|Project Name:||Deleterious Aggregates—Identification, Testing, Mitigation, and Use of Local Materials|
Office of Infrastructure Research and Development |
|Team:||Pavement Materials Team|
Infrastructure Research and Technology Strategic Plan and Roadmap|
|Project Description:||The goal is to mitigate the water sensitivity of mixes using these materials. In hot-mix asphalt, the use of phosphoric acid-modified asphalt already shows promise. In subsequent years, materials deleterious to Portland cement concrete will be examined. Aggregates suspected of deleterious properties will be analyzed by physical, chemical, and petrographic properties. Most research aggregates will be characterized by the Aggregate Image Measurement System for shape, angularity, and texture. The Micro-Deval test can also be a tool to see how aggregates breakdown in the presence of water. Potential issues include Minus No. 200 minerals and size, aggregate surface chemistry and absorption, development of a better methylene blue test for active clays, and evaluation of surfacing aggregates.|
Bituminous Mixtures Laboratory|
Aggregate and Petrographic Laboratory
|Start Date:||October 1, 2010|
|End Date:||September 30, 2013|
|Goals:||Material characterization of minus No. 200 size materials on aggregates and their effect on the quality of bond at the aggregate surface both in asphalt and concrete mixtures.|
|Background Information:||How much asphalt is lost by absorption in aggregate? Can it be reduced? How important is bond to aggregate in Portland cement concrete? This research is intended to lower construction costs by allowing the use of local aggregates that may be inferior because of the presence of small quantities of deleterious clays or other adverse properties or components. In year one, we plan to chemically characterize aggregates containing deleterious clays and investigate the mechanism of water absorption by such materials.|
|Test Methodology:||Examination of the nature of the fine materials in aggregate and how it effects the quality of the bond. Also the potential interaction of carbonate aggregate deterioration through reactivity and freezing and thawing pressures from absorbed water and deicing chemicals in aggregates and mixtures in service.|
|Expected Benefits:||As the supply of quality aggregates diminishes, agencies will be forced to use locally available aggregates of lower standard. This research will enable agencies to better select local aggregates to construct long-lasting pavements.|
|Deliverables:||1. Name: Guidelines for the evaluation of the aggregate interface zone as affected by coatings, texture, minerals, and minus No. 200 fine materials.|
Product Type(s): Research report
Description: Guidelines for the evaluation of the aggregate interface zone as affected by coatings, texture, minerals, and minus No. 200 fine materials. Report of the methods of testing and characterization tools found to be useful in examining the importance of the Interfacial Transition Zone (ITZ) at the boundary of the aggregate surface and the binder, whether it is an asphaltic material or a hydraulic cementitious paste.
2. Name: Report on the importance of alkali-carbonate reaction (ACR) in concrete pavements containing carbonate coarse aggregates.
Product Type(s): Research report
Description: Report on the importance of ACR in concrete pavements containing carbonate coarse aggregates and whether alkali-silica reactivity (ASR) is also involved in pavement deterioration.