Inducing superhydrophobicity in aluminum and concrete: implications on durability and performance

Superhydrophobic and self-cleaning materials have been an extensive topic of research owing to their corrosion resistance, anti-fouling, and anti-icing properties. In the past, superhydrophobicity in aluminum has been obtained by a variety of techniques involving etching by sandblasting, chemical etching, boiling in water, etc. followed by treatment with a fluorochemical and organic solution. However, these techniques are not controlled, might not be easy to implement on a large scale and mostly make use of fluorochemicals, which are risky for human health and the environment. Therefore, there is a need for a rapid and controlled fabrication process that can provide patterned superhydrophobicity without compromising the environment or human health. In this thesis, a rapid, controlled and environmentally friendly procedure for fabricating a superhydrophobic and self-cleaning aluminum surface has been developed, achieving a contact angle of 158.06° and a sliding angle of 1.94°. In the two-step process, a rough surface was obtained using the laser etching technique in under 3 minutes using laser etching technique, which resulted in a precisely controlled pattern with a dual-scale roughness on the surface (~20-30 μm). Finally, low surface energy was imparted to the surface by treatment with stearic acid where a low concentration of 2x10-4 M and no more than 10 seconds of exposure was found to be sufficient. Unlike various superficially coated materials, this superhydrophobic surface is durable and does not lose its properties after dipping in water for up to 4 days, at extreme surrounding temperatures of -18°C to 100°C or on encountering fine sand or mud. Thus, this rapid and controlled process for obtaining superhydrophobic aluminum can be potentially deployed for large-scale, structural applications where aluminum is used. Inspired by superhydrophobic aluminum, a similar study was conducted on mortar. Use of ethanolic stearic acid was a common practice for production of superhydrophobic mortar. Knowing that ethanol is a cement hydration inhibitor, it was important to study the extent of hydration in the same. A significant decrease in the heat of hydration and therefore the compressive strength was observed in the superhydrophobic mortar was observed. Therefore, we propose an alternative hydrophobic mortar which was produced using superhydrophobic sand and sandblasting the surface to increase the roughness. Superhydrophobic sand was produced using ethanolic stearic acid which was dried to evaporate the ethanol. The hydrophobic mortar achieved a contact angle of ~ 125° and its resistance to water absorption was the same as superhydrophobic mortar. However, this procedure does not hinder the hydration reaction of the cement and does not fully compromise the compressive strength of mortar.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Civil Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2022

Author dc:creator

• Sharma, Ravi

Contributors dc:contributor

• Garg, Nishant

• Superhydrophobic
• Aluminum
• Mortar

Statement dc:rights

• Copyright 2022 Ravi Sharma

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/117607

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F117607