Basic properties of cement paste mixed with calcium hydroxide-ettringite composite type expansive additive

K. Handa, G. Ye

Research output: Chapter in Book/Conference proceedings/Edited volumeConference contributionScientificpeer-review

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Abstract

In this study, we targeted a calcium hydroxide and ettringite composite-type expansive additive (EA) and obtained the basic characteristics of the EA mixed cement paste in order to create a method for calculating volume expansion based on the hydration reaction of the PCEA system. Expansion strain, setting time, and compressive strength were measured. In addition, we observed the state of EA after hydration using a micro-CT scanner and scanning electron microscope, and elucidated the expansion mechanism. Our results show that strain rapidly increased and the compressive strength decreased when the replacement ratio of the EA (Crep) exceeds 6.4%. At the same time, radial cracks were generated from the hydrated EA particles, suggesting that the EA itself grew to expand the cement paste. Although no ettringite was confirmed inside the EA when the Crep was 5.1%, when the Crep was 10.3%, ettringite was formed vertically from the surface of C3A with a large amount of pores. These results show that simultaneous formation of ettringite and pores causes rapid expansion.
Original languageEnglish
Title of host publication4th International Rilem Conference on Microstructure Related Durability of Cementitious Composites
Subtitle of host publicationMicrodurability 2020
EditorsGuang Ye, Hua Dong, Jiaping Liu, Erik Schlangen, Changwen Miao
PublisherDelft University of Technology
Pages513-519
Number of pages7
ISBN (Electronic)978-94-6366-422-6
Publication statusPublished - 2021
Event4th International Rilem Conference on Microstructure Related Durability of Cementitious Composites - Online, Delft, Netherlands
Duration: 29 Apr 202127 May 2021
Conference number: 4
https://www.microdurability2020.com/99721

Conference

Conference4th International Rilem Conference on Microstructure Related Durability of Cementitious Composites
Abbreviated titleMicrodurability
CountryNetherlands
CityDelft
Period29/04/2127/05/21
Internet address

Keywords

  • Expansive additive
  • Calcium hydroxide
  • Ettringite
  • micro-CT scanning
  • SEM

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