Behavior of calcium silicate hydrate in aluminate solution

Using calcium hydroxide and sodium silicate as starting materials, two kinds of calcium silicate hydrates, CaO center dot SiO2 center dot H2O and 2CaO center dot SiO2 center dot 1.17H(2)O, were hydro-thermally synthesized at 120 degrees C. The reaction rule of calcium silicate hydrate in aluminate solution was investigated. The result shows that CaO center dot SiO2 center dot H2O is more stable than 2CaO center dot SiO2 center dot 1.17H(2)O in aluminate solution and its stability increases with the increase of reaction temperature but decreases with the increase of caustic concentration. The reaction between calcium silicate hydrate and aluminate solution is mainly through two routes. In the first case, Al replaces partial Si in calcium silicate hydrate, meanwhile 3CaO center dot Al2O3 center dot xSiO(2)center dot(6-2x) H2O (hydro-garnet) is formed and some SiO2 enters the solution. In the second case, calcium silicate hydrate can react directly with aluminate solution, forming hydro-garnet and Na2O center dot Al2O3 center dot 2SiO(2)center dot nH(2)O (DSP). The desilication reaction of aluminate solution containing silicate could contribute partially to forming DSP.