Browsing by Author "Buttlar, William"

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    Investigation of Low Temperature Cracking in Asphalt Pavements National Pooled Fund Study 776
    (Minnesota Department of Transportation, 2007-10) Marasteanu, Mihai; Zofka, Adam; Turos, Mugur; Li, Xinjun; Velasquez, Raul; Li, Xue; Buttlar, William; Paulino, Glaucio; Braham, Andrew; Dave, Eshan; Ojo, Joshua; Bahia, Hussain; Williams, Christopher; Bausano, Jason; Gallistel, Allen; McGraw, Jim
    Good fracture properties are an essential requirement for asphalt pavements built in the northern part of the US and in Canada for which the predominant failure mode is cracking due to high thermal stresses that develop at low temperatures. Currently, there is no agreement with respect to what experimental methods and analyses approaches to use to investigate the fracture resistance of asphalt materials and the fracture performance of asphalt pavements. This report presents a comprehensive research effort in which both traditional and new experimental protocols and analyses were applied to a statistically designed set of laboratory prepared specimens and to field samples from pavements with well documented performance to determine the best combination of experimental work and analyses to improve the low temperature fracture resistance of asphalt pavements. The two sets of materials were evaluated using current testing protocols, such as creep and strength for asphalt binders and mixtures as well as newly developed testing protocols, such as the disk compact tension test, single edge notched beam test, and semi circular bend test. Dilatometric measurements were performed on both asphalt binders and mixtures to determine the coefficient of thermal contraction. Discrete fracture and damage tools were utilized to model crack initiation and propagation in pavement systems using the finite element method and TCMODEL was used with the experimental data from the field samples to predict performance and compare it to the field performance data.
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    Investigation of Low Temperature Cracking in Asphalt Pavements National Pooled Fund Study – Phase II
    (Minnesota Department of Transportation, 2012-08) Marasteanu, Mihai; Buttlar, William; Bahia, Hussain; Williams, Christopher; Moon, Ki Hoon; Teshale, Eyoab Zegey; Falchetto, Augusto Cannone; Turos, Mugurel; Dave, Eshan; Paulino, Glaucio; Ahmed, Sarfraz; Leon, Sofie; Braham, Andrew; Behnia, Behzad; Tabatabaee, Hassan; Velasquez, Raul; Arshadi, Amir; Puchalski, Sebastian; Mangiafico, Salvatore; Buss, Ashley; Bausano, Jason; Kvasnak, Andrea
    The work detailed in this report represents a continuation of the research performed in phase one of this national pooled fund study. A number of significant contributions were made in phase two of this comprehensive research effort. Two fracture testing methods are proposed and specifications are developed for selecting mixtures based on fracture energy criteria. A draft SCB specification, that received approval by the ETG and has been taken to AASHTO committee of materials, is included in the report. In addition, alternative methods are proposed to obtain mixture creep compliance needed to calculate thermal stresses. Dilatometric measurements performed on asphalt mixtures are used to more accurately predict thermal stresses, and physical hardening effects are evaluated and an improved model is proposed to take these effects into account. In addition, two methods for obtaining asphalt binder fracture properties are summarized and discussed. A new thermal cracking model, called "ILLI-TC," is developed and validated. This model represents a significant step forward in accurately quantifying the cracking mechanism in pavements, compared to the existing TCMODEL. A comprehensive evaluation of the cyclic behavior of asphalt mixtures is presented, that may hold the key to developing cracking resistant mixtures under multiple cycles of temperature.