EFFECTS OF ALKALI ADDITION ON THE MECHANICAL PROPERTIES AND DURABILITY OF CONCRETE

This article reports on a study undertaken to examine the effects of alkali addition on the mechanical properties and durability of concrete. The authors focus on the effect of alkalis on strength development, drying shrinkage, freeze-thaw durability, and microstructure of concrete. The authors found that 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, the harmful effects do not extend to the elasticity modulus measured under compression or direct tension. Shrinkage tests 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 (with and without added alkali) resist well to freezing and thawing while showing similar air-void systems. The authors conclude that a higher concrete alkali content decreases the strength of the concrete, regardless of the manner in which the higher alkali content was achieved (high-alkali clinkers, the use of a cement with higher alkali content, or external addition of alkali sulphate, carbonate, or hydroxide).

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    Elsevier

    The Boulevard, Langford Lane
    Kidlington, Oxford  United Kingdom  OX5 1GB
  • Authors:
    • Smaoui, N
    • Berube, M A
    • Fournier, Benoit
    • Bissonnette, B
    • Durand, B
  • Publication Date: 2005-2

Language

  • English

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  • Accession Number: 00989018
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Apr 29 2005 12:00AM