Publications

Published: 04/07/2019

By: Hamed Majidifard, Nader Tabatabaee, William G. Buttlar

Published: 03/25/2019

By: Punyaslok Rath, Joshua E. Love, William G. Buttlar, and Henrique Reis

The usage of Ground Tire Rubber (GTR) in asphalt pavements has gained renewed interest due to its potential sustainability, economic, and performance benefits. This study focuses on asphalt mixtures designed with three different rubber modifier products including (1) a terminal-blend GTR, (2) a dry-process, chemically processed rubber product, and (3) a terminal-blend rubber-polymer hybrid product.

Published: 10/31/2018

By: Amir H. Alavi , William G. Buttlar

Modern smartphones are equipped with various sensors along with on-board storage, computing and communication capabilities. Owing to these features, they can become an intelligent, scalable, autonomous and potentially cost-free component of the next generation civil infrastructure monitoring systems in future smart cities. Over the past few years, there has been a growing interest in the

Published: 02/05/2019

By: Behzad Behnia, William G. Buttlar, and Henrique Reis

An acoustic-emission approach to evaluate the low-temperature cracking performance of asphalt binders is presented. The acoustic activity of a thin film of asphalt binder bonded to a granite substrate is monitored while the layer is exposed to decreasing temperatures from around 20°C to approximately −50°C. Results of eight different asphalt binders at three different aging

Published: 01/10/2019

By: William G. Buttlar, Jim Meister, Behnam Jahangiri, and Hamed Majidifard

A comprehensive lab and field investigation was carried out to evaluate the performance of recycled asphalt mixtures in Missouri by researchers at the University of Missouri-Columbia, in collaboration with the Missouri Department of Transportation and the Midwest Transportation Center. Sixteen field sections were evaluated, including a number of sections from the recent Long-Term Pavement Performance

Published: 12/11/2017

By: Oliver Giraldo-Londoño, Daniel W. Spring, Glaucio H. Paulino, William G. Buttlar

Rate-dependent fracture processes can be investigated by means of cohesive zone models (CZMs). For instance, one approach enhances existing CZMs with phenomenological expressions used to represent the fracture energy, cohesive strength, and/or maximum crack opening as a function of the crack opening rate. Another approach assumes a viscoelastic CZM in front of the crack tip.

Published: 01/25/2017

By: B. C. HillO. Giraldo-LondoñoG. H. PaulinoW. G. Buttlar

Tensile cracking in asphalt pavements due to vehicular and thermal loads has become an experimental and numerical research focus in the asphalt materials community. Previous studies have used the discrete element method (DEM) to study asphalt concrete fracture. These studies used trial-and-error to obtain local fracture properties such that the DEM models approximate the experimental

Published: 06/21/2016

By: Brian Hill, William G. Buttlar

Asphalt polymer modification typically yields improved mixture performance. Little research has been conducted to determine how SBS polymer affects mixture performance in interaction plots. Furthermore, research to date has not used digital image correlation to measure the fracture process zone (FPZ) size and its compression with crack propagation. Mixtures containing five distinct asphalt binders were

Published: 02/03/2019

By: Behnam Jahangiri, Hamed Majidifard, James Meister, and William G. Buttlar

This study investigates the performance of eighteen different dense-graded asphalt mixtures paved in Missouri. The sections contain a wide range of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS), and different types of additives. The large number of sections investigated and the associated breadth of asphalt mixtures tested provided a robust data set to

Published: 11/26/2018

By: Hamed Majidifard, Behnam Jahangiri, William G. Buttlar, Amir H. Alavi

This paper presents innovative machine learning methods called gene expression programming (GEP) and hybrid artificial neural network/simulated annealing (ANN/SA) to predict the fracture energy of asphalt mixture specimens. The GEP and ANN/SA models are developed using an experimental database including a number of disk-shaped compact tension (DC(T)) test results for fracture energy. The fracture energy

Published: 11/21/2016

By: Behzad Behnia, William G. Buttlar, Henrique Reis

The present work for the first time reports observations and modeling to characterize three-dimensional spiral-shaped fracture patterns in a bi-axially stressed layer of asphalt material bonded to an aluminum substrate. Five different asphalt materials with different fracture characteristics are investigated. A logarithmic spiral model was found to mathematically represent the 3D helix-shaped cracks observed. A

Published: 04/26/2016

By: Megan E. McGovern, William G. Buttlar, Henrique Reis

Because in the field asphalt concrete acoustic properties (i.e., velocities and corresponding attenuations) are unknown, a modified version of the non-collinear wave mixing method is proposed to evaluate oxidative aging levels. Longitudinal transducers mounted on angle wedges are employed to launch subsurface dilatational waves to allow evaluation when there is only access to one side

Published: 05/07/2017

By: Megan E. McGovern, William G. Buttlar, and Henrique Reis

Except for the relatively small zones within pavements that are subjected to loadings, the primary challenge in asphalt concrete (AC) pavement design and maintenance is to prevent and/or control environmentally induced distresses. Distresses, including block and thermal cracking, and possibly raveling of construction joints, tend to accelerate with time; as a result, it is critical

By: Megan E. McGovern, William G. Buttlar, and Henrique Reis

Published: 01/01/2017

By: Megan E. McGovern, Behzad Behnia, William G. Buttlar, and Henrique Reis

This study evaluated the oxidative aging of asphalt mixtures by both nondestructive and fracture performance tests and investigated the possibility of estimating the low-temperature fracture properties of aged mixtures by using a nonlinear ultrasonic approach. Asphalt mixture samples, oven aged for 12, 24, 28, 32, and 36 h at 135°C, were compacted, made into test

Published: 11/06/2019

By: Z. Sun, B. Behnia, W. G. Buttlar, and H. Reis

An acoustic emission (AE)-based approach to evaluate low-temperature cracking susceptibility of both asphalt binders and asphalt mixtures is presented. The AE binder testing approach consists of a thin film of asphalt binder bonded to a granite substrate exposed to decreasing temperatures ranging from 20°C to −50°C. Because of the differential thermal contraction between the granite

Published: 09/26/2016

By: Zhe Sun , Behzad Behnia , William G. Buttlar , Henrique Reis

An acoustic emission (AE) approach to evaluate the effectiveness of rejuvenators in restoring aged asphalt concrete to its low-temperature performance grade is presented. Specimens, oven-aged for 36 h at 135 °C, were treated with rejuvenators (10% of binder weight). After 2, 4, 6, and 8 weeks of dwell time, the specimens were tested using AE