Diatom biosilica as a supplementary cementitious material

The use of supplementary cementitious materials (SCMs) is a key method used to reduce the embodied carbon of cement-based materials. Uncertainty in traditional SCM markets has led to increased interest in alternative, natural SCM materials. In this work, biosilica derived from freshly cultured diatom frustules (grown by Thalassiosira pseudonana and Phaeodactylum tricornutum) was assessed as an alternative SCM for the first time. The chemical reactivity of each biosilica source was assessed using a small-scale version of ASTM C1897 (the R3 test) previously developed by the authors. The chemical reactivity of T. pseudonana frustules was relatively high (i.e., greater than that of blast furnace slag, but lower than that of metakaolin). P. tricornutum frustules exhibited a lower chemical reactivity, similar to a Class F fly ash. Results demonstrate the potential to grow highly reactive biominerals using diatoms and highlight the potential tunability of diatom biosilica for use as a novel, sustainable SCM.