INVESTIGATION ON THE FORMATION PROCESS OF β-C_2S FROM HYDROTHERMALLY SYNTHESIZED CSH WITH Ca(OH)_2, BY USE MAINLY OF ~(29)Si-NMR and TMS-GC

摘要

Although it Is possible to prepare -C_2S by heating at about 900°C on the coexisting system of CSH and Ca(0H)_2 which was hydrothermally synthesized from the suspension with CaO/SiO_2 mole ratio of 2.0, the mechanism of the reaction had not been clearly understood. In the present work, hydrothermal synthesis was done at 80, 120, 160 and 200°C.The hydrate samples thus obtained were then heated at 300° ～ 1000°C and the change of the structure of the silicate anions in the heated samples was examined by use of ~(29)Si-NMR, IR and TMS-GC. The results showed that the higher the hydrothermal synthesis temperature, the longer the silicate anion chain which made up the CSH in the samples( Q~2/Q~1 equals 0.7, 1.1, 1.2, and 1.3 for the samples synthesized at 80, 120, 160 and 200°C respectively). Dimer, tetramer and pentamer were formed when the samples were heated at 300° ～400°C and monomer( -C_2S) formed when heated at 500°C.