Details:

Creators:
Schlorholtz, Scott M.
Corporate Creators:
Iowa State University. Materials Analysis and Research Laboratory
Corporate Contributors:
Iowa. Dept. of Transportation ; Iowa. Highway Research Board
Iowa. Dept. of Transportation ; Iowa. Highway Research Board Less -
Subject/TRT Terms:
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Acceptance Tests Alkali Silica Reactions Evaluation Field Tests Fine Aggregates Fly Ash Laboratory Tests Petrography Potassium Sodium
Publication/ Report Number:
IHRB Project TR-628
Resource Type:
Tech Report
Geographical Coverage:
United States
Corporate Publisher:
Iowa State University. Materials Analysis and Research Laboratory
Abstract:
Sodium and potassium are the common alkalis present in fly ash. Excessive amounts of fly ash alkalis can cause efflorescence problems in concrete products and raise concern about the effectiveness of the fly ash to mitigate alkali-silica reaction (ASR). The available alkali test, which is commonly used to measure fly ash alkali, takes approximately 35 days for execution and reporting. Hence, in many instances the fly ash has already been incorporated into concrete before the test results are available. This complicates the job of the fly ash marketing agencies and it leads to disputes with fly ash users who often are concerned with accepting projects that contain materials that fail to meet specification limits. The research project consisted of a lab study and a field study. The lab study focused on the available alkali test and how fly ash alkali content impacts common performance tests (mortar-bar expansion tests). Twenty-one fly ash samples were evaluated during the testing. The field study focused on the inspection and testing of selected, well documented pavement sites that contained moderately reactive fine aggregate and high-alkali fly ash. A total of nine pavement sites were evaluated. Two of the sites were control sites that did not contain fly ash. The results of the lab study indicated that the available alkali test is prone to experimental errors that cause poor agreement between testing labs. A strong (linear) relationship was observed between available alkali content and total alkali content of Class C fly ash. This relationship can be used to provide a quicker, more precise method of estimating the available alkali content. The results of the field study failed to link the use of high-alkali fly ash with the occurrence of ASR in the various concrete sites. Petrographic examination of the pavement cores indicated that Wayland sand is an ASR-sensitive aggregate. This was in good agreement with Iowa DOT field service records. It was recommended that preventative measures should be used when this source of sand is used in concrete mixtures.
Format:
PDF
Collection(s):
US Transportation Collection
Main Document Checksum:
[+]
urn:sha256:bfb6895a1a2ada1d30eccc3c4e349fe10261325954ce06224541042bac0e6b47
Download URL:
https://rosap.ntl.bts.gov/view/dot/28896/dot_28896_DS1.pdf
File Type:

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