Studies on the evaluation of permeability and corrosion resisting characteristics of Portland pozzolan concrete

(1985) Studies on the evaluation of permeability and corrosion resisting characteristics of Portland pozzolan concrete. Masters thesis, King Fahd University of Petroleum and Minerals.


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The aggressive service conditions of the Estern Saudi Arabia necessitate the production of quality concrete which is dense and impervious, so that it inhibits the penetration of chloride and sulfate salts which are uniquely effective in setting up corrosion of rebars and the chemical deterioration of hardened cement paste. Pozzolan is considered to be one of the potential admixtures which assists in the production of dense and impermeable concrete resulting in reduced sulfate attack and rebar corrosion. This investigation was formulated to evaluate the effect of using pozzolan on the permeability, porosity and the general quality of concrete made with typical local aggregates consisting of finely graded beach/dune sands and crused limestone. The experimental program was designed to vary the pozzolan substitution from 0 to 40% and water cement ratio in the range of 0.35 to 0.55. The performance of pozzolans from four different sources was also evaluated. The effects of hydration reaction of pozzolan on the properties of concrete was studied over a period of one year, by measuring water permeability, porosity, pulse-velocity and compressive strength. Accelerated corrosion tests were carried out in the laboratory to determine the effectiveness of pozzolan in inhibiting rebar corrosion. Exposure-site tests were carried out to evaluate the corrosion resistance characteristics of pozzolan concrete made with salt contaminated mixing water. The exposure-site samples were monitored to determine the time to cracking. Carbonation depth, weight loss of rebars, and pH measurements were carried out on these samples after 11 months of exposure in the field. Results show that concrete incorporating 20% fly ash added as a replacement of cement reduces the porosity, permeability and improves the general quality of concrete. Pozzolan concretes show significantly better performance than straight portland cement concrete in terms of resistance against rebar corrosion. Pozzolan concrete contaminated with salts do not show any noticeable aggravation in the rebar corrosion process due to the presence of fly ash. Reaction between fly ash and calcium hydroxide [Ca(OH) ] of the hydrated cement paste does not reduce the pH value below those observed for the no-fly ash concretes. Carbonation depths of about 1.0 cm were observed in a relatively short period of 11 months of concrete exposure. The best performance in terms of porosity, permeability and pulse-velocity, among the four pozzolans evaluated, was exhibited by French fly ash. These results indicate that pozzolan drawn from different sources may exhibit significantly different levels of performance necessitating careful evaluation and characterisation before actual use.

Item Type: Thesis (Masters)
Subjects: Civil Engineering
Department: College of Design and Built Environment > Civil and Environmental Engineering
Committee Advisor: Zafar, Z.
Committee Members: Bader, Maher A. and Abbasi, A. F.
Depositing User: Mr. Admin Admin
Date Deposited: 22 Jun 2008 13:46
Last Modified: 01 Nov 2019 13:49