AASHTO R 15:2018 Standard Practice for Evaluation of Asphalt Additives and Modifiers.
The testing is divided into two phases. Phase I tests the modified binder (with tests of appropriate unmodified controls), while Phase II tests the modified asphalt mixture. The purpose of dividing the testing into two phases is to use the faster and easier tests of Phase I as a screening method. If an asphalt additive or modifier shows no promise in Phase I, there may be no need to continue to Phase II. This would not apply if the additive/modifier interacts specifically with the aggregate, e.g., in the case of anti-stripping agents.
This standard practice details the tests and procedure for evaluating asphalt modifiers to be used for paving. The modified asphalt binder is compared, as is appropriate, either with the same asphalt binder unmodified or with asphalt binder from the same base crude refined to a specification grade mimicking the specification-defining properties of the modified asphalt binder as closely as possible.
In most respects the evaluation procedures are those desirable for an unmodified asphalt binder. Both modified asphalt binder and asphalt mixture using modified asphalt binders are evaluated. Performance-based testing is emphasized.
The procedures go beyond those that would be desirable for unmodified asphalt binder in that unmodified control asphalt binders are used and tested specifically for those properties to be enhanced by the modifier.
If testing (at appropriate additive levels) indicates that the functional purpose of the additive is not fulfilled, testing of the additive may be terminated.
If any of the other important performance properties of the modified asphalt binder are either unsatisfactory or significantly degraded, and cannot be remedied by, e.g., further modification, evaluation of the modifier may likewise be terminated.
If the results of evaluation according to this standard practice are positive, small-scale field trials and economic cost-benefit analysis may be warranted.
If the additive/modifier is being promoted by a supplier to a customer or evaluating laboratory, e.g., a governmental agency, a suggested list of information to be provided by the supplier to such a customer/evaluator is provided in Appendix X1.AASHTO R 15 pdf download.