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PMSS Project Details

 

Project ID:FHWA-PROJ-11-0069
Project Name: Determining an Aggregate's Potential for Forming Alkali-Silica Reactivity (ASR) Gels in Concrete
Status: Active
Contact:
Last Name:Arnold
First Name:Terry
Telephone:202-493-3305
E-mail:terry.arnold@dot.gov
Office: Office of Infrastructure Research and Development
Team:Pavement Materials Team
Project Description:The broad objective of this project is to understand the fundamental changes that take place when the alkali silica reaction is accelerated. It is anticipated that this research will be instrumental to providing fundamental information regarding changes induced in the mechanism of the ASR reaction by accelerating it under aggressive laboratory conditions. This will in turn aid in the design of a more reliable rapid test method with better correlation to field performance.
Laboratories: Chemistry Laboratory
Concrete Laboratory
Aggregate and Petrographic Laboratory
Start Date: October 1, 2011
End Date: December 31, 2016
Goals:The key project objective is to develop a rapid test method to determine the potential of an aggregate to form alkali-silica reactivity (ASR) gels in concrete.
Background Information: Of all the current standard test methods to evaluate the reactivity of aggregates, the concrete prism test (ASTM C 1293) is considered to be the best indicator of field performance. However, this test method also has its drawbacks, including the long testing period and significant leaching of alkalis from the specimens during the course of the test. There has been considerable interest in recent times to develop an alternative test method which is quicker but still reliable. However, not many studies investigate the changes in the ASR mechanism when the reaction is accelerated and how the nature of the gel produced by these accelerated test methods compares with field samples. Information regarding various aspects of ASR such as silica dissolution and changes in the pore solution chemistry occurring in aggressive testing environments may be key to designing a more reliable screening test for aggregates.
Test Methodology: The work will attempt to correlate expansion tests with pore solution analysis, microstructural damage, silica dissolution from the aggregate as well as nature of gel formation. The experimental program will include testing three different systems, namely concrete, mortar, and aggregates at different temperatures.
Expected Benefits:The expected benefit is the ability to use local aggregates, which may have been rejected by American Society for Testing and Materials (ASTM) 1260 and ASTM 1293 tests.
Deliverables:Name: Test to evaluate aggregates' potential for forming alkali-silica reactivity (ASR) gel.
Product Type(s): Research report, Draft standard, specifications, or guidelines
Description: The approach involves chemically attacking the aggregate and evaluating the products. Soluble Si will be examined using x-ray fluorescence (XRF), and the presence of alkali-silica reactivity (ASR) will be determined using Raman spectroscopy.
Keywords: Concrete Aggregates
Alkali Silica Reactions
Spectroscopy
Infrastructure
Research
Pavements
Research
Subject Areas: Pavements