Effect of nanosilica/metakaolin ratio on the calcium alumina silicate hydrate (C-A-S-H) formed in ternary cement pastes

Supplementary Cementitious Materials (SCM) such as Metakaolin and Nanosilica can be used in blended Portland cements to improve performance of the cement matrix. The use of these materials can also change hydrate formation, altering properties of Calcium Silicate Hydrate (C-S-H) such as chemical composition and molecular structure. The objective of this research was to study the combined effect of these SCM's in different metakaolin/nanosilica ratios forming ternary mixtures with OPC, evaluating properties of both C-S-H and overall paste. Results showed these mixtures had the highest strength values and lowest portlandite content at 28 days. Furthermore, their C-A-S-H was formed in higher content, had higher aluminum inclusion and longer molecular chains. Analyzing the results, a synergistic effect between nanosilica and metakaolin, dependent on their ratio in paste composition, was observed.

Automated summary

By studying the combined effect of Metakaolin and Nanosilica in different ratios, this research found that ternary mixtures with OPC had higher strength values, lower portlandite content, and increased C-A-S-H content with longer molecular chains. A synergistic effect between nanosilica and metakaolin, dependent on their ratio in paste composition, was observed.