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EVA Modified Asphalt PDF Print E-mail
Written by Szabolcs Biro   

In many asphaltic compositions it is particularly desirable to have a high degree of flexibility combined with toughness and durability.  High ductility is especially desirable for meeting the specifications demanded in industrial asphalts used in materials such as roofing shingles, built-up roofs, canal linings, pipe coatings, etc.  Additionally, because of the temperature stress to which these asphalts may be subjected, it is desirable to have an asphalt which can withstand low temperatures over time without developing significant brittleness and not flow at high temperatures.  The parameters of these conditions may also be expressed as the well known physical properties of asphalt:  viscosity, penetration and softening point.

It has been discovered that paving asphalts (especially of the hot mix, hot laid type) may be modified so as to have improved stability and rheological properties by the addition of certain copolymers of ethylene with vinyl acetate or lower alkyl esters of acrylic acid and methacrylic acid to an asphalt, provided said asphalt has an asphaltene content below a critical level.  More specifically, an asphalt cement or binder having both enhanced storage stability and creep reisistance relative to conventional binders (i.e., straight-run asphalts obtained from residua from vacuum distillation of crude oil) is formed when the asphalt used in said binder has an asphaltene content of about 7 wt% or less, based on wt% of the asphalt.
These blends comprise a homogeneous dispersion of polymeric additive in asphaltic material.  The blends can be used hot, cut back with lighter hydrocarbons (as cub-back asphalts are used) or as aqueous emulsions.  The compositions of our invention can be used in a conventional manner such as by spraying, brushing, precoating, e.g., dipping, or the like.


Ethyl vinyl acetate is an asphalt modifier which is typically added at concentrations between 2-5% by weight of asphalt binder. It is typically dispersed to the hot asphalt binder at temperatures between 149-171oC. Benefits of this polymer modifier include the fact that only moderate agitation is necessary.  Furthermore, the blends can be stored for weeks without succumbing to separation. Consistent with many other polymer modified asphalts, the compatibility of the EVA and asphalt binder is vital for achieving the desired properties.

Studies have shown that at lower polymer contents (3% by weight), EVA modified binders exhibit dispersed polymer particles in a continuous bitumen matrix. EVA modified binder properties, such as morphology and storage stability, are influenced by the characteristics of the base bitumen and binders. Generally, increases in EVA concentration yield greater improvements in the binder; however, these increases also lead to reductions in storage stability. Other studies have shown that, when EVA and SBS modified binders are compared to neat binders, SBS binder exhibit a significantly higher elastic recovery than neat binders. Also, EVA binders tend to exhibit fewer improvements in elastic recovery while losing ductility and elastic recovery at a greater rate.
 

 

 

ECOPATH has extensive experience in binder design where emphasis is placed on achieving specified binder in the most cost effective manner. ECOPATH provides unique solutions for every asphalt concern, moreover ECOPATH is dedicated to developing solutions with economic efficiency as a priority. Please contact us for further information on binder design services. 
Last Updated ( Tuesday, 30 June 2009 18:32 )