Use of Carbonated Waste Hardened Cement Powder as a Supplementary Ce- mentitious Material

Author(s): Bao Lu, Caijun Shi
Paper category: Proceedings
Book title: Proceedings of the International Conference on Sustainable Materials, Systems and Structures (SMSS2019) New Generation of Construction Materials
Editor(s): Marijana Serdar, Nina Štirmer, John Provis
ISBN: 978-2-35158-217-6,
Vol 1. ISBN: 978-2-35158-223-7
e-ISBN: 978-2-35158-218-3
Publisher: RILEM Publications SARL
Publication year: 2019
Pages: 439-439
Total Pages: 1
Language : English

Abstract: Recovering aggregates from recycled concrete produces a large amount of powder, which contains hardened cement paste and is classified as a corrosive hazardous material. This work used CO2 to treat hardened cement powder and to investigate how incorporation of uncarbonated and carbonated waste hardened cement powder into cement affect the hydration and microstructure development of cement. Carbonated waste hardened cement powder consists mainly of calcite and silica gel. Replacement of cement by uncarbonated waste paste powder content from 10 to 30% by the mass of cement decrease the strength of cement, while replacement of cement with 10-20% carbonated waste paste powder, but with 30% carbonated waste paste powder decrease the early strength of the cement. The presence of calcite in carbonated waste paste powder leads to the formation of hemicarbonate and monocarbonate thus to a stabilization of ettringite compared with the pure cement paste, in which a part of ettringite converts to monosulphate. Hemicarbonate is less stable than monocarbonate. It exists only for one week, then transforms to monocarbonate. The presence of silica gel significantly
reduces the calcium hydroxide and results in the formation of more C-S-H. Replacement of cement by carbonated waste paste powder also leads to a lower porosity and a higher compressive strength compared with the pure cement paste.

Online publication : 2019
Publication type : full_text
Public price (Euros) : 0.00