Use of soy methyl ester prior to cracking as a surface treatment method to minimize chloride penetration of cracked concrete
Abstract
Concrete is used in a large number of civil engineering structures. Some of these structures may be susceptible to corrosion caused by the ingress of deicing salts. While service life models have been developed to predict the rate of chloride ingress, many of these models base their calculations on the properties of uncracked concrete. However, concrete in service may crack due to tensile forces and environmental loading. Cracks may provide an easier path for chlorides to enter the concrete, which may cause the rebar to corrode faster than it would have if the concrete was in an uncracked condition. There are also numerous sealants that can be applied to concrete, both topically and admixed, that can also be used to reduce the rate of chloride ingress into concrete. This thesis focuses on chloride ingress in plain and sealed concrete that is cracked after it is sealed. The sealer used in this work is a Soy Methyl-Ester (SME) that contains 2% Polystyrene (PS). Soy Methyl-Ester is a byproduct of soy bean oil and is hydrophobic in nature. As a byproduct of soy bean oil, it is biodegradable, non-toxic, and sustainable. The SME-PS was topically applied to the concrete specimens. Both sealed and unsealed beams were cracked in flexure and ponded with a 23.3% Sodium Chloride (NaCl) solution in order to examine the effectiveness of SME-PS at reducing the penetration depth of the chlorides. Titration results show a reduction in the chloride content in roughly the first 12 mm. Furthermore, sealed and unsealed concrete cylinders were used to test for diffusion coefficient, tortuosity, and drying rate. The cracks were imaged using x-ray tomography. This work suggests an increase for the diffusion coefficient in the presence of cracks. However, the diffusion coefficient for cracked samples that were sealed prior to cracking was shown to be lower than the respective unsealed sample. It also discusses however that in addition to the vertical crack that forms, debonding along the reinforcement steel is important for chloride ingress.
Degree
M.S.C.E.
Advisors
Weiss, Purdue University.
Subject Area
Civil engineering
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