Specification Corner

Alabama DOT
Our first 424 T Superpave thin lift job has been constructed. It is a #4 NMAS mix at 70 lb/sy. ALDOT area personnel are happy with the results. We have approved OGFC mixes with Evotherm 3G instead of fiber to mitigate drain down. These mixes passed our drain down criteria of 0.30% at 325°F and 350°F by AASHTO T305. Future specification changes may include lowering our minimum prime coat rates. Trial projects that have been discussed include cold central plant recycling, balanced mix design, open graded crack-relief interlayer, and Superpave thick lift.

Colorado DOT
CDOT has developed a pilot project specification, increasing the longitudinal joint density from 92% to 94% of the theoretical maximum specific gravity with a tolerance of +/- 4%. CDOT also continues working with the Colorado APA to develop a balanced mix design specification utilizing HWT and IDEAL-CT as our preferred performance tests.

Florida DOT
We will be lowering our maximum allowed temperature for mixtures containing polymer modification from 370°F to 355°F. The change is based on feedback from polymer/binder producers indicating that higher temperatures (>355°F) are actually detrimental to the quality of the binder. 355°F would be an absolute maximum temperature, and target temperatures would be 20-30°F lower. Any truck load with a measured temperature >355°F would have to be wasted.

Illinois DOT
We do not have any specification changes at this time.

Indiana DOT
We have fully implemented Superpave 5. Target 5% air voids at 50 gyrations. We have seen an increase in density of about 1.5% across the board for what amounts to a zero cost specification change.

Minnesota DOT
We have no changes to standard specifications but are piloting a few Superpave 5 projects.

Montana DOT
We do not have any specification changes at this time.