Authors: Virginia Carrera Moises GarciaMorales Pedro Partal Crispulo Gallegos
Publish Date: 2009/12/02
Volume: 49, Issue: 6, Pages: 563-572
Abstract
Reactive modification is lately gaining acceptance as a successful way to give added value to bitumen a crude oil refining byproduct In order to study the effect of both bitumen type and processing method isocyanatebased reactive modification was carried out with four types of bitumen from different sources by following two different procedures “waterfree” and “waterinvolved” processing The polymer used MDI–PPG was synthesized from the reaction of 44′diphenylmethane diisocyanate with a low molecular weight polypropylene glycol The results obtained demonstrate that the addition of small quantities of this reactive polymer to bitumen endows the resulting modified binder with an improved performance at high inservice temperatures Interestingly two different modification pathways have been identified the first one which occurs during mixing is the result of chemical reactions between NCO groups of the reactive polymer with functional groups containing active hydrogen atoms mainly –OH such as those typically present in the most polar bitumen fractions the second one has been proved to be a consequence of series reactions involving water Both pathways but mainly the latter lead to bituminous paving materials showing a more complex microstructure with the consequent change in their rheological response Finally very different degrees of modification depending on the colloidal features of the asreceived bitumen were observed
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