Influence of secondary raw materials on synthesisof tobermorite in lime–silicate composite

Influence of secondary raw materials on synthesisof tobermorite in lime–silicate composite

Paper in proceedings (conference paper)

Crystalline calcium silicate hydrate (CSH) phases, primarily tobermorite, arise in the microstruc-ture of autoclaved aerated concretes (AACs) during autoclaving, which affects the concrete'simportant characteristics. Calcium oxide/hydroxide and silicon oxide are the feedstocks for thehydrothermal reactions. When producing AACs, aside from commonly used raw materials, it isalso possible to utilize secondary raw materials rich in silicon oxide. The use of such secondaryraw materials provides the opportunity for the construction industry to lower its impact on theenvironment. This work describes the investigation of individual added secondary raw materials’influence on the microstructure of AAC. The tested materials were as follows: high-temperaturefly ash, FBC ash, slag, ground container glass, and zeolite. The materials were mixed with quick-lime at a molar ratio of calcium oxide to silicon oxide of 0.73 and 1.0. Autoclave reactors were usedfor the synthesis of tobermorite under laboratory conditions. Autoclaving took place at 170 and190◦C with hydrothermal soaking times of 4, 8, and 16 h. The additive with the most significantimpact on microstructure was fly ash, while ground container glass showed the greatest influenceon mechanical characteristics.

Crystalline calcium silicate hydrate (CSH) phases, primarily tobermorite, arise in the microstruc-ture of autoclaved aerated concretes (AACs) during autoclaving, which affects the concrete'simportant characteristics. Calcium oxide/hydroxide and silicon oxide are the feedstocks for thehydrothermal reactions. When producing AACs, aside from commonly used raw materials, it isalso possible to utilize secondary raw materials rich in silicon oxide. The use of such secondaryraw materials provides the opportunity for the construction industry to lower its impact on theenvironment. This work describes the investigation of individual added secondary raw materials’influence on the microstructure of AAC. The tested materials were as follows: high-temperaturefly ash, FBC ash, slag, ground container glass, and zeolite. The materials were mixed with quick-lime at a molar ratio of calcium oxide to silicon oxide of 0.73 and 1.0. Autoclave reactors were usedfor the synthesis of tobermorite under laboratory conditions. Autoclaving took place at 170 and190◦C with hydrothermal soaking times of 4, 8, and 16 h. The additive with the most significantimpact on microstructure was fly ash, while ground container glass showed the greatest influenceon mechanical characteristics.

autoclaved aerated concrete, fly ash, glass, secondary raw material, zeolite

autoclaved aerated concrete, fly ash, glass, secondary raw material, zeolite

ČERNÝ, V.; DROCHYTKA, R.; KULÍSEK, K.; HÚŠŤAVOVÁ, J.

2019

01.09.2018

Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co

Berlin

ICAAC ‐ 6th International Conference on Autoclaved Aerated Concrete

2509-7075

ce/papers

2

4

Federal Republic of Germany

439

444

6

https://doi.org/10.1002/cepa.842