Quantitative assessment of self-healing in cementitious systems

The discussions around self-healing cements have grown over the past decade as researchers in construction materials aim to find a more sustainable approach to cement and supplementary cementitious materials (SCM). Current efforts in self-healing cements have used a variety of designs ranging from micro-encapsulated healing agents, embedded in concrete or cement during the mixing process, to enzymes or bacteria which consume a calcium-sourced nutrient solution to precipitate mineral growth, healing cracked or void spaces. Within many of these concepts, ideal or altered conditions are often needed to adjust for the high pH levels of the concrete or the harsh mixing process. As such, altering the concrete mix design to adjust for self-healing potential may result in further deterioration issues such as altered cement reactions, increased void space, or strength loss. Subsequently, with this rise in processes for self-healing cements and other SCMs, there lacks in the literature a simplified, novel method for quantifying self-healing in construction materials. Many such methods currently used to quantify healing result in topological crack healing which fails to capture crack depth. Other methods use weight-change and compressive testing to correlate to a quantified value. Many such methods fail to grasp the breadth of capability in collecting meaningful data and consistently reproducing quantified results. In the following report, we first present a novel approach for self-healing cements in the form of an aqueous calcium nitrite solution that, within less than 24 hours, can produce significant crystal growth, filling cracked space with upwards of 60% efficiency. These crystals additionally act as nucleation sites for continual carbonation to form on the surface of precipitated calcium nitrite crystals, strengthening and healing the cracked cement spaces. Secondly, we propose a new method for quantifying self-healing cements through a Laser Scanning Confocal Microscope (LSCM), used to track the mineral precipitation occurring in the cracked space. The results from the LSCM proved consistent in multiple samples and the resulting mineral precipitate would correlate directly with the concentration of calcium nitrite solution and quantified growth.

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

2023

Author dc:creator

• Doehring, Jacob William

Contributors dc:contributor

• Garg, Nishant

• Cement
• Self-healing
• Quantitative
• Cementitious
• Calcium Nitrite

Statement dc:rights

• Copyright 2023 Jacob W Doehring

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/120409

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F120409