Summary of Rubber Modified Asphalt Product Specifications around ...
Summary of Rubber Modified Asphalt Product Specifications around ...
Summary of Rubber Modified Asphalt Product Specifications around ...
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9.0 <strong>Summary</strong> and Recommendations for the MTO, Ontario, Canada<br />
After comparing the different specifications from various agencies on rubber modified asphalt,<br />
the following summary and recommendations can be drawn:<br />
1. The Crumb <strong>Rubber</strong> Modifier (CRM) is an important component <strong>of</strong> the asphalt rubber and<br />
rubber modified asphalt. The typical specifications for CRM from various agencies are<br />
summarized in Table 1. The CRM generally used in terminal blend is much finer than the<br />
one used in field blend. For field blended asphalt rubber, Ontario’s CRM gradation is<br />
finer than that <strong>of</strong> California and Arizona. However, California also uses a high nature<br />
rubber and extender oil which Ontario doesn’t use. The asphalt modifier specified by<br />
California shall be a resinous, high flash point, aromatic hydrocarbon compound.<br />
Ontario’s CRM is also finer than the Type A <strong>of</strong> Arizona, Grade A <strong>of</strong> Texas, New Jersey,<br />
and China. It is similar as Type B <strong>of</strong> Arizona and Grade B <strong>of</strong> Texas, but it is coarser than<br />
Grade C <strong>of</strong> Texas and Types A, B, and C <strong>of</strong> Florida. Finer CRM makes it easier to blend<br />
and interact with a base asphalt binder. Ontario’s CRM is on the medium to fine side.<br />
However, it doesn’t have a maximum moisture content requirement. Additives such as<br />
calcium carbonate, which can absorb moisture and keep CRM dry during mixing, are not<br />
used in Ontario specifications.<br />
2. In Ontario, asphalt rubber is called rubberized asphalt cement. It generally consists <strong>of</strong> a<br />
Type III asphalt rubber binder according to ASTM 6114, which is suitable for cold<br />
regions. The blending temperatures <strong>of</strong> Ontario rubberized asphalt cement are slightly<br />
lower than that <strong>of</strong> California, similar to Arizona andNew Jersey, and higher than those <strong>of</strong><br />
Florida. New Jersey and Arizona require a longer blending time <strong>of</strong> 60 minutes minimum.<br />
California uses an asphalt modifier (extender oil) to promote interaction <strong>of</strong> CRM and<br />
base asphalt cement.<br />
3. The terminal blend asphalt is a type <strong>of</strong> rubberized asphalt cement where crumb rubber is<br />
blended with base PG graded asphalt cement at an asphalt refinery or terminal. Unlike the<br />
asphalt rubber field blend rubberized asphalt cement, the terminal blend is stable without<br />
the need <strong>of</strong> agitation during store or transportation. It can be used just like conventional<br />
liquid asphalt cement, but it contains rubber between 5-20% by weight <strong>of</strong> asphalt cement<br />
depending on agency specification. California required the solubility test <strong>of</strong> terminal<br />
blend to be minimum 97.5%.<br />
4. According to the Ontario specification, terminal blend asphalt cement is required to meet<br />
the Type III asphalt rubber binder according to ASTM D6114 as well as PGAC grade<br />
specified. However, it may be difficult to meet the PGAC solubility requirement and<br />
ASTM 6114 asphalt rubber requirement.<br />
5. For rubber modified asphalt gap-graded mix, the asphalt cement content <strong>of</strong> Ontario mix is<br />
at the lower side compared with other agencies, such as California and Arizona, probably<br />
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