Enhancing Asphalt Mixture Performance with Crumb Rubber: A Sustainable Solution for Improved Durability and Mechanical Properties

Asphalt crumb rubber is a type of pavement material formed by mixing asphalt cement with crumb rubber that is derived from recycled tires. This eco-friendly approach aids in waste reduction and promotes environmental preservation by incorporating recycled materials into pavement construction. The study aimed to examine the behavior of asphalt mixtures modified with crumb rubber, made by blending recycled tire-derived crumb rubber with asphalt cement. Adding crumb rubber improved the performance of asphalt mixtures, with 8% crumb rubber enhancing the Marshall stability by 20% and 34% for 40/50 and 50/60 grades, respectively. The moisture susceptibility of both grades also improved. Crumb rubber is a sustainable material that can improve the performance of asphalt mixtures

The Effect of Rubber Crumbs on Marshall Properties for Warm Mix Asphalt

A new pavement technology has been developed in Highway engineering: asphalt pavement production is less susceptible to oxidation and the consequent damages. The warm mix asphalt (WMA) is produced at a temperature of about (10-40) oC lower than the hot asphalt paving. This is done using one of the methods of producing a WMA. Although WMA's performance is rather good, according to previous studies, as it is less susceptible to oxidation, it is possible to modify some of its properties using different materials, including polymers. Waste tires of vehicles are one of the types of polymers because of their flexible properties. The production of HMA, WMA, and WMA modified with proportions of (1, 1.5, and 2%) of rubber crumbs by the dry method are accomplished in this work. Marshall Test and volumetric properties determination are performed to evaluate its performance. The results showed that using 1% of rubber crumbs as a replacement for fine aggregate in the warm asphalt mixture produced the best properties of the WMA compared to the conventional WMA

Evaluating Iraqi Modified Asphalt Concrete Moisture Resistance Based on Strength Ratio and Fracture Energy Parameters

Two types of polymers (plastomer (functionalized polyethylene (PE)) and elastomer (styrene-butadiene-styrene (SBS))) were used for shifting up asphalt binder performance grade (PG) and tensile strength resistance (moisture damage) of the asphalt concrete mixture. It is found that adding 3.5% functionalized polyethylene (PE) polymer to the binder is more effective than adding 4% styrene-butadiene-styrene (SBS) to shift up asphalt PG by two grades to PG 76-16. Furthermore, the viscosity of the binder increased about 200% when using 4% SBS, while there is no significant effect on viscosity when 3.5% PE is used. Therefore, there is no need to increase the temperature of mixing and compaction which may affect polymers. The indirect tensile test was used for measuring tensile strength ratio of dry and wet samples (conditioned according to ASTM D4867) and found that this ratio increased by 10 to 18% when using 4% SBS and 3.5% PE, respectively. Fracture energy (area under the strength-strain curve) and elasticity were estimated for neat and modified mixture samples

Impact of urban morphological changes on traffic performance of Jadriyah intersection

The realization of the nexus between morphological changes and road intersection performances remains a challenge in urban studies. Despite the effort spent on minimizing the traffic associated problems (such as congestion and delay) in urban intersections, namely using roundabouts, signalized intersections, and actuated traffic signal controls, there are still traffic performance inefficiencies within intersections. Traffic congestion in the intersection arises for two reasons, namely by densification formed in the surrounding area and by the lack of effective traffic management. In this paper, a morphological analytical approach was adopted to explain the urban intersection changes for a 1 sq. km study area within Jadriyah neighborhood. The study spans three historical phases (1999, 2009, and 2019) and describes the changes to urban morphology by integrating land-use development with traffic data. Problems regarding urban variation in this prominent intersection were measured and then compared in terms of the Level-of-Service (LOS). The deployment of measurement and analytical methods include two sets of measurements: firstly, the study of the morphology of urban form structures, and secondly the data analysis of volume, pedestrian movement, saturation flow, and signal timing during peak hours whilst counting the daily trips generated for each type of changed land use pattern. Analysis of the collected data revealed that the urban morphology of transformed land use over time impacted the traffic volume for each phase on the level of intersection performance. Results thus showed a considerable decline of the urban intersection LOS in Jadriyah neighborhood; the uncontrolled land use expansion led to an increase in the peak volume at a rate of 155 veh/hr per year, whilst the percentage increase in pedestrians was 200% per hour. The paper concluded that ignoring densification and land use development at the urban design level over time has given rise to real impact, whether increasing traffic saturation or delay, on the performance of intersections and thus influence the transportation planning level

Moisture Susceptibility of Sustainable Warm Mix Asphalt

Sustainable pavements are pavements that meet the requirements of present generation without influencing the capability of the future generation to meet their needs. One of the problems of the warm mix asphalt is that it has low resistance to moisture damage; therefore, the aim of this research paper is to study the possibility of producing more durable warm mixes against the moisture damage with the use of recycled concrete aggregate (RCA) which has not been studied before. Six replacement rates (0, 20, 40, 60, 80, and 100%) for the coarse version aggregate (VA) with RCA were studied. The Marshall mix design method was used to determine the optimum asphalt cement content for each replacement rate. Thereafter, specimens with the optimum asphalt cement content were prepared and tested in the indirect tension test to evaluate their moisture susceptibility. The results revealed that the mixes with higher percentage of RCA possess higher optimum asphalt content. Moreover, an improvement of 13 and 28% in Marshall stability and tensile strength ratio (TSR), respectively, was obtained in case that the VA was entirely replaced by the RCA