Cement-Free Refractory Concretes. Part 4. Refractory Concretes based on Silica Sol Binders
- PDF / 556,012 Bytes
- 9 Pages / 594 x 792 pts Page_size
- 73 Downloads / 182 Views
Vol. 61, No. 2, July, 2020
SCIENTIFIC RESEARCH AND DEVELOPMENT CEMENT-FREE REFRACTORY CONCRETES. PART 4. REFRACTORY CONCRETES BASED ON SILICA SOL BINDERS1 Yu. E. Pivinskii2,3 Translated from Novye Ogneupory, No. 3, pp. 20 – 29, March, 2020.
Original article submitted November 15, 2019. Compositions, technology features, and the main properties of cement-free refractory concretes (CFRC) based on a silica-sol binder are considered. Concretes of high-alumina and corundum compositions of CFRC, as well as in the Al2O3–SiO2–SiC–C system predominate in this group. Improved thermal and thermomechanical properties of CFRC compared with the properties of LCRC are largely due to mullitization as a result of interaction of nanodispersed SiO2 (silica sol and microsilica) with reactive alumina of the matrix system. Extensive and effective use of CFRC based on silica binders is achieved in blast furnace production (chutes, cold and hot shotcreted blast furnace shafts) and for lining cement production furnaces. Keywords: low-cement refractory concrete (LCRC), cement-free refractory concrete (CFRC), silica sols, silica binder, mullitization, matrix system, initial and “hot” strength, concrete lining.
FEATURES OF TECHNOLOGY AND MAIN PROPERTIES
Within the group of cement-free refractory concretes (CFRC) those based on a silica-sol binder acquire a leading position. This is due to a set of engineering and economic
During preparation of refractory concretes of corundum, aluminosilicate, and silica compositions there is significant interest in a binder based on a silica-sol. The expediency of using sols of oxides (hydroxides) on the whole and silica-sol in particular in refractory technology emerges from some of their specific properties. Sol solutions exhibit good adhesion properties of oxide composition powder. They are characterized by the greatest reaction capacity and facilitate low-temperature sintering. Silica sols are lyophilic colloidal systems. The surface of the nucleus of their particles is covered with silane groups SiOH whose dissociation gives rise to occurrence of a double electric layer and a negative sol particle charge [11, 12]. It is well known that colloidal silica in combination with other solid particles (refractory concrete components) due to a gel formation mechanism may form branched chains. This process is initiated with water removal. During concrete drying hydroxyl groups Si–OH form at the surface of siloxane bonds –Si–O–Si– at a particle surface, which determines formation of a spatial network (Fig. 1). The bases of contemporary technology for preparing silica-sol were laid down even in 1940. As noted in an Aler
factors. The main ones are a significant advantage compared with LCRC in engineering and operating properties determined by their composition and also thermal and thermomechanical properties [1 – 7]. In particular, with use of CFRC based on a silica-sol binder the uncertain complexity of LCRC and ULCRC is resolved successfully connected with their primary heating in the temperature range for d
Data Loading...
