Self-Healing Potential and Phase Evolution Characterization of Ternary Cement Blends

Area of Science:

• Materials Science
• Civil Engineering
• Construction Materials

Background:

• Autogenous self-healing in cementitious materials offers potential for extending structural service life.
• Understanding the mechanisms and influencing factors of self-healing in advanced cement blends remains crucial.

Purpose of the Study:

• To investigate the self-healing capacity of ternary cement blends incorporating metakaolin (MK), ground granulated blast-furnace slag (BFS), limestone (LS), and siliceous filler (F).
• To analyze the impact of different blend compositions on healing efficiency at various curing ages.

Main Methods:

• Optical microscopy was used to examine micro-crack morphology and healing precipitation.
• Global healing product mass was monitored.
• X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were employed to identify and quantify mineral formation.
• A self-healing potential index was developed based on mass measurements.

Main Results:

• The formulation with 10% metakaolin (MK) demonstrated the highest early-age healing potential (<28 days).
• Formulations with 20% ground granulated blast-furnace slag (BFS) and 10% limestone (LS) or siliceous filler (F) exhibited higher healing potential at later ages (cracked after 28 days).
• Calcite, C-S-H, and portlandite were identified as primary healing products, with calcite's proportion increasing over time.

Conclusions:

• Ternary cement blends show significant potential for autogenous self-healing of micro-cracks.
• The optimal blend composition for self-healing is dependent on the age of the material at cracking.
• XRD and TGA are effective tools for monitoring the evolution of self-healing product phases.