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337.8 Thickness of Friction Courses . 337-8 . 1 FC42 .5 and FC -9 . 5 : The thickness of the friction course layer will be the plan thickness as shown in the Contract Documents . For construction purposes , the plan thickness will be converted to spread rate as defined in 3344 . 4 . Q Plan quantities are based on a Gm,,, of 2 . 540 , corresponding to a spread rate of 110 lbs . per square yard per inch . Pay quantities will be based on the actual maximum specific gravity of the mix being used. 337-8 .2 FG5 : The total thickness of the FC - 5 layer will be the plan thickness as shown in the Contract Documents . For construction purposes , the plan thickness will be converted to spread rate based on the combined aggregate bulk specific gravity of the asphalt mix being used as shown in the following equation : Spread rate (lbs . per square yard) = t x Gsb x 40 . 5 Where : t = Thickness (in. ) (Plan thickness) Gsb = Combined aggregate bulk specific gravity from the verified mix design The weight of the mixture shall be determined as provided in 320 -2 . 2 . Plan quantities are based on a Gsb of 2 . 635 , corresponding to a spread rate of 80 lbs . per square yards . Pay quantities will be based on the actual combined aggregate bulk specific gravity (Gsb) of the mix being used . 337-9 Special Equipment Requirements for FC-5 . 337-9 . 1 Fiber Supply System : Use a separate feed system to accurately proportion the required quantity of mineral fibers into the mixture in such a manner that uniform distribution is obtained. Interlock the proportioning device with the aggregate feed or weigh system to maintain the correct proportions for all rates of production and batch sizes . Control the proportion of fibers to within plus or minus 10 % of the amount of fibers required . Provide flow indicators or sensing devices for the fiber system, interlocked with plant controls so that the mixture production will be interrupted if introduction of the fiber fails . When a batch plant is used, add the fiber to the aggregate in the weigh hopper or as approved and directed by the Engineer. Increase the batch dry mixing time by 8 to 12 seconds , or as directed by the Engineer, from the time the aggregate is completely emptied into the pugmill . Ensure that the fibers are uniformly distributed prior to the addition of asphalt rubber into the pugmill . When a drum-mix plant is used, add and uniformly disperse the fiber with the aggregate prior to the addition of the asphalt rubber. Add the fiber in such a manner that it will not become entrained in the exhaust system of the drier or plant . 337-9 .2 Hydrated Lime Supply System : For FC - 5 mixes containing granite , use a separate feed system to accurately proportion the required quantity of hydrated lime into the mixture in such a manner that uniform coating of the aggregate is obtained prior to the addition of the asphalt rubber. Add the hydrated lime in such a manner that it will not become entrained in the exhaust system of the drier or plant. Interlock the proportioning device with the aggregate feed or weigh system to maintain the correct proportions for all rates of production and batch sizes and to ensure that all mixture produced is properly treated with hydrated lime . Control the proportion of hydrated lime to within plus or minus 10 % of the amount of hydrated lime required. Provide and interlock flow indicators or sensing devices for the hydrated lime system - 107 - FPID ( S ) : 4231864 - 58 - 01 i"