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Title: Tests for chemical reactivity between alkalies and aggregate. Report 3, Further investigation of the mortar-bar test
Authors: United States. Army. Office of the Chief of Engineers
Houston, Billy J.
Keywords: Aggregates
Mortar bars
Publisher: U.S. Army Engineer Waterways Experiment Station.
Engineer Research and Development Center (U.S.)
Description: Technical memorandum
Abstract: Tests were conducted to ascertain the effect of the differences between Corps of Engineers method (CRD-C 123) and American Society for Testing Materials method (ASTM C-227) for determining alkali-aggregate reactivity in mortar bars. Principal differences are (a) grading of aggregate used in the mortar; (b) age of bars at time of initial measurement; and (c) number of times bars are measured. Test bars made of six cement-aggregate combinations were tested using CRD and ASTM gradings and measuring sequences. Also, blotting paper liners were placed in the exposure containers to improve the relative humidity of the air surrounding the bars in the containers. Results indicate: (a) There was a significant difference, in some cases, between the 1-yr expansion of bars containing ASTM graded reactive aggregates that were measured according to the ASTM specified measuring sequence and bars containing CRD graded aggregate that were measured according to the CRD specified measuring sequence. Where there was a significant difference, the ASTM bars expanded more than the CRD bars. (b) There was no significant difference in the 1-yr expansion of bars measured initially at 24 + 2 hr and those measured at 44 + 4 hr age. (c) Subsequent measurement of bars after absorptive liners were placed in the exposure containers showed an abrupt increase in expansion of the bars in most cases. It is evident that the air surrounding the bars is not always of the desired relative humidity when bars are exposed in plastic containers of the type prescribed in CRD-C 123, It is recommended that CRD-C 123 be revised to conform to ASTM C-227, and that absorptive liners be placed in all containers where the relative humidity inside the container is questionable.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Technical Memorandum

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