Preparation Of Calcium Silicate Insulation By Waste AAC

The development of AAC industry has been greatly restricted by the waste. The amount of the waste AAC is huge, and the land has been occupied too much. Calcium silicate insulation material has many advantages, such as low density, high strength, easy processing, excellent heat insulation effect. Calcium silicate insulation material has made a significant contribution to the energy conservation and emissions reduction in today. The development of calcium silicate insulation material is conform to the sustainable development strategy.Waste AAC has been used as the main siliceous raw material, zirconium residue and diatomite used as minor siliceous raw material. Using different proportions of siliceous raw materials to prepare tobermorite type calcium silicate thermal insulation material. Improve the mechanical properties of materials by adding clay powder and poly vinyl acetate emulsion, etc. The flexural strength, line shrinkage, phase composition and structure have been charactered by mechanical test instrument, XRD, nitrogen adsorption, etc. The main phase of calcium silicate insulation material whose 70% raw materials were waste AAC were well crystallized tobermorite, bulk density is 285 kg/m3, thermal conductivity is 0.069 W/(m·K), flexural strength is 0.26 MPa. The flexural strength of calcium silicate insulation material whose whole raw materials were waste AAC has reached 0.51 MPa when clay powder occupied 50% and polyvinyl acetate emulsion 7%. Use AAC after calcination at high temperature to prepare calcium silicate insulation material. And it is found that the latter has a better performance in physical and mechanical properties.The micro structure change of 11.3 A tobermorite at 725℃ has been studied. Tobermorite with basal spacing (d(002)) of 1.13 nm was synthesized with submicron-sized amorphous silicon dioxide and calcium oxide. The structure and morphology changes of tobermorite calcined at 725℃ for 2 h were investigated. The results show that dehydroxylation tobermorite and monoclinic α-CaSiO3 crystals appear after calcination. The dehydroxylation tobermorite is amorphous, disordered and metastable. The morphology of calcined tobermorite is similar to that of uncalcined tobermorite, i.e., needle-like and lamellar, due to the lamellar twining and accumulative generation of the particles. Some nano-sized tobermorite crystals transform into monoclinic α-CaSiP3 crystals after calcination at 725℃ for 2 h.The rehydration of 11.3 A tobermorite dehydration has been studied. The high temperature dehydration was gained by tobermorite calcination at 725℃ for 2 h. The changeof hydrochloric acid insoluble matter, effect calcium and combined water content had been studied in order to analysis the rehydration reaction process and it was been found that the reaction process meet the logarithmic change:F(t)= k1ek2t+k3. XRD, SEM, TEM and nitrogen adsorption had been used to study the phase and structure change in the rehydration reaction. From the research results, it can be concluded that the products of 11.3 A tobermorite rehydration include the new generation of 11.3 A tobermorite and CSH gel. In the process of rehydration, the lamellar structure of dehydroxylation tobermorite will dissolve and dehydroxylation tobermorite will transform into CSH gel. As the reaction continued, CSH gel will transform into 11.3 A tobermorite.