Project Info
Development of a new standard method for determining chemical admixture dosage in concrete
Lori Tunstall
ltunstall@mines.edu
Project Goals and Description:
Complex surfactant mixtures, called air-entraining agents (AEAs), are used in concrete to purposefully introduce a small volume of tiny, well-dispersed air bubbles into the concrete to protect the concrete against frost damage. Control of the air volume and bubble distribution in concrete is essential--if the bubbles are too large or occupy too large a volume, the concrete will be weakened; however, if the air entrainment is insufficient the concrete will degrade prematurely. Despite the importance of proper control, the industry still relies on empirical, qualitative assessments to determine proper dosage. These methods are increasingly ineffective with the increasing complexity of concrete mixtures, which now include multiple types of chemical admixtures and cement alternatives. In partnership with Krüss Scientific, our group is working to develop new methods for determining accurate dosage. The ultimate goal of this project is to contribute to a new ASTM standard that can be used industry-wide to accurately and reproducibly predict proper AEA dosage.
Our group will work closely with Krüss Scientific, specialists in interfacial chemistry, to develop novel application methods for air-entraining agents in concrete, utilizing their dynamic foam analyzer and tensiometer. This includes weekly brainstorming sessions with Krüss scientists.
More Information:
Grand Challenge: Restore and improve urban infrastructure.
For more information on the use of air entraining agents in concrete and current gaps in our understanding, please refer to: https://www.sciencedirect.com/science/article/pii/S0008884621002064?casa_token=g_N6MNKZ7SoAAAAA:DBk-mUJKMb45VMa4lAXi0XFJXDKMVXoq60Nsa8W_GbV2-FX2CaPDkk72Vc50AYKMaGwJlAL7Ow
Primary Contacts:
Prof. Lori Tunstall, ltunstall@mines.edu
Student Preparation
Qualifications
Most importantly, the student should be willing to learn new things, have a meticulous attention to detail, and a strong work ethic. The student should also be comfortable with handling chemicals safely and measuring accurate concentrations of chemical solutions. Training will be provided.
TIME COMMITMENT (HRS/WK)
5 hours per week
SKILLS/TECHNIQUES GAINED
Skills and techniques the student will gain:
- accurately measure surface tension as a function of surfactant concentration
- construct adsorption isotherms
- experience with multiple instruments, including Krüss K100 (tensiometer) and DFA (dynamic foam analyzer), BET surface area through nitrogen adsorption, etc.
- making air-entrained concrete samples
- air void image analysis of concrete
- foam index test (ASTM-C1827)
- development of ASTM standards
MENTORING PLAN
I will personally train the student(s) on the laboratory techniques required and meet with the student(s) once per week to discuss research progress, questions, etc. I am also available to assist the student(s) in the lab, as needed, throughout the week, and available to answer questions via email in between meetings.
PREFERRED STUDENT STATUS
Junior
Senior