Surface characterization of carbonated recycled concrete fines and its effect on the rheology, hydration and strength development of cement paste

Xiaowei Ouyang*, Liquan Wang, Shida Xu, Yuwei Ma, Guang Ye

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

9 Citations (Scopus)

Abstract

Carbonation treatment can effectively improve the performance of recycled concrete aggregate and fines due to the reactions of CO2 with CH and C–S–H gel of cement paste. To better understand the mechanisms involved in the performance improvement, the surface properties of carbonated recycled cement paste powder (CRP) and its effect on the rheology, hydration and strength development of cement paste was studied. The results showed that during the carbonation, the surface of CRP was covered by a layer of amorphous silica gel. The generated CaCO3 was wrapt by the silica gel and seldom exposed. The silica layer led to the poor flowability of CRP-cement paste due to that the silica gel on the surface of CRP has a strong affinity for H2O. During the very early hydration, the silica gel dissolved and then CaCO3 was exposed. CaCO3 is capable of chemically absorbing Ca2+, which facilitated the nucleation of C–S–H nuclei and stabilized the C–S–H phase. As a result, the C–S–H grew densely, uniformly and perpendicularly on the surface of CRP. In addition, the chemically absorbing Ca2+ enabled the chemical bond to be formed between CaCO3 and C–S–H. Due to increased C–S–H resulted from reactions of silica gel with CH at the interface and the stronger bond formed between CaCO3 and C–S–H, the interface between CRP and hydration products was much stronger than that between recycled cement paste powder (RP) and hydration products.

Original languageEnglish
Article number103809
Pages (from-to)1-10
Number of pages10
JournalCement and Concrete Composites
Volume114
DOIs
Publication statusPublished - 2020

Bibliographical note

Accepted Author Manuscript

Keywords

  • Carbonation treatment
  • Hydration
  • Recycled concrete aggregate
  • Recycled concrete fines
  • Rheology
  • Strength development

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