Publications

Published: 01/19/2021

By: William Buttlar, Behnam Jahangiri, Punyaslok Rath, Hamed Majidifard, Loreto Urra, James Meister, Henry Brown

In the past, traditional asphalt mixtures involved relatively simple combinations of virgin asphalt binder and aggregates to meet performance requirements. However, modern, heterogeneous asphalt mixtures exhibit more complex behavior due to a proliferation of new ingredients and because of the interactions that subsequently occur. As a result, recent asphalt mixes require advanced performance tests to

Published: 05/25/2021

By: William G. Buttlar and Punyaslok Rath

Full report coming soon. Every year almost 300 million scrap tires are generated in the United States. Recycled rubber obtained from scrap tires can be used in a number of beneficial ways. One of the most beneficial uses involves producing Ground Tire Rubber (GTR) from scrap tires and using the GTR to create Rubber-Modified Asphalt

Published: 02/25/2021

By: Behnam Jahangiri, Punyaslok Rath, Hamed Majidifard, Loreto Urra, William G. Buttlar

This study investigates the lab and field performance of four asphalt mixtures placed in Missouri, USA, containing reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS). Laboratory tests including disk-shaped compact tension fracture (DC(T)), indirect tension (IDT) creep and strength, Illinois flexibility index (I-FIT), indirect tensile cracking test (IDEAL-CT), and the Hamburg wheel tracking test (HWTT)

Published: 02/16/2021

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

The Hamburg wheel tracking test (HWTT) is a widely used testing procedure designed to accelerate and simulate the rutting phenomena in the laboratory. Rut depth, as one of the outputs of the HWTT, is dependent on a number of parameters related to mix design and testing conditions. This study introduces a new model for predicting

Published: 04/22/2020

By: He Wang, Punyaslok Rath, William G. Buttlar

Published: 03/12/2020

By: Hamed Majidifard, Yaw Adu-Gyamfi, William G. Buttlar

Published: 12/20/2019

By: Willima G. Buttlar and Punyaslok Rath

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

Highlights A comprehensive literature review of smartphone-centric research for civil infrastructure monitoring. Emphasis placed on sensing capabilities of smartphones and their crowdsourcing power. A case study to prove smartphones as cost-effective tools for real-time data collection. Discussing the limitations, challenges and future directions for widespread application of smartphone-driven monitoring systems.

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

Highlights An efficient mixed-mode rate-dependent cohesive zone model is presented in detail. Rate-dependent springs and damage elements are coupled to model mixed-mode fracture. The model is implemented as a user-defined element in Abaqus. The model results agree well with test results for a wide range of strain rates. The accuracy of the model is similar

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