Tobermorit solid solutions

With a CaO/SiO ratio of 1.0, the products were a tobermorite gel, CSH(I), tobermorite solid solution, xonotlite, hydrogarnet solid solution, y-AlO(OH) and anhydrite. The tobermorite substituted about 15 mol% Al O and the crystal had a plate-like shape. 

With a CaO/SiO ratio of 2.0, the product s were port landite, JT-C S hydrate, ci-C S hydrate, tobermorite solid solution, xonotlite, hydrogarnet solid solution and anhydrit e. The strength of the products was smaller than that of 0.5 or 1.0 CaO/SiO. ... 

As a general rule, the strengths of the product were less than that of the products having a 0.5 or 1.0 CaO/SiO molar ratio. The product obtained from the 15% 2 3 ition at 160 C ej ibited the following properties t e strength was 101 kg/cm, the total pore volume was 1.190 cm /g, reaction phases obtained were tobermorite solid solution and hydrogarnet solid solution, crystal of tobermorite was mostly plate granular habits. 

Fuji and Kondo (FI8) calculated the thermodynamic properties of C-S-H, using solubility data and properties of 1.4-nm tobermorite and CH given by Babushkin et al. (B62). The C-S-H was treated as equivalent to a solid solution of these two compounds. For the composition 1.7Ca0 Si02-2.617H20, they found A//f° =-2890 kJ mol" , Gf° =... 

For this reason some hypothetical models have been proposed, as a solution of this problem. In the oldest one the C-S-H phase was considered as a solid solution of Ca(OH)2 in tobermorite [58]. In the second the C-S-H phase was presented as a defected 1.4 nm tobermorite stracture, with the Ca + and OH ions between the layers [59]. 

The effect of aluminum ions on the transformation of C-S-H into 1.1 nm tobermorite was investigated by Mitsuda and Taylor [184], The solid solution of aluminum ions in tobermorite enlarges also the stability field of this phase in relation to xonothte [185], Diamond [186] found the maximum Al/(Si+Al) ratio in tobermorite to be 0.15 above this value the hydrogamet phase is appearing. Aluminum is tetrahedrally coordinated and accelerates the formation of 1.1 nm tobermorite. Finally, Mitsuda and Taylor [184] revealed that alkalis (l%Na20+1.7%K20) are activating the tobermorite formation from zeolite and calcium hydroxide. 

The higher differences, in phase composition are observed in the pastes autoclaved in the saturated water vapour at temperature range 120-200 °C. The phase composition of the calcium sihcate hydrates is primarily the function of C/S in the starting mixture. In Portland cement paste without additions the C-S-H (I) is transformed quickly to the C-S-H (II) and the latter already at 25 °C into a-C2SH [194, 199]. The proper addition of the ground quartz gives the 1.1 nm tobermorite. This phase contains aluminium in solid solution, which causes the transition to xonotlite, at temperatures exceeding 160 °C difficult... 

Q Tobermorite solid soIution+Hydrogarnet solid solution 0 Xonot I i te... 

C) Tobermorite solid so 1ution+ Hydrogarnet solid solution + i-A10(OH)... 

Tobermorite solid so1ution+Hydrogarnet solid solution+ Anhydrite ... 

Tobermorite solid so1ution + Hydrogarnet solid solution 0 [Pg.104]

Calcium Silicates Hydrates (CSH) is the major hydration product of Portland Cement. It has been intensively studied for several decades. CSH can be obtained by hydration of C3S and P-C2S or by precipitation fi om aqueous solutions containing a Ca salt and silicate ions. CSH has a wide range of chemical composition. Many studies [1-5] indicate that its molar ratio Ca/Si can vary fixrm 0.7 to 2 (or more) [6] and is in most cases near to 1.7 [7]. There has been indirect evidence that CSH (obtained by reaction between CaO and Silica) has a layered structure similar to that of natural Tobermorite and/or Jennite [8]. Recent solid state NMR [9-10], intfared spectroscopy [11], EXAFS [12] and thermogravimetry works [14] have... 

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