Performance of compacted Mg(OH)2 after carbonation


Akca A. H. , Ma S., Esposito D., Kawashima S.

INTERNATIONAL CONFERENCE ON “CEMENT - BASED MATERIALS TAILORED FOR A SUSTAINABLE FUTURE", İstanbul, Turkey, 27 - 29 May 2021, pp.94-99

  • Publication Type: Conference Paper / Full Text
  • City: İstanbul
  • Country: Turkey
  • Page Numbers: pp.94-99

Abstract

Carbon emissions due to Portland cement production pose a significant threat to the environment. Therefore,
developing alternative binders is critical for a sustainable future. In this study, it is aimed to utilize Mg(OH)2 as a
binder to produce CO2-negative concrete. Owing to the fact that Mg(OH)2 reacts with CO2 and H2O to form various
kinds of hydrated magnesium carbonates to gain strength, this process can eliminate Portland cement entirely and
sequester CO2 from other industrial emitters. However, environmental conditions such as CO2 concentration and
humidity highly affect carbonation degree and resultant strength development. Since Mg(OH)2 cement systems do
not rely on hydration, it is desirable to limit water content to that only needed to facilitate carbonation reaction.
Considering this, water to binder ratio was kept as low as possible at 0.25. Subsequently, compaction was required
to cast and densify the specimens. The focus of this study was to determine the role of compaction pressure on
carbonation degree and strength gain. Three different compaction pressures were applied during casting into
cylindrical molds – 0.01 MPa, 3 MPa and 6 MPa. Then the specimens were cured in an incubator, which maintains
a condition of 20% CO2 concentration and 80 ± 5% humidity at 25 ± 2 °C. The compression test results showed
that the initial compaction is vital to gain strength since the specimens compacted under 0.01 MPa showed almost
no strength development. On the other hand, the