Goal
Reduce fossil fuel use at the hot mix asphalt plant, decrease emissions at the plant, and decrease worker exposure to emissions during placement.
Requirements
Reduce the mixing temperature of hot mix asphalt by a minimum of 50°F from that recommended as the mixing temperature by the asphalt binder supplier. Mixing temperature shall be measured as the temperature of the mixture as it exits the mixing drum (for drum plants) or pugmill (for batch plants). This reduced temperature mix must comprise a minimum of 50% of the total project pavement (hot mix asphalt or portland cement concrete) by weight.
Documentation
PT-3 Warm Mix Asphalt
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Comment on credit PT-3
Addressing NPS BG comments:
1. We have investigated energy with WMA using life cycle assessment and concluded that since the additive is added in such small quantities the energy saved by lowering 50F is MUCH, MUCH more. I believe this is only more so with some of the plant foaming technologies.
2. WMA is being used more and more in the U.S. every day. For instance, TxDOT paved over 1 million tons of WMA in 2009. I believe (this is my opinion here) that WMA will be standard industry practice in 5 years.
3. What asphalt plant will do it? TxDOT and others have had great success using a permissive spec with a pre-approved product list. In other words, do it if you like. You may be surprised how often contractors will opt for WMA. Recently, we did a pilot project on a NPS job where the contractor placed 10,000 tons of WMA and wanted to place more. It will not cost more but rather less. By the way, TxDOT also has a spec that requires WMA if they wish to use it.
4. Agreed - WMA will likely become industry standard practice. Our intention with Greenroads is to keep it current. Once everyone does something as standard practice, then it's not likely to remain in GR for points.
PT-3
Is the energy saved in running the burner 50 degrees cooler offset by the energy used in the manufacture and distribution of the additives?
NPS-BG
PT-3
General comments to this Section: Although used extensively in Europe (not necessarily a reason to do it here) WMA has not been used much in the United States. Therefore, performances here, over time and across a variety of conditions, are not known. Examples shown in this Section are experimental, and so special money was programmed to study an unknown product. The State of Colorado did an experiment with MWA near the Eisenhower tunnel. It was testing asphalt workability at colder temperatures to determine if its use could extend the paving season.
NPS-BG
PT-3
If I want to use WMA today, what asphalt plant will turn down the burner and put the additive(s) in the hopper when the trucks come by for my 5,000 ton Park Service job? And how much more will that cost?
NPS-BG
PT-3
Of all the technologies in the group, this one seems to have the most potential to move into almost universal use. If it becomes the common asphalt type used, then the NPS will use it, and it would cease to be a special enviro-thing that one could get sustainability points for.
NPS-BG
Greenroads Manual Version 1.0 Review
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Thanks,
The Greenroads Team
