Title page for ETD etd-06102012-040303

Type of Document Master's Thesis
Author Smith, David Gilman
URN etd-06102012-040303
Title Determination of chloride diffusion constants for concretes of differing water to cement ratios and admixtures
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
Weyers, Richard E. Committee Chair
Ardekani, Siamak A. Committee Member
Walker, Richard D. Committee Member
  • Corrosion and anti-corrosives
Date of Defense 1988-08-05
Availability restricted
Reinforced concrete exposed to chlorides is subject to

rapid deterioration once the concentration of the chloride

ion in the concrete reaches a critical level to cause

corrosion of the reinforcing steel. The chloride ion diffuses through concrete according to Fick's Law, which is a function of time, a driving concentration, and a diffusion constant. The diffusion constant varies with temperature and

the variety of concrete .

The research included determination of diffusion

constants for six types of concretes after 8 weeks and 16 weeks of ponding with an NaC1 solution. In addition, one set of these samples was subjected to the outside environment

while the other was indoors under controlled conditions. The mixes included water to cement ratios of 0.35, 0.40, 0.45, and 0.50, and two water to cement ratios of 0.45 with 15%

cement replacement with pozblan admixtures (silica fume and

type'F flY ash). Thus, the effects of temperature, water to cement ratio, and pozzolanic admixtures in regard to the diffusion constant for concrete were found.

The method by,which a diffusion constant was found is as 1)X3% solution of-NaC1 is ponded on top of a four

inch thick 'specimen of concrete. 2) Powder samples of the

paste are taken at specified time at depths of -0.5, 1.0

1,:5, and 2-.5 inches. 3) These samples are analyzed for

chloride content by potentiometric titration. 4) The data is

fit to Fick's Law by nonlinear regression and an effective

diffusion constant determined.

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