SYNTHESIS AND CRYSTAL STRUCTURE OF HYDRATED CALCIUM SILICATES IN THE CaO - SiO_2 - H_2O SYSTEM

Beta C_2S was prepared at 600°-1000°C from hillebrandite，Ca^-_(SiO_3)(OH)_2，which was hydrothermally made using quartz below10m and CaO eith Ca/Si=2.0at250°C for 20h in stirring suspensions under saturated steam pressure.Hillebrandite shows fibrous or lath-like crystals lying on(001)elongated to b with a=16.588(2)，b=7.2670(8)，c=11.787(1)，beta=90.231(7)°，specific surface area of 10.1m^2g(BET)，crystallite size of483，and single chains(MASNMR)。在heating hillebrandite was decomposed into beta-C2Sat 600°C and further transformed into alpha‘L phase at 650°-900°C，alpha’H phase at 1170°C，and alpha phase at 1430°C.Samples heelow 1430°C were stabilized into beta form by cooling to room temperature.The crystals of beta-C_2S obtained by heat treatment at 600°-1000°C retained the same morphology and crystallographic orientations of hillebrandite，and gave the following crystallite size and specific surface area：289-6.3m^2/g(600°C)，360-5.2m^2/g(800°C)，721-2.5m^2/g(1000°C)。The results of calorimetry showed the hyfaster the rate of beta-C&lt；D22@&gt；D。Within2weeks at w：s=1.0and20°C，perfectly hydrated products of C-S-H with Ca(OH)&lt；@D22@&gt；D2were obtained from the beta-C&lt；@D22@&gt；D2S prepared at 600°C.Analytical electron microscopy of the C-S-H in the beta-C&lt；@D22@&gt；D2S pastes cured for 28days gave a mean Ca/Si ratio which vary grely with w：s ratio；1.97(w：s=1.0)，1.86(2.0)，1.70(5.0)and 1.51(20)。MASNMR spectroscopy of the C-S-H showed a strong Q&lt；@D11@&gt；D1 and a weak Q&lt；@D12@&gt；D2in the absence of Q&lt；@D10@&gt；D1，Q&lt；@D13@&gt；D1 and Q&lt；@D14@&gt；D1。This suggests that the silicate anions of the C-S-H in beta-C&lt；@D22@&gt；D2S pastes are mixtures of dimer and short single chain。

beta C_2S was prepared at 600゜-1000゜C from hillebrandite, Ca^-_(SiO_3)(OH)_2, which was hydrothermally made using quartz below 10 m and CaO eith Ca/Si=2.0 at 250゜C for 20 h in stirring suspensions under saturated steam pressure. Hillebrandite shows fibrous or lath-like crystals lying on (001) elongated to b with a=16.588(2) , b=7.2670(8) , c=11.787(1) , beta=90.231(7)゜, specific surface area of 10.1 m^2g (BET), crystallite size of 483 , and single chains (MASNMR). On heating hillebrandite was decomposed into beta-C2S at 600゜C and further transformed into alpha'L phase at 650゜-900゜C, alpha'H phase at 1170゜C, and alpha phase at 1430゜C. Samples heated below 1430゜C were stabilized into beta form by cooling to room temperature. The crystals of beta-C_2S obtained by heat treatment at 600゜-1000゜C retained the same morphology and crystallographic orientations of hillebrandite, and gave the following crystallite size and specific surface area: 289 - 6.3 m^2/g (600゜C), 360 - 5.2m^2/g (800゜C), 721 - 2.5m^2/g (1000゜C).The results of calorimetry showed the faster the rate of beta-C<@D22@>D2S hydration, the lower the treatment temperature of hillebrandite. Within 2 weeks at w:s = 1.0 and 20゜C, perfectly hydrated products of C-S-H with Ca(OH)<@D22@>D2 were obtained from the beta-C<@D22@>D2S prepared at 600゜C. Analytical electron microscopy of the C-S-H in the beta-C<@D22@>D2S pastes cured for 28 days gave a mean Ca/Si ratio which vary greatly with w:s ratio; 1.97 (w:s = 1.0), 1.86 (2.0), 1.70 (5.0) and 1.51 (20). MASNMR spectroscopy of the C-S-H showed a strong Q<@D11@>D1 and a weak Q<@D12@>D2 in the absence of Q<@D10@>D1, Q<@D13@>D1 and Q<@D14@>D1. This suggests that the silicate anions of the C-S-H in beta-C<@D22@>D2S pastes are mixtures of dimer and short single chain.