The basic process used to modify asphalt cement with polymers (primarily SBS polymer) is to introduce both liquid asphalt cement and polymer pellets into a heated mixing (or wetting) tank, where they are mixed and the polymer is softened. The mixture is then pumped out through a mill (or grinder) into a storage tank. This mixture is usually made at a higher concentration (about 8% to 12% by weight) than the finished product to minimize the energy required.  At this stage, a chemical additive (cross-linker) is added to chemically finish the chemical bonding. The mixture is then transferred to a finished product tank, where it is diluted to the final concentration (about 2% to 2.5%).

Our blending technology utilizes the Modified Asphalt Contactor™ reactor for the mixing tank. The higher effective blending and heating capabilities will allow milling to be accomplished in a single pass, eliminating the need for multiple passes. This will result in significant energy savings due to the large motor of the mill (typically 200-300 HP), which would otherwise be operated for three to six times longer. This also would result in reduced processing time. 
 

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.

Ethylene polymers are characterized by a low polarity and low reactivity plastomers. They are like waxes in this respect, having a low dielectric constant and being soluble in hot oils, hot wax and hot hydrocarbons. They also are well known to be inert. For some uses it is desirable to modify the ethylene polymers to make them flexible, to impart more polarity to the polymers, and to be able to use them in reaction with other resins. To obtain high degree of polarity (to improve the dispersion of these materials in asphalt) high level of ester are required, which turn adversely affects the inherit advantage of the long ethylene chain (low cost, good temperature behavior, etc.) while retaining the hydrocarbon chain as the major feature of the polymer.  
Commercially available thermosetting resins such as phenolics, epoxys etc. have been found to be useful because of retention of their performance at elevated temperatures. This retention of performance is associated with the crosslinking or curing action inherent in the structure of the thermosetting resins utilized. However, this retention of high temperature performance is accompanied by high stiffness of such material or if some stiffness is desired by providing a higher degree of toughness. For these reasons ECOPATH has developed the technology to blend flexible polymers into the thermosetting resin.

 

The addition of PPA has long been known to increase the performance grade (PG) of the asphalt binder.  Many studies have shown that appropriate introduction and dosing of PPA into asphalt binder can yield cost effective solutions which translate to improved performance properties.

 Studies have shown that PG grade of the asphalt binder tends to increase with the addition of PPA. This increase has been attributed to the stiffening of one of the two main phases in the asphalt. This study indicated that the stiffening effects were base binder dependent.  However, the following mechanisms were proposed to explain the stiffening of the PPA modified asphalt: formation of PPA aducts, alkylation of aromatics, cross linking of neighboring asphalt segments, formation of ionic clusters and the cyclization of alkyl aromatics.    

Asphalt rubber (AR) (usually called ground tire rubber (GTR) modified asphalt or crumb rubber modified  (CRM) asphalt ) originally was designed to fall under the specifications of ASTM D6114 - 97(2002). This type of modified asphalt is consistent with traditional asphalt rubber where a crumb rubber concentration by total weight is necessary. This type of modified asphalt binder has been shown to exhibit excellent properties with regards to safety, noise reduction, and field performance.

ASTM D8-88 defines AR as “a blend of asphalt cement, reclaimed tire rubber, and certain additives in which the rubber component is at least 15% by weight of the total blend and has reacted in hot asphalt cement sufficiently to cause swelling of the rubber particles." Research has shown that the addition of crumb rubber to virgin asphalt produces binders with improved resistance to rutting , fatigue cracking, and thermal cracking, and also reduces reflective cracking at reduced thickness of asphalt overlay.

Research has shown that crumb rubber modification of asphalt binder has many similar effects to polymer modification. The major changes noted by these researchers are seen with the increase in the high temperature stiffness, and these are often seen to exceed levels normally achieved by polymer modification. Similarly it has been shown that crumb rubber modifier also results in a reduction of dependency on temperature and loading frequency. However, it also has been suggested that the main function of crumb rubber is that of interactive filler as crumb rubber remains as particulates even after mixing. As the crumb rubber particles do not dissolve in the asphalt, they have been shown to swell in the asphalt, resulting in effective volumes that are larger than their initial volume.