Application of Response Surface Method for Analyzing Pavement Performance

Hot mix asphalt (HMA) is a common material that has been largely used in the road construction industries. The main constituents of HMA are asphalt binder, mineral aggregate, and filler. The asphalt binder bounds aggregate and filler particles together and also waterproofs the mixture. The aggregate acts as a stone skeleton to impart strength and toughness to the structure, while the filler fills pores in the mixture which can improve adhesion and cohesion as well as moisture resistance. The HMA behavior depends on individual component properties and their combined reaction in the mixture. Asphalt binder properties change due to different factors. Over the years, asphalt pavement materials age, causing binder embrittlement which adversely affects pavement service life. Response Surface Method (RSM) is a set of techniques that are used to develop a series of experiment designs, determining relationships between experimental factors and responses, and using these relationships to determine the optimum conditions. Incorporating RSM in pavement technologies can beneficially help researchers to develop a better experimental matrix and give them the opportunity to analyze the changes in pavement performance in a faster, more effective, and reliable way.

The Effect of Carbon Fibers on the Tensile Behavior of Bitumen Beams

Fatigue cracking is one of the most important types of failures, which decrease the asphalt pavement service life. Carbon fibers are amongst of the additives that have high tensile strength. It is expected this fiber reduce pavement cracks which increases the fatigue life of pavement. This paper experimentally investigated the effect of the carbon fibers on bitumen specimens. Hence, the effects of fiber characteristics such as length and fiber percentage on the indirect tensile strength and Marshall stability of asphalt mixture were studied. Then, the effect of fibers on bitumen and mastic behavior, which is the main objective of the study, was evaluated. Beam specimens were subjected to three-point bending tests to determine the effect of carbon fibers. Carbon fibers had a positive effect on the tensile strength of bitumen beams at loading rates of 0.5, 2, and 5 mm/min up to 100%. Mastic exhibited a similar behavior to pure bitumen in combination with fibers.   

Truck Platooning on Flexible Pavements in Illinois

Truck platoons have many benefits over traditional truck mobility. Truck platoons have the potential to improve safety and reduce fuel consumption between 5% and 15%, based on platoon configuration. In Illinois, trucks carry more than 50% of freight tonnage and constitute 25% of the traffic on interstates. Therefore, expected fuel savings would be significant for trucks. Deployment of truck platoons within interstate highways may have a direct effect on flexible pavement performance, as the time between consecutive axle loads (i.e., resting time) is expected to decrease significantly. Moreover, platoons could potentially accelerate pavement damage accumulation due to trucks’ channelized position, decreasing pavement service life and increasing maintenance and rehabilitation costs. The main objective of this project was to quantify the effects of truck platoons on pavements and to provide guidelines to control corresponding potential pavement damage. Finite-element models were utilized to quantify the impact of rest period on pavement damage. Recovered and accumulated strains were predicted by fitting exponential functions to the calculated strain profiles. The results suggested that strain accumulation was negligible at a truck spacing greater that 10 ft. A new methodology to control pavement damage due to truck platoons was introduced. The method optimizes trucks’ lateral positions on the pavements, and an increase in pavement service life could be achieved if all platoons follow this optimization method. Life cycle assessment and life cycle cost analysis were conducted for fully autonomous, human-driven, and mixed-traffic regimes. For example, for an analysis period of 45 years, channelized truck platoons could save life cycle costs and environmental impacts by 28% and 21% compared with human-driven trucks, respectively. Furthermore, optimum truck platoon configuration could reduce life cycle costs and environmental impacts by 48% and 36%, respectively, compared with human-driven trucks. In contrast, channelized traffic could increase pavement roughness, increasing fuel consumption by 15%, even though platooning vehicles still benefit from reduction in air drag forces. Given that truck platoons are expected to be connected only in the first phase, no actions are required by the agency. However, in the second phase when truck platoons are also expected to be autonomous, a protocol for driving trends should be established per the recommendation of this study.

Response Surface Methodology Optimization in Asphalt Mixtures: A Review

The application of statistical modeling and optimization approaches such as response surface methodology (RSM) is important for the excellent potential to tackle different constraints and goals and the analysis of the relationships between independent factors influencing a particular response. This chapter provides a simple yet detailed literature review on the utilization of RSM for the design of experiments, modeling, and optimization of virgin and alternative materials into asphalt binder and mixtures for sustainability. Meanwhile, an in-depth analysis based on the literature reviewed in terms of asphalt binder modification employing RSM with various independent parameters were summarized. Also, a critical review of the application of RSM to optimize the engineering and mechanical performance characteristics of asphalt concrete mixtures is presented in this chapter. The current chapter concluded that the use of RSM statistical analysis in a highway materials perspective provides a broader understanding of the factors that control pavement performance throughout the pavement service life.

Truck-Platoonable Pavement Sections in Illinois’ Network

Truck platooning has many benefits over traditional truck mobility. Literature shows that platooning improves safety and reduces fuel consumption between 5% and 15% based on platoon configuration. In Illinois, trucks carry more than 50% of freight tonnage and constitute 25% of the traffic on interstates. Deployment of truck platooning within interstate highways would result in significant fuel savings, but may have a direct impact on flexible pavement performance. The channelization of the platoon and reduced rest time between consecutive loads would accelerate the damage accumulation at the channelized position. Ultimately, this would lead to pavement service life reduction and a subsequent increase in maintenance and rehabilitation costs. Therefore, the main objective of this project is to quantify the effects of platooning on flexible pavements and provide guidelines for the state of Illinois by considering the aforementioned factors. Although the benefits of platooning are quantifiable, not every truck route is platoonable. For efficient platooning, trucks need to travel at a constant high speed for extended distances. The integrity of the platoon should be preserved because interfering vehicles would compromise the platooning benefits and road safety. An introduced high-level approach considers the volume/capacity of a roadway and the expected number of highway exit and entry conflicts. Using these parameters, each roadway section is assigned a level of platoonability, ranging from one to five—with five being the highest. A framework was developed to analyze the Illinois highway network. It was found that 89% of the network highway is platoonable under average capacity conditions.