| Abstract [eng] |
The aim of this work: during hydrothermal treatment from trepel and calcium oxide to synthesize heat-resistant monobasic calcium hydrosilicates, form plates and investigate their physical and mechanical parameters. The syntheses were performed in an stirred and non-stirred suspension autoclave, when molar ratio of calcium oxide and silica was 0,83 and 1. The syntheses were performed in a water vapor environment at 200-220 °C temperature with a water and solids ratio of 10, also isothermal holding time of 4-72 hours. Methods of instrumental analysis revealed that the main product of the synthesis is tobermorite, which amount in the product increases by increasing isothermal holding time. The optimal synthesis parameters were determinated by autoclaving in non-stirred suspension: molar ratio of calcium oxide and silica is 0,83, temperature – 200 °C, duration of isothermal holding – 16 hours. From the obtained synthesis products, 60x20x20 mm samples were formed by casting under a vacuum of 0.25 and were dried at 40-400 °C temperature for 24 hours. Investigating the drying kinetics, identical temperatures were selected and dried for 90 minutes, recording the results every minute. The results showed that samples completely dried after 80 minutes at 180 °C temperature. The physical and mechanical properties of the samples were investigated. The volume of the samples was determinated by measuring them with a caliper and pycnometer, calculations performed according to the obtained results showed that the density of samples ranged from 290 kg/m3 to 410 kg/m3. Based on data was estimated that the samples are porous and the porosity reaches 88%. The compression strength of samples showed that the strongest ones were dried at 300-400 °C (1.3-1.46 MPa) and the ones which were treated hydrothermically second time (1.45-2.0 MPa). Thus, a mixture of trepel and calcium oxide can be used to produce heat-resistant monobasic samples, which are formed by molding under vacuum, just the technological parameters have to be chosen that the drying temperature and duration would be economical and the final synthesis product retains as much of tobermorite as possible. |
