Experimental Study and Numerical Modeling of Diffusion and Reaction Behaviour in Cement-based Composites under Sulphate Attack

• Author / Creator

  Ou, Chiqian

• This thesis describes several approaches evaluating the resistance of cement-based composites under adverse external-sourced sulfate attack. The conventional approach of evaluation by means of measuring expansion was discussed in comparison with the sulfate diffusion, which was quantified as a function of depth. A numerical model was established to simulate the diffusion-reaction behavior of sulfate ingress with the results of sulfate diffusion. Particularly, a visual assessment on sulfate diffusion by image analysis was originally developed by the author. The results from visual assessment were corroborated to the results from expansion measurement and numerical model. Besides CSA Types GU and HS cement, a 30:70 blend of fly ash and cement Type GU was also examined. The specimens so produced were immersed in a sulfate solution as per ASTM C1012 and retrieved variously after 7, 14, 28, 56 and 84 days of exposure. A control group was set with the specimens submerged in water environment in comparison. As expected, Type HS cement performed best with minimum expansion and sulfate ingress, as well as the sulfate diffusion area detected in image analysis. On the other hand, the Type GU cement showed lower expansion and sulfate ingress in comparison to the fly ash blended binder. Although bearing identical porosity, the blended binder had the smallest median pore size. Therefore, the sulfate ingress and consequent ettringite production likely cracks the blended system more than the other two. Significantly, after longer durations of sulfate exposure, the blended system showed higher tensile strength which implies a healing of cracks through ettringite formation whereas sulfate exposure had limited effect to the compressive strength of all the binders examined.

• Subjects / Keywords

  • Numerical modelling
  • Cement-based composites
  • Experimental study
  • Sulphate attack

• Graduation date

  Spring 2016

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3RX93T9R

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.