Pozzolanic Reaction of Carbonated Wollastonite Clinker

Abstract

Carbonated wollastonite-based clinker is proposed as a potential novel supplementary cementitious material. The clinker can be synthesized from limestone and a silica source, and exhibits a CO₂-footprint after carbonation, which is approximately 60-70% less than the one of Portland cement. When carbonated, a silica-rich amorphous phase forms besides various polymorphs of calcium carbonate. When the carbonated clinker is blended with Portland cement, hydration is accelerated, and a significant pozzolanic reaction of the silica-rich amorphous phase takes place. This leads to a positive contribution to compressive strength. In a blend with 30% replacement of Portland cement by the carbonated wollastonite-based clinker almost the same mortar compressive strength is reached after 28 days compared to the plain Portland cement. Further investigations, especially regarding the production of the carbonated clinker, the durability of concrete incorporating this novel material, and life cycle analyses as well as economical assessments are needed.