Study of comparative engineering properties of specialty mortars for combating concrete corrosion
Date
2000
Authors
Lal, Nilesh Radhakrishan
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Advisor
Pitt, John M.
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Abstract
This thesis is composed of two experimental investigations, which address the issue of concrete sewer pipe corrosion. The first section "Study of Modified Portland Cement Mortar" discusses hydrogen sulfide corrosion and sulfur reducing microorganisms and their deteriorating effects on concrete structures focusing mainly on the sewerage system. The study involved performing laboratory experiments on a Pozzolan based Portland cement mortar. Durapoz[Registered trademark symbol] a pozzolanic admixture was added to the cement mortar and the specimens cast were exposed to harsh corrosive environments simulated in the laboratory. The second part "Study of Sodium Silicate Based Sump Mortar" also references the issue of concrete corrosion, but involves study of a new feasible approach towards the sewer pipe lining and concrete protection. Silicate based sump mortar was developed in-house utilizing the laboratory grade sodium silicate solution and a by-product of crushed stones as filler material, and was critically evaluated to determine its effectiveness to prevent concrete corrosion. For both parts of the study, the specimens were subjected to various concentrations of sulfuric acid, and the data like weight loss, change in compressive strengths, and change in color was analyzed. Experimental investigations were also performed to determine the physical properties of these specialty mortars.
The results of the experiments performed in Part 1 of the study demonstrated than Pozzolan modified cement mortar is more resistant to acid attack than the conventional Portland cement mortar. This is as expected since the Pozzolanic admixture in reacting calcium hydroxide considerably reduces the amount of freely available calcium hydroxide, and also reduces permeability. In Part 2, experimental results demonstrate than the silicate based sump mortar is highly resistant to the acidic environment; this is due to the fact that after curing the mortar primarily consisted of mass of silica, a non-sulfuric acid- reactive material. Research activities for both the parts, also included various experimental setups to evaluate the bond strength, compressive strength, setting time and determination of other parameters to evaluate the feasibility of the specialty mortars.
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Thesis