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The importance of environmental consciousness and sustainability is increasing among transportation governing bodies worldwide. Many government bodies are concerned with maximizing the usage of recycled substances in road construction. Therefore, assessing the effect of recycled materials consumption is essential, mainly when designing new 'green' pavement types. The primary objective of this study is to investigate the impact of different treatments on improving the interfacial transition zone (ITZ) of coarse recycled concrete aggregate (CRCA) and its application in asphalt mixes. Such an aim is accomplished by enhancing its physical and mechanical characteristics, as well as its microstructure. The surface morphology, chemical composition, and intermix phases of the ITZ area and calcium silicate hydrate (CSH) compounds for CRCA were evaluated using scanning electron microscopy (SEM), an energy-dispersive X-ray analyzer (EDAX), and X-ray diffraction analysis (XRD). The performance of asphalt mixtures that included treated and untreated CRCA was also examined using different tests. It was found that heat treatment is an effective technique for enhancing the ITZ. However, cracks were seen in the mortar of CRCA when exposed to high temperatures (500 °C), which adversely affects the characteristics of the mortar. Acid treatment appeared to be an effective approach for improving the ITZ area. Nevertheless, the treatment that used acetic acid, a weak acid, was more effective than HCl acid, a strong acid. The outcomes revealed that the ITZ microstructure is significantly enhanced under different treatment types; however, microstructure improvements mainly included increased surface homogeneity and CSH compounds and a reduced Ca/Si ratio. It was also found that the asphalt mixtures with different proportions of untreated CRCA exhibited enhanced resistance to rutting. Furthermore, their tensile strength ratio (TSR) values were above the minimal level requirements. Moreover, the asphalt mixture with 30% CRCA, which was treated with various treatment methods, demonstrated a significant improvement in the mixtures' mechanical properties; therefore, its application is highly successful and an environmentally friendly solution. [ABSTRACT FROM AUTHOR]

The availability of high-quality aggregate for infrastructure development in Canada has significantly decreased. This reduction has posed significant challenges, particularly in large urban areas across Canada. Moreover, exploring the potential of incorporating innovative by-products into pavement structures has displayed potential advantages in technical, economic, and environmental aspects. The methodology presented in this paper is based on several research projects from over the past twenty years. This case study is based on the several research projects that have been conducted at the Centre for Pavement and Transportation Technology (CPATT) in Canada. The focus of this paper is developing a framework that can be used to evaluate the use of recycled materials in asphalt pavement. These include recycled concrete aggregate (RCA); recycled asphalt roof shingles (RAS); recycled crumb rubber (RCR); and recycled asphalt roof shingles (RAS) in asphalt pavement. In addition, the use of RCA in concrete pavement will also be evaluated. In addition, the use of RCA in concrete pavement will also be evaluated. A methodology and strategy for implementing these materials and designs into specifications, while also managing risk, are outlined. Finally, the work presents a life cycle assessment analysis, including the analysis of cost and sustainability. Overall, the paper illustrates the process of evaluating products, technologies, and designs from technical, economic, and environmental viewpoints, and then implementing them in a robustly engineered way. Generally, the collected data results from the lab, field performance of the test sites, and sustainability and Life Cycle Cost Assessment (LCCA) analyses are very promising. For example, the Hot Mix Asphalt (HMA) pavement design with a 40% RAP was the most environmentally friendly. Meanwhile, it was determined that the HMA mix comprising 20% RAP and 20% Crumb Rubber Modifier (CRM) was found to be the most creative and environmentally friendly option. According to another study, higher storage durations were shown to improve RAP and virgin binders' blending, thereby raising the general quality of HMA and RAP mixtures. Furthermore, the study discovered that mixtures containing various types of untreated CRCA in different amounts had higher Indirect Tensile Strength (ITS), rutting resistance, and stiffness modulus than the control mix, which contained 0% coarse recycled concrete aggregate (CRCA). This suggests that the effective utilization of recycled materials is a viable approach with the capacity to significantly enhance the adoption of recycled components in asphalt pavements. [ABSTRACT FROM AUTHOR]

Geosynthetic materials (i.e., geogrids, geotextiles and other geocomposites) act as an interlayer system and are widely used in construction applications. In pavement structures, geosynthetic layers provide potential benefits such as reinforcement, reflective cracking mitigation, increased fatigue life, and improved drainage and filtering. However, few studies have addressed the installation and construction practices of geosynthetics in pavements. Furthermore, the study of geosynthetics and their contribution during construction are limited. In this paper, a full-scale field study was conducted and three trial sections were constructed; two types of geosynthetics, a fibreglass geogrid and a geogrid composite, were installed in the asphalt binder course and at the interface between the subgrade and base layer, respectively, to be compared with a control section without geosynthetic reinforcement. Trial sections were instrumented to monitor the pressure applied on the subgrade, the strain in the base lift of the asphalt binder course, the temperature, and the moisture within the pavement structure during construction. In addition, post-construction field testing was performed to measure the stiffness of the pavements after construction. The results indicated that geosynthetic-reinforced pavements can maintain pavement resilience during construction and significantly mitigate the disturbances caused by construction activities. The geogrid embedded in the asphalt layer was demonstrated to reduce the pressure at the subgrade caused by paving equipment by 70% compared with the control section, while simultaneously reducing the longitudinal and transverse strain at the bottom of the asphalt layer by 54% and 99%. Observations from the geogrid composite test section also demonstrate the potential to minimize the impacts of future freeze–thaw at the subgrade due to the improved drainage and indirect insulation effect. [ABSTRACT FROM AUTHOR]

This study investigated the sensitivity of the Illinois flexibility index test (I-FIT) and the disc-shaped compact tension [DC(T)] test with respect to oxidative aging and testing temperature. For this purpose, five plant-produced surface course asphalt mixtures covering a wide range of performance-graded asphalt cement (PGAC) were utilized. As for oxidative aging sensitivity, two methods of forced-draft oven aging, at 85°C for 120 h and at 95°C for 72 h, were utilized. Furthermore, to measure the temperature sensitivity, the I-FIT test was conducted at 23°C, 24°C, 25°C and PGAC intermediate temperatures, while the DC(T) test was conducted at −18°C , −24°C , and −30°C. In this study, the analysis of the I-FIT test results from oxidative aging showed that both methods of aging caused a reduction in flexibility index values of asphalt mixtures, and the flexibility index values after two methods of aging were statistically comparable. Moreover, even though oxidative aging caused a reduction in DC(T) fracture energies of asphalt mixtures containing hard PGAC, the fracture energies before and after the two methods of aging were statistically similar for asphalt mixtures. The analysis of the I-FIT test results from testing temperature sensitivity showed that the flexibility index values of asphalt mixtures containing hard PGAC at 23°C were statistically dissimilar to those at 25°C when the testing temperature dropped from 25°C to 23°C. Consequently, regarding the I-FIT test, the comparable flexibility index values from the two methods of oxidative aging suggested utilization of forced-draft oven aging at 95°C for 72 h as a less time-consuming method compared to forced-draft oven aging at 85°C for 120 h to evaluate the effect of oxidative aging. In addition, the variability in flexibility index values due to the drop in testing temperature suggested exercising caution when conducting the test on asphalt mixtures containing hard PGAC. [ABSTRACT FROM AUTHOR]

Volumetric properties of hot mix asphalt (HMA) are necessary requirements to ensure good performance for asphalt mixtures. This research is conducted to evaluate the influence of coarse recycled concrete aggregate (CRCA) on the volumetric properties of HMA. Mix design of HMA mixture was performed for CRCA at various percentages 0%, 15%, 30%, and 60%, and the effects of the utilization of CRCA on HMA volumetric properties were evaluated. Additionally, various treatment methods were performed to evaluate the effect of various treatment types of CRCA on the HMA volumetric properties. To achieve this objective, presoaking, heat treatment followed by a short mechanical treatment were conducted. The obtained results showed that the use of the combination approach between different treatments appears to be very successful for enhancing physical properties of CRCA. The natural aggregate (NA) replacement by CRCA leads to increasing the optimum asphalt content (OAC) for the mixtures, whereas the property voids in mineral aggregates (VMA) is decreased. Compared to the mixture with 30% untreated CRCA, a little improvement and a slight increase in VMA and voids filled with asphalt (VFA) properties, respectively, were seen for mixtures with 30% treated CRCA with different treatment techniques. The CRCA addition with different proportions is very successful for both untreated and treated CRCA due to achieving all Ministry of Transportation Ontario (MTO) requirements for volumetric properties of HMA. However, CRCA treated with various treatment methods appears to be more successful than untreated CRCA application. [ABSTRACT FROM AUTHOR]

Braking and turning by heavy vehicles can trigger shear-related distress in asphalt surfaces. The evolutionary increase in vehicle tyre pressure and wheel load will result in an increase in such surface failures in the future. Shear-related distress may result from delamination at the surface layer interface, or excessive shear creep within the asphalt surface layer itself. Both deformation and delamination distress appear visually identical at the surface. When subsequently cored, secondary (or symptomatic) debonding of the interface may result in asphalt deformation distress being misdiagnosed as a delamination failure. Regardless the mechanism, a broad range of properties may be responsible and a systematic diagnosis is required to determine the root cause. A framework for the diagnosis of shear distress in asphalt surfaces is presented. The framework contains three levels of investigation, including the location of the distress (at the surface layer interface or within the surface layer), the element within the interface/asphalt responsible and finally, the components or characteristics that resulted in a reduced shear resistance. The framework relies on the assessment of surface performance relative to comparable surfaces of adequate performance. Surface age, thermal gradient and traffic-induced shear stress states must all be comparable for a meaningful diagnosis to be made. The developed framework has been used to successfully determine the root cause of shear creep in the heavy braking zone of a runway at an Australian airport. Its application is recommended for other surface distress investigations, where the environmental and traffic factors are comparable. The framework may also be adapted to forensic investigation of other distress modes. [ABSTRACT FROM AUTHOR]

The rutting resistance of hot mix asphalt (HMA) Superpave™ mixes in surface course materials was investigated using asphalt material characterisation tests and a digital imaging processing (DIP) technique. The effects of the type of aggregate, the type of binder and the binder content on rutting resistance were quantified. Two types of aggregate were examined: Superpave™ SP12.5 and high friction SP12.5 FC2. Both a modified (PG Plus) and an unmodified binders were considered at the optimum binder content and the optimum content plus an additional 0.5%. To accurately identify the effect of each variable, the shear upheave of these mixes was also quantified. The DIP technique involved estimating the number of aggregate contacts, the total contact length and internal structure index of two-dimensional images of the experimentally tested samples. The results showed that both the rutting resistance and stiffness of HMA surface mixes were sensitive to aggregate type, binder type and binder content. A high friction aggregate provided a better internal structure characteristic, as well as superior rutting resistance and stiffness for HMA mixes. The use of PG Plus and the addition of 0.5% to the optimum binder content negatively affected HMA stiffness and rutting resistance. However, the levels of rutting resistance for all mixes were acceptable (rut depth < 12.5 mm), even when the shear upheave was considered. Internal structure indices measured by DIP were effective for capturing changes in the internal HMA structure with respect to aggregate type and asphalt cement content. [ABSTRACT FROM AUTHOR]

The sensitivity of the fatigue resistance of surface hot-mix asphalt (HMA) mixes is evaluated for three primary design variables. Aggregate type, binder type, and binder content as well as their interaction have been quantified with respect to their effects on HMA fatigue life, rutting resistance, and stiffness. The objective was to optimize the design by extending fatigue performance while reducing the confounded negative effect on rutting resistance. Two aggregate types were used in the evaluation. Two binders of the performance grading (PG) 64-28 were also employed: a modified binder that meets national specifications and an unmodified binder at two binder levels (optimum and optimum plus 0.5%). Aggregate texture was compared visually using high-resolution scanning electron microscopy (SEM) images. The results showed that the value of modifying the binder to produce softer mixes can be compromised when a high-friction aggregate is used due to the irregular shape of the texture, which produces stiffer mixes. A slight adjustment to the amount of binder (+0.5%) can decrease this effect. Superior HMA fatigue performance was exhibited by the regular 12.5 aggregate and the modified binder at the optimum binder content plus the additional 0.5%. This conclusion was reached through the integration of the positive effects of the investigated variables, which revealed only an insignificant reversible impact on rutting resistance. The findings of this study can therefore be considered a guide for designing HMA with superior fatigue performance for use in pavement design. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper summarizes a research study that involved a partnership between Centre for Pavement and Transportation Technology located at University of Waterloo and Interlocking Concrete Pavement Institute. This research study involved the construction of eight crosswalks with different base and bedding materials at two test sites and was directed at defining the performance mechanics for designs with various bases and setting beds. The objective was to quantify the structural performance of four different interlocking concrete pavement designs under two loading scenarios. The Test Track typically experienced loaded garbage trucks up to 56 000 kg of maximum load. The Ring Road experienced traffic volume of a typical urban road. This research evaluated eight crosswalks of four different designs in these two locations. Sand set concrete base concrete header was one of the designs. Similarly, the combination of asphalt base, granular base, steel header, aluminum header, and concrete header were other designs of the crosswalks studied. Strain gauges, moisture probes, earth pressure cells, and thermistors were installed in the crosswalks to continuously monitor the structural and environmental impact from various loading conditions. Continued surveys were all performed as part of the research. Maximum recommended lifetime design equivalent single axle loads (ESALs) for bituminous set concrete base concrete header design was 7.5 million ESALs and sand set asphalt base asphalt header was recommended to have 1.5 million design ESALs. This paper presents the performance mechanics of the crosswalks from construction (2007-2009) to May 2010. [ABSTRACT FROM AUTHOR]

Traffic noise is a growing problem throughout the world. Noise barriers, traditionally used for reducing noise exposure, are expensive and inefficient in some cases. Pavement surface characteristics play a key role in noise generation and propagation. Information about noise-reducing characteristics of various Portland cement concrete (PCC) and asphalt concrete (AC) pavements can therefore help public agencies in selecting an appropriate surface that maximizes the structural durability, reduces the noise, and ensures adequate skid resistance for safety. In this study, tire-pavement close proximity (CPX), in-vehicle, and controlled pass-by (CPB) noise were measured at 80-100 km/h for 32 PCC and AC pavements in southern Ontario. The results have indicated that certain textures are needed to allow for air escape from the tire-road interface, which limits the generation and (or) propagation of tire-pavement noise. Both fine-graded Superpave and stone mastic asphalt (SMA) were shown to be promising for noise reduction and have good durability characteristics. However, careful placement and finishing are essential to produce a uniform lower order macrotexture and to attain the noise-reduction benefit. [ABSTRACT FROM AUTHOR]

Pavement roughness immediately after construction is a key measure of quality. The use of smoothness specifications requires an understanding of the influences on as-built roughness for both transportation agencies and contractors. This paper uses data from the Long-Term Pavement Performance (LTPP) program to examine four factors to determine their effects on the as-built roughness of a pavement. These factors include the extent of surface preparation prior to resurfacing, overlay thickness, type of overlay material and pavement roughness prior to resurfacing. Various statistical procedures including paired data analyses, regression analyses and a repeated measures analysis are performed to investigate these effects and any interactive effects. The extent of surface preparation, overlay thickness and pavement roughness prior to resurfacing are determined to have statistically significant effect (at a 95 % significance level) on the as-built roughness of a pavement either directly or interactively with another variable. The overlay mix type is determined not to have an influence on as-built pavement roughness. Data from the Canadian Long-Term Pavement Performance (C-LTPP) program is used to validate the results for overlay thickness and pavement roughness prior to resurfacing. A series of prediction equations are also developed to allow for estimating the as-built roughness of a pavement under various conditions. Pavement designers, construction engineers and contractors should understand the effects that influence the as-built roughness of a pavement so that they can maximize their designs, smoothness specifications and/or bidding of contracts with smoothness specifications. [ABSTRACT FROM AUTHOR]

The Canadian Long Term Pavement Performance (C-LTPP) study, initiated in 1989, involves 65 sections located at 24 sites constructed with various asphalt overlay rehabilitation treatments. This study investigates the impacts of the various alternative rehabilitation treatments on pavement roughness progression. A series of models are developed for predicting the rate of pavement deterioration occurring for the first 8 years of service. The models examine both within-site factors and between-site factors. Site location is found to be the primary influence on the rate of pavement deterioration. Overlay thickness and the amount of cracking prior to rehabilitation are also determined to influence pavement deterioration at a strong statistical level. Models are provided for benchmarking the performance of pavements across Canada, for comparison with individual project designs, and for estimating the performance of designs with different overlay thickness. [ABSTRACT FROM AUTHOR]

• Various preheating levels of Hot In-place Recycling (HIR) were simulated by temperature and heating time in laboratory. • Effect of preheating to the recycled asphalt mixture was evaluated through performance tests. • Workability of recycled material was assessed by gyratory compacter attached program. • Bond strength between recycled layer and aged materials was tested through self-developed direct shear tester. Pavement preheating is of great significance for hot in-place recycling technology. In this study, different preheating temperatures (100 °C, 120 °C and 150 °C) and heating times (60 min, 120 min and 180 min) were set to simulate different preheating conditions for recycled asphalt pavement materials. Rutting tests, low-temperature bending beam tests, and freeze-thaw tests were conducted to investigate the effect of the different heating temperatures on the overall performance of recycled asphalt mixtures. Direct shear tests and gyratory compaction were used to evaluate the bond strength between the old and recycled pavement layers and the workability of the regenerated mixtures under the various heating conditions, respectively. The results showed that the performance and workability of a new pavement surface are both significantly affected by the preheating conditions and that the minimum preheating temperature of 120 °C can guarantee good performance and workability of recycled asphalt mixtures. [ABSTRACT FROM AUTHOR]

The interface between asphalt and aggregate. • The adhesive properties of FAM composed of basalt, steel slag, and andesite were investigated. • The roughness of aggregate and the distribution of asphalt in the aggregate surface were estimated with qualitative and quantitative methods. • Movement rules and failure mechanisms of FAM were evaluated quantitatively. Quantitative analysis was conducted in this study using a three-dimensional field microscope, scanning electron microscope, energy dispersive spectroscopy, and molecular simulation to investigate the surface and interface adhesive properties of three fine aggregate asphalt mixtures (FAM): basalt, steel slag, and andesite. The roughness of the aggregate and the contact angle of the asphalt on the aggregate surfaces also were analyzed quantitatively. Molecular dynamics simulations were carried out to evaluate the adhesive properties, molecular diffusion, and interfacial failure mechanisms of the basalt-, steel slag-, and andesite-based FAM. The average roughness values of the basalt, steel slag, and andesite were found to be 138.2 µm, 244.0 µm, and 185.2 µm, respectively. The stripping percentages of the basalt, steel slag, and andesite were 11.3%, 3.3%, and 10.8%, respectively. The diffusion coefficients of the resins (3.32 × 10−9 m2/s) and asphaltenes (3.05 × 10−9 m2/s) were higher than the diffusion coefficient of the oils (2.98 × 10−9 m2/s). The results indicate that the surface roughness and adhesive capacity of the aggregate used in this study can be ranked in decreasing order as steel slag, andesite, and basalt. The asphaltenes and resins contributed to the asphalt's increased adhesion to the aggregate particles. Both adhesive and cohesive failure were found for the basalt-, steel slag-, and andesite-based FAM, but the steel slag FAM exhibited more cohesive failure, whereas the basalt and andesite FAM exhibited more adhesive failure. [ABSTRACT FROM AUTHOR]

• Asphalt binder properties are not sufficient to capture low-temperature cracking resistance of asphalt mixtures. • DC(T) and SCB tests are able to characterize low-temperature cracking resistance of asphalt mixtures. • Mixture-based low temperature PG can capture the effect of RAP, binder content, and physical interaction between aggregates and asphalt binders. • Mixture-based low temperature PG can capture the effect of asphalt mixture components. This research was focused to investigate the low-temperature cracking resistance of five plant produced SP12.5 surface course asphalt mixtures by conducting the Disc-Shaped Compact Tension (DC(T)), Semi-Circular Bend (SCB) and Bending Beam Rheometer (BBR) tests. The DC(T) and SCB testing were conducted at three temperatures, −18, −24 and −30℃, to characterize the cracking resistance and determine the mixture-based low-temperature Performance Grade (PG) of asphalt mixtures by using the suggested minimum threshold values of DC(T) fracture energy. Moreover, BBR testing was conducted on the recovered asphalt binders from the same asphalt mixtures. The analysis of tests results showed that the DC(T) and SCB fracture energies at three temperatures were statistically comparable and characterized the low-temperature cracking resistance similarly. Even though, the low temperature PG of the recovered asphalt binders were within the Superpave specifications, in some cases, they were mismatched with the mixture-based low-temperature PG. Dissimilar to the SCB fracture energies, the DC(T) fracture energies had better relationships with the low-temperature properties of the recovered asphalt binders. Considering the low-temperature PG of the recovered asphalt binders and the mixture-based low-temperature PG, the DC(T) and SCB tests are essentially needed to reliably evaluate the low-temperature cracking resistance of asphalt mixtures. Moreover, the relationships between the DC(T) fracture energies and the recovered asphalt binder properties revealed that there was a better correlation between the DC(T) fracture energies at three testing temperatures and the recovered asphalt binders' temperatures corresponding to the stiffness value of 300 MPa. [ABSTRACT FROM AUTHOR]

Bio-asphalt replaced petroleum-asphalt for paving asphalt pavements, which is a technology with a wide range of application prospect. This work is aimed at improving the performance of aged bio-oil modified asphalt (bio-asphalt) for use in road pavement construction. Biochar and bio-oil are renewable resources and use in this research that are pyrolyzed from waste wood. The effects of different aging conditions on biochar-modified bio-asphalt and ordinary bio-asphalt were investigated in terms of their chemical functional groups, molecular formulas, radius distribution functions, rheological parameters, and phase separation. The aging conditions considered in this research are short-term aging, ultraviolet (UV) aging, pressure aging vessel (PAV), and low-temperature hardening. Biochar plays a significant role in the UV aging process. This study found that, with an increase in biochar modification, the alkyl group numbers increased and the sulfoxide and carbonyl numbers decreased during the aging process of bio-asphalt. It also shows that the inclusion of biochar improved the aging resistance of the bio-asphalt, but that biochar modification did not affect the bio-asphalt's low-temperature hardening performance. Four asphalt components were studied: saturates, asphaltenes, resins, and aromatics (SARA). The effects of biochar on saturates and aromatics were significant, and the biochar was able to adsorb these components. This study also found that, with an increase in UV aging and PAV, the phase separation grows. • Biochar and bio-oil are renewable resources, which were derived from sawdust. • The chemical change and phase separation of biochar-modified bio-asphalt were investigated. • The molecular model and numerical model of biochar-modified bio-asphalt were built. [ABSTRACT FROM AUTHOR]