Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Influence of supplementary cementitious materials on hydration, microstructure development, and durability of concrete
In recent years the use of supplementary cementitious materials in the production of concrete has become an ever more frequent trend, since such use contributes to a sustainable concrete industry. The main reason for this lies in the reduction of the specific energy requirement and of carbon dioxide emissions in the production of cement (OPC). One such environmentally friendly product is fly ash (FA), which occurs as a by-product of coal-fired thermal power plants. In the first part of the thesis the hydration of OPC and FA at early ages, as well as at later ages, was monitored by means of calorimetry and thermogravimetry. During the first hours the FA retarded the hydration of OPC, particularly the belite hydration. Up to an age of 28 days, the FA exerted a physical nucleation effect on the OPC hydration, which did not compensate for the dilution effect. Furthermore, between 21 and 28 days, a decrease was observed in the amount of calcium hydroxide (CH), and a corresponding increase in the amount of bound water relative to the OPC content, due to a pozzolanic reaction, indicating a change in the hydration products that are formed in the FA blended cement, i.e. less CH and more C-S-H and AFm phases relative to the OPC content. Comparing the two investigated types of FA, siliceous and calcareous FA, no clear difference can be observed with regard to the decrease in the amount of CH. On the other hand, the amount of hydrated products increased significantly up to 28 days, and then not changed much up to one year in the case of the cement paste with siliceous FA. In contrast, in cement paste made by using calcareous FA, the amount of hydrated products increased gradually up to one year. Over a period of one year the consumption of CH was 50% greater in the case of cement pastes containing 30% FA than in the case of cement paste without such an addition. This phenomenon was reflected over time in the observed increase in the mechanical strength of the binder. After 90 days, the compressive strength of concrete in ...
Influence of supplementary cementitious materials on hydration, microstructure development, and durability of concrete
In recent years the use of supplementary cementitious materials in the production of concrete has become an ever more frequent trend, since such use contributes to a sustainable concrete industry. The main reason for this lies in the reduction of the specific energy requirement and of carbon dioxide emissions in the production of cement (OPC). One such environmentally friendly product is fly ash (FA), which occurs as a by-product of coal-fired thermal power plants. In the first part of the thesis the hydration of OPC and FA at early ages, as well as at later ages, was monitored by means of calorimetry and thermogravimetry. During the first hours the FA retarded the hydration of OPC, particularly the belite hydration. Up to an age of 28 days, the FA exerted a physical nucleation effect on the OPC hydration, which did not compensate for the dilution effect. Furthermore, between 21 and 28 days, a decrease was observed in the amount of calcium hydroxide (CH), and a corresponding increase in the amount of bound water relative to the OPC content, due to a pozzolanic reaction, indicating a change in the hydration products that are formed in the FA blended cement, i.e. less CH and more C-S-H and AFm phases relative to the OPC content. Comparing the two investigated types of FA, siliceous and calcareous FA, no clear difference can be observed with regard to the decrease in the amount of CH. On the other hand, the amount of hydrated products increased significantly up to 28 days, and then not changed much up to one year in the case of the cement paste with siliceous FA. In contrast, in cement paste made by using calcareous FA, the amount of hydrated products increased gradually up to one year. Over a period of one year the consumption of CH was 50% greater in the case of cement pastes containing 30% FA than in the case of cement paste without such an addition. This phenomenon was reflected over time in the observed increase in the mechanical strength of the binder. After 90 days, the compressive strength of concrete in ...
Influence of supplementary cementitious materials on hydration, microstructure development, and durability of concrete
Simcic, Tina (Autor:in) / Pejovnik, Radovan Stanislav / De Schutter, Geert
01.01.2015
Hochschulschrift
Elektronische Ressource
Englisch
DDC:
690
| British Library Online Contents | 2018
| British Library Online Contents | 2018
| British Library Online Contents | 2018