期刊
CEMENT AND CONCRETE RESEARCH
卷 35, 期 2, 页码 203-212出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.cemconres.2004.05.007
关键词
alkalies; concrete; shrinkage; freezing and thawing; mechanical strengths
Increasing the concrete alkali content from 0.6% to 1.25% of Na2Oe of the cement mass by adding NaOH to the mixture water has harmful effects on most mechanical properties (compressive, splitting, direct tensile, and flexure strengths) of concrete made with a water-to-cement (w/c) ratio of 0.41 and limestone aggregates not susceptible to alkali-silica reaction (ASR), however not on the elasticity modulus measured under compression or direct tension. Shrinkage tests at 50% RH and 23 degreesC started after 7 days at 100% RH and 23 degreesC show that the low-alkali concrete shrinks more than the high-alkali one, despite similar water losses. Freeze-thaw tests performed on air-entrained concretes show that the two concretes resist well to freezing and thawing while showing similar air-void systems. Wien examined under the scanning electron microscope (SEM), the hydrates in the two concretes present similar microstructure; however, the high-alkali concrete shows a more reticular and porous microtexture, which could explain the reduction in strength. (C) 2004 Elsevier Ltd. All rights reserved.
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