Beneficial effects of small amounts of nano-silica on the chemical stability of cement pastes exposed to neutral pH environments

J. A. Jain, N. Neithalath

Research output: Chapter in Book/Report/Conference proceedingConference contribution

4 Scopus citations

Abstract

Synopsis: The effects of small dosages of nano-silica as a partial cement replacement material on the Ca ion leaching resistance of cement pastes exposed to deionized water is reported in this paper. Plain and modified cement paste specimens (containing either 6% or 9% of silica fume, or 0.5% or 1.5% of nano-silica) are subjected to leaching in deionized water for different durations after 56 days of curing in saturated limewater. The mass loss, change in porosity, and the changes in calcium hydroxide (CH) and C-S-H contents from thermogravimetric analysis between the specimens cured under saturated limewater for the entire duration and the specimens leached for different times are used to bring out the beneficial effects of these cement replacement materials when pastes are exposed to a leaching medium. The nano-silica modified cement pastes are observed to demonstrate lower mass loss and a lower increase in porosity when subjected to leaching. Using the changes in CH and C-S-H contents between the saturated and the leached pastes, it is shown that leaching and continuing cement hydration and/or pozzolanic reaction are essentially coupled, especially for the modified pastes. The paste with higher nano-silica content is seen to demonstrate increased C-S-H contents when undergoing leaching. The net Ca ion loss from both CH and C-S-H phases are seen to be lower for the pastes incorporating nano-silica as compared to those containing silica fume. The plain paste is seen to suffer the highest amount of Ca ion loss. A simplified method of calculating the apparent depth of the CH dissolution front is also reported, which is seen to highlight the influence of nano-silica and silica fume in improving the leaching resistance of pastes.

Original languageEnglish (US)
Title of host publicationNanotechnology of Concrete
Subtitle of host publicationThe Next Big Thing is Small - Session at the ACI Fall 2009 Convention
Pages59-74
Number of pages16
Edition267 SP
StatePublished - Dec 1 2009
Externally publishedYes
EventACI Fall 2009 Convention - New Orleans, LA, United States
Duration: Nov 8 2009Nov 12 2009

Publication series

NameAmerican Concrete Institute, ACI Special Publication
Number267 SP
ISSN (Print)0193-2527

Other

OtherACI Fall 2009 Convention
Country/TerritoryUnited States
CityNew Orleans, LA
Period11/8/0911/12/09

Keywords

  • C-S-H
  • CH dissolution front
  • Calcium hydroxide
  • Leaching
  • Nano-silica
  • Silica fume

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Building and Construction
  • Materials Science(all)

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