Anush K. Chandrappa

Development of Pavement-Surface Temperature Predictive Models: Parametric Approach

AbstractRapid urbanization has been causing a change in the urban climate resulting in urban heat islands (UHIs). In the area of transportation pavement infrastructure and its effect on UHI, the impact of these changes can be reduced by using road materials that are low-temperature sensitive. Previous studies indicated that an increase in the impervious nature of urban grounds is one of the main causes of UHI, which is principally affected by pavement surface temperatures. Further, the associated predictive models focused on pavement temperature profiles along the depth of the system, discounting surface parameters such as solar flux and surrounding air temperature. This study established pavement-surface temperature models based on meteorological factors, which can be used to estimate heat energy flux from different pavement materials and systems. The models encompassed more than 670 data points, which were robust and represented low bias and very high precision (depicted by Radj2≥98% and Se/Sy≤0.13), an...

Relationships Between Structural, Functional, and X-Ray Microcomputed Tomography Parameters of Pervious Concrete for Pavement Applications

Several countries have begun using pervious concrete (PC) pavements to reduce the adverse effects of impermeable surfaces resulting from high-impact development. Pore parameters and their relationship to other PC properties are not yet fully understood; however, this information is essential for rational designs of PC pavements. This study investigated the strength, functional, and permeability properties of 18 PC mixtures and used X-ray computed microtomography methods to determine the three-dimensional pore parameters and their relationships, which were thought to affect PC properties. The major findings of this study included the observation that the failure mode in compression was of the shear brittle type, in which the failure plane was inclined at 45° to the ground, and impact abrasion resistance was higher for larger-sized aggregates and was chiefly attributable to the individual aggregate particles debonding. Permeability was more sensitive at low hydrostatic pressure than at higher pressures. The sphericity and compactness of pores had positive correlations with each other, unlike the relationship between surface area and sphericity. The tortuosity calculated for six of the PC mixtures was less than one; this finding was attributed mainly to the single-sized pore structure. Tortuosity increased with an increase in porosity and permeability and decreased with increasing surface area and pore radius. This research should move the current understanding of PC pore structure one step forward and, therefore, will be helpful in modeling PC in a rational manner.

Predictive Models for Storage Modulus and Loss Modulus of Asphalt Mixtures

AbstractComplex modulus of an asphalt mixture constitutes two components: E′ representing the ability of the mixture to store energy (elastic behavior), and E′′ reflecting the capacity of the material to dissipate energy (viscous behavior). The main objective of this study was to develop predictive equations for the two components, E′ and E′′, to better quantify and assess the performance of conventional and modified mixtures alternate to standard laboratory testing. The dataset used in this effort encompassed 163 conventional dense graded asphalt concrete (DGAC), 13 asphalt-rubber asphalt concrete (ARAC) gap-graded, and 9 asphalt-rubber friction course (ARFC) open-graded mixes covering 5,550 data points. Aggregate gradation, binder, and volumetric property parameters were used as predictor variables. Squared-error optimization mathematical techniques were employed in developing predictive models. The statistical goodness of fit measures of E′ and E′′ predictive models were very good to excellent. Validat...

Effect of pore structure on fatigue of pervious concrete

Pervious concrete (PC) is a class of porous pavement whose properties are largely influenced by pore parameters. Under repeated vehicular loads, PC undergoes reduction in stiffness leading to failure. The purpose of this study was to understand the influence of porosity and pore sizes on fatigue of 13 PC mixtures encompassing 104 beams, and establish stiffness reduction model / damage evolution in respect of repeated loads for PC based on the existing model used for conventional concrete. Fatigue life and stiffness depend on porosity at the fractured face of specimens as investigated using image analyses, which was more influential than the volumetric porosity determined through ASTM C1754. The reduction in stiffness followed S-curve depicting three distinct stages of damage evolution. The damage model fitted the experimental data with very high accuracy (R2 > 0.95) and precision. The specimens shifted from secondary to tertiary stage when the reduction in initial stiffness was 65–85%, which occurred at 90–98% of the total life. This study is envisioned to assist in the development of fatigue test protocols as well as recommend PC pavements as part of the maintenance and rehabilitation programmes.