Evidence of scawtite and tilleyite formation at ambient conditions in hydrated Portland cement blended with freshly-precipitated nanosize calcium carbonate to reduce greenhouse gas emissions

Lewis J. McDonald, Waheed Afzal* (Corresponding Author), Fredrik Glasser

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Activated calcium carbonate (a-CaCO3) is used partially to replace Portland cement. a-CaCO3 is comprised of nanoscale calcium carbonate, in amorphous and calcite forms, and its enhanced carbonate activity converts calcium carbonate from being an inert filler to a reactive component. Its reaction with the C-S-H phase alters the conventional hydrate mineralogy with spontaneous formation at ~20°C of scawtite, Ca7(Si6O18)CO3·2H2O and tilleyite, Ca5Si2O7(CO3)2. Compressive strength measurements show that up to 20 mass% cement replacement by calcium carbonate does not decrease 7- and 28-day compressive strengths compared to a Portland cement benchmark. a-CaCO3 also accelerates the hydration of silicate clinker minerals. Using activated calcium carbonate as a supplementary cementing material enables substantial reduction of CO2 emissions, firstly by capturing part of the CO2 from cement kilns to make nanoscale calcium carbonate and secondly, by using the aCaCO3 capture product to replace part of the cement.
Original languageEnglish
JournalJournal of Building Engineering
Publication statusAccepted/In press - 16 Dec 2021

Keywords

  • carbon capture and use (CCU)
  • cement mineralogy
  • circular economy
  • Calcium Carbonate
  • Portland cement

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