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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]

Development of an adequate performance model based on an appropriate condition index has been a major challenge for engineers particularly in case of a new type of design such as pervious concrete pavement structures (PCPSs) which suffer from limited long term performance data sets especially in colder climates. Soft computing techniques are significantly efficient at dealing with subjective, incomplete, and limited data. This paper proposes three most effective soft computing methods: fuzzy sets, the Latin Hypercube Simulation technique, and the Markov Chain process. A novel comprehensive condition index based on severity, density, and weighting factors of distresses occurring on PCPS has been developed incorporating fuzzy sets. A combination of homogeneous and nonhomogeneous Markov Chain has been applied to develop performance models. Transition probability matrices are presented using probability distribution functions rather than single values. A simulation technique is then used to incorporate the probability distribution function operations to compute the future condition of the pavements. The future performance of the pavements is expressed by both single expected values and suitable probability distribution functions. Ultimately, a probabilistic versus deterministic performance curve is presented. DOI: 10.1061/(ASCE)TE. 1943-5436.0000052 CE Database subject headings: Markov process; Fuzzy sets; Simulation; Concrete pavements; Cold regions; Computer applications.

Two types of analysis were conducted to examine the impacts of midcentury scenarios of anthropogenic climate change on flexible pavement infrastructure in southern Canada. An analysis of deterioration-relevant climate indicators at 17 southern Canadian sites revealed that over the next 50 years low temperature cracking will become less problematic, structures will freeze later and thaw earlier with correspondingly shorter freeze season lengths, and higher extreme in-service pavement temperatures will raise the potential for rutting. Pavement performance simulations conducted using the mechanistic-empirical pavement design guide and data from the Canadian long term pavement performance program for six of these sites also suggest that rutting issues will be exacerbated by climate change and that maintenance, rehabilitation, or reconstruction will be required earlier in the design life. While the simulated effect of climate change was found to be modest, both in absolute terms and relative to variability in pavement structure and baseline traffic loads, pavement engineers would benefit by incorporating longer time series of weather and climate in their designs. Although the analysis was conducted for southern Canada, many of the findings and impacts may be similar for the northern United States. DOI: 10.1061/(ASCE)0733-947X(2009) 135:10(773) CE Database subject headings: Canada; Climatic changes; Pavement design; Asphalt pavements; Pavement management; Flexible pavements.

Safe integration of autonomous vehicles (AVs) into the current public road system may imply potential improvements to roadway infrastructure. However, the current research effort is lacking in one of the important infrastructure to vehicle (I2V) areas, that is, roadway conditions, especially pavement friction. Motivated by the fact that pavement friction plays a critical role in safe driving for conventional vehicles and the fact that rear-end crashes are the most common type of crashes involving autonomous vehicles, this paper presents a first-of-its-kind effort to evaluate the driving safety of AVs with respect to pavement friction. An explicit relation was derived between pavement friction and traffic safety in terms of the stopping sight distance. The statistical characteristics of pavement network friction were determined from field friction measurements. A typical scenario was created to define rear-end crashes involving self-driving vehicles. The probabilities of rear-end crashes were estimated using the Monte Carlo method, and their implications were discussed. It was found that there is no urgent need to increase pavement friction requirements with respect to rear-end crashes involving self-driving vehicles. The findings may also be used to improve the extent of AV operational domains (ODs) and facilitate highway agencies to assess the readiness of road infrastructure in the form of roadway condition to support autonomous driving. [ABSTRACT FROM AUTHOR]

The angularity of coarse aggregates significantly influences the performance of asphalt pavement. However, the research remains in the qualitative stage, and no universal evaluation standard has been proposed. This research proposes image-based methods to quantitatively analyze the angularity of coarse aggregates, thereby providing corresponding evaluation standards. First, aggregate levels of 4.75–9.5, 9.5–13.2, and 13.2–16 mm were obtained by sieving experiments, which were then abraded 0, 400, 800, and 1,200 times using a Los Angeles abrasion machine. Subsequently, the aggregate particle angularity parameters, including circumference, area, convex hull circumference, convex hull area, and total number of corner points, were calculated. Meanwhile, the aggregate imaging system (AIMS) gradient, skeleton extraction, convex hull, and uncompacted void content (UVC) methods were used to evaluate the angularities of the aggregates. Thereafter, the AC-13C-type mixture test specimens were formed using different angularity aggregates. On this basis, the angularity-related pavement skid resistance and rut resistance tests were conducted. The results show that the skeleton extraction method performs excellently for evaluating all aggregate levels, while the convex hull method is suitable for 9.5- and 13.2-mm aggregates, the AIMS gradient method is suitable for assessing 4.75- and 9.5-mm aggregates, and the UVC method is suitable for assessing 9.5- and 13.2-mm aggregates. [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]

This paper is concerned with the development of a new measurement device for the realistic assessment of braking capability of landing airplanes for winter runways. The conventional and current practice of runway condition monitoring has been focused on identifying the maximum tire-pavement frictional drag (µ value) and often neglected the characteristics of actual aircraft braking systems as well as the comprehensive effects coming from various factors such as deformable contaminants on the winter runway. The braking availability tester (BAT) proposed in this paper is designed to take a different approach for the realistic assessment of braking availability of landing airplanes. The main idea of the BAT is to mimic the braking operation of actual aircrafts as closely as possible by incorporating the same brake mechanism and antiskid braking system (ABS) used in existing aircrafts. In doing so, the BAT also incorporates a suite of sensors for monitoring the status of braking operation in real time. This paper details the design concepts and operation principles of the BAT. Preliminary test results are also presented to verify the main functionality of the BAT. [ABSTRACT FROM AUTHOR]

Pervious concrete pavement (PCP) is of significant importance in the field of stormwater management in terms of reducing runoff volume. Stormwater managers should initially ensure that PCP adequately performs over time to be able to implement it in a stormwater management system. Performance models are intended to predict the performance of an asset over its service life. To develop a performance model commonly long-term performance data are essential. No performance model has been developed for PCP to date because PCP long-term performance data are rarely available. In such a case, expert knowledge is an alternative method to collect data for developing a performance model. This research aims to develop performance models for PCP for the first time by using an integrated Markov chain technique (combination of homogenous and non-homogenous techniques) through incorporation of expert knowledge. Both deterministic and stochastic approaches are applied to build up Markov models by using expected values and the Latin hypercube simulation technique, respectively. Both approaches provide consistent results although the stochastic Markov model provides more detailed results. Short-term experimental field data are also incorporated to validate the Markov performance models. [ABSTRACT FROM AUTHOR]

Because pervious concrete pavement (PCP) has a porous structure and can percolate water to an underground layer, it has been proposed as a stormwater best management practice (BMP), an environmentally friendly product, and sustainable paving materials. This porosity makes PCP susceptible to freeze-thaw damage in cold climates. Therefore, PCP has not been widely applied and investigated in such a climate. Long-term performance data are rarely available, and no performance model has been developed for PCP to date. The main objective of this research is to integrate expert knowledge (using the Markov-chain process) and experimental data (PCP field investigations) to build a performance model for PCP through incorporation of the Bayesian technique. The combination of these sources of data is an efficient and effective approach to build a performance model for a new type of pavement, such as PCP, which has not had a long-term performance database. As a result, a robust linear performance model is developed and applied to predict the service life of PCP. The service life of PCP is estimated to be approximately nine years using the developed performance model. In general, the expert knowledge leads to more conservative results rather than experimental data. [ABSTRACT FROM AUTHOR]

Pervious concrete pavement (PCP) has the potential to provide significant technical, economical, and environmental benefits. To better understand the beneficial impacts of PCP, its performance must be comprehensively evaluated and quantified. To evaluate the PCP performance, its pavement condition should be assessed. The primary aim of this research is to evaluate the PCP condition through incorporation of an adequate panel rating method. Two panel rating methods are evaluated for this purpose: visual digital inspection and in situ inspection. Field investigations are also conducted to record the surface distresses by describing their severity and density using the Ministry of Transportation of Ontario protocol. Finally, a model is developed and validated which relates mean panel rating (i.e., surface distress rating) to a pavement distress. It is concluded that the only significant variable (i.e., distress) in this model is raveling. [ABSTRACT FROM AUTHOR]

This paper focuses on trenchless technology cost savings due to elimination of traffic disruptions associated with utility cuts. Typical construction durations and traffic control plans for two lane roads have been utilized to develop equations for calculating traffic disruptions. The results show that as traffic levels increase, the user delay costs can be significant. It is suggested that the methodology presented can enable the decision maker to consider total costs, including user delay costs associated with typical traffic control plans, and that in certain cases this can make trenchless technology the most economic alternative. [ABSTRACT FROM AUTHOR]

Using recycled concrete aggregates (RCAs) as coarse aggregate in concrete has the potential to supplement current natural aggregate reserves, divert construction and demolition debris from landfills, and promote the adoption of sustainable civil infrastructure. As many of the design equations used to calculate structural concrete properties are based on empirical data for natural aggregate concrete, using these equations for RCA concrete may not be applicable. This study examined the bond of reinforcement in concrete produced using RCA as coarse aggregate. One natural aggregate (NA) and three RCA sources were evaluated and used as coarse aggregate in 14 separate concrete mixtures with four compressive strength levels. Various concrete mechanical properties, including compressive strength, splitting tensile strength, modulus of rupture, and fracture energy, were tested, and correlations between these properties and reinforcement bond were studied. The reinforcement bond was measured using 48 beam-end specimens incorporating several bonded lengths. The results showed that bond strength of RCA concrete was reduced by up to 21% in comparison to NA concrete, and that there was a strong correlation between bond strength and coarse aggregate crushing strength. A regression model was developed to relate bond strength to coarse aggregate strength, concrete compressive strength, and the bonded length. Using this model, experimentally predicted development lengths were calculated to be up to 9% greater for RCA concrete members in comparison to NA concrete members. Overall, this study was directed at providing guidance on the evaluation of multiple RCA sources and their respective impact on the bond of reinforcement in structural concrete. [ABSTRACT FROM AUTHOR]

Pervious concrete pavement can effectively reduce both the volume of water and the concentration of many sediment-associated contaminants in urban runoff. However, chloride from road salt is recognized as a threat to surface and groundwater resources because it is a conservative ion and does not readily bind to soil particles. To better understand and manage water resources in urban environments experiencing annual freeze-thaw cycles, this study examines the impact of road salt (sodium chloride) and sand applications on water and chloride movement in pervious concrete structures in a laboratory setting. Water movement and salt retention were characterized within pervious concrete slabs under frozen and thawed conditions. Laboratory experiments were repeated using both brine (23% salt solution) and fresh water as well as varying additions of sand (typical of winter sand application rates in Canada) to provide a range of temperatures experienced in cold-climate urban environments. Performance testing (via infiltration capacity) was conducted to assess the suitability of pervious concrete in climates where road sand and salt application is necessary. For all experimental conditions studied, chloride was rapidly transported through the pervious concrete. The complete freezing of pore water throughout the concrete slab reduced water and salt movement within the concrete matrix, while sand application reduced water movement through pores and delayed peak flow. The infiltration capacity of the pervious concrete structures, as tested, exceeds the probable maximum water loading rate that will be encountered in Southern Ontario, Canada, with or without sand, frozen or unfrozen. From a groundwater management and source water protection perspective, the data indicate that pervious concrete pavement structures may contribute to chloride contamination of groundwater if used in salt vulnerable areas and groundwater recharge zones. [ABSTRACT FROM AUTHOR]