Study of bitumen crystallization by temperature-modulated differential scanning calorimetry and rheology
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arlos Gracia-Fernández Thermal Analysis, Rheology and Microcalorimetry Applications, TA Instruments—Waters Cromatografía, Alcobendas 20108, Madrid, Spain
Silvia Gómez-Barreiro Departament of Applied Physics, CESUGA, University College of Dublin, A Coruña 15190, Spain
Jorge López-Beceiro University of A Coruña, Higher Polytechnic School, Campus de Esteiro, Ferrol 15403, Spain
Javier Nebreda Corvisa, Productos Asfálticos y Aplicaciones, Madrid 28021, Spain
Ramón Artiagaa) University of A Coruña, Higher Polytechnic School, Campus de Esteiro, Ferrol 15403, Spain (Received 9 November 2011; accepted 14 February 2012)
Asphalt bitumens are complex colloidal systems of high viscosity and complex behavior, which are mainly used for making asphalt concrete for road surfaces. Thermal and rheological characterizations are needed to understand their complex behavior, particularly at the processing stage. Prediction of properties at short and long observation times is usually performed through time-temperature superposition (TTS) models, which make use of some calculated shift factors. The influence of crystallization-like transformation processes on the validity of these shift factors is investigated here by temperature-modulated differential scanning calorimetry (TMDSC). Four asphalt emulsions are considered in this work, each one with a specific transformation behavior. The structure-properties relationships are explained on the basis of the transformation profiles and rheological data.
I. INTRODUCTION
The importance of bitumen nowadays is undeniable since a very large majority of the roads are made of asphalt, which is constituted by a mixture of mineral aggregates and about 5 wt% of bitumen. Despite this low bitumen content, the performance of the road pavement depends to a large extent on the properties of bitumen itself, since it constitutes the only deformable component.1 During the last few decades the properties specified for road pavements have become more and more exigent, due to the increasing number of vehicles and load weight of some of them.2 To minimize the road pavement deterioration and, thereby, to increase the long-term durability of a flexible pavement, the bituminous layers should be improved with regard to performance-related properties, such as resistance to permanent deformation, low-temperature cracking, load-associated fatigue, wear, stripping and aging.3 a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2012.73 1410
J. Mater. Res., Vol. 27, No. 10, May 28, 2012
http://journals.cambridge.org
Downloaded: 13 May 2014
A common strategy to improve the quality of the bituminous layer consists in using polymer-modified bitumen (PMB). Modification of bitumen with synthetic polymers constitutes a route to meet the new technical demands. To this aim, several thermoplastics and elastomers have been mixed with bitumen, typically in an amount lower than 10%.2 The properties of a PMB are dependent on the characteristics of the polymer and bitumen, the polymer content and
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