binder. After initial results showed an improvement for the modified bitumen regarding the effect of ageing, the investigation continued using Fourier transform infrared spectroscopy (FTIR), where the microstructure distribution of the modified binder before and after ageing was observed. Finally, there was no doubt that the effect of ageing on mixtures should be investigated. For this step, the indirect tensile strength (ITS) test, which highlights the strength changes that occur for the mixtures after ageing, was selected. The results indicated that the tensile strength of mixtures made with modified bitumen showed better resistance against ageing when NC was added, which is in good agreement with the results of previous binder tests. The results of this study show that the modification of bitumen using nano-clay as an additive improves the ageing resistance of the binder, which is consequently reflected in the strength of the asphalt mixture.

The reclaimed asphalt pavement (RAP) has become a moderately common practice in most countries; Hence, rejuvenating materials with RAP have earned publicity in the asphalt manufacturers, mainly due to the increasing raw material costs. In this study, the crumb rubber (CR) and waste frying oil (WFO) utilized as waste materials to restore the properties and enhance the rutting resistance of the RAP. Several physical, rheological, chemical properties of bituminous binders were tested. The result showed that the RAP bituminous binders incorporating WFO and CR decreased softening points and the increased penetration value; these translate to an increase in penetration index. Moreover, the viscosity of the WFO/CR combination reclaimed asphalt pavement binder showed better workability and stiffness, as well as a low storage stability temperature (less than 2.2 °C) with an acceptable loss upon heating. Without chemical reaction was observed between the waste-frying oil with the rubberized binder and the reclaimed asphalt pavement binder. Additionally, the WFO/CR rheological properties combined with the reclaimed asphalt pavement binder were comparable to the control sample. The incorporation of CR with WFO as a hybrid rejuvenator enhanced the rutting resistance. Therefore, the presence of WFO/CR has a considerable influence on the RAP binder properties while preserving a better environment and reducing pollution by reusing waste materials.

Researchers are exploring the utilisation of reclaimed asphalt pavement (RAP) as a recycled material to determine the performance of non-renewable natural aggregates and other road products such as asphalt binder, in the construction and rehabilitation stage of asphalt pavements. The addition of RAP in asphalt mixtures is a complex process and there is a need to understand the design of the asphalt mixture. Some of the problems associated with adding RAP to asphalt mixtures are moisture damage and cracking damage caused by poor adhesion between the aggregates and asphalt binder. There is a need to add rejuvenators to the recycled mixture containing RAP to enhance its performance, excepting the rutting resistance. This study sought to improve asphalt mixture performance and mechanism by adding waste frying oil (WFO) and crumb rubber (CR) to 25 and 40% of the RAP content. Moreover, the utilisation of CR and WFO improved pavement sustainability and rutting performance. In addition, this study prepared five asphalt mixture samples and compared their stiffness, moisture damage and rutting resistance with the virgin asphalt. The results showed enhanced stiffness and rutting resistance of the RAP but lower moisture resistance. The addition of WFO and CR restored the RAP properties and produced rutting resistance, moisture damage and stiffness, which were comparable to the virgin asphalt mixture. All waste and virgin materials produce homogeneous asphalt mixtures, which influence the asphalt mixture performance. The addition of a high amount of WFO and a small amount of CR enhanced pavement sustainability and rutting performance.