Two models based on local microscopic relaxations to explain long-term basic creep of concrete

Area of Science:

• Materials Science
• Civil Engineering
• Solid Mechanics

Background:

• Concrete exhibits long-term basic creep, a phenomenon crucial for structural integrity.
• Understanding the micromechanics of creep is essential for accurate material modeling.

Purpose of the Study:

• To propose and validate two models (exhaustion and work-hardening) for explaining concrete's basic creep.
• To elucidate the relationship between microscopic relaxations and macroscopic creep strain.
• To explain the accelerated characterization of creep kinetics using indentation techniques.

Main Methods:

• Development of an exhaustion model and an adapted work-hardening model.
• Analysis of activation energy distribution and evolution in creep processes.
• Comparison of model predictions with phenomenological features of concrete creep.

Main Results:

• Both models successfully explain key features of concrete's basic creep.
• Macroscopic creep strain is attributed to local microscopic relaxations.
• Applied stress influences creep manifestation, not the rate of relaxation.

Conclusions:

• The proposed models provide a unified framework for understanding concrete creep.
• The findings support the use of indentation for rapid, quantitative creep characterization.
• The physical origin of relaxations is suggested to be related to disjoining pressures.