Analysis On Microstructure And Primary Exploring Of Contact Hardening Mechanism Of C-s-h Superfine Powder Made With Hydrothermal Synthesis

The composition of traditional autoclaved hydrated silicate primarily includes the Tobermorite, Xonotlite and Hydrogarnet which are good crystals, but the study on C-S-H gel formed at the initial stage is few due to the levity of compositon and amorphous state. In this thesis the compositon and microstructure of the C-S-H powder manufactured using dynamic autoclaved technology with designed autoclaved schedules were investigated with XRD, DSC/TG, BET, SEM, TEM, IR etc. measurement technologies. This study will provide the guidance to perfecting the C-S-H system and give a primary exploring of the contact hardening mechanism of binding materials, the application in coating and rubber , and supplying viable way to surface-modifying of the powder.The C-S-H superfine powder with poor crystal, large specific surface area and nm-order size was manufactured using dynamically autoclaved technology, fly ash, diatomaceous earth and quartz sand as the siliceous materials, and the lime as calcium material. The results of microanalysis on composition, microstructure and morphology of the C-S-H superfine powder show that the main components were CSH(B) which was poor crystal and C-S-H gel which is similar to the former of Tobermorite or Xonotlite. The powders have the specific surface area up to 64.6m2/g, the porosity 0.16ml/g, and the optimized pore radius 0.9nm. The observation with SEM show that the diameter of the particle was about 20μm, most of which are like-globular or fibre, and the distribution was reasonably homogeneous. The observation with TEM found that the superfine powders pile up loosely by the particles with diameter about 50nm, or stagger and stack by fibres with diameter about 10~20nm, according to the kind of siliceous material.The aggregate structure of [SiO4]4- in the siliceous material has effect on the reaction degree and the morphology of the C-S-H superfine powder. The higher the aggregate structure of [SiO4]4-, the lower the reaction degree, and the more fibrous the synthetic product.The bulk samples with high strength and water-resistance were manufactured by pressing the C-S-H superfine powder based on the mechanism of the non-stable minerals with gaining strength by contacting each other. The compressive strength of the bulk samples manufactured under 40Mpa is above 8 MPa, and the soften coefficient is above 0.7. And the particls with 5 pressing-cycle are still contact hardening.The changes on the crystal, the bond and the morphology of the powder were investigated by a series of modern testing technology. The results show that in the progress of pressing and cycle-pressing, the crystalline degree increases, and also the density, the strength of the blocks decreases conversely, the structure state of the powder grow to ordering. The contact produced in the contact-hardening structure is anti-water and reversible.With the results and theory analysis, the structure model which is fit for the C-S-H superfine powder studied in this paper was proposed.