Carbonated wollastonite - An effective supplementary cementitious material?

Area of Science:

• Materials Science
• Civil Engineering
• Geochemistry

Background:

• Supplementary cementitious materials (SCMs) are crucial for improving concrete performance and sustainability.
• Wollastonite, a calcium silicate mineral, has been explored for its pozzolanic properties.
• Carbonation of wollastonite clinker (CS) alters its microstructure and reactivity.

Purpose of the Study:

• To evaluate carbonated wollastonite clinker (CS) as a potential SCM for mortar and concrete.
• To investigate the microstructural changes in CS during carbonation and its incorporation into cementitious systems.
• To assess the impact of CS on the compressive strength development of blended mortars.

Main Methods:

• Microstructural analysis of unground CS clinker, carbonated CS slurry, and CS-blended mortar using scanning electron microscopy (SEM).
• Production of reference mortar (pure Portland cement) and CS-blended mortar (30 mass-% CS replacement).
• Assessment of compressive strength development in the produced mortars.

Main Results:

• Carbonation of CS decalcifies calcium silicates, yielding calcium carbonate (CaCO3) and amorphous silica (SiO2).
• The amorphous SiO2 component of CS demonstrates reactivity when used as an SCM.
• Mortars blended with CS showed influenced calcium-silicate-hydrate (C-S-H) formation and contributed to compressive strength development.

Conclusions:

• Carbonated wollastonite clinker (CS) is a viable SCM for use in mortar and concrete.
• The amorphous silica derived from CS plays a key role in enhancing the mechanical properties of cementitious materials.
• CS contributes to improved compressive strength through its influence on C-S-H microstructure.