No abstract

The influence of different types of deflocculants, PCE and sodium tripolyphosphate, on the rheological properties of the cement matrix was studied. It was established that composite deflocculant consisting of sodium tripolyphosphate and PCE Castament FS 20 provides the best rheological properties of the cement matrix and affects the composition of the hydration products. During the drying process of matrix with composite deflocculants mineral stratlingite additionally formed, which contributes to increment of strength properties. Comparative studies of refractory castable strength properties with chamotte aggregate showed that the compressive strength of concrete samples with composite deflocculants after hardening and after drying and burning is almost two times higher than the strength of samples with separate deflocculants.

The possibility of obtaining heatproof coatings on fireclay refractories by self-propagating high-temperature synthesis in the system MgO -SiO 2 -Al using as the binder liquid sodium glass with the additives sodium tripolyphosphate and titanium dioxide, the latter activating the SHS process, is investigate. The optimal composition is determined and the physical-mechanical properties and the macro-and microstructure of the coatings are investigated.Protective heatproof coatings and methods of synthesizing them are chosen on the basis of certain criteria, among which are, for example, good adhesion of the coating to the refractory, closeness of the CLTEs of the coating and the base, and others.In the last ten years the energy-efficient method of selfpropagating high-temperature synthesis (SHS), discovered in 1967 by A. G. Merzhanov and his colleagues, has been used to obtain ceramic refractories and protective coatings on steel [1]. SHS is an intense exothermal interaction of the components in the condensed phase that propagates along a reaction mix similarly to a wave of combustion. The method is characterized by low energy consumption, simple equipment, high speed of the process, high productivity, purity of the products, possibility of synthesizing ceramics with different composition and function, as well as mechanisms of phase and structure formation in the final product which are unusual from the stand point of conventional materials engineering. The exothermal interaction during SHS can proceed in the form of a wave of combustion (classical SHS) and in a fast volume reaction regime (thermal explosion) [1].The SHS method has been used to synthesize refractories in the system MgO -MgAl 2 O 4 [2], masonry mortar in the system Al -Fe 2 O 3 -chromite ore [3], materials based on aluminomagnesia and chromomagnesia spinel [4,5], the refractory system SiC -Al 2 O 3 [6], and materials based on mullite [7]. The SHS method is also convenient to use for producing single refractories, for example, high-temperature articles and various coats, coatings, and solutions.The objective of the present work is to synthesize by the SHS method heatproof coatings on fireclay refractories, used as linings for tanks in heating units, for example, for melting aluminum. The system MgO -SiO 2 -Al was chosen to obtain refractory and chemically stable phases -aluminomagnesia spinel and mullite.Secondary resources -shards of magnesite brick (MgO) (TU 32-34-032-94), silicon dioxide SiO 2 (grade B quartz dust) with particle size less than 315 mm and PAP-2 (GOST 5494-95) aluminum powder -were used as the component of the reaction mixture. The source heat release, supporting the flow of the SHS process in this system, must be a reaction of aluminothermic reduction of silicon oxide. STUDY PROCEDUREThe system MgO -SiO 2 -Al was investigated to obtain protective heatproof coatings based on a spinel phase and aluminosilicate. Silicon dioxide SiO 2 and aluminum powder served as exothermal reagents, magnesium oxide MgO served as the filler and liquid s...

No abstract