Enhancing the performance of warm mix asphalt pavement that incorporates recycled asphalt shingles is the topic of a study issued under the National Cooperative Highway Research Program. The report, Using Recycled Asphalt Shingles with Warm Mix Asphalt Technologies (NCHRP Research Report 890), describes performance tests of warm mix asphalt with a variety of recycled content with regard to stiffness, durability, optimal temperatures, moisture susceptibility; and other parameters. The practical outcome of the project is a set of proposed revisions to AASHTO provisional standard PP 78-17 that expands its application to warm mix asphalt mixtures with recycled asphalt shingles. The research also produced a set of proposed best practices for the processing of recycled asphalt shingles. For more information, link to the report. (11-1-18)
The Institute for Transportation at Iowa State University has released a report concerning a 2016 survey of state highway agencies and paving contractors to understand applications, barriers, and existing opportunities for increasing the use of recycled concrete aggregate (RCA). The report indicates that agencies and contractors are interested in increasing RCA use but there is a lack of knowledge on how to best make use of it in concrete mixtures. The report also indicates that restrictive specifications and complex permitting standards serve as barriers to increasing RCA use. Further policy development from the Federal Highway Administration, the American Concrete Pavement Association, and state DOTs is planned. For more information, link to the report. (January 2018)
An evaluation of systems to track transportation asset management (TAM) in terms of return on investment has been issued in a report under the National Cooperative Highway Research Program (NCHRP Research Report 866). The report, issued under NCHRP Project 20-100, provides objective approaches that can be used by transportation agencies to estimate the return on investment in TAM systems such as pavement management systems, bridge management systems, and maintenance management systems. Benefits of TAM systems, such as AASHTOWare Bridge Management software, include more proactive agency approaches to asset management, better prioritization, more robust analytical tools, and better data quality. The report includes an associated spreadsheet tool, the NCHRP Project 20-100 ROI Calculator. The calculator includes factors and procedures from the Highway Economic Requirements System State Version (HERS-ST), which can be used to perform life cycle analysis to reduce waste, prevent pollution, and encourage recycling. For more information, link to the report.
The U.S. Department of Transportation has released a report concerning Caltrans’ evaluation of the second Strategic Highway Research Program (SHRP 2) Pavement Renewal Solutions rePave tool. The web-based software tool is to help pavement designers and project engineers select pavement rehabilitation strategies and examine projects with service lives of 30-50 years. Caltrans concluded that the rePave tool is user-friendly and efficient, requiring a minimal amount of data. The report highlights the existing tools that Caltrans uses to evaluate rehabilitation for asphalt-surfaced pavements, concrete surfaced pavements and composite pavements, noting the limitations of existing tools such as overestimation or underestimation of rehabilitation needs and the need for a greater amount of engineering judgement. The Caltrans Headquarters Pavement Program plans to develop training materials for the tool. For more information, link to the report. (4-3-17)
The Illinois State Tollway Authority has announced savings of approximately $218.5 million due to adopting the use of sustainable materials between 2004 and 2016. Illinois reused concrete pavement as a base for hot mix asphalt instead of conventional reconstruction along 32 miles of Interstate 88 to save $29.5 million. The tollway also has incorporated sustainable asphalt materials such as recycled asphalt shingles, and reclaimed asphalt pavement to reconstruct and widen the I-90 and I-39 tollways and construct shoulder lanes. In addition, the authority rebuilt the west end of I-90 with higher levels of supplementary cementitious materials which saved the state $8 million. For more information, link to the report. (June 2017)
A review of the use of recycled concrete aggregate (RCA) in new construction has been issued by the Minnesota Department of Transportation. The report evaluates the current state of practice across the U.S. and historical performance data to understand differences between RCA pavements and non-RCA pavements. It includes an economic analysis and provides guidelines from the American Concrete Institute, Federal Highway Administration and AASHTO for suggested uses and quality types of concrete. The report recommends that the use of recycled fines not be permitted during construction and that mitigation techniques should be used to prevent alkali-aggregate related distress. For more information, link to the report. (3-4-17).
The Transportation Research Board has issued a report under the National Cooperative Highway Research Program (NCHRP) concerning the management of aging bridges. The report addresses the reuse of bridge foundations to reduce costs and traffic impacts, and to provide environmental benefits. The report provides a review of the national bridge system that highlights reasons at the state level for reusing foundations. The report discusses methods for investigating reuse, design of reused foundations, and construction techniques and performance monitoring. The report also focuses on case studies from Colorado, Illinois, Maine and Ontario. For more information, link to the report. (2-27-17)
The Transportation Research Board’s National Cooperative Highway Research Program has released a report concerning the use of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) in asphalt mixtures. The report summarizes current practices for the use of RAP and RAS in the design, production and construction of asphalt mixtures. The report also focuses on collecting information about the use of high percentage RAP, RAS and/or a combination of RAP and RAS. For more information, link to the report. (9-9-16)
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