Alkali Content of Fly Ash – Measuring and Testing Strategies for Compliance

dc.contributor.author Schlorholtz, Scott
dc.contributor.department Institute for Transportation
dc.date 2018-02-16T10:33:21.000
dc.date.accessioned 2020-06-30T04:52:19Z
dc.date.available 2020-06-30T04:52:19Z
dc.date.embargo 2015-05-29
dc.date.issued 2015-04-01
dc.description.abstract <p>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.</p>
dc.format.mimetype PDF
dc.identifier archive/lib.dr.iastate.edu/intrans_techtransfer/76/
dc.identifier.articleid 1075
dc.identifier.contextkey 7155800
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath intrans_techtransfer/76
dc.identifier.uri https://dr.lib.iastate.edu/handle/20.500.12876/45040
dc.language.iso English
dc.source.bitstream archive/lib.dr.iastate.edu/intrans_techtransfer/76/IADOT_ISU_Schlorholz_Alkali_Content_Fly_Ash_Compliance_TR_628_2015_Summary.pdf|||Sat Jan 15 01:50:46 UTC 2022
dc.subject.disciplines Civil Engineering
dc.subject.keywords Alkali
dc.subject.keywords Alkali silica reactions
dc.subject.keywords Fly ash
dc.subject.keywords Materials
dc.subject.keywords Materials tests
dc.subject.keywords Potassium
dc.subject.keywords Portland cement
dc.subject.keywords Sodium
dc.title Alkali Content of Fly Ash – Measuring and Testing Strategies for Compliance
dc.type article
dc.type.genre report
dspace.entity.type Publication
relation.isOrgUnitOfPublication 0cffd73a-b46d-4816-85f3-0f6ab7d2beb8
File
Original bundle
Now showing 1 - 1 of 1
Name:
IADOT_ISU_Schlorholz_Alkali_Content_Fly_Ash_Compliance_TR_628_2015_Summary.pdf
Size:
367.31 KB
Format:
Adobe Portable Document Format
Description:
Collections