Influence of chemical admixtures and mineral additives on rheological properties and shrinkage of cement mixtures

Mindaugas Macijauskas

Doctoral dissertation

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When designing concrete and reinforced concrete structures with large open surfaces, the distance between the laid deformation of joints is intentionally restricted. This is done in order to control manifesting shrinkage deformations during the curing of concrete mixture, which typically cause cracking of the final structures. Also, due to the specifics of concreting technologies used for these structures, the concrete mixtures are subject to additional requirements of rheological characteristics (yield stresses, plastic viscosity and thixotropy). Therefore, the need to design reliable concrete mixtures, suitable for such technologies arises. Seeking to avoid cracks and increase the distance between deformation joints, one of the options is to evaluate the effects of a variety of widely used chemical admixtures and mineral additives can have on the mixture’s technological properties and drying shrinkage deformations under different technological conditions.

The dissertation is comprised of an introduction, three chapters, general conclusions, a list of used references, and a list of the author's scientific publications on the subject of the dissertation.

The introductory chapter defines the problem, the relevance of the thesis, the aim and objectives of the thesis, describes the research object, research methodology, scientific novelty of the thesis, practical significance of work results, and defensible statements. Publications published by the author on the subject of the dissertation, reports in conferences, and the structure of the dissertation are presented at the end of the introduction. The first chapter provides analysis of referenced sources. The rheological properties of cement mixtures are analysed, and methods used for the assessment of thixotropy of mixtures are described and discussed accordingly. Subsequently, the effect of different factors on the rheological properties of mixtures and on drying shrinkage of curing mixtures is discussed. At the end of the chapter, conclusions are drawn and the objectives of the dissertation are refined. In the second chapter, the materials used for the research and their main properties and characteristics are described, the composition of the mixtures are presented, and the formation of their samples described. Test methods and laboratory equipment are analysed and described in conjunction. In the third chapter, the research and analysis of the rheological properties and thixotropy of cement pastes and the research of drying shrinkage in curing cement mixtures is presented. The impact of chemical admixtures and mineral additives on the shrinkage of mixtures with design technological properties is described and analysed.

6 scientific articles have been published on the subject of the dissertation and 5 reports have been presented at conferences in several countries.

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DOI: https://doi.org/10.20334/2019-032-M

Book details

Data sheet

Year:
2019
ISBN:
978-609-476-189-8
Imprint No:
2019-032-M
Dimensions:
162×230
Pages:
172 p.
Cover:
Softcover
Language:
Lithuanian
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