Aged Asphalt Mixtures Research Articles

Performance of asphalt mixture incorporating kaolin clay at different aging

In the fast-changing construction industry, the usage of natural material resources is tremendous. In order to comply with the demand of construction, waste materials have been used as a replacement of natural mineral resources. In pavement engineering, waste materials can be added into road composition. Kaolin clay is one of industrial waste materials successfully been used as a replacement of cement in concrete, but in the pavement, it has lack extensive study. In this investigation, kaolin clay partially replaced bitumen and the performance of aged asphaltic concrete AC14 were investigated. Kaolin clay replaced bitumen at 0%, 3%, 6% and 9% by weight of bitumen were used through this study. Tests conducted to measure the mixture performance were Marshall Stability, resilient modulus and dynamic creep test. Generally, it shows that the samples of unaged and long-term aging of asphalt mixture containing kaolin clay at 6% to 9% showed excellent, while 9% kaolin clay were most favorable for short term aging.

Comparing Laboratory Conditioning Protocols to Longer-Term Aging of Asphalt Mixtures in the Southeast United States

AbstractThis paper uses mixture tests on cores from a full-scale and untrafficked test section to evaluate mixture conditioning protocols intended to simulate asphalt mixture damage experienced fro...

Comprehensive evaluation of long-term aging of asphalt mixtures in hot climatic condition

Aging is an inevitable phenomenon in hot mix asphalt production and during in-service period of flexible pavement operation. This paper presents an experimental evaluation of long-term aging of asphalt mixtures in Qatar. Aging of asphalt mixture was conducted on two different states i.e. (1) traditional compacted specimen at a temperature of 85°C and (2) loose mixtures at an elevated temperature of 135°C. Test results indicated that the current practice of asphalt mixture conditioning in a forced-draft oven to simulate long-term aging in the field is not sufficient for pavements in Qatar which experience the hot climatic condition. To simulate long-term aging of asphalt mixture in field, oven aging duration needs to be extended from the standard 5 days at a temperature of 85°C for compacted specimens to 75 and 45 days for wearing and base layer, respectively based on the dynamic modulus test results. Conditioning on loose mixtures at an elevated temperature of 135°C can be an alternative option in terms of time efficiency and cost.

Dynamic modulus and phase angle prediction of laboratory aged asphalt mixtures

Performance of asphalt mixture is highly influenced by oxidative aging. A considerable amount of research has been dedicated to study the aging process of asphalt binder, while the effect of other contents of the mixture on aging characteristic, such as aggregates and additives, has been overlooked. This work investigates the effect of aging on dynamic modulus and phase angle by conducting dynamic modules test on asphalt mixtures aged at nine different levels in laboratory. Test results are used to determine the parameters of a kinetic-based aging model. The model is then incorporated into a set of regression models to predict dynamic modulus and phase angle master curve of the aged mixtures. The regression models are constructed based on the relation of sigmoidal coefficients of the master curves and shift-factor parameters with a normalized kinetic-based aging function. The proposed model is validated for a mixture aged at a predefined condition by comparing the predicted phase angle and dynamic modulus with lab measurements.

A Comprehensive Evaluation of Rejuvenator on Mechanical Properties, Durability, and Dynamic Characteristics of Artificially Aged Asphalt Mixture.

In this study, the aged asphalt binder and mixture were laboratory prepared through short-term ageing testing and long-term ageing testing. Firstly, the effect of rejuvenator on physical properties of aged asphalt binders was investigated. In addition, a series of laboratory tests were performed to evaluate the influence of ageing and rejuvenator content on the mechanical properties, durability and dynamic characteristics of asphalt mixtures. Physical test results of asphalt binder testified that rejuvenator used can efficiently recover the aged asphalt binder. However, the effect of ageing and rejuvenator content exhibits different trends depending on the physical property tests conducted. Moreover, artificially aged asphalt mixture with rejuvenator has better ability to resist moisture damage and ravelling. In addition, the ITSR value is more suitable to evaluate the moisture susceptibility for asphalt recycling. Although rejuvenator improves the thermal cracking resistance and fatigue property of aged asphalt mixture, rejuvenated mixture shows greater modulus and inferior ability to resist reflective cracking than the unaged mixture. Moreover, rejuvenated mixture shows less dependence on frequency at high temperature regions and stronger dependence at low temperature regions compared to unaged and long-term aged mixtures.

The laboratory performance of asphalt mixture with Amorphous poly alpha olefins (APAO) modified asphalt binder

In this paper, asphalt binder was blended with 0%, 4%, 6%, and 8% Amorphous poly alpha olefins (APAO) to prepare modified asphalt binders. Based on the penetration, ductility, softening point, and Dynamic Shear Rheometer (DSR) test, 6% APAO was the optimal dosage in asphalt binder performance perspective. The dense graded aggregate was mixed with APAO modified asphalt binder to prepare the APAO modified asphalt mixture. The volumetric parameters of the asphalt mixture with APAO modified asphalt binder was tested. The standard Marshall stability test, immersion Marshall test, Freeze-thaw splitting test, and Marshall stability of aged asphalt mixtures test were conducted on asphalt mixtures with APAO modified asphalt binder. Based on the Marshall stability test, immersion Marshall test, and Freeze-thaw splitting test, asphalt mixture with 6% APAO possessed the best high temperature performance, the highest moisture damage resistance, and the least splitting tensile strength loss after the freeze-thaw conditions. The tensile strength decreased after the addition of APAO. There was only negligible tensile strength difference between asphalt mixture with 4% APAO and 6% APAO. Based on the Marshall stability and retained Marshall stability ratio (RMSR) of asphalt mixtures after aging, the optimal content of APAO was 6%. Therefore, 6% APAO was the optimal content for both modified asphalt binder and APAO modified asphalt mixture.

Environmental burden evaluation of hot in-place recycling of asphalt pavement based on discrete event simulation

Hot in-place recycling (HIR) is deemed as an environmental-friendly maintenance measure of asphalt pavement due to its complete recycling of aged asphalt mixture. However, the environmental burden of HIR process itself is remarkable but has been conventionally ignored. This study presented a discrete event simulation (DES) method to estimate and compare the environmental burdens of two HIR methods, the remixing method (A) and the repaving method (B). The simulation results indicated: (1) with the same paving mass, the emissions of A were greater than those of B by 19–21%; (2) with the same paving length, the emissions of A were less than those of B by 23–26%. Optimizations of the construction process were further conducted considering air emission, fuel consumption and construction time. Optimal truck number subject to transportation distance was recommended. And the impact of increasing truck capacity and altering truck dumping process calculated, with the former decreasing environmental burdens and the latter bringing trivial benefit. The developed DES model provides quantitative estimations of environmental burdens and allows for optimization of HIR construction process subject to field conditions.

Selecting a Laboratory Loose Mix Aging Protocol for the NCAT Top-Down Cracking Experiment

The objective of this study was to select a laboratory loose mix aging protocol for the NCAT top-down cracking (TDC) experiment. Field aging of asphalt mixtures was characterized using cumulative degree-days (CDD), which was defined as the accumulation of daily high temperature throughout mixtures’ service life. Performance data from over 80 existing pavements showed that TDC typically initiated after a critical field aging condition of approximately 70,000 CDD. A laboratory experiment was conducted to select an aging protocol that was representative of this critical CDD. Materials used in the experiment were from five projects in Michigan, Washington, and Alabama. Four loose mix aging protocols were evaluated in terms of their effects on the rheological and oxidation properties of asphalt binders. Results from the dynamic shear rheometer (DSR), bending beam rheometer (BBR), and Fourier transform infrared spectroscopy (FT-IR) tests showed that the 24-h, 135°C protocol yielded the most significant level of asphalt aging, followed by the 12-h, 135°C protocol, 5-day, 95°C protocol, and 6-h, 135°C protocol, respectively. No significant difference in the oxidation–hardening relationship of asphalt binders was observed for mixes aged at 95°C versus 135°C. Among the four aging protocols, the 5-day, 95°C protocol was most representative of 70,000 CDD of field aging. Additionally, DSR and FT-IR results indicated that loose mix aging of 8-h at 135°C and 5 days at 95°C were likely to achieve an equivalent aging level; thus, the 8-h, 135°C protocol was recommended as an alternative protocol to simulate 70,000 CDD of field aging.

Evaluation of Chemical and Rheological Aging Indices to Track Oxidative Aging of Asphalt Mixtures

Oxidative age hardening in asphalt binder leads to embrittlement. Embrittled asphalt is prone to fatigue and thermal cracking. Therefore, the ability to predict asphalt binder oxidative age hardening within a pavement throughout its service life could inform improved pavement material selection, design, and maintenance practices. Studying the evolution of oxidative aging requires the use of key properties to track oxidation levels, termed aging index properties (AIPs) here. The objective of this study is to identify suitable rheological and chemical AIPs to track oxidation levels in asphalt materials. A wide range of laboratory and field aged materials were evaluated in this study. A range of chemical AIPs determined by Fourier transform infrared spectroscopy (FTIR) absorbance peaks and areas were evaluated based on their correlation with laboratory aging duration. Rheological AIPs were evaluated based on the strength of their relationship to the chemical changes induced by oxidation. The rheological AIPs evaluated included the dynamic shear modulus, zero shear viscosity, Glover-Rowe parameter, and crossover modulus. The chemical AIP evaluation that most strongly correlated with laboratory aging duration is the carbonyl plus the sulfoxide absorbance peaks. The results indicate that both the dynamic shear modulus and Glover-Rowe parameter constitute rheological AIPs that relate directly to the chemical changes induced by oxidation.

Evaluation of moisture and temperature effect on crack healing of asphalt mortar and mixtures using healing agents

This study investigated the effect of temperature and moisture ingress on the crack healing ability of long term aged AC-13 asphalt mortar and mixtures. Base bitumen emulsion (BBE) and two maltene based cationic emulsions were applied on the cracks of fractured semi-circular samples of the asphalt mortar and mixtures to promote healing. Test results indicated that wet cracks of long term aged asphalt concrete could be healed using healing agents (HAs). Moisture infiltration before drying of the HAs was found to be detrimental to crack healing but initial moisture state of the crack was less influential to the ultimate healing for selected HAs. Increase in temperature increased the extent of crack healing in dry asphalt materials while moisture at 25 °C–45 °C had a minimal effect on crack healing. Water ingress had a nominal effect on the multiple fracture-rehealing performance. Generally, carefully selected HAs applied at higher pavement temperatures have the potential to heal and reheal wet cracks of asphalt pavements provided that sufficient time is allowed for the HAs to dry.

Viscoelastic Fatigue Damage Properties of Asphalt Mixture with Different Aging Degrees

In order to reveal the effects of aging on fatigue damage evolution pattern of asphalt mixture, and to reveal the fatigue damage patterns of asphalt pavement during its service life more accurately, the viscoelastic fatigue damage model for the aged asphalt mixtures was proposed based on the Burgers viscoelastic model. The dissipation energy was taken as the damage variable, and the direct tension fatigue tests for asphalt mixture in five different aging degrees were conducted. The viscoelastic parameters of the aged asphalt mixtures were obtained.The calculationmethod of the cumulative fatigue damage was proposed, which considers the aging effects. Moreover, the critical fatigue damage degree and fatigue life calculation equations were derived by employing the fatigue damage model, which were calculated and compared. The calculation errors range from 3% to 18%, which was within an acceptable error range of 30%. The research results show that the aging has a prominent impact on fatigue properties of asphalt mixtures, which could be illustrated by the change of the parameters of the viscoelastic fatigue damage model for the aged asphalt mixtures. The prediction precision of fatigue life is acceptable for using the proposed viscoelastic fatigue damage model.

Influence of temperature on the cracking behavior of asphalt base courses with structural weaknesses

Abstract Asphalt pavement is known to be deteriorated by the repetitive traffic loading, climatic condition, aging of asphalt mixture etc. after opening to traffic. Crack plays a critical role in pavement deterioration. Several studies have been conducted to obtain a better understanding with respect to climate related pavement fracture behavior. However, the limitation of the previous researches was that most of them were conducted by laboratory experiment or numerical simulation. The main objective of this study is to determine the relationship between the continuously changed temperature and the relative crack opening in asphalt base course by analyzing the data collected from an in-service asphalt pavement. To achieve this objective, four artificial transverse cracks were first induced on the asphalt subbase of a test track, and then their temperatures and crack opening were recorded by monitoring systems. Diurnal and annual trends of temperature and relative crack opening as well as their relationship were investigated and discussed. In this study, a test track with defined asphalt layers was constructed, which was specially equipped with sensors that continuously monitored the temperatures and opening widths of structural cracks in the test track. On the basis of the findings obtained, it is possible for the first time to make direct statements about the deformation conditions occurring in an asphalt base layer as a result of temperature.

State of the Art Study on Aging of Asphalt Mixtures and Use of Antioxidant Additives

The detrimental effects of hardening in asphalt pavements were first recognized by pioneering pavement engineers in the 1900s and have been studied extensively during the last 70 years. This hardening process, referred to as asphalt aging, is generally defined as change in the rheological properties of asphalt binders/mixtures due to changes in chemical composition during construction and its service life period. Aging causes the asphalt material to stiffen and embrittle, which affects the durability and leads to a high potential for cracking. This paper presents the state of the art on asphalt and asphalt mixture aging and use of antioxidant additives to retard the aging. A picture of complex molecular structure of asphalt and its changes due to atmospheric condition and various protocols used to simulate aging in laboratory environment are also discussed. Emphasis is given on recent studies on simulation of aging of asphalt mixtures as there has been limited research on mixtures compared to the asphalt binder. Finally, this paper presents the application of antiaging techniques and its mechanism, use of various types of antioxidant additives to retard aging of asphalt and, hence, improve the performance of asphalt pavements.

Performance of Waste Cooking Oil on Aged Asphalt Mixture

Asphaltic concrete pavement is popular worldwide, but this type of pavement requires frequent maintenance and rehabilitation as it cannot cope up with the increasing number of traffic vehicles and loads. Therefore, modifying asphalt pavement to reduce the damages and defects is necessary, thereby enhancing the serviceability of pavement. This study presents the effect of waste cooking oil on asphalt mixture at different ageing conditions. A 60/70 penetration-grade asphalt binder was used, and 5% of this binder was replaced with untreated and treated waste cooking oil. Asphalt mixtures were prepared at the selected 5% optimum bitumen content and under two tests, i.e. Marshall stability and resilient modulus. The findings showed the better stability and resilient modulus of long-term aged samples incorporated with treated waste cooking oil than the unaged and short-term aged samples. The incorporation of untreated waste cooking oil caused reduced performance compared with the controlled and long-term aged samples. This result can be attributed to the high acid value of waste cooking oil. Therefore, treated waste cooking oil can be used as a binder replacement given its significantly higher performance at the mentioned ageing condition than the controlled mixture.

Retarding aging of asphalt binders using antioxidant additives and copolymers

The rheological properties of asphalt binders change with aging. Aging is accelerated at elevated temperatures due to binder oxidation, leading to fatigue cracking and eventually pavement failure under heavy and repeated traffic loading. This study examined the effect of various antioxidant additives and copolymers with antioxidant agents on retarding the aging of asphalt binders. The performance of antioxidants was evaluated at the binder and mastic levels. Two unmodified binders were tested and fine asphalt mixtures made with these binders and three different aggregates were prepared and evaluated. Fatigue characteristics of asphalt binders and fine portion of asphalt mixtures (FAM) were determined before and after aging and an aging index was defined to evaluate the effect of antioxidants and copolymers on aging. The results showed that certain antioxidants and copolymers such as Redicote AP, Solprene and Calprene may retard the aging and improve the rheological properties of the asphalt binders. In addition, the results of FAM testing confirmed the favourable effect of certain antioxidants on improving the resistance to fatigue. In addition, the type of aggregate was found to influence the rate of aging of asphalt mixtures.

Investigation into crack healing of asphalt mixtures using healing agents

This study investigated the crack healing ability of aged and unaged AC-13 basalt asphalt mixtures using five healing agents. Notched semicircular asphalt mixtures were cracked and healed using the healing agents and the recovered critical load at fracture was adopted as a healing indicator. Crack healing was found to be dependent on the type of healing agent, healing time and aging of mixture. A maximum healing up to 73% was obtained after 8 days of uninterrupted healing. Multiple fracturing-rehealing of the healed mixture didn’t significantly affect the healing index (HI) of the successive cycles. The re-healing performance was sensitive to the drying rate of healing agents, and a high drying rate reduced the re-healing performance. The first day of healing had the highest contribution to the ultimate healing potential, and further increase in the healing duration resulted in a steady increase in healing index. The high healing performance indicated that carefully selected healing agents have the potential to heal cracks in asphalt pavements.

Comparison of influence of ageing on low-temperature characteristics of asphalt mixtures

Ability of relaxation of asphalt mixtures and thus its resilience to climate change and traffic load is decreasing by influence of aging – in this case aging of bituminous binder. Binder exposed to climate and UV ages and becomes more fragile and susceptible to damage. The results of the research presented in this paper are aimed to finding a correlation between low-temperature properties of referential and aged asphalt mixture specimens and characteristics (not low-temperature) of bituminous binders. In this research there were used conventional road binders, commonly used modified binders and binders additionally modified in the laboratory. The low-temperature characteristics were determined by strength flexural test, commonly used in the Czech Republic for High Modulus Asphalt Mixtures (TP 151), and semi-cylindrical bending test (EN 12697-44). Both of the tests were extended by specimens exposed to artificial long-term aging (EN 12697-52) – storing at 85° C for 5 days. The results were compared with characteristics of binders for finding a suitable correlation between characteristics of binders and asphalt mixtures.

Evaluation of age retardation effect of antioxidants in dense-graded asphalt (DGA) mixture using large molecular size

This study evaluated the effectiveness of antioxidant (AO) on retarding aging of asphalt mixture using the large molecular size (LMS) of gel-permeation chromatogram (GPC) technique. A polymer stabilizer (designated as KL) and a hydrated lime (HL) were used for preparing dense-graded asphalt (DGA) mixes to examine the effect of the AOs on age retardation. The asphalt mixtures prepared with and without AO were aged artificially in two stages; the short-term aging (SA) for one hour at 160°C and the long-term aging (LA) for one week at 76°C. The LMS values were used in the statistical test for estimation of age retardation effect of the AOs and for predicting absolute viscosity. It was found that the KL and HL were effective for inducing reduction of aging significantly at α=0.05 after SA and LA. Therefore, it was found that the LMS, which was obtained by GPC test, was a dependable variable that can be used for evaluation of age retardation. It was also observed that the KL and HL did apparently have an effect of reducing the AV, predicted by LMS, after SA and LA.

Study of the Diffusion of Rejuvenators and Its Effect on Aged Bitumen Binder

Aged asphalt mixture is heavily involved in pavement maintenance and renewed construction because of the development of recycling techniques. The aged bitumen binder has partially lost its viscous behavior. Rejuvenators are therefore designed and used in this recycling procedure to enhance the behavior of such aged reclaimed bitumen. However, tests have not yet been clearly specified to understand the diffusion characteristics of rejuvenators in aged bitumen. In this research, molecular dynamic simulation is proposed and conducted with Materials Studio software to study the diffusion behavior of rejuvenators in aged bitumen at the molecular level. Two rejuvenators, named R-1 and R-2, were included. The difference between these two rejuvenators is their chemical composition of C=O. The diffusion coefficient is determined by studying the molecular movement. Results illustrate that the proposed models can be used to study the diffusion of rejuvenators in aged bitumen sufficiently. In the meantime, a dynamic shear rheometer (DSR) is used to evaluate the recovery influence on aged bitumen resulting from rejuvenators. The experimental results strengthen the model simulations and indicate that the aging index of bitumen has a significant influence on the rejuvenating effect. Research results indicate that rejuvenators have a sufficient rejuvenating effect on the long-term aged bitumen and a limited effect on short-term aged bitumen.

Use of Nonlinear Acoustic Measurements for Estimation of Fracture Performance of Aged Asphalt Mixtures

This study evaluated the oxidative aging of asphalt mixtures by both nondestructive and fracture performance tests and investigated the possibility of estimating the low-temperature fracture properties of aged mixtures by using a nonlinear ultrasonic approach. Asphalt mixture samples, oven aged for 12, 24, 28, 32, and 36 h at 135°C, were compacted, made into test specimens, and evaluated by using a noncollinear wave-mixing approach. In addition, the embrittlement temperature and fracture energy of the replicate samples were assessed by using the acoustic emission test and the disk-shaped compact tension test. Comparison of results from the three testing methods clearly showed similar trends. This finding suggests that the fracture properties of mixtures can be estimated by using the noncollinear ultrasonic wave-mixing approach, which is a nondestructive method which does not require core extraction in the field.