Compensating for Concrete Shrinkage with High-Calcium Fly Ash

Shrinkage of concrete during hardening is a serious problem in attempts to maintain the integrity of concrete structures. One of the methods of combating shrinkage is compensating for it using an expansive agent. The purpose of this work is to develop and study an expanding agent to concrete, including high-calcium fly ash and calcium nitrate as an expansion activator. The content of Ca(NO3)2 can be used to regulate the degree of expansion of the additive itself during hydration and, accordingly, to control shrinkage, thus obtaining shrinkage-free or expanding concrete. Shrinkage–expansion deformations of concrete can also be regulated by the amount of expanding additive replacing part of the cement. With the Ca(NO3)2 content of fly ash being 10% or more, concrete experiences expansion in the initial stages of hardening. The transition of deformation through 0 to the shrinkage region occurs depending on the composition and content of the additive after 8–15 days of hardening. It has been established that replacing cement with pure fly ash with a curing period of 90 days or more has virtually no effect on the strength of concrete, either in bending or in compression. The use of an expanding additive containing 5–15% Ca(NO3)2 reduces the strength of concrete by an average of 9%, despite the fact that calcium nitrate is a hardening accelerator.

Authors
Barabanshchikov Yurii1 , Krotova Vasilia1 , Usanova Kseniia 1, 2
Journal
Publisher
MDPI Multidisciplinary Digital Publishing Institute
Number of issue
10
Language
English
Pages
3167
Status
Published
Volume
14
Year
2024
Organizations
  • 1 Scientific and Technological Complex for Digital Engineering in Construction, Peter the Great St. Petersburg Polytechnic University, 195251 St. Petersburg, Russia
  • 2 Academy of Engineering, RUDN University, 117198 Moscow, Russia
Keywords
concrete; cement; high-calcium fly ash; calcium nitrate
Date of creation
04.11.2024
Date of change
04.11.2024
Short link
https://repository.rudn.ru/en/records/article/record/157698/
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