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Low temperature cracking performance of WMA with the use of the Superpave indirect tensile test
KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
Bozok University, Engineering and Architecture Faculty.
KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.ORCID iD: 0000-0003-0889-6078
2012 (English)In: Construction and Building Materials, ISSN 0950-0618, Vol. 30, 643-649 p.Article in journal (Refereed) Published
Abstract [en]

Low temperature cracking of wax modified bitumen and asphalt mixtures were studied using the Dynamic Shear Rheometer (DSR), Bending Beam Rheometer (BBR), Superpave IDT and Thermal Stress Restrained Specimens Test (TSRST). Two types of commercial waxes (FT-paraffin and Asphaltan-B) were added to 70/100 penetration grade bitumen. Hot Mix Asphalt (HMA) fracture mechanics was used to determine fracture parameters. Master curves obtained from DSR and BBR test results showed stiffening effect due to wax additive at low temperature. The analysis of covariance was performed using a General Linear Model (GLM) on the Superpave IDT test results for Energy Ratio (ER) by using SPSS (Statistical Program for Social Sciences). Statistical analysis of Superpave IDT results showed a minor negative effect of wax modification at lower temperatures. Statistical analysis also showed that fracture parameters are highly temperature dependent and the two types of aggregate used did not play any significant role in low temperature cracking performance. Results obtained from TSRST tests indicate wax modification has a minor negative effect in low temperature cracking performance of asphalt mixtures.

Place, publisher, year, edition, pages
2012. Vol. 30, 643-649 p.
Keyword [en]
Low temperature cracking, Wax, Warm mix asphalt, Superpave IDT, HMA fracture mechanics
National Category
Infrastructure Engineering
Research subject
Järnvägsgruppen - Infrastruktur
URN: urn:nbn:se:kth:diva-49723DOI: 10.1016/j.conbuildmat.2011.12.013ISI: 000301990300075ScopusID: 2-s2.0-84855497420OAI: diva2:460275
QC 20120504Available from: 2011-11-29 Created: 2011-11-29 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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