Cracking Resistance Of Mixtures Research Articles

An Evaluation of Asphalt Mixture Crack Resistance and Identification of Influential Factors

The crack resistance of asphalt pavement mixtures directly impact pavement service condition and pavement distress. And characterizing the crack resistance of a pavement mixture can reflect the crack resistance potential of asphalt pavement. This study analyzes several representative highway sections based on time, material, and service conditions to identify the mixture type of three layers. Semi-circular bending tests are conducted at 15 °C, and load–displacement curves are recorded. Factor independence analysis is performed, and combinations showcasing the cracking performance of the surface layer, middle layer, and bottom layer are selected. Analysis of variance (ANOVA) evaluating the indices versus selected factors for the three layers identifies significant influencing factors, and the crack resistance is analyzed based on these significant factors. The crack resistance of the middle layer with the highest truck loads is significantly lower than the two other lanes and the shoulder. Transverse crack spacing (TCS) can be used to directly evaluate the crack resistance of the mixture. The Factor dots upper rate (FUDR) and absolute Factor dots upper rate (absFUDR) indices are introduced to quantify the percentage deviation of a factor specimen from the average crack resistance index–fracture energy ratio, indicating whether the crack curve becomes sharper or flatter. The factor dots upper rate index is then applied to characterize the factors, and the results are reasonable. It is found only on the surface and middle layers that the service age has significant impacts on crack resistance, the Transverse crack spacing has significant impacts on crack resistance index, and the Factor dots upper rate can identify the brittleness of mixtures with different factors.

Evaluation the Usage of Local Materials in HMA Surface Layer

The importance of roads and all the facilities related to the mobility of people, goods, and vehicles in the world exceed the social and economic significance but play a main role in politics and government decisions. As a result of the increasing population in Iraq and the dramatical growth in heavy vehicles twenty years ago and due to the rising percentage of new construction projects in the country, the need appeared to assess and improve the hot mix asphalt layers used in the construction of flexible pavements. In this research, a hot mix asphalt surface layer was used with a 12.5 mm nominal maximum aggregate size from one aggregate source (Al Nibaie quarry) and one penetration grade type of asphalt binder (40 -50), also in this research work has been added one type of polymers by several percentages namely, Crumb Rubber Modifier (CRM) to enhance the properties of asphalt binder which in turn improves HMA. The evaluation process included the preparation of two types of mixtures (unmodified and modified mixtures) by using the Superpave mix design method and to estimate the ability of mixtures to resist the three main types of failure that may be flexible pavement exposed to, Wheel track test was used to simulate the permanent deformation resistance of mixtures, flexural beam fatigue test to determine the fatigue cracking resistance of mixtures and indirect Tensile Strength test was used to determine the strength to moisture damage for prepared mixtures. Results demonstrated that adding modified waste polymer to the asphalt cement with different percentages significantly improved mechanical and durability properties.

Influence of fiber-asphalt interface property on crack resistance of asphalt mixture

This paper aims to analyze the interface property between fibers and asphalt, and study its influence on the crack resistance of the asphalt mixture. Four fibers (basalt fiber A (BF-A), basalt fiber B (BF-B), polyester fiber (PEF) and polyacrylonitrile fiber (PAF)) were selected in the study. The interface adhesion parameters were obtained by conducting the novel fiber-asphalt pullout test, and the micromorphology of the fiber-asphalt interface area was also observed. The crack resistance of the mixture was determined using the indirect tensile asphalt cracking test (IDEAL-CT) and the semi-circular bending test (SCB). Basic crack resistance indicators such as CTIndex and flexibility index (FI) were used for analyzing. Meanwhile, digital image correlation (DIC) technology was adopted to quantitatively characterize the crack inhibition mechanism of fibers in the fiber-asphalt mixtures. The results showed that the interface adhesion strength between BF-A and asphalt is the largest at 25 ℃, followed by BF-B, PEF and PAF. The addition of fibers can effectively improve the CTIndex and FI of asphalt mixtures, and it is found that the interface adhesion characteristics between fibers and asphalt have a great influence on the crack propagation process. The crack opening velocity curve obtained from the DIC analysis can quantitatively characterize the crack development law of the asphalt mixture. The coefficient of determination R2 between the interface adhesion strength and the DIC index (stage I velocity change rate and timing point 1 time) exceeded 0.85. The results can provide scientific references for the design and application of fiber reinforced asphalt mixture.

Sustainable asphalt mixtures by partial replacement of fine aggregates with low-grade magnesium carbonate by-product

The utilisation of large quantities of raw materials for asphalt mixtures manufacturing, such as aggregates, is an environmental issue that must be addressed. This concern has led to valorising waste and by-products as more sustainable alternative raw materials. This research is aimed at evaluating the use of a low-grade magnesium carbonate (LG-MC) by-product as a partial replacement of fine aggregates and as a filler of asphalt mixtures. A mechanical analysis has been performed studying the effect of this by-product on the moisture sensitivity, cracking resistance and cohesion loss resistance of asphalt mixtures. Cracking resistance was assessed under different temperatures (20, 5 and −5 ºC) and conditions (unconditioned and aged). Results indicated that moisture sensitivity and cohesion loss resistance of asphalt mixtures with LG-MC by-product were not affected, obtaining similar results to those of the reference mixture. A protective effect in the mixture cracking resistance was observed using LG-MC. At low temperatures or after ageing, this by-product tends to maintain ductility to a greater extent. The study indicates that LG-MC is suitable as a partial substitute for the fine fraction of aggregates, as well as for the total amount of filler in asphalt mixtures manufacturing for road pavements.

Prospective application of coal gangue as filler in fracture-healing behavior of asphalt mixture

Coal gangue powder, which is an environmental waste, was used as filler to investigate its facilitation effect on microwave heating and self-healing of asphalt mixture. In this work, two types of fillers named coal gangue powder (CGP) and coal gangue ash (CGA) were utilized to prepare various mixtures to replace conventional limestone powder (LMP) by six rates of 0%, 15%, 35%, 50%, 75%, and 100%. Firstly, the micromorphology and composition properties of different fillers were performed by scanning electron microscopy (SEM) and X-ray fluorescence (XRF) test. Secondly, the semi-circular bending (SCB) test was conducted to analyze the low-temperature fracture performance of mixtures. Then, the microwave heating capacity and behaviors of fillers and mixtures were studied on the basis of infrared thermography imaging. Ultimately, the mixtures healing efficiency was evaluated with five fracture-healing-fracture cycles and the electromagnetic parameters were determined via a microwave network vector analyzer. Test results reveal that mixtures with appropriate CGA and CGP filler proportion both possess better microwave heating effect, while the excessive dosage of CGA or CGP filler will result in mixtures’ uneven surface temperature distribution. It is found that 50% CGA or 50% CGP can be a prospective substitution because this rate not only obtains excellent healing effectiveness at 60-s microwave heating but also improve the low-temperature crack resistance of mixture. Moreover, the higher dielectric and magnetic losses of CGA and CGP provide an explanation for promoting microwave heating. The aforementioned results show that coal gangue powder waste has prominent application in asphalt mixture cracking and self-healing and thus improve its utilization in this method.

Identification of parameter to assess cracking resistance of asphalt mixtures subjected to aging and moisture conditioning

This study comprehensively evaluated different parameters based on tensile strength testing to assess the cracking resistance of asphalt mixtures subjected to aging and moisture conditioning. For this purpose, two sources of aggregates were selected to produce hot and warm mix asphalt mixtures. Asphalt mixtures were subjected to short term and long term aging, three levels of moisture conditioning (freeze thaw cycles), and tested at two temperatures (15 °C and 25 °C). The load-displacement data was used to determine the fracture work density, fracture energy, toughness index, cracking resistance index, cracking tolerance index, and rate dependent cracking index. It was noticed that moisture conditioning increased the variability of the different parameters. The cracking tolerance index and rate dependent cracking index parameter had a much higher coefficient of variation (CoV) with a maximum value close to 50%. Indirect tensile strength, fracture energy, and fracture work density appropriately captured the effect of moisture on cracking resistance of mixtures. The cracking resistance index, cracking tolerance index, and rate dependent cracking index increased with an increase in the moisture conditioning level. The Statistical analysis showed that tensile strength, fracture work density, and fracture energy were significantly influenced by different aging and moisture conditions evaluated. Fracture energy showed better association with fatigue life of asphalt mixtures subjected to three freeze-thaw cycles compared to tensile strength. Further, the fatigue life prediction models showed that both indirect tensile strength and fracture energy significantly influence the fatigue life of asphalt mixtures subjected to aging and moisture conditioning.

Influence of Basalt Fibers on the Crack Resistance of Asphalt Mixtures and Mechanism Analysis.

The paper aims to investigate the influence of basalt fiber (BF) on the crack resistance of the asphalt mixture and conduct a mechanical analysis. First, two typical asphalt mixtures, namely AC-13 and SMA-13, were designed. The impact of BF on the mixture design results was analyzed. Then, several macroscopic tests, namely the four-point bending test, indirect tensile test, and semicircular bending test (SCB), were conducted to assess the effect of BF on the cracking resistance of asphalt mixtures. Finally, the influence of BF on the cracking resistance of asphalt mixtures was analyzed based on an environmental scanning electron microscope (ESEM) observation. The results show that: (1) BF increases the optimal asphalt content of AC13 and decreases the optimal asphalt content of SMA-13, which is caused by the different asphalt-absorption capacity of BF and lignin fiber (LF). (2) BF enhances both the fatigue crack resistance and temperature crack resistance of asphalt mixtures. The enhancement on the SMA-13 is more significant, indicating that the enhancement of BF on asphalt mixtures is related to the type of aggregate gradation. (3) BFs in the asphalt mixture lap each other to form a spatial network structure. Such structure can effectively improve the crack resistance of the mixture by dispersing the load stress and preventing the flow of asphalt mastic. The study results provide an effective method to design crack-resistant asphalt mixtures.

Laboratory Evaluation on Performance of Recycled Asphalt Binder and Mixtures under Short-Term Aging Conditions

As asphalt materials are exposed to very high temperatures before construction, such as in the transportation stage or the storage stage, short-term aging of asphalt material occurs. At these stages, diffusion or blending between RAP (reclaimed asphalt pavement) binder and virgin binder may occur. In this study, recycled blends, incorporating SBS modified binder, RAP binder and recycling agents, were prepared with incremental RAP binders of up to 40%, and RTFO (Rolling Thin-Film Oven) tests in condition times of 300 and 600 min were conducted on the recycled blends. Characterization tests included ΔTcr, complex modulus master curve, a G-R (Glover-Rowe) parameter on recycled blends, and dynamic modulus, fracture test, and midpoint bending fatigue tests on mixtures. The ΔTcr and the G-R parameter results showed that aging time significantly affected the cracking resistance of the recycled blends. Compared to the virgin SBS modified asphalt binder, the recycled blends tended to be more sensitive to the aging process. The complex modulus master curve of binders and the dynamic modulus and phase angle results of mixtures show that the binder/mixtures appear to be stiffer with an increase in the RAP binder dosage. Generally, the low temperature cracking and fatigue cracking resistance of virgin mixtures is better than that of RAP mixtures, especially for high RAP binder dosage mixtures, and longer aging times have a negative impact on the cracking resistance of mixture. However, when we extend RTFO aging time, the higher dosage of RAP mixtures show better cracking resistance than the lower dosage of RAP mixtures. The reason for this could be that the chemical process may occur between the virgin SBS modified asphalt binder and the RAP binder at high temperatures.

The role of binders in mixture cracking resistance measured by ideal-CT test

The Indirect Tensile Asphalt Cracking Test (IDEAL-CT) is a newly developed test method that has high potential of reliably evaluating fatigue cracking of asphalt mixtures. In this study two binder fatigue testes, Linear Amplitude Sweep (LAS) and Binder Yield Energy Test (BYET), were used to measure the performance of asphalt binders. Advanced analyses on LAS/BYET data were employed to determine binder fatigue parameters that could explain binder’s role in mixture cracking resistance. The results indicate that the role of binders in mixture behavior in the IDEAL-CT tests can be successfully defined using the outputs from the LAS and BYET tests.

Relationships among Chemistry, Rheology, and Fracture/Fatigue Performance of Recovered Asphalt Binders and Asphalt Mixtures Containing Reclaimed Asphalt Pavement

Because of limited amounts of natural resources, reclaimed asphalt pavement (RAP) has gained popularity in the asphalt pavement industry to meet sustainability requirements in asphalt pavement. Concerns have been raised in relation to the intermediate temperature cracking performance of asphalt mixtures containing RAP. The objective of this study was to evaluate the intermediate temperature cracking resistance of asphalt mixtures and recovered asphalt binders containing RAP. Seven plant-produced asphalt mixtures from three transportation agencies with various RAP contents and the extracted asphalt binders were evaluated with respect to intermediate temperature cracking resistance. Asphalt binder experiments included chemical and rheological characterization of recovered asphalt binders. Chemical characterization consisted of Fourier transform infrared spectroscopy and saturates/aromatics/resins/asphaltenes component analysis. Linear amplitude sweep and time sweep tests were also performed to characterize the rheological properties of asphalt binders. Asphalt mixture experiments included four-point bending beam fatigue and semi-circular bend tests. Results indicated that, as expected, asphalt mixtures with high RAP contents resulted in asphalt binders and mixtures with reduced cracking resistance. Relationships between the asphalt binder chemical and rheological parameters and asphalt mixture cracking resistance were also investigated. Asphalt binder rheological and chemical parameters were well correlated. Asphalt binder rheological parameters showed reasonable to strong relationships with the four-point bending beam fatigue test result. The work presented in this paper is part of FHWA Transportation Pooled Fund Project TPF-5(294) “Develop Mix Design and Analysis Procedure for Asphalt Mixtures Containing High RAP and/or RAS Contents.”

Crack resistance investigation of mixtures with reclaimed SBS modified asphalt pavement using the SCB and DSCT tests

An investigation for crack resistance of hot mix asphalt (HMA) with reclaimed SBS modified asphalt pavement (RAP-SBS) by semi-circular bending (SCB) test was conducted. The effect of RAP-SBS content and rejuvenating agent (RA) on crack resistance of recycled mixture was analyzed at medium and low temperature. Meanwhile, the horizontal strain field at crack tip and crack development characteristics of recycled mixture were analyzed by digital speckle correlation technique (DSCT). Besides, the effects of long term aging (LOTA) and freeze–thaw (F-T) cycles on the crack resistance were also analyzed. The results show that crack resistance of recycled mixture decreases in accordance with the quadratic polynomial as RAP-SBS content increases at medium and low temperature, regardless of RA. RA can significantly improve the crack resistance of mixture with high content of RAP-SBS, when RAP-SBS content is 30%, the crack resistance is close to that of virgin mixture, but the anti-aging property is poor. The mortar of recycled mixture is easy to form a weak interface, and RA can prolong the cracking time, and the horizontal strain peak at crack tip is also increased. The influence degrees of crack resistance are shown in the order from temperature, RAP-SBS content to LOTA. As RAP-SBS content increases, the sensitivity of the low temperature crack resistance to the F-T cycle increases. The exponential fitting model can express the relationship between crack resistance and F-T cycles, and the damage degree of crack resistance contains rapid damage stages and stable damage stages as F-T cycles increased.

Performance Characterization of Hot Mix Asphalt with High RAP Content and Basalt Fiber.

Incorporating reclaimed asphalt pavement (RAP) into asphalt mixtures achieves astonishingly environmental and economic benefits. However, there is hesitation to use higher RAP content due to the concern regarding the deterioration in pavement performance, especially the cracking resistance. Basalt fiber has been considered an effective additive to reinforce the performance of asphalt mixtures and, subsequently, the reinforcement effect is also expected for high-RAP content mixtures. Therefore, this study investigated the effect of basalt fiber on the pavement performance of asphalt mixtures with 0%, 30%, 40%, and 50% RAP contents against high-temperature performance, moisture susceptibility, low-temperature and intermediate-temperature cracking resistance, based on the wheel-tracking test, the uniaxial penetration test, the freeze-thaw splitting test, the low-temperature bending beam test, the semicircular bend fracture test and the indirect tensile asphalt cracking test, respectively. In addition, a performance-space diagram was developed to determine the mixture performance shift caused by basalt fiber. The results showed that adding basalt fiber compensated for the detrimental effect caused by RAP, leading to significant enhancement in moisture susceptibility and low- and intermediate-temperature cracking resistance of mixtures with high RAP content, along with the enhancement in high-temperature performance, indicating that basalt fiber can contribute to the use of high RAP content.

Distribution of mortar film thickness and its relationship to mixture cracking resistance

ABSTRACT The film thickness of asphalt mortar, which is a mix of binder and fine mineral aggregates, has been considered as an important indicator for assessing the durability of asphalt mixture. This study proposes a novel method to characterise distribution of mortar film thickness in asphalt mixture through image processing techniques. Four asphalt mixtures with unmodified and modified binders were produced at various compaction temperatures in the laboratory. Their internal images were scanned and analysed. The values of mortar film thickness along the boundary of each aggregate in the scanned image were measured. And their mean value (Tm) and standard deviation (SDt) were calculated for characterising the distribution of mortar film thickness. The results indicate that both binder modification and compaction temperature have significant effects on the mortar film distribution. Furthermore, the proposed parameters were employed for understanding the correlation between the mortar film thickness and mixture cracking resistance. The flexibility index of short-term and long-term aged mixtures were measured and correlated with the mortar film parameters. The findings show that asphalt mixture with a lower mortar film thickness and a wider distribution is more sensitive to oxidative aging, which may result in a dramatic decrease of mixture’s resistance to cracking.

Investigating the ANN model for cracking of HMA in terms of temperature, RAP and fibre content

ABSTRACT Using high contents of the RAP material in newly produced asphalt mixtures leads to a reduction in the crack resistance of the mixtures. This shortcoming can be compensated using some methods such as polymer modification, rejuvenation, fibre-reinforcement, etc. In this paper, the effect of Cyclogen as a rejuvenator and glass fibre was investigated on the cracking behaviour of recycled asphalt mixtures. For this aim, the fracture energy and critical value of J integral (Jc)of semi-circular bending (SCB) asphalt specimens in terms of RAP content, Fibre content and testing temperature were investigated in this study and the results were used to develop an experimental model to predict the crack resistance of asphalt mixtures in terms of temperature and fibre and RAP content using the artificial neural network (ANN) and the multiple regression methods. The results indicated that the fracture energy and Jc valueof asphalt mixtures declined by increasing the RAP contentat intermediate temperatures. However, the reduction in fracture energy and Jc valuecould be compensated using the fibres. Both investigated models were appropriate for predicting the cracking behaviour of fibre-reinforced recycled asphalt mixtures. Nevertheless, the level of correlation was much higher for the ANN approach than the multiple regression model.

Effect of low-temperature modifiers on HMA mixture aging and cracking resistance

The Superpave Performance Grade of an asphalt binder can be improved by adding different combinations of polymers and low-temperature modifiers. Although using various modifiers is not new, their effect, in particular softening oils, on long-term aging is not yet well understood. The objective of this study is to evaluate the effect of two widely-used oils to adjust binder grades on volumetrics, workability and fatigue cracking resistance of mixtures subjected to short- and long-term aging. Eight combinations of softening oils and polymers were used to prepare PG 58-34 binders. The mixtures prepared with these combinations were oven-aged for six and 14 h and used to compare their Flexibility Index (FI) results following Semi-Circular Bending Illinois FI test (SCB-IFIT) procedure. In addition, the effects of binder composition and aging on the compaction effort were assessed using the Superpave Gyratory Compactor (SGC) data. Furthermore, extracted and recovered binders of these mixtures were tested following the Linear Amplitude Sweep (LAS) test at intermediate temperature. Overall results indicate that oils used and aging susceptibility of the eight mixtures affected FI results differently. There is a good relationship (R2 = 83%) between the FI values and the absolute value of the LAS-B parameter of the extracted and recovered binders. This finding shows that FI sensitivity to aging is at least initially driven by the binder properties. The main finding from the analysis of the LAS-B parameter is that ΔTc measured for the 20-hr Pressure Aging Vessel (PAV) aging cannot be assumed to represent long-term oven aging of mixtures exceeding six-hours of oven aging at 135 °C.

Mixture-based rheological evaluation tool for cracking in asphalt pavements

Cracking is a major distress that limits the durability of asphalt pavements. Various fatigue and fracture-based tests and analyses can be used to assess cracking resistance of asphalt mixtures in order to design more economical and durable mixtures. This mixture cracking resistance is affected by the rheological properties of the asphalt binder, both stiffness and relaxation ability as indicated by measured dynamic modulus and phase angle, respectively. One significant breakthrough involves the use of binder Black space (shear modulus versus phase angle) and the Glover–Rowe (G-R) parameter that is a function of these two rheological properties as an indication of cracking resistance. However, binder characterisation is not adequate to fully represent mixture performance and therefore there is a need for a mixture-based evaluation tool. The objectives of this study were to: (1) investigate the applicability of a representative temperature and frequency combination for mixture-based Black space evaluation; (2) evaluate the ability of mixture Black space to track the effect of aging and rejuvenation (when recycling agents are used with recycled materials); (3) explore the use of a mixture-based G-R parameter (G-Rm) for cracking resistance evaluation and (4) investigate a possible correlation between G-Rm and Flexibility Index (FI) from a semi-circular bending (SCB) test. Test results indicate a reliable temperature–frequency combination for G-Rm, which was sensitive to aging, recycled materials content, binder performance grade and recycling agent dose. Test results also indicate a good correlation between the G-Rm parameter and the FI.

Comparison of two low-temperature cracking tests for use in performance-based asphalt mixture design

ABSTRACT Cracking is one of the main causes requiring replacement of asphalt pavement, but the traditional mix design methodologies do not require testing of asphalt mixture cracking resistance. Two cracking tests, Thermal Stress Restrained Specimen Test (TSRST) and Semi-Circular Bending (SCB), were evaluated in this study to determine their suitability for adapting as part of mixture type testing and quality control protocol. Eight different mixtures were used to evaluate the test methods, having a wide range of maximum aggregate size, mix type, binder grade and target application. Half of the mixtures were plant-produced, while the other half were laboratory-produced. The results showed that TSRST is the preferred method for mix design because of smaller result variability and better distinguishing between the different mixtures. At the same time, a reasonable correlation exists between TSRST and SCB tests. This makes it possible to use the simpler SCB test for pre-screening samples to further test using the TSRST. The equivalent ageing protocol is a pre-requisite to be able to compare the test results. The fraass breaking point, a measure of bitumen low-temperature cracking resistance, did not provide good correlation with either of the mixture cracking tests.

Effects of moisture on warm mix asphalt containing Sasobit

The asphalt industry has been at the forefront of sustainable development. Warm Mix Asphalt (WMA) has been developed to cope with issues such as high energy prices and air pollution. These mixes require less energy and generate fewer pollutants during production in comparison with conventional Hot Mix Asphalt (HMA). Although a promising technology, the durability of WMA is not clear because long-term WMA fieldperformance data is limited. This study investigated the susceptibility of Sasobit-modi ed WMA to moisture, since moisture damage is a major cause of premature pavement failure in asphalt concrete. To this end, WMA samples were made using di fferent concentrations of Sasobit and the results were compared with those from HMA mixtures. The e ffect of hydrated lime as an anti-stripping agent was also investigated. The tensile strength ratios indicate that the introduction of hydrated lime and Sasobit increased the resistance ofasphalt mixtures to moisture. Fracture energy and toughness were used to evaluate the crack resistance of specimens under dry and wet conditions. In comparison with Sasobit, hydrated lime increased crack resistance of mixtures. The results indicate that hydrated lime can be used as a compatible and eff ective anti-stripping agent for WMAs containing Sasobit.

Use of performance-based testing for high RAP mix design and production monitoring

In 2014 the Wisconsin Department of Transportation and industry developed a pilot programme for hot mix asphalt with higher recycled asphalt content that required use of performance tests during mix design and production. Following the balanced mix design concept mixture tests were selected to address rutting resistance after short-term ageing and durability after long-term ageing. The tests selected were the Hamburg Wheel Tracking test, the Semi-Circular Bend (SCB) test at intermediate temperature, and the Disc-Shaped Compact Tension test at low pavement temperatures. Asphalt binder extraction and grading from aged mix was also required. The focus of this paper is to summarise the mixture performance test and recovered binder data gathered during the pilot project on State Highway 77 in Ashland County, WI, suggest modifications to the SCB test procedure, and to present accelerated ageing protocols for continued use of performance testing in practice. SCB test results collected during the project at 25°C did not relate well to values published in the literature or show adequate sensitivity to changes in mix properties. The effects of test temperature and an alternative analysis method are presented. Based on the results, recommendations include use of a climate-based approach for test temperature selection and inclusion of post-peak analysis to better discriminate between mix composition and ageing conditions. Accelerated long-term-ageing protocols involving loose mix ageing at 135°C for 12 and 24 h are compared to American Association of State Highway and Transportation Officials (AASHTO) R30 compacted mix ageing using recovered binder and mixture fracture properties. Results found that 12 h loose mix ageing produced similar recovered binder grading to AASHTO R30, whereas the effect of ageing on mixture fracture tests was inconclusive. The relationship between laboratory and field ageing is investigated through comparison of field cores to laboratory-aged plant-produced mix from a project constructed in SE Minnesota in 2006. Lastly, the laboratory performance of the high recycled and conventional mix designs are compared on the basis of mixture cracking resistance and recovered asphalt binder properties after extended ageing. The high recycle mix exhibited equal or better performance relative to the conventional mix across all selected performance tests. This comparative analysis also provides an example of how the inclusion of performance testing can influence the material selection process and produce test results indicative of improved overall performance of the mix.

Differences in cracking resistance of asphalt mixtures due to ageing and moisture damage

The ageing phenomenon and moisture damage become key factors to evaluate mixture cracking resistance. In this paper, the effect of ageing and water on cracking resistance and fatigue behavior in a bituminous mixture is studied. Specimens were tested by a direct tensile test (Fénix test) to obtain fracture energy values whereas variation of complex modulus and dissipated energy density was obtained by a strain sweep fatigue test (EBADE test). Results show a significant reduction in cracking resistance and fatigue life of the mixture after ageing (failure strain is reduced approximately by 35%). Water in standard conditions has very little influence.