Rock Products

MAR 2013

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Page 29 of 99

SPECIAL REPORT Michigan Department of Transporta��� tion stated that RCA ���performs compa��� rably or better than virgin aggregate because of the cementitious action that can still occur within the compacted base, adding more supporting strength for the highway.��� (RMRC, 2008) FHWA concluded that the engineering, eco��� nomic and environmental benefits of using RCA should give states reason to seriously consider using it in their re��� spective transportation system, noting that it is the aggregate base of choice in some states. (FHWA, 2004) ronmental Protection agencies ad��� dress use of RCA. Uniformity in how this is addressed would allow pro��� ducers doing business across state lines a clear understanding of the re��� quirements and not necessitate mul��� tiple paths to obtain approval for the same material. n Recycled Concrete Aggregate is cur��� rently being used to some degree in the vast majority of the state Departments of Transportation across the country. RCA has proven to be both a viable and valuable alternative to the use of virgin aggregates for base courses. The performance is equal to, if not better than, virgin aggregate base course when used appropriately. Sig��� nificant research has been conducted and published for over 10 years. An AASHTO specification has been in place since 2002. Potential concerns, including precipitates, leachates, durability testing and the existence of asphalt pavement and brick have been addressed. Limiting factors to states more fully adopting the use of RCA in��� clude the following: n n Uniform Application of Specifcations. Most states developed a specification based on their research and/or expe��� rience. The survey only revealed one state that referenced AASHTO M 319, which was first published in 2002 with the most recent publication date being 2010. AASHTO specifica��� tions are developed by consensus of state highway agency members and are balloted for approval prior to publication. This specification pro��� vides a sound foundation for a speci��� fication and includes notes and appendices to address issues that have been noted. The adoption of AASHTO M 329 is encouraged. Uniform Consideration of the Environmental Impacts. Some variation exists in how the in��� dividual state Department of Envi��� 28 ROCKproducts ��� MARCH 2013 n Technology Transfer Between States. Significant time and resources could be saved by taking advantage of re��� search that has been completed. The time and effort of conducting similar research by states in close proximity that reach similar conclusions pre��� vents timely acceptance of any new technology, as well as potentially in��� creasing cost due to differences across state lines. Advancing and Improving Existing Specifcations. A means to continually improve ex��� isting specifications is needed to help identify and address remaining con��� cerns that state agencies have. Per��� haps the establishment of an Expert Task Group could take the lead on this similar to what has been suc��� cessfully implemented with other materials. Recycled Concrete Aggregate has proven to be a quality material capa��� ble of meeting the engineering re��� quirements for use as an aggregate base. It is also considered by most states to be an environmentally ac��� ceptable material which also provides the potential for an economical alter��� native to virgin aggregates. It has demonstrated the ability to success��� fully provide an alternative to the use of virgin aggregates as an aggregate base course. Many states have incorporated its use into their specifications to take advan��� tage of equal or better engineering properties, the environmentally friendly advantage of saving natural resources and reducing landfill space and realizing the potential economic benefits it offers. We encourage the states and FHWA work cooperatively with the industry to help more states reap the advantages that using RCA offers. E BIBLIOGRAPHY CMRA. (2012). Concrete Recycling Home Page. Retrieved October 13, 2012, from Concrete Recycling: Cooley, B. E. (2007). Evaluation of Recycled Portland Cement Concrete Pavements for Base Course and Gravel Cushion Material. Pierre, S.D.: South Dakota Department of Transportation. Donaldson, C. N. (2011). Sustainable Assessment of Recycled Concrete Aggregate (RCA) Used in Highway Construction. Washington, D.C.: Proceedings of the 90th Annual Meeting of the Transportation Research Board. FHWA. (2004). Transportation Applications of Recycled Concrete Aggregate - FHWA State of the Practice National Review FHWA-HRT-04-024. Washington, D.C.: US DOT. RMRC. (2008, July 28). User Guidelines for Byproducts and Secondary Use Materials in Pavement Construction. Retrieved September 14, 2012, from Recycled Materials Resource Center: ols/uguidelines/rcc3.asp Van Dam, S. T. (2011). Using Recycled Concrete in MDOT's Transportation Infrastructure Manual of Practice. Lansing, MI: Michigan Department of Transportation. Willett, J. C. (January, 2012). Mineral Commodity Summaries. Reston, VA: US Geological Survey. Willett, J. C. (2010). U.S. Geological Survey Minerals Yearbook. Reston, VA: USGS.

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