The industrialization of repairs and construction of many elements in the linings of heating plant requires refractory concrete items of enhanced strength and spalling resistance [I], which may be obtained, for example, by using bauxite [2] or silicon carbide materials [3].Special value is attached to improving the quality of refractory concrete by incorporating silicon-carbide waste products in the concrete mixture.The aim of the present work* was to investigate and select a composition for SiC-containing concrete articles of the minimum cost in the system containing SiC waste + chamotte--SiC sagger scrap + corundum scrap with predetermined properties as follows: o11o compressive strength after drying at II0~ (holding for 8 h) not less than 12.5 MPa; o~6o compressive strength after firing at 1400~ (4-h holding) not less than 12.5 MPa; the change I in the linear dimensions of the concrete specimen s (along the axis of vibroforming) after firing at 14000C not more than 0.5%; spalling (thermal-shock) resistance T (1300 ~ --water) not less than i0 heat cycles.The problem was tackled by using simplex-network experiment planning [4] and the zeneral preference function [5].The following factors were selected: X: --mass proportion of silicon-carbide waste from the heat-insulation fillings in the production of SiC heaters at the Zaporozhe refractories factory, %; X2 --mass proportion of scrap chamotte--SiC saggers, %; X3 --mass proportion of finely dispersed corundum waste from the Yurginsk abrasives combine, %.The optimization parameters # were taken to be: o,~o --compressive strength after drying, MPa; ~I~oo --compressive strength after firing at 1400~ ~a; >--open porosity of the specimens after firing at 1400~ %; y --the apparent density of the specimens after firin~ at 14000C, g/cmS; T --thermal-shock resistance (1300~ --water), heat cycles; I --the change in the linear dimensions of the concrete specimens after firing at 1400~ %; S --the cost of 1 ton of concrete body, rubles.The concrete filler was taken from the materials in the system being studied (ZX i = i) and the bond consisted of high-alumina cement (about 72% AI~03).The scrap from chamotte--SiC saggers (33.86% SiC) was crushed in a laboratory jaw crusher and screened into fractions 20-10, 10-5, 5-2, 2-0.5, and minus 0.5 mm (obtained in a ballmill).The silicon-carbide waste (86.68% SiC) consists of a sintered skin, and after jaw crushing was screened into 3-l-mm fractions.The corundum waste (95.5% Al=Os) had the following grain-size composition: 1.8% fraction >250~, 3.3% 250-200 D, 10.9% 200-160 ~, 13.8% 160-125 u, 21.7% 125-100 ~, 25.4% !00-80 ~, 9.4% 80-63 B, 2.0% 63-50 ~, 3.0% 50-40 ~, 8.7%< 40u. The specimen cubes with edges of 7 cm were prepared by vibromolding on a laboratory vibrating table using 2950 oscillations per second and an amplitude of 0.37 mm in accordance with the planning matrix (Table i). Two specimens were prepared from each body.The sufficiency of the quadratic model so produced was checked with respect to the tcriterion on three s...
At present, in the majority of steel plants of the country the upper structure of the walls of soaking pits is laid manually of 4-6 rows of chamotte brick and the remainder of the walls of large silica blocks and panels, the life of which is 8-12 months [i]. The edge is subject to mechanical action and thermal shocks, which leads to failure of the monolithic lining, a reduction in service lives to 2.5-3 months, and a sharp decline in sanitary and hygienic working conditions in the shop.There have been positive results of tests of edges of aluminosilicate concrete with a high alumina filler, high alumina cement* [2], and clay--phosphate binder [3].This article presents the results of production and testing of concrete parts with the use of production wastes [4].The experimental parts for the soaking pit wall edge were produced in the Khristoforov Refractory Block and Concrete Plant.Scrap from silicon carbide parts (86.68% SiC, 12.06% Si02, 0.15% C), bauxite (68.32% Al2Os, 3.58% Fe203), and commercial grade chamotte (31.15% AlaOs) were used as the filler of the concrete and high-alumina and alumina cements as the binder.The use of bauxites as fillers for refractory concrete is assumed to be possible with not more than 5% Fe203 in it.The original materials (with the exception of 20-0-mm fraction ground bauxite obtained from Borovichi Refractory Compound) were ground in an SM-741 jaw crusher and then in an OTsD-50 cone mill.The pulverized materials were separated into the 20-5-and 5-0-mm fractions (Table i). The mixture was mixed in a cement mixer.The parts were produced from plastic mixtures by the vibroforming method.+ The compositions of the mixtures are shown in Table 2.The mixtures were compacted with IV-47 deep vibrators a total of 12 parts of special configuration ( Fig. i) with a weight of 4.8 tons was prepared.
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