DETERIMINATION OF AIR VOID CONTENT AND MIXING WATER VOID CONTENT OF HARDENED CONCRETE USING ELECTRON MICROSCOPE TECHNIQUES--PARTS I AND II
The use of the scanning electron microscope (SEM) to identify possible causes of failure of hardened concrete was examined. The three causes of failure researched were excess air content (Part I), and improper water-cement ratio and detgree of hydration (Part III). Part II is a collection of unbound photographic arrays of air contents investigated in Part I to be used as visual comparison standards for determination of air content of hardened concrete. In Part I the SEM was used at a low magnification (80X) to photograph hardened concrete of various air content (1-20%). A comparison standard was then prepared using 12 photographs to represent each air content. It is proposed that this standard be utilized for determination of air content of hardened concrete. Statistical analysis of the proposed standard indicates an accuracy of about plus or minus 1.5%. For the analysis described in Part III, concrete samples of water-cement rations ranging from .40-1.20 were prepared. The hydration time allowed, representing degree of hydration, varied from 1 day to 90 days (almost 100% hydration). SEM microphotos were taken at high magnification at each level of hydration for each of the water-cement ratios. The microphotos were then examined with emphasis upon trends that would aid in distinguishing between water-cement ratios and degree of hydration. A set of photographs was selected to illustrate an array scheme that is proposed to be developed for estimation of water-cement ratio and degree of hydration of an unknown based upon capillary morphology changes. Presented along with the proposed scheme is a selection of characteristics features that were identified as being indicative of water-cement ratio and/or degree of hydration. It is suggested that these features be utilized in these cases where determination strictly by the proposed standard is not sufficiently accurate. /FHWA/
- Prepared in cooperation with North Carolina Department of Transportation and Highway Safety and the Federal Highway Administration.
North Carolina State University, RaleighHighway Research Program, P.O. Box 5993
Raleigh, NC United States 27607
- Mullen, W G
- Bodvarsson, G W
- Publication Date: 1978-6
- Pagination: 114 p.
- TRT Terms: Air voids; Concrete hardening; Electron microscopes; Failure; Hydration; Moisture content; Scanners; Statistical analysis; Water cement ratio
- Uncontrolled Terms: Hardened concrete
- Old TRIS Terms: Air voids content; Scanning
- Subject Areas: Data and Information Technology; Highways; Materials;
- Accession Number: 00189966
- Record Type: Publication
- Source Agency: Federal Highway Administration
- Report/Paper Numbers: FHWA-NC-75-2-0 Final Rpt.
- Files: TRIS, USDOT
- Created Date: May 26 1979 12:00AM