FDOT has changed the weighted percentage of roadway density for payment from 35% to 40%. This is an incremental step with a potential to go to 45% in two years. FDOT recognizes the importance of this material property and would like to see contractors achieve higher densities and a corresponding higher pay factor.
Starting in 2019, all mixes will be designed at 65 gyrations. We do not see a large difference between 50 and 75 gyration designs, so this will simplify JMF management for the DOT and industry. Heavier traffic applications will use polymer-modified binder.
We are moving from QC testing/control charts on an individual project basis to running QC for the JMF regardless if project mix is delivered. This will be a more rational approach to QC.
We are eliminating the option to use PG 58-28 on certain projects. PG 64-28 will be the standard grade.
We are expanding the use of continuous thermal profiling.
We are adding Gmm to the properties that must be managed with a control chart to improve consistency.
We just released our 2019 Construction and Material Specifications Book, which includes our relatively new joint core acceptance. The new specification is section 447; it was previously Supplemental Specification 806.
The maximum % RAS has been reduced from 5.0% to 3.0% for mixes that do not contain RAP (currently no designs exclude RAP). However, when using RAS, no more than 25% RAP may be used. Also, RAS is no longer allowed in surface mixes. A few research projects guided us in this direction.
We have updated our mix plant calibration procedures (Supplement 1101) for drum plants, which requires at least two rates (low and high) compared to a single rate. We also added a new method for asphalt binder calibration.
We will soon be adding a supplemental specification for fog seals and void reducing asphalt membrane (VRAM) binder.
We have replaced the direct tension test (DTT) for asphalt binders with the Delta Tc parameter of -1.0 or better required (one PAV) and a minimum stiffness requirement of 150 MPa for the first BBR beam. We have also increased our elastic requirements by 15% to bring the testing values closer to those with the DTT.
The DTT test has kept REOB in control (low amounts, 3% maximum) or entirely out of our market. Our goal with the new specification is to keep the same quality binders that we currently have.
Fuente de la noticia: http://eng.auburn.edu/research/centers/ncat/newsroom/2019-spring/2019springspecs.html