Equipment World Digital Magazine
Issue link: http://read.dmtmag.com/i/597582
EquipmentWorld.com | November 2015 57 With equipment maintenance software that will turn a chaotic shop into an effi cient operation. Take control of your shop... § Preventative maintenance scheduling & alerting § Work order & time card management § Mechanic planning & scheduling tools § Parts inventory control & analysis § Fuel & fl uid tracking § Skills & certifi cation management § Low risk—Software comes with a 12-month money back guarantee! 1-800-683-3196 | www.HCSS.com RAP processing options Not all RAP is created equal or will per- form the same. Here's a breakdown of four options for processing RAP from the National Cooperative Highway Research Program*. Type: Minimal Processing Description: Screening only to remove oversized particles (may be accom- plished in line during feed of RAP in the plant) Suitable conditions: RAP from a single source Concerns: Single-source RAP piles are finite quantity – when stockpile is de- pleted, new mix designs will be needed with another RAP stockpile Type: Crushing Description: Breaking of RAP chunks, agglomerations, and/or aggregate particles in order to avoid large par- ticles that may not break apart during mixing or particles that exceed the mix's nominal aggregate maximum size (NMAS) Suitable Conditions: RAP contains large chunks (anything larger than 2 inches) or RAP aggregated NMAS exceeds the recycled mix's NMAS Concerns: Generating excess dust and uncoated surfaces Type: Mixing Description: Using a loader or exca- vator to blend RAP from different sources; usually done in combination with crushing and/or fractionating Suitable conditions: RAP stockpile con- tains materials from multiple sources Concerns: Good consistency of RAP characteristics must be verified with a RAP QC plan Type: Fractionating Description: Screening RAP in to mul- tiple size ranges Suitable Conditions: High RAP content mixes (above 30 percent to 40 percent) are routine Concerns: Highest cost, requires ad- ditional RAP bin(s) to simultaneously feed multiple fractions *Report 752 - Improved Mix Design, Evaluation, and Materials Manage- ment Practices for Hot Mix Asphalt with High Reclaimed Asphalt Pavement Content; Source: National Cooperative Highway Research Program. has been able to use 40 percent RAP in warm mixes for thinlay work for limited residential proj- ects, as the Texas Department of Transportation doesn't allow RAP in thinlay mixes for their projects. "We modify the mix and use a warm mix additive," Fuller says, "which helps maintain the tem- perature. For one project in a subdivision, we were able to lay a 40 percent RAP mix for about the same cost as a two-course chip seal. It's in its fifth or sixth season, and it's going to last another four to five years." In addition to additives, the emulsions created by foaming equipment at the plant helps with coating RAP and provides a bet- ter mixture with the old oil and new oil, Wrucke adds. "With that foamer you're basically forcing an emulsification that's in the process, and when the water breaks off that's when you get the cooler tem- peratures too." Continued use For Benson, the performance of the County Road 26 speaks volumes for the quality of WMA and RAP mixes. "We haven't noticed any issues with cracking," he says. "Typically we end up having a lot of thermal cracking in roads the next spring after construc- tion following our cold winters. With either the warm mix or the RAP we haven't seen it get more brittle or have more cracking." After the success of this project, Benson and Wrucke presented the details of their experience with WMA and RAP at multiple conferences and passed on their specifications and plans with fellow county engineers and road superintendents. "We're at the point now where if the low bid came in with warm mix, we would definitely take it over a higher-priced hot mix," he continues. "We're going to continue to leave that as an option with our contracts — bid it with RAP and the option to use either hot mix or warm mix."