Shrinkage behavior of cementitious mortars mixed with seawater

Morteza Khatibmasjedi, Sivakumar Ramanthan, Prannoy Suraneni, Antonio Nanni

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Abstract

The shrinkage behavior of cementitious materials mixed with seawater is investigated. Cement mortar mixtures were prepared with two water-to-cementitious materials ratios (w/cm = 0.36 and 0.45), two binder compositions (namely, ordinary portland cement (OPC) and OPC with 20 % fly ash replacement), and two types of water (tap water and seawater). The autogenous and drying shrinkage behavior of thesemixtures are examined using ASTM standard testmethods for 65 days. The use of seawater as mixing water increased the autogenous shrinkage. At w/cm 0.36, the ultimate autogenous shrinkage increased from 213 μs in the mixture with tap water to 387 μs in the mixture with seawater; the corresponding values were 149 and 314 μs, respectively, formixtures with w/cm 0.45. An acceleration of the cement hydration at early ages caused by the seawater is identified as the cause of the increase in autogenous shrinkage in mixtures with seawater. At w/cm 0.36, seawater did not have a strong effect on the drying shrinkage, and tested mixtures had ultimate drying shrinkage values between 543 and 663 μs. At w/cm 0.45, inmixtures without fly ash, ultimate drying shrinkage increased from 838 μs in the mixture with tap water to 1,027 μs in the mixture with seawater. In mixtures with fly ash, the ultimate drying shrinkage increased from 738 μs in the mixture with tap water to 1,370 μs in the mixture with seawater. The drastic increase in the drying shrinkage in mixtures containing fly ash and seawater at w/cm 0.45 seems to be due to changes in mass loss behavior and the development of a finer pore size distribution. In applications where drying shrinkage may be a concern, the use of fly ash in seawatermixed concrete could be problematic and lead to increased cracking risk. While the trends observed here will also hold in concrete, quantifying drying shrinkage and cracking of concrete based on the drying shrinkage of mortar mixtures is complex and depends on many other factors.

Original languageEnglish (US)
Article numberACEM20180110
JournalAdvances in Civil Engineering Materials
Volume8
Issue number2
DOIs
StatePublished - Mar 13 2019

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Keywords

  • Autogenous shrinkage
  • Drying shrinkage
  • Fly Ash
  • Mortar
  • Seawater

ASJC Scopus subject areas

  • Ceramics and Composites
  • Civil and Structural Engineering
  • Mechanics of Materials
  • Polymers and Plastics
  • Metals and Alloys
  • Materials Chemistry

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