Thermal Resistance of Calcium Aluminate Cement Based Composites

Abstract

Building structures can be exposed to extreme conditions during their lifetime. One of these extreme situations is fire, or more precisely, exposure to extreme temperatures. In this case, there is a high likelihood of damage occurring to building materials, which could lead to the final collapse of a whole structure. Ordinary concrete, based on Portland cement, does not resist high temperatures very well; it is suitable for temperatures up to 400 °C. However, when exposed to higher temperatures decomposition of portlandite and dehydration of CSH gel will show. The aim of this thesis is to develop of such cement-based composites with better thermal resistance in regard to the application to structures with higher fire hazard i.e. boards for a tunnel lining or as face panel for improving thermal resistance. The first step was research into an optimization of material composition, which takes into account a choice of raw materials, their characterizations and setting of their amounts. For better thermal stability calcium, aluminate cement was chosen as a binder. The remaining components were basalt aggregate and basalt fibres; furthermore, the combination of different lengths of basalt fibres was investigated also. The second step was an assessment of a thermal resistance of these designed composites. This was performed by virtue of experimental measurement of physical properties. The particular characteristics of concrete were determined after being exposed to three different temperatures; specimens were pre-treated by three thermal loadings (105 °C, 400 °C, and 1000 °C). In the third part, the issue of optimal length fibres combination was investigated with the employment of similar approach of determining the residual properties. From the achieved results were concluded, that designed fibre reinforced, calcium alumina cement based composites with basalt aggregate proved its applicability in civil structures, and the optimal basalt fibres combination of longer: shorter fibres was found in the ratio of 90:10.

Building structures can be exposed to extreme conditions during their lifetime. One of these extreme situations is fire, or more precisely, exposure to extreme temperatures. In this case, there is a high likelihood of damage occurring to building materials, which could lead to the final collapse of a whole structure. Ordinary concrete, based on Portland cement, does not resist high temperatures very well; it is suitable for temperatures up to 400 °C. However, when exposed to higher temperatures decomposition of portlandite and dehydration of CSH gel will show. The aim of this thesis is to develop of such cement-based composites with better thermal resistance in regard to the application to structures with higher fire hazard i.e. boards for a tunnel lining or as face panel for improving thermal resistance. The first step was research into an optimization of material composition, which takes into account a choice of raw materials, their characterizations and setting of their amounts. For better thermal stability calcium, aluminate cement was chosen as a binder. The remaining components were basalt aggregate and basalt fibres; furthermore, the combination of different lengths of basalt fibres was investigated also. The second step was an assessment of a thermal resistance of these designed composites. This was performed by virtue of experimental measurement of physical properties. The particular characteristics of concrete were determined after being exposed to three different temperatures; specimens were pre-treated by three thermal loadings (105 °C, 400 °C, and 1000 °C). In the third part, the issue of optimal length fibres combination was investigated with the employment of similar approach of determining the residual properties. From the achieved results were concluded, that designed fibre reinforced, calcium alumina cement based composites with basalt aggregate proved its applicability in civil structures, and the optimal basalt fibres combination of longer: shorter fibres was found in the ratio of 90:10.