Browsing by Author "Zofka, Adam"
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Item Development of Simple Asphalt Test for Determination of RAP Blending Charts(2004-06-01) Zofka, Adam; Marasteanu, Mihai O; Clyne, Timothy R; Li, Xinjun; Hoffmann, OlivierThere are two main reasons why the use of RAP (reclaimed asphalt pavement) as a construction material is profitable. First, the use of RAP is economical and can reduce material and disposal problems. Second, using RAP conserves natural resources. According to Federal Highway Administration (FHWA) nearly 30 million tons of RAP are recycled into Hot Mix Asphalt (HMA) pavements every year and thus RAP is the most recycled material in the United States. The purpose of this study was to investigate the possibility of developing a simple test that could be used to obtain asphalt binder properties that are required in developing blending charts to select the appropriate percentage of RAP. Based on the laboratory testing and data analysis it was found that Bending Beam Rheometer (BBR) tests performed on thin beams of asphalt mixture can be successfully applied into derivation of the creep compliance (and stiffness) of asphalt mixtures. It was shown that recently proposed Hirsch model can be then used to back-calculate the binder stiffness. The detailed procedure that leads to constructing blending charts and obtaining the critical temperatures was proposed. It was concluded that additional research is needed to further investigate Hirsch model and refine it to obtain reasonable stiffness values and binder m-values. It is recommended to employ the proposed procedure only in low temperature grading since the addition of RAP affects mostly the low temperature PG limit.Item 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, JimGood 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.