Graduation Year

2021

Document Type

Thesis

Degree

M.S.

Degree Name

Master of Science (M.S.)

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Christopher Alexander, Ph.D.

Committee Member

Alberto Sagüés, Ph.D.

Committee Member

Sarah (Ying) Zhong, Ph.D.

Committee Member

Margareth Dugarte Coll, Ph.D.

Keywords

Calcium silicate cement, Durability, Initiation, Propagation

Abstract

Corrosion of reinforcing steel is a major area of study for assessing durability of reinforced concrete infrastructure. Conventional concrete infrastructure designs use ordinary Portland cement (OPC) as the primary cementitious material. However, the world's current challenge to achieve sustainable development requires the cement industry to reduce its environmental impact, as it is responsible for 8% of the anthropogenic CO2 emissions. Hence, a new type of cement has been developed. This novel calcium silicate cement (CSC) reduces the carbon dioxide emissions during its manufacturing process as compared to OPC, providing an environmentally-sound alternative for reinforced concrete fabrication.

Corrosion of steel reinforcement has been widely studied for OPC-based concrete. Therefore, corrosion-based structural life of traditional concrete formulations can be accurately forecasted. Nevertheless, new cement technologies may imply different concrete material properties, for which the long-term performance of these new concrete formulations needs to be evaluated.

This thesis presents experimental results comparing the corrosion durability of two formulations of the aforementioned non-hydraulic, calcium silicate cement concrete to that of one type of ordinary Portland cement concrete. Cured CSC-based concrete has a lower pore water pH (9-11) than OPC-based concrete, likely resulting in a corrosion initiation stage that is comparatively shorter. However, CSC-based concrete has a higher resistivity than OPC-based concrete, making the formation of corrosion macrocells more difficult. Corrosion experiments were performed to evaluate the corrosion-related durability of these two formulations. The array of tests included exposure to fresh water and salt water (each alternate wetting and drying regimes) for different steel types. Additionally, accelerated corrosion propagation tests were performed to assess the ability of each concrete formulation to accommodate corrosion products as an indicator of the duration of the corrosion propagation stage. The corrosion performance of each concrete formulation was evaluated in terms of chloride diffusivity, corrosion rate, and the critical corrosion penetration required to crack the concrete. This thesis provides a comparative estimate of corrosion-related service life based on the necessary assumptions for a novel calcium silicate cement-based reinforced concrete.

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