Mixed messages: new specifications adopted by AASHTO encourage the use of the recycled shingles in making hot mix asphalt.
Using recycled asphalt shingles in hot mix asphalt (HMA (High Memory Area) In PCs, the first 64K of extended memory from 1024K to 1088K, which can be accessed by DOS. It is managed by the HIMEM.SYS driver. It was discovered by accident that this area could be used by DOS, even though it was beyond the traditional ) has been a developing technology for more than two decades with growing acceptance by both construction contractors and government agencies. With the recent spike in asphalt and cement prices, there is increasing pressure to find such acceptable recycled supplements to virgin materials. A new national material standard has helped improve the sophistication so·phis·ti·cate
v. so·phis·ti·cat·ed, so·phis·ti·cat·ing, so·phis·ti·cates
1. To cause to become less natural, especially to make less naive and more worldly.
2. of engineering recycled asphalt shingles (RAS (1) See network access server.
(2) (Remote Access Service) A Windows NT/2000 Server feature that allows remote users access to the network from their Windows laptops or desktops via modem. See RRAS and network access server. ) into the mix. Recyclers, HMA producers and agencies can now use this standard as a guide to carefully design shingles shingles: see herpes zoster.
or herpes zoster
Acute viral skin and nerve infection. Groups of small blisters appear along certain nerve segments, most often on the back, sometimes after a dull ache at the site; pain becomes into the mix based on the RAS percent asphalt content, asphalt performance grade, aggregate gradation gradation: see ablaut. and amount of deleterious deleterious adj. harmful. materials. The industry has come a long way since the original shingle shingle
Thin piece of building material made of wood, asphaltic material, slate, metal, or concrete, laid in overlapping rows to shed water. Shingles are widely used as roof covering on residential buildings and sometimes also for siding (see Shingle style). recyclers and HMA producers first dumped ground shingles into their mix. There is now a means to optimize for best value by guaranteeing final pavement performance while optimizing production cost savings using RAS as an engineered commodity.
NEW AASHTO AASHTO American Association of State Highway and Transportation Officials SPEC
Late last year, the American Association American Association refers to one of the following professional baseball leagues:
Most studies that have analyzed the impact of including RAS in HMA have concluded that there is potential for savings in costs of virgin asphalt binder due to the addition of RAS without sacrificing pavement performance if appropriate quality assurance and quality control procedures are followed. This is the most important economic driving force accelerating the development of shingle recycling today.
The cost of virgin asphalt binder has been rising rapidly, especially in recent months. Figure 1 on page 32 displays one representation of this trend using the New Jersey Department of Transportation The New Jersey Department of Transportation (NJDOT) maintains the State Highway system in New Jersey. It is headed by the Commissioner of Transportation. The present Commissioner is Kris Kolluri, Esq, who was sworn into office as Commissioner on March 13, 2006. published data on asphalt cement selling prices from suppliers in the northern part of the state. This chart shows the relative change over 17 years. This New Jersey data indicates there has been nearly a 70 percent increase in asphalt cement prices compared to a year ago.
It is notable that the mineral aggregates used in manufacturing shingles are also valuable commodities in HMA. Even the fiber in recycled shingles can be an asset to the pavement matrix in the right application and depending on the type of mix. Finally, the prices for landfilling construction and demolition debris, such as mixed roofing material, are also increasing. As environmental regulations and landfill prohibitions continue to increase, so will the tipping fees for roofing debris.
The new AASHTO standard specification also allows the use of either manufacturers' (post-industrial) shingle scrap or tear-off (post-consumer) shingle scrap as an additive in HMA. It is estimated that about 11 million tons of tear-off roofing material is generated each year in the United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. . This is about 10 times the amount of manufacturers' scrap.
In addition, AASHTO adopted a companion recommended practice to provide additional guidance for designing new HMA which incorporates RAS. Specific considerations include: shingle aggregate gradation, performance grade (PG) of the virgin and RAS binder and relative reduction of the virgin asphalt binder due to replacement by RAS binder. There are multiple references to various quality assurance and quality control (QA/QC QA/QC Quality Assurance/Quality Control ) requirements for processing and recycling of the RAS.
Requirements within the AASHTO specification include a number of important details. First, the final RAS product must be sized and screened such that 100 percent passes a 1/2-inch sieve screen. This is important became it was found that the size of RAS can be expected to affect the fraction of shingle asphalt binder that contributes to the final blended binder. For example, the AASHTO recommended practice states that material that is ground 1/2-inch maximum can be expected to release lower levels of available asphalt shingle binder in the range of about 20 to 40 percent of total RAS asphalt binder. RAS ground to a finer size passing a No. 4 sieve can be expected to effectively utilize as much as 95 percent of the total available asphalt. The designer must be prepared to adjust the performance grade of virgin asphalt binder to compensate for this effect.
Second, the actual maximum addition rate of RAS is left as an option for the contractor. Most states have established fixed maximum limits on the amount of RAS in the HMA, usually 5 percent by weight. The AASHTO spec provides for a means of designing adjustment of virgin asphalt binder used based on the measured effectiveness of the RAS asphalt. The HMA designer must determine the asphalt binder content of the new HMA as part of the volumetric volumetric /vol·u·met·ric/ (vol?u-met´rik) pertaining to or accompanied by measurement in volumes.
Of or relating to measurement by volume. design procedure. During the production of the new HMA, shingle asphalt binder present in the RAS will mix with the virgin asphalt binder to produce a final blended binder. The new AASHTO spec states that if the quantity of RAS asphalt binder exceeds 0.75 percent by weight of the new HMA, the RAS binder and the virgin asphalt binder shall be further evaluated to ensure the performance grade of the final blended HMA complies with the originally specified performance grade requirements.
To help maintain the engineering performance of the final HMA pavement, the new AASHTO spec limits the maximum amount of deleterious material allowed in the RAS. The AASHTO spec states that lightweight extraneous ex·tra·ne·ous
1. Not constituting a vital element or part.
2. Inessential or unrelated to the topic or matter at hand; irrelevant. See Synonyms at irrelevant.
3. materials (e.g., paper, wood, plastics) shall not exceed 0.05 percent of the material retained on the No. 4 sieve. Heavyweight extraneous materials (e.g., metals, glass, rubber, nails, soil, brick, tars, etc.) shall not exceed 0.5 percent as determined on material retained on the No. 4 sieve. It is recognized that these are stringent limits suggested by AASHTO, but recycling professionals continuously work to develop improved systems to clean up the mixed roofing material and tear-off RAS.
Recently, the CMRA CMRA Commercial Mail Receiving Agency
CMRA Construction Materials Recycling Association
CMRA Central Motorcycle Roadracing Association
CMRA Capital Market Risk Advisors, Inc. was awarded a $74,000 grant from the U.S. EPA EPA eicosapentaenoic acid.
n.pr See acid, eicosapentaenoic.
n. to examine the barriers to the recycling of tear-off asphalt shingles. The CMRA intends that the project will accelerate the national development and implementation of tear-off asphalt shingle recycling. The project partners will attempt to address the key barriers to reaching full-scale commercialization of this promising technology.
The primary goal of this new EPA project is to develop and demonstrate recommended best practices that provide for superior quality assurance and quality control that can be utilized by profitable shingle recycling operators throughout the nation. The project has three principal objectives:
* Demonstrate successful and appropriate environmental and worker health protection procedures;
* Document materials engineering benefits and methods of QA/QC to optimize their pavement performance effects; and,
* Develop operational guidelines that maximize cost-efficiency while attaining minimum environmental, worker health and safety, and engineering standards.
The project is being produced by the CMRA with key partner support from a wide variety of public and private agencies and companies. This project will build directly on the substantial efforts of other research and development efforts in order to help bring tear-off shingle recycling technology Recycling technology
Methods for reducing solid waste by reusing discarded materials to make new products. The three integral phases of recycling are the collection of recyclable materials, manufacture or reprocessing of these materials into new products, and to full-scale implementation.
One spin-off benefit of this project will be an update of the Web site www.ShingleRecycling.org that was originally produced by the CMRA with funding from EPA in 1999. One of the other partners in the original Web site development was the University of Florida University of Florida is the third-largest university in the United States, with 50,912 students (as of Fall 2006) and has the eighth-largest budget (nearly $1.9 billion per year). UF is home to 16 colleges and more than 150 research centers and institutes. , Department of Environmental Engineering Sciences and it will be again be involved in this tear-off shingles recycling project.
In addition, several state departments of transportation have adopted material specifications over the years providing for the use of RAS in HMA. The CMRA Web site, www.ShingleRecycling.org, is in the process of being updated with the known recycled shingle specifications from various states. As a general rule, the states have been leading the way in the research and development of shingles recycling, even though there has been notable support from FHWA FHWA Federal Highway Administration (US DoT) , RMRC RMRC Recycled Materials Resource Center (University of New Hampshire; Durham, NH)
RMRC Recreational Marine Research Center (Michigan State University)
RMRC Risk Management Resource Center and EPA.
The state of Minnesota has sponsored several research studies on the use of recycled shingles in HMA over the past 15 years. Continuing this trend, several recycling projects are currently underway. The Minnesota Office of Environmental Assistance (OEA OEA Organizacion de Estados Americanos (OAS in English)
OEA Organização dos Estados Americanos (Portuguese: Organization of American States)
OEA Office of The Employment Advocate ) is one of several agency sponsors of an extensive lab study project. The Minnesota Department of Transportation The Minnesota Department of Transportation (Mn/DOT, pronounced "min-dot") oversees transportation by land, water, and air in the U.S. state of Minnesota. The cabinet-level agency is responsible for maintaining the state's trunk highway system (including state highways, U.S. (Mn/DOT) is directing the research to determine if and how a new tear-off spec can be developed. Mn/DOT's current spec only allows the use of manufacturers' shingle scrap in HMA. Mn/DOT is analyzing the asphalt cement (AC) content, asphalt performance grade (PG), aggregate gradation and deleterious debris in a series of tests consistent with the protocol in the new AASHTO spec. Mn/DOT is not only comparing tear-off shingle scrap to manufacturer shingle scrap, but also to other control mix type without any RAS of either type. The University of Minnesota (body, education) University of Minnesota - The home of Gopher.
Address: Minneapolis, Minnesota, USA. , Department of Civil Engineering's asphalt lab is also conducting a controlled set of HMA laboratory analyses to provide empirical data on HMA strength. These indirect tensile tests will help analyze in the lab how shingles might affect the low temperature cracking properties of shingle-derived HMA. Another project is also underway in Minnesota sponsored by the Solid Waste Management Coordinating Board (SWMCB SWMCB Solid Waste Management Coordinating Board (Minnesota) ). This SWMCB project will include a new controlled road construction demonstration this year utilizing tear-off-derived HMA compared side-by-side with manufacturers'-derived HMA. Lab performance tests and pavement surveys will help analyze if there are any different impacts between the two types of scrap shingles and a "virgin only" mix without any RAS.
The Missouri Department of Transportation The Missouri Department of Transportation (MoDOT) is a state government organization in charge of maintaining public roadways of the U.S. state of Missouri. External links
MoDOT is conducting a lab analyses project similar to the Minnesota OEA study. MoDOT intends to produce additional lab data to further analyze the HMA supplemented with tear-offRAS. The University of Minnesota Department of Civil Engineering has performed similar lab analyses using its equipment to measure indirect tensile strength tensile strength
Ratio of the maximum load a material can support without fracture when being stretched to the original area of a cross section of the material. When stresses less than the tensile strength are removed, a material completely or partially returns to its for as part of a cooperative study with the Mn/DOT. These two states are taking leading roles in the research and development of using recycled shingles in HMA.
The author is a consultant with Dan Krivit and Associates and can be contacted at email@example.com.