Addition Of Reclaimed Asphalt Pavement Research Articles

On the effect of nano calcium carbonate on the flexibility and tensile-shear cracking resistance of greener WMA asphalt concretes containing RAP contents

Asphalt mixtures are widely used materials for paving roads, however, they need a significant amount of virgin materials, and their preparation process is environmentally unfriendly. In this regard, using less harmful production processes and using recycled materials can be beneficial. In the current study, the cracking resistance parameters (fracture toughness and fracture energy) of warm mix asphalt (WMA) mixtures, prepared with high contents of reclaimed asphalt pavement (RAP) were investigated, while different contents of nano calcium carbonate (NC) were used as a modifier. The cracking resistance studies were done for the full range of mode I/II fracture conditions. From the results, it is seen, that the addition of RAP increases both fracture toughness and fracture energy, regardless of the mode mixity and NC contents (respectively by an average, of 30 % and 20 %). The NC also made the mixture more resistant to cracking, so the enhancement of fracture energy by up to 30 % and the enhancement of fracture toughness by up to 20 % is observed. The NC optimum content was calculated in the range of 2–4 % (in weight of binder), varied based on the considered variables. As a result of increasing the material’s brittleness by adding RAP and NC, the flexibility index showed a decrease. In separate evaluations, the effect of variables on strength parameters was studied statistically, showing that the fracture toughness in mode II, is about 1.2–1.5 times higher than fracture toughness in mode I. Also, theoretical frameworks were used to predict the trend of fracture data, showing the consistency of experimental results and theoretical predictions.

Full range of mode I and II cracking performance of asphalt mixtures containing low to high reclaimed asphalt pavement (RAP) contents; modified by recycling agent and substituting of a softer binder

Reclaimed asphalt pavement (RAP) is a recycled material that can decrease the consumption of virgin materials; however, it increases stiffness and brittleness, resulting in cracking. In this regard adding recycling agents and using soft binders can be a solution. In this study, base binder (PG 64–22) with recycling agent and softer binder (PG 58–22) are used to enhance the fracture behavior of asphalt mixtures containing low to high RAP contents (20%, 40%, and 60%). The fracture test was performed using a semi-circular bending (SCB) specimen under pure mode I, two mixed mode I and II, and pure mode II loading. Also, the effect of air voids content is reviewed. Results show that the addition of RAP in mixtures prepared with PG 64–22 binder and recycling agent increases the fracture toughness from 1.22 to 1.25, 1.27, and 130 MPa√m, and reduces the fracture energy from 3.46 to 3.44, 3.36, and 3.24 KJ/m2 (respectively for of 20%, 40% and 60% substitution). By comparing the effect of binder types, although the fracture toughness of mixtures prepared with PG 58–22 binder was lower than mixtures prepared with PG 64–22 binder and recycling agent (at most 11% lower), but the fracture energy of mixtures prepared with PG 58–22 binder was superior (6–19% higher). Based on the data, regression equations of linear trends were extracted, and the relationship between fracture toughness and fracture energy data was clustered and formalized.

Investigation of resilient modulus and permanent deformation of tropical soil with Reclaimed Asphalt Pavement

By the end of 2020, the mechanistic-empirical method for pavement design had come into effect in Brazil. Several studies have analyzed the use of alternative or non-conventional materials in pavement structures and have shown that local soils can be improved by the incorporation of Reclaimed Asphalt Pavement (RAP). Therefore, this paper aims to analyze the performance of mixtures of Brazilian lateritic soil with RAP for applications in granular layers of asphalt pavements. Different proportions of the mixture were used: mixture 1 (0 % RAP, 100 % Soil), mixture 2 (25 % RAP, 75 % Soil) and mixture 3 (50 % RAP, 50 % Soil). The study’s methodology involves the characterization of lateritic soil, the mechanical performance analysis of the proposed mixtures by the resilient modulus and permanent deformation tests, and mechanistic-empirical pavement performance simulation, using the specific Brazilian MeDiNa software, which was developed and calibrated for specific Brazilian traffic, climate and material conditions. The results indicated that the addition of RAP to lateritic soil can improve the performance of the material for granular layers of asphalt pavements. In addition, the mixture with 25 % RAP showed the best behavior, in terms of the appearance of a cracked area and a less significant worsening, in terms of deformation, when compared to the soil without the addition of RAP. Thus, this study contributes to knowledge in the transportation infrastructure field, regarding the mechanistic-empirical parameters for composite mixtures of lateritic soils and RAP and enabling the implementation of satisfactory sustainable solutions involving the disposal of waste in pavement construction.

Evaluation of the impact of long-term aging on fracture properties of warm mix asphalt (WMA) with high RAP contents

This study aimed to investigate the effects of long-term aging on the fracture characteristics of Warm Mix Asphalt (WMA) containing Reclaimed Asphalt Pavement (RAP). To this end, various RAP contents (0, 50, 75, and 100%) and one WMA additive (Zycotherm) were used. The Semi-Circular Bending (SCB) fracture test was conducted at intermediate temperature and fracture parameters, including the fracture force, fracture toughness, strain energy, J-integral, stiffness, and flexibility index were measured to identify the impact of aging and RAP addition on different fracture properties of WMA mixtures. To remedy the problem concerning the amorphous trend of fracture properties over the service time and intersecting the curves of fracture parameters versus service time, the area beneath the fracture parameter was employed as a reliable index for comparing different mixes. Then, summations of the area of all fracture parameters versus service time for various mixtures with different RAP content were identified as the overall fracture resistance of each mixture. Finally, an analysis of variance (ANOVA) was determined to statistically assess the results of the SCB fracture test. This study highlights the importance of considering long-term aging effects on WMA mixtures containing RAP and the potential benefits of using high RAP content in flexible pavements. Overall, this research can help agencies make a more precise decision regarding the consequences of high RAP content on the long-term performance of asphalt pavements.

Evaluation of thermal cracking probability for asphalt concretes with high percentage of RAP

The paper presents determination of the probability of thermal cracking of asphalt mixtures with different reclaimed asphalt pavement (RAP) content on the basis of laboratory tests and analytical evaluation using thermal stress development method. Probability was evaluated taking into consideration: the type and gradation of the mixture and the quality and content of RAP. Thermal stresses were determined using two models: elastic and viscoelastic. Addition of RAP decreases the low-temperature properties of all the tested asphalt mixtures. In the case of wearing and binder courses, addition of 20% of RAP increases the cracking temperature by around 5–6 °C.

Energy evolution in fracture process of hot mix asphalt containing reclaimed asphalt pavement and rejuvenator

The fracture of hot mix asphalt (HMA) is accompanied by the energy absorption and release. Energy includes the dissipated energy (Ud), elastic strain energy (Ue) and post crack energy (Up). The dissipated energy is closely related to the plastic behavior, while the elastic strain energy is related to the reversable deformation. This study established a framework to analyze the energy evolution by investigating Ud, Ue and Up within the semi-circular bending (SCB) test. The development of Ud, Ue and Up was explored considering the whole fracture process from the low to the intermediate temperature for specimens with different content of reclaimed asphalt pavement (RAP). Three temperatures, −10 °C, 0 °C and 25 °C, were selected in the SCB test. Reclaimed asphalt pavement (RAP) with the content from 0% to 100% was incorporated to reveal the impact of RAP on the energy evolution during the fracture process. Rejuvenator was added to present the possible benefit in enhancing the resistance to fracture. Meanwhile, a brittleness parameter (BI) considering these energy parameters were proposed to show the effect of RAP on the brittleness of HMA. Results indicated that at −10 °C and 0 °C, a low content of RAP (25%) could generate positive effect on fracture resistance in terms of fractur energy. At 25 °C, fracture energy increased with the increase of RAP content, and the optimum RAP content was 75%, at which the fracture energy reached to the maximum value. At −10 °C and 0 °C, the total energy and Ue both increased with a high rate, and the magnitude of Ud was relatively small. The inclusion of 75% RAP made the increase of Ud more obvious than the specimens without the addition of RAP. No matter for mixtures with 0 or 75% RAP, Ue decreased quickly after the peak load and Ud increased sharply and was almost consistent with the total energy, indicating the quick failure after the peak load. At 25 °C, after the peak load, the total energy and Ud still increased with very high rates, indicating significant plastic deformations were induced due to the increase of temperature. From −10 °C to 25 °C, rejuvenator presented positive effect on enhancing the fracture resistance. The enhancement was mainly due to the improvement of the dissipated energy and the post-peak energy. RAP could apparently increase the brittleness index (BI), and rejuvenator could decrease BI due to the softening behavior.

Laboratory Investigation of Reclaimed Asphalt Mixtures Containing Cyclogen and Vacuum Bottom Rejuvenators

The use of reclaimed asphalt pavement (RAP) to create recycled asphalt mixture is attracting great interest because of landfill space decrease and natural resources saving. Also, incorporating rejuvenators is an effective method to promote the utilization of RAP materials in hot mix asphalt (HMA) production. The main goal of this study was to evaluate the effect of Cyclogen and vacuum bottom (VB) rejuvenators on the performance of RAP mixtures against moisture sensitivity, rutting resistance, and tensile strength. In this regard, mixtures were constructed with different RAP contents (0, 35, and 70% by asphalt mix weight) and virgin aggregates. Furthermore, three contents of Cyclogen (0, 5, and 10%) and VB (0, 15, and 30%) by the weight of RAP binder were used. The laboratory test results revealed that RAP materials enhanced the indirect tensile strength, rutting resistance, and moisture sensitivity of asphalt samples. Moreover, increasing RAP content improved the rutting resistance and permanent deformations of asphalt samples. The addition of RAP also enhanced the resilient modulus and tensile strength of asphalt samples; this increase was subject to RAP content applied. Furthermore, the effect of rejuvenators on the performance characteristics of RAP mixtures showed that adding VB and Cyclogen decreased tensile strength, resilient modulus, and strain creep and increased the moisture sensitivity of RAP mixtures.

Prediction Models for Modified Pavement Mixtures by Reclaimed Asphalt in Terms of Durability Indicators

The asphaltic pavement is often subjected to various types of distress during the service life caused by excessive load, construction practices, deficient materials, and environmental conditions. A lot of pavements may occur due to moisture damage because of the presence of water on the pavement's surface, which affects the pavement's service life. It needs periodic maintenance, which requires materials and money. So many countries take the economic side by reusing old, damaged pavement and mixed with new materials in addition to its sustainable benefits, the old material called reclaimed asphalt pavement (RAP). This study examines the effect of adding RAP on durability indicators, including tensile strength ratio, retained Marshall Stability, and durability Index, in addition to prediction statistical models for reclaimed asphalt pavement mixtures in terms of durability indicators. To achieve the goals of this study, the asphalt mixtures are designed according to the superpave system; the samples are compacted by a superpave gyratory compactor with a diameter of 100 mm and prepared with (6%, 13%, 19%, and 25%) RAP content with three conditioning periods of (1, 3, and 7) days and two aging periods (short term aging for loose mixture at 135˚C for 4 hours long term aging for 120 hours at 85˚C), and two testing temperature of 25˚C and 60˚C. The results indicated that stability increased as the RAP content increased compared to the control mix, and indirect tensile strength increased with RAP addition for both aging periods. Also, results illustrated that the tensile strength ratio for specimens tested at 25˚C is higher than that tested at 60˚C temperature.

Effect of Bitumen Production Process and Mix Heating Temperature on the Rheological Properties of Hot Recycled Mix Asphalt

Heavy traffic loads require the replacement of damaged pavements, so a huge amount of reclaimed asphalt pavement (RAP) material is now available and must be recycled in order to avoid landfill and to achieve both environmental and economic benefits. The most common and profitable solution to reuse RAP is associated with the hot recycling technique, as it allows recovering both solid and binding components of RAP. Several factors influence the performance of hot recycled mix asphalt (HRMA). Among those, this paper focuses on the role played by the origin of the virgin bitumen, i.e. the oil-distillation process, and by the mixing temperature adopted during HRMA production. The objective was to evaluate the rheological properties of mixtures produced using a high amount of RAP (50%), two different rejuvenators, two mixing temperatures (140 °C or 170 °C) and two neat bitumen types derived from different distillation processes (visbreaker and straight-run). The results showed that the addition of RAP led to an increase in the dynamic modulus and a decrease in the phase angle, while the use of rejuvenators partly tended to rebalance these characteristics. The visbreaker bitumen showed a higher sensitivity to short-term aging than the straight-run, determining higher mix stiffness and lower viscous features. The higher mixing temperature also determined an increase in the complex modulus and a reduction in the phase angle as a result of the higher mobilization of the aged bitumen from the RAP.

Development of a Model to Estimate Percentage of Reclaimed Asphalt Pavement (RAP) Binder Contribution Based on Design and Performance of Super High RAP Mixes

Reclaimed asphalt pavement (RAP) is one of the most recycled materials. The allowed RAP percentage in asphalt mixes is typically limited because of concerns over variability, binder stiffness, cracking performance, and generally the unknown associated with RAP. With abundant RAP stockpiles, the use of higher percentage RAP in asphalt mix may be warranted if performance can meet or exceed low RAP (LR) mixes (20% RAP or lower). In this study, high RAP (HR) mixes (40% RAP) and super high RAP (SHR) mixes (greater than 40% RAP) were designed, and their performance was compared with LR mixes. Mixes that cover two climates, Eastern and Western Washington, were included in this study. A lower performance grade (PG) virgin binder and a bio-based rejuvenator were used in HR and SHR mixes to allow the blended binder to meet the target PG required by the Washington Department of Transportation (WSDOT). Mix volumetrics and binder PGs of these mixes were designed close to each other, indicating the feasibility to produce RAP mixes up to 100% RAP. Overall, the addition of RAP improves the rutting performance but reduces the cracking performance of SHR mixes. Two measures were evaluated to mitigate SHR mixes’ cracking potential, including adding extra 0.5% virgin binder or 50% rejuvenator above the original dose, which improved the cracking performance of SHR mixes but reduced the rutting resistance. Based on these results, a recycled binder contribution model was developed to estimate the percentage of RAP binder contribution based on rutting and cracking performance testing.

Laboratory investigation of bituminous concrete using Reclaimed asphalt pavement and waste Engine oil

The conventional method of preparing bituminous mixes incorporating bitumen and virgin aggregates requires a huge amount of energy to produce along with environmental concerns. In pavement industry, the usage of Reclaimed Asphalt Pavement (RAP) material is growingup dueto financial considerations and the necessity of environmental conservatism. The effective utilisation of reclaimed asphalt pavement waste in bituminous pavement can overcome its disposal issue as well as it is cost effective too. Whereas replacing RAP with virgin aggregates have some drawbacks related to workability and overall quality of the pavement. Reclaimed Asphalt Pavement is subjected to environmental degradation hence affected due to aging. Long term aging effect is very prominent in reclaimed asphalt pavement materials. Hence, it becomes stiff and difficult to employ. To make it workable and its efficacious usage rejuvenators are needed. The addition of oil-containing additives can be useful as rejuvenators. For the present study, Waste Engine Oil (WEO) has been used as a rejuvenating agent. The main objective of this research is to evaluate the effect of RAP with or without rejuvenator in the Hot Mix Asphalt (HMA) mixtures. To assess the performance of the bituminous mixes Marshall properties, Tensile Strength Ratio (TSR) and Indirect Tensile Strength (ITS) for moisture susceptibility were performed. The HMA mixture with 20%, 30%, 40%, 50%, 60%, and 70% of RAP content were prepared and subsequently 1.5% of waste engine oil (by the weight of RAP content) was added to other HMA mixes containing the same RAP proportion. Corresponding result indicates that with the addition of RAP to the HMA mixes showed improved Marshall Properties, Tensile Strength and resistance against moisture susceptibility. Whereas, addition of WEO improves the Marshall Properties but decrement in Tensile Strength was observed.

Determination of composite modulus of concrete containing reclaimed asphalt pavement using micromechanical modelling and soft computing techniques

Portland cement concrete (PCC) containing reclaimed asphalt pavement (RAP) is an eco-friendly material, which is beneficial to the economy, society and environment. Before the material can be implemented in the field, a comprehensive evaluation of the effect of the RAP addition on PCC is of great necessity. Modulus of elasticity (MOE), an important measure of concrete material stiffness, dictates the stress and strain in concrete structures. This paper aims to propose a modeling approach to determining the MOE of PCC containing RAP aggregates as a virgin coarse aggregate replacement. Analytical models for individual and composite phases of RAP-PCC were presented and compared. Soft computing techniques including artificial intelligence (AI) algorithms were applied. The study shows that the calibrated model could successfully predict the MOE of RAP-PCC at different curing ages and RAP replacement levels. The proposed approach can serve as a rapid but accurate tool for the determination of the MOE with any RAP replacement levels using limited experimental data.

Research on the influence of RAP and aged asphalt on the performance of plant-mixed hot recycled asphalt mixture and blended asphalt

The overuse of resources and environmental destruction has led to the development of renewable research. Research on reclaimed asphalt pavement (RAP) has received widespread attention. In this study, reclaimed milling material from China’s Changyu Highway, which has been in operation for 15 years, was used to study the influence of aged asphalt content on the rheological properties, high-temperature performance, low-temperature performance and microscopic performance of blended asphalt and the impact of RAP content on the high-temperature stability, low-temperature crack resistance, water stability and resilience performance of recycled asphalt mixtures. The results show that the impact of aged asphalt content on the performance of base asphalt shares the same trend with the influence of RAP content on the performance of recycled asphalt mixture. With the admixing of aged asphalt, the blended asphalt is harder, increases in elasticity, and decreases in viscosity. The high-temperature performance improves, but the low-temperature performance worsens. With the addition of RAP, the water stability of the recycled asphalt mixtures improves, the high-temperature stability improves, and the low-temperature crack resistance worsens. This result is consistent with dynamic modulus test results. Overall, based on the micro and macro properties of blended asphalt and asphalt mixtures, a reasonable RAP content of 30% for road performance is given when the gradation is ATB-25.

Performance Evaluation of Fatigue and Fracture Resistance of WMA Containing High Percentages of RAP

Sustainability and durability are the key requirements of pavement structure. Sustainability of asphalt pavement structure involves utilization of Warm Mix Asphalt (WMA) technologies with the addition of Reclaimed Asphalt Pavement (RAP), where durability of asphalt involves performance parameters like fatigue and fracture resistance properties etc. Utilizing the RAP content in asphalt mix increases the mixing and compaction temperature which may degrade the performance of asphalt. Hence, numerous studies have recommended different WMA technologies to decrease mixing and compaction temperature of asphalt mix containing RAP. The present research work evaluates the fatigue and fracture performance of WMA and Hot Mix Asphalt (HMA) with varying percentages of RAP and Sasobit. Different mixes of WMA and HMA were designed with varying percentages of RAP (0, 20, 40 and 60%) through Marshall Mix design. Sasobit (organic/wax-based additive) was used as WMA technology to prepare WMA at varying percentages (0, 2, 4 and 6%). The fatigue behavior of asphalt was evaluated using four-point bending test, where fracture resistance of asphalt was determined using Semi Circular Bending (SCB) test in the laboratory. Fatigue and fracture resistance of WMA were improved with the increase in percentages of Sasobit and RAP content, while the addition of RAP in HMA showed a decreasing trend of fatigue and fracture resistance due to the stiffer nature of RAP. Furthermore, WMA was identified as economical for construction besides other benefits like improved properties and environment friendly asphalt mix. Doi: 10.28991/cej-2021-03091741 Full Text: PDF

Multi-scale performance evaluation and correlation analysis of blended asphalt and recycled asphalt mixtures incorporating high RAP content

Circular utilization of reclaimed asphalt pavement (RAP) becomes a promising trend for sustainable construction due to economic benefits and conservation of non-renewable natural resources. This paper explored properties indexes of blended asphalt and performances of recycled asphalt mixtures (RAM) as well as their correlation analysis, aiming to facilitate further application of asphalt mixtures incorporating high RAP content. Rheological properties and microscopic properties of blended asphalt with virgin asphalt, two rejuvenators and high proportions of aged asphalt were determined. The road performances of high dosage RAP recycled asphalt mixtures were investigated and their links with properties indexes of blended asphalt were also evaluated. The results indicate that incorporating rejuvenators and virgin asphalt in aged asphalt can improve its viscous characteristic and rebalance its colloidal stability, functional group indexes and microstructures. N rejuvenator demonstrates stronger permeation and superior regeneration effect on aged asphalt. The addition of RAP deteriorates moisture susceptibility, cracking resistance and fatigue performance of RAM and conversely promotes its permanent deformation. Rutting critical temperature and creep rate of blended asphalt exhibit higher prediction accuracy on rutting resistance of RAM than |GTS| and complex viscosity, according with quadratic equation. It is suggested that fatigue critical temperature of asphalt might be one of the factors dictating fatigue resistance of RAM with high RAP content.

Mechanical Performance of Reclaimed Asphalt Pavement Modified with Waste Frying Oil and Crumb Rubber

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.

Dynamic Modulus Characteristics of Mixtures Containing Recycled Asphalt Pavements, Warm Mix Additives, and Antistrip Agents

Abstract The utilization of reclaimed asphalt pavement (RAP) has proven to be a promising technology to solve some of the environmental issues and resource shortages in many parts of the world. The objective of this study was to investigate dynamic modulus and phase angle of surface type mixtures using two warm mix asphalt (WMA) technologies (i.e., warm mix additive E and foaming), and two liquid antistripping agents (ASAs). A total of 20 mixtures were designed and tested. Viscoelastic master curve modeling, statistical analysis, as well as continuous relaxation spectrums were conducted to obtain a better understanding of the properties of the mixtures. The results implied that RAP or WMA technologies had significant effects on mechanical performances, which should be carefully considered during mix design, but ASA agents, statistically, did not have such effects. In addition, the influence of RAP depended on WMA technology type, and the effects of ASA agents relied on aggregate and RAP source. The rheological index showed that both WMA technologies and ASA materials had negative impacts on the rheological properties of the mixtures, but the addition of RAP mitigates this impact only for mixtures containing ASA additives. Furthermore, the continuous relaxation spectrum confirmed the negative influences of WMA technologies and no obvious effects of ASA materials.

Mechanical characterization of warm mix asphalt mixtures made with RAP and Para-fiber additive

Asphalt recycling can help reserve natural resources and save money. However, in producing hot mix asphalt (HMA), utilizing reclaimed asphalt pavement (RAP) high heat rate is produced which leads to the stiffening of asphalt binder and producing toxic gases. This in turn will cause massive environmental pollution. As a money-saving technology, Warm Mix Asphalt (WMA) produces asphalt mixture at lower temperatures, and reduces environmental pollution as well as ageing and stiffness of the asphalt binder. This study is aimed at investigating the use of two techniques to decrease environmental pollution, save energy and costs, and improve asphalt mixture performance: WMA technique and RAP materials in asphalt mixtures. The Para-fiber additive was also employed in different values. With respect to the RAP, the use of virgin aggregates was decreased. To compare and evaluate the mechanical performance of asphalt mixtures, tests including resilient modulus, dynamic creep, indirect tensile strength, indirect tensile fatigue, and boiling water tests were conducted. According to the results, using RAP led to an increase in resilient modulus of mixtures and improved the resistance against permanent deformation. Also, by the addition of Para-fiber, the fatigue life of asphalt was improved. Moreover, according to the results of the fatigue test, it was shown that by the addition of RAP, the fatigue life of mixtures was decreased remarkably, yet it was enhanced by using Para-fiber.

Fatigue and Thermal Cracking of Hot and Warm Bituminous Mixtures with Different RAP Contents

This paper presents results of laboratory tests on hot and warm bituminous mixtures produced with Reclaimed Asphalt Pavement (RAP). Additives were used to produce warm bituminous mixtures. Fatigue behaviour and thermomechanical behaviour at low temperature were investigated. Fatigue was studied by analysing the tension/compression fatigue test results. Four different failure criteria were used in order to evaluate fatigue life. The low temperature behaviour of the materials was characterized using the Thermal Stress Restrained Specimen Test (TSRST). For each material, three replicates were performed. The experimental device was improved so that radial strains in two directions could be measured during the tests. Tri-dimensional behaviour could thus be investigated. The results of both tests were analysed and the influence of the void content, RAP content, type of additives and manufacturing process was evaluated. The results show that RAP addition and warm bituminous mixtures could be combined to obtain mixtures with performances comparable to classical hot mixtures.

Prediction of Dynamic Modulus of Hot Mix Asphalts with Reclaimed Asphalt Pavement

This study evaluated the viscoelastic properties of a performance grade (PG) binder blended with different percentages of binders recovered from reclaimed asphalt pavement (RAP) for conditions (materials, climate, and specifications) prevailing in Oklahoma. The viscoelastic properties of the blended binders were then used to estimate dynamic modulus ( E ∗ ) values of the new mixes with RAP by using the Witczak model through time-temperature superposition (TTS) principles. The recovered binder from RAP was found to be significantly stiffer than the virgin binder (PG 64-22). The addition of RAP increased the complex modulus ( G ∗ ) of the base binder, so did the E ∗ of the corresponding mix. The creep stiffness resistance of the asphalt binder at low service temperatures decreased with the addition of RAP. With up to 10% RAP binder, no notable changes were observed in the viscosity and PG grade of the virgin binder. With 25% and 40% RAP binder, the PGs of the blended binders were found to be PG 70-16 and PG 76-16, respectively. It was observed that the E ∗ master curves predicted from PGs of the blended binders were in close agreement with those estimated from the laboratory-measured E ∗ data. The dynamic shear rheometer (DSR) data of rotational thin film oven (RTFO)-aged blended binders predicted significantly lower E ∗ values compared to the measured ones. The E ∗ values predicted from rotational viscosity (RV) test data were found to be higher than the measured E ∗ values. The findings of this study are expected to provide transportation professionals with a better understanding of new mixes with high RAPs.