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A study was undertaken to evaluate the influence of an organic and a chemical additive on the short- and long-term ageing properties of warm-mix asphalt containing reclaimed asphalt pavement. Various mechanical tests, including dynamic creep, indirect tensile strength, semi-circular bending and resilient modulus, were conducted. The results indicated that the mixture containing reclaimed asphalt pavement without additives showed a higher flow number in both non-ageing and ageing processes, indicating higher resistance to rutting. The mixture containing the chemical additive demonstrated higher resistance to moisture susceptibility in comparison to the one with the organic admixture. Moreover, the mixtures containing recycled asphalt pavement and the chemical additive showed higher fracture energy than mixtures containing recycled asphalt pavement and the organic additive, while the latter showed the highest resilient modulus in the non-ageing and ageing process. [ABSTRACT FROM AUTHOR]

The study investigated the effects of laboratory ageing on the fluxed and water-foamed asphalt binders in scope of Fourier transform infrared spectroscopic measurements of ageing indicators and changes in their chemical composition. The investigated binders included two paving grades, two polymer modified asphalt binders, and a highly modified asphalt binder. The bio-flux additive was produced from rapeseed methyl esters in an oxidation reaction in the presence of a metal catalyst and organic peroxide. The use of the bio-origin additive, in particular oil derivatives, was aimed at softening and better foaming of asphalt binders. This modification is possible due to the good mixability of vegetable oils with an asphalt binder, which gives a homogeneous product with reduced stiffness. The study involved the rolling thin film oven, short-term, and the pressure ageing vessel, long term, and ageing to induce oxidation on the evaluated asphalt binders. The addition of the bio-flux additive has significantly decreased the measured content of ketone compounds related to oxidation in both non-aged and aged asphalt binders, although this effect after ageing were far smaller in magnitude. Additionally, both ageing processes decreased significantly the absorbances in the ester spectral bands specific to the bio-flux additive. All mentioned effects were similar in magnitude in all tested asphalt binders. [ABSTRACT FROM AUTHOR]

This paper evaluates the fracture properties of mixtures subjected to different short-term ageing conditions obtained from semi-circular bending test. Response Surface Method (RSM) was used to develop an experimental matrix based on the central composite design. Ageing temperature, ageing duration and duration in humidity and ultraviolet chamber were selected as short-term ageing parameters, while fracture toughness or stress intensity factor (K), broken aggregate (BA) and adhesion failure (AF) were regarded as responses. Image analysis technique was employed for quantification of failures (including adhesion and cohesion failures) on the fractured surface of mixtures. The susceptibility of mixtures' fracture properties to temperatures was also determined in terms of KTS. The responses were analysed using RSM. The results showed that ageing temperature and ageing duration were the dominating ageing factors affect responses. Ageing increment resulted in higher K and BA while exhibited contradictory effects on AF. Test temperature increment reduced the fracture toughness. The KTS was increased at higher temperatures. Lastly, RSM and image analysis technique exhibited great reliability and capability to study the behaviour of the responses exposed to various ageing conditions. [ABSTRACT FROM AUTHOR]

This study investigated the effect of short-term and long-term ageing on the dynamic modulus of foamed warm mix asphalt (WMA) produced by water injection and traditional hot mix asphalt (HMA). Four asphalt binders (PG 64-22, PG 64-28, PG 70-22 and PG 76-22) and one aggregate (limestone NMAS 12.5 mm) were used in the preparation of the laboratory-produced asphalt mixtures. The short-term and long-term ageing of the asphalt mixtures were simulated using AASHTO R 30. The experimental test results showed lower dynamic modulus values for foamed WMA than those obtained for traditional HMA for both short-term and long-term oven-aged specimens. By comparing the dynamic modulus values of the short-term and long-term oven-aged specimens, it was observed that some mixtures, such as those prepared using PG 64-22, had a smaller increase in dynamic modulus for foamed WMA mixtures than traditional HMA mixtures, while a comparable increase in dynamic modulus for both foamed WMA and HMA was observed for other mixtures, such as those prepared using PG 70-22 and PG 76-22. This suggests that the binder type plays a significant role in determining the ageing characteristics of foamed WMA and HMA mixtures. [ABSTRACT FROM AUTHOR]

The field performance of bituminous roads depends highly upon the rheological properties of the bitumen used. Therefore, it is paramount that the determination of the rheological properties of bitumen binders is done accurately. Determining the time it takes for a specimen to reach the desired test temperature before starting any rheological examination is one such important aspect. This time is known as the time for thermal equilibrium. This study focuses on determining the time it takes for a specimen to achieve the thermal equilibrium. Here, the unaged, rolling thin film oven (RTFO) aged and pressure aging vessel (PAV) aged bitumen binders were subjected to an oscillatory test at 10 rad/s using a Dynamic Shear Rheometer (DSR) and the variation of the complex modulus with time was analyzed. The observed results clearly showed that the test temperature and aging significantly affects the time it takes for a sample to reach the thermal equilibrium. [ABSTRACT FROM AUTHOR]

• Four machine learning models were developed to predict the rheological properties of recycled plastic modified bitumen. • The proposed CatBoost model achieved the highest performance compared to the other models. • The feature variables were ranked according to their impact on predictions by SHAP analysis. • The interaction of feature and target variables were analysed by partial dependence plots. • Machine Learning models served as an effective & reliable tool for predicting RPMB properties. Recycled plastics can be used to improve the rheological properties of neat bitumen. The rheological properties of recycled plastic modified bitumen (RPMB) depend on multiple factors, including the modified bitumen composition and ageing conditions. In this study, four ensemble machine learning (EML) models were developed based on experimental data records, aimed at predicting the rheological properties of RPMB in terms of complex shear modulus and phase angle at both unaged and short-term aged conditions. The performance of four EML models was evaluated using various metrics such as Mean Absolute Error (MAE), Root Mean Squared Error (RMSE), coefficient of determination ( R 2) and Objective Function Value (OBJ). The results indicated that CatBoost exhibited the highest accuracy, achieving a coefficient of determination of 0.98 for complex shear modulus prediction and 0.93 for phase angle prediction. Additionally, SHapley Additive exPlanations (SHAP) analysis, individual conditional expectation and partial dependence plots were utilised to identify the magnitude and impact of inputs variables on complex shear modulus and phase angle, as well as analyse the relationship between input and output variables. The findings highlighted that the temperature and frequency of the dynamic shear rheometer test, the amount of polymer and the penetration of the base bitumen are key factors influencing the rheological properties of RPMBs. The proposed approach provides useful information to decision-makers for effectively evaluating the composition of bitumen mixtures and the rheological properties of RPMBs based on specific project conditions. [ABSTRACT FROM AUTHOR]

An appropriate bitumen content and its properties in hot mix asphalt (HMA) mixture impact on the long-term mechanical strength of the laid asphalt pavement and the required road operation properties. During the production of a HMA mixture in an asphalt mixing plant (AMP), relationships between the structure and interaction of the mixture are established based on technological processes that specify bitumen batching and component mixing. These processes ensure the long-term strength, texture, evenness, the degree of damage and rheological properties of road pavement. The presented mathematical model enables us to determine the distribution of oxygen pressure by time in differently sized drops of bitumen during their fall into a mixer. The model considers oxygen diffusion, which depends on temperature, and heat conductivity, which depends on temperature, density and specific heat. An active experimental investigation under real production conditions demonstrated that the method of bitumen discharge from a batcher, temperature and time spent mixing materials with hot mineral aggregates impact on properties of bitumen binder within the produced HMA mixture. Parameters of technological processes for mixing of bitumen with mineral aggregates that occur in a bitumen batching system (BBS) are stochastic and impact on the composition of bitumen binder as well as physical and mechanical properties of the produced HMA mixture, namely, air void content, stability, flow and Marshall quotient. [ABSTRACT FROM PUBLISHER]

Bitumen holds the aggregate in hot mix asphalt (HMA). Without asphalt binder, HMA would simply be crushed stone or gravel. A bitumen batching system (BBS) is comprised of bitumen storage, transportation, weighing and discharge equipment in an asphalt mixing plant (AMP). The function of the equipment is to batch the binder heated up to working temperature and to discharge it into a mixer in batches. In the entire system, the binder is exposed to high temperature and oxygen. Bitumen is slowly oxidized when it is in contact with oxygen. The degree of oxidation is highly dependent on temperature, time and thickness of a bitumen film. This article models the key factors influencing on the dynamics of bitumen oxidation in BBS equipment. Stone mastic asphalt (SMA) mixture was produced from the same materials according to the same job-mix formula (JMF) in neighbouring batch type AMP by changing the mixing time of materials from 20 to 60 s. Bitumen binder was separated from the taken SMA samples and its gradation was identified. Thus, Marshall specimens were produced and tested. PenetrationPen25of bitumen binder recovered in rotary evaporator, softening pointTspwas determined and penetration indexIpwas calculated. The presented findings of experimental investigation show that the properties of bitumen binder in BBS working at two different technologies changed inconsistently. Due to gravitation, the bitumen intensively flowing into a mixer (BBS1) is impacted by oxidation more than the bitumen batched by a high-pressure pump (BBS2). [ABSTRACT FROM PUBLISHER]