mulberry purse Specification CornerMark W

Specification Corner

Mark Woods, Tennessee DOT is currently discussing removing its “AC content for bidding purposes, mulberry purse ” which requires bidding HMA contractors to bid all mixes of each type at a specified predetermined AC content. Once produced, pay items are adjusted for the actual design/produced AC content and indexed. The department is currently discussing the potential effects of removing this requirement and allowing contractors to bid mulberry purse at their design AC values. The department is also discussing tightening it spay factor tables for gradation and asphalt content to encourage even more consistent production.Dale Rand, Texas DOT January 2011, the Texas DOT approved a special specification (SS 3224) that replaces the standard hot mix Item 341, which comprises approximately 75 percent of the HMA placed mulberry purse in Texas. This special specification is a culmination of other special provisions to Item 341. Some of the highlights of the new special specification(SS3224) are as follows:Allows the use of mulberry purse RAP and RAS on all projects and sets maximum amounts of recycled asphalt binder that can be used in each mixture.Allows the use of WMA on all projects.Allows the use of “Substitute Binders” on all projects. (Note: This provision allows a contractor to use, for example, a PG 64 22 in lieu of a PG70 22 provided the mixture meets all specification requirement such as Hamburg Wheel, etc., for the originally specified binder grade.)SS 3224 also addresses sample custody issues. It requires that all samples (specifically roadway cores) be placed in “security bags” if the samples are ever out of the engineer’s possession. (Note: Texas DOT worked with a vendor to develop custom security bags.) The bags havea unique ID number on the inside and once sealed cannot be opened without damaging the bags. SS 3224 also provides incentives for contractors to use the Pave IR system to measure thermal segregation. SS 3224 will be used as the template for the Texas DOT to rewrite all remaining HMA specifications (Superpave, SMA, PFC etc).Allen Myers, Kentucky Transportation Cabinet Kentucky Transportation Cabinet is currently reviewing its Standard Specifications in preparation for a new manual in 2012. The following are some changes being considered for the asphalt area:Update the section involving reclaimed asphalt materials. Add requirements for reclaimed asphalt shingles. Use the concept of “effective asphalt binder content replacement” (by the reclaimed materials) for determining the appropriate grade of virgin asphalt binder.