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Evaluation of fracture and moisture damage performance of wax modified asphalt mixtures
KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
Bozok Univ, Yozgat, Turkey .
KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.ORCID iD: 0000-0003-0889-6078
2012 (English)In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, Vol. 13, no 1, 142-155 p.Article in journal (Refereed) Published
Abstract [en]

In this study the fracture and moisture damage characteristics of wax modified asphalt mixtures were evaluated. Two types of commercial waxes (FT-paraffin and Asphaltan B) were added to bitumen of penetration grade 70/100. Using this wax modified and unmodified bitumen; total 48 specimens were produced from two sources of aggregates and two levels of gradation. Bitumen properties were determined by conventional test methods, Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) testing. Thermal Stress Restrained Specimen Test (TSRST) was used to evaluate low temperature cracking resistance and cracking behavior of asphalt mixture was investigated at 0 degrees C using Superpave Indirect Tensile Test (IDT). The influence of wax on the asphalt mixture resistance to cracking and moisture damage performance has been evaluated using Hot Mix Asphalt (HMA) fracture mechanics and Superpave IDT test results. The addition of FT-paraffin and Asphaltan B showed better cracking and moisture damage resistance of the asphalt mixture compared to unmodified mixture, but FT-paraffin showed the largest effect on cracking resistance while Asphaltan B showed highest resistance to moisture damage. In BBR test results, mixtures modified with FT-paraffin showed lower limit m value (LmT) which implies minor negative effect in stress relaxation. However, according to TSRST results, the mixtures with both waxes had nearly same fracture temperature as mixture with unmodified bitumen.

Place, publisher, year, edition, pages
2012. Vol. 13, no 1, 142-155 p.
Keyword [en]
HMA fracture mechanics, superpave IDT, moisture damage, cracking, low temperature performance, wax
National Category
Infrastructure Engineering
URN: urn:nbn:se:kth:diva-98962DOI: 10.1080/14680629.2011.644120ISI: 000305177400010ScopusID: 2-s2.0-84863608671OAI: diva2:540021

QC 20120706

Available from: 2012-07-06 Created: 2012-07-05 Last updated: 2012-08-28Bibliographically approved
In thesis
1. Thermally Induced Fracture Performance of Asphalt Mixtures
Open this publication in new window or tab >>Thermally Induced Fracture Performance of Asphalt Mixtures
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

A major distress mode in asphalt pavements is low temperature cracking, which results from the contraction and expansion of the asphalt pavement under extreme temperature changes. The potential for low temperature cracking is an interplay between the environment, the road structure and importantly the properties of the asphalt mixture. The thermal cracking performance of asphalt concrete mixtures can be evaluated by conducting thermal stress restrained specimen tests (TSRST) which is known to be correlated well with the fracture temperatures observed in the field. Although TSRST provides a good estimation of the field performance, it may be unrealistic to implement the obtained results in a design framework. On the other hand, recent studies showed Superpave indirect tension tests can be used to evaluate fracture performance (fatigue, moisture damage, low temperature cracking, etc.) of the asphalt concrete  mixtures. In addition, the obtained elastic and viscoelastic parameters from the Superpave IDT tests can be used as an input parameter to establish a design framework. The study presented in this thesis has a main objective to develop a framework using Superpave IDT test results as input parameters in order to evaluate the low temperature cracking performance of asphalt concrete mixtures. Moreover, the study aims to investigate micro-mechanically the low temperature cracking behavior of bitumen using atomic force microscopy (AFM) as a tool.

The numerical model has been developed by integrating fracture energy threshold into an asphalt concrete thermal fracture model, considering non-linear thermal contraction coefficients. Based on the asphalt concrete mixture viscoelastic properties, this integrated model can predict thermally induced stresses and fracture temperatures. The elastic, viscoelastic and fracture energy input parameters of the model were measured by conducting indirect tension tests and the thermal contraction coefficients were measured experimentally. The proposed model has been validated by comparing the predicted fracture temperatures with the results obtained from TSRST tests. It was found that, while there is a quantitative discrepancy, the predicted ranking was correct. In the measurement of the thermal contraction coefficients it was observed that the thermal contraction coefficient in asphalt concrete is non-linear in the temperature range of interest for low temperature cracking. The implications of having non-linear thermal contraction coefficient were investigated numerically.

In an effort to understand the effect of bitumen properties on low temperature fatigue cracking, AFM was used to characterize the morphology of bitumen. The AFM topographic and phase contrast image confirmed the existence of bee-shaped microstructure and different phases. The bitumen samples were subjected to both environmental and mechanical loading and after loading, micro-cracks appeared in the interfaces of the bitumen surface, confirming bitumen itself may also crack. It was also found that the presence of wax and wax crystallization plays a vital role in low temperature cracking performance of bitumen.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. x, 18 p.
Trita-TEC-LIC, ISSN 1653-445X ; 12:006
Low temperature cracking, asphalt concrete fracture mechanics, viscoelasticity, non-linear thermal contraction coefficient, atomic force microscopy, wax, wax crystallization
National Category
Infrastructure Engineering
Research subject
SRA - Transport
urn:nbn:se:kth:diva-101384 (URN)978-91-85539-91-8 (ISBN)
2012-09-14, B25, Brinellvägen 23, KTH, Stockholm, 09:00 (English)
TrenOp, Transport Research Environment with Novel Perspectives

QC 20120828

Available from: 2012-08-28 Created: 2012-08-27 Last updated: 2012-08-28Bibliographically approved

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