Volumetric Measurement in Water Bath - An Inappropriate Method to Measure Autogenous Strain of Cement Paste

Volumetric measurements of autogenous strain are frequently performed by placing the fresh cement paste in an elastic rubber membrane immersed in water. The change in volume of the cement paste is measured by the amount of water displaced by the immersed sample, for example by measuring its weight change underwater. Volumetric and linear measurements of autogenous strain should in principle give identical results. However, the measuring results from the volumetric method are typically 3-5 times the results from the linear technique, depending on the type of cement paste and the experimental conditions. Some sources of error in the volumetric method have been identified by different authors and eliminated or compensated for. In this study, absorption of water from the buoyancy bath through the rubber membrane is identified as the principal artifact of the volumetric method and cause of most of the discrepancies between volumetric and linear measurements. Water absorption is driven by a lowering of the water activity in the cement paste due to self desiccation and to dissolved salts in the pore fluid. Very high water absorption in the membrane-enclosed cement paste samples was registered from the moment of casting. The influence of this error on the volumetric measurements was of the same order of magnitude as the autogenous strain itself. By performing the measurements in a paraffin oil bath instead of a water bath, water absorption through the elastic membrane was eliminated. Volumetric measurements performed in paraffin oil were almost identical to linear measurements performed on the same cement pastes. This shows that the principal artifact of the volumetric method was individuated and eliminated. Nevertheless, the presence of many other artifacts makes the volumetric method very difficult to use in practical applications

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• Corporate Authors:

  Technical University of Denmark

  Department of Civil Engineering
  Brovej, DTU - Building 118
  DK-2800 Kgs. Lyngby,   Denmark 

  Portland Cement Association

  5420 Old Orchard Road
  Skokie, IL  United States  60077
• Authors:
  • Lura, Pietro
  • Jensen, Ole Mejlhede
• Publication Date: 2005-2

Language

• English

Media Info

• Media Type: Print
• Edition: Technical Report
• Features: Figures; Photos; References;
• Pagination: 26p

Subject/Index Terms

• TRT Terms: Buoyancy; Cement paste; Desiccation; Measurement; Paraffin; Salts; Volume changes; Volumetric analysis
• Uncontrolled Terms: Autogenous strain; Linear measurement; Oil bath; Volumetric measurement; Water absorption; Water bath
• Subject Areas: Highways; Hydraulics and Hydrology; Materials; I32: Concrete;

Filing Info

• Accession Number: 01022698
• Record Type: Publication
• Report/Paper Numbers: PCA R&D Serial No. 2925
• Files: TRIS
• Created Date: Apr 11 2006 11:31AM