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Milwaukee, WI, United States

Faheem A.,Bloom Companies LLC | Hintz C.,University of Wisconsin - Madison | Bahia H.,University of Wisconsin - Madison | Al-Qadi I.,University of Illinois at Urbana - Champaign | Glidden S.,Mathy Technology and Engineering Services Inc.
Transportation Research Record | Year: 2012

This study proposed the fractional voids test for mineral fillers introduced by Rigden in 1947 and currently adopted as the European norm, as part of asphalt mixture design and quality control. Laboratory testing conducted in this study included a large collection of natural and manufactured fillers currently used in various regions of the United States. Results showed that filler fractional voids influenced mastic viscosity and nonrecoverable compliance. These mastic properties were also found to be highly correlated with mixture performance measures. This study used mixture performance limits to derive mastic limits based on mixture-to-mastic correlations. Regression models developed to predict mastic performance as a function of filler fractional voids and asphalt binder properties were proposed as a means for incorporating fractional voids into the mix design procedure as a quality control measure. This paper discusses the tested materials and the analysis approach and summarizes the data justifying the proposed limits.

Faheem A.F.,Bloom Companies LLC | Bahia H.U.,University of Wisconsin - Madison
Road Materials and Pavement Design | Year: 2010

Many studies have focused on modelling the stiffening effect of mineral filler on asphalt binder. However, the interaction between both constituents was always a challenge to address. Current European as well as North American specifications includes limits on stiffening effects of fillers that are mostly empirically driven and hard to include in a mixture design process. This study offers a model that allows estimation of stiffening effects based on primary binder and filler properties. This study builds on a conceptual model provided in an earlier publication for understanding the mechanism by which the filler stiffens the asphalt mastic. The model hypothesizes that change of mastic complex modulus with filler content follows two phases; a diluted phase and a concentrated phase. In the diluted phase, the stiffening effect of the filler on the binder follows a linear filling trend where interaction between filler and binder is minimal. On the other hand the effect of the filler departs from the linear trend once its concentration enters the concentrated phase. The deviation from the linear trend indicates the start of the significant interaction between the filler particles and the asphalt binder. In this study a model is proposed for the effect of mineral filler on asphalt binder complex modulus at given temperature and frequency. The model is defined using three main parameters, (a) Initial Stiffening Rate, (b) Terminal stiffening rate, and (c) Critical filler concentration. The results presented in this study provide measurable filler and binder properties that can be used to estimate these three parameters, which are indicators of the mineral filler interaction with asphalt binder. The model provides an effective tool to determine the role of basic filler and binder physical and chemical properties on the overall complex modulus of the mastic. © 2010 Lavoisier, Paris.

Schmitt R.L.,University of Wisconsin - Platteville | Faheem A.,Bloom Companies LLC | Al-Qadi I.L.,Urbana University
Airfield and Highway Pavement 2013: Sustainable and Efficient Pavements - Proceedings of the 2013 Airfield and Highway Pavement Conference | Year: 2013

The objective of this paper is to present a quantitative decision-support process for selecting nondestructive testing (NDT) technologies to evaluate critical characteristics during asphalt pavement construction. The literature lists mix segregation, in-place compaction, smoothness, temperature segregation, layer thickness, layer bond, and pavement modulus as critical characteristics governing quality pavement construction. Available technologies that measure one or more of these characteristics are identified for unique attributes of test measure, test portability, complexity, test time, environmental limitations, reliability, approved test protocols, training, and cost. A quantitative ranking system determines the most appropriate NDT technologies for quality-assurance measurement. A case study selection is demonstrated uniquely for one agency to measure predefined critical characteristics of in-place compaction, thermal segregation, and modulus using three NDT technologies: infrared thermography, ground penetrating radar, and the portable seismic pavement analyzer. Results from field testing reveal additional aspects of pavement quality measurement beyond traditional density and smoothness measurements. © 2013 American Society of Civil Engineers.

Wang H.,University of Illinois at Urbana - Champaign | Wang H.,Rutgers University | Al-Qadi I.L.,University of Illinois at Urbana - Champaign | Faheem A.F.,Bloom Companies LLC | And 3 more authors.
Transportation Research Record | Year: 2011

This study, part of the NCHRP 9-45 Project, analyzed the effect of mineral filler properties on asphalt mastic and the rutting potential of asphaltic mixture. The mineral filler properties were characterized by four tests: Rigden voids (RV), fineness modulus (FM), calcium oxide (CaO) content, and methylene blue value. The rheological properties of asphalt binder and mastic were characterized with the use of apparent viscosity and multiple stress creep recovery tests. Dynamic modulus and flow number tests were conducted to examine the asphaltic mixture rutting potential. The tested mixtures included several variables: four asphalt binder types, including virgin and polymer modified; two aggregate gradations; and a selected group of fillers. The study concluded that asphalt mastic performance was significantly affected by the fractional voids in the filler and possibly by the CaO content and FM. This effect, however, depended on binder type. On the one hand, the styrene-butadiene-styrene modified binder showed the strongest effect as a result of the mineral filler inclusion when tested as mastic. On the other hand, RV and CaO content showed relatively greater correlation with the mixture rutting potential, as compared with other filler properties. Addition of RV improved the prediction models for dynamic modulus and flow number. The effect of RV on the mixture rutting potential was more pronounced for the coarse mixture than for the fine mixture.

Shangguan P.,University of Illinois at Urbana - Champaign | Al-Qadi I.L.,University of Illinois at Urbana - Champaign | Leng Z.,Hong Kong Polytechnic University | Schmitt R.L.,University of Wisconsin - Platteville | Faheem A.,Bloom Companies LLC
Transportation Research Record | Year: 2013

This paper demonstrates that ground-penetrating radar (GPR) is an effective tool for quality assurance and quality control during flexible pavement compaction and after construction. Density is one of the most important properties of asphalt concrete layers in flexible pavement. It is critical to monitor the change in asphalt concrete density during compaction; GPR can be used to measure asphalt mixture density nondestructively and rapidly. However, it is challenging to apply the GPR method during compaction because of the unknown effect of roller-sprayed water on the GPR signal. This paper presents the results of a study on the effect of surface water on the GPR signal when a 2-GHz antenna is used. It was found that the higher-frequency components of the ultrawide band signal were affected by water; however, the lower-frequency components were not significantly influenced. The process consisted of a band-pass filter with a passing band from 200 to 800 MHz and extracting the surface reflection amplitude after filtering. The extracted feature was found to be insensitive to the presence of surface water. Therefore, this technology could be used effectively during the compaction process. Field data collected from two construction projects were used for validating this approach. The proposed approach was found to be feasible for monitoring compaction status. Pavement thickness and density profiles were also obtained by GPR after construction. The density values obtained by GPR were similar to those obtained by nuclear density gauge.

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