The influence of different types of siliceous raw materials on tobermorite formation in lime-silica composite

摘要

Autoclaved aerated concrete (AAC) is ecological building material with useful properties. The main mineral compound of AAC is tobermorite, it increases its mechanical properties. There is examined the usage of nature and artificial siliceous materials in this study. Main aim of the study is to demonstrate the influence of individual types of materials on the tobermorite creation and to determine optimal lime/silica ratio. First step of the research focuses on analysis of the used materials. In the second step on the creation of calcium hydrosilicate phases under ideal conditions (temperature of 190°C, pressure of 1.3 MPa) of autoclave reactors (volume of 250 ml). The autoclaved samples are next analyzed by X-ray diffraction and scanning electron microscopy for qualitative evaluation of created mineral phases. The results show that the most suitable non-traditional silica component is coal fly ash. Fly ash has the optimal combination of amorphous and crystalline SiO_2 in combination with Al_2O_3. These properties provided the highest proportion of created tobermorite even in more energy-saving autoclaving mode.