Microstructure Changes in Hardened Cement Paste after Freezing – Thawing Cycles

Authors

  • Gintautas SKRIPKIŪNAS Vilnius Gediminas Technical University
  • Džigita NAGROCKIENĖ Vilnius Gediminas Technical University
  • Jadvyga KERIENĖ Vilnius Gediminas Technical University
  • Eugenijus JANAVIČIUS Kaunas University of Technology
  • Giedrius GIRSKAS Vilnius Gediminas Technical University
  • Algimantas ŠPOKAUSKAS Vilnius Gediminas Technical University

DOI:

https://doi.org/10.5755/j01.ms.19.1.3835

Keywords:

hardened cement paste, microstructure, freeze-thaw cycle, sodium silicate, calcium chloride

Abstract

This article analyses the results of the freezing – thawing with deicing salt test where changes in the microstructure of the surface layer in contact with aggressive environment of hardened cement paste produced with and without sodium silicate (hereinafter NTS) admixture were observed after freeze-thaw cycles in the presence of calcium chloride. After
56 cycles of freezing – thawing with deicing salt test micro-cracks and cavities were observed in the microstructure of the surface layer of hardened cement paste with and without NTS admixture. In the case of hardened cement paste with NTS admixture changes in the microstructure of the surface layer are less prominent: the number and size of cavities and micro-cracks are smaller. The test revealed that compressive stress, which before freezing – thawing with deicing salt test was very similar in hardened cement paste with and without NTS admixture (85.4 MPa and 82.8 MPa respectively), changed after 56 cycles of freezing – thawing with deicing salt test as follows: reduced by 39.5 % in concrete without NTS admixture and increased slightly (2.5 %) in hardened cement paste with NTS admixture. Based on the test results the authors arrived at the conclusion that sodium silicate solution can be effectively used to extend the useful life of hardened cement paste exposed to freeze-thaw cycles and affected by CaCl2.

DOI: http://dx.doi.org/10.5755/j01.ms.19.1.3835

Downloads

Published

2013-03-19

Issue

Section

CONSTRUCTION MATERIALS