Structure-Mechanical Properties of Plasticized Mixes Based on Highly Concentrated Ceramic Binding Suspensions (HCBS) of High-Alumina Chamotte

Abstract

Plastic mixes based on high-alumina chamotte HCBS and a multifractional refractory filler are prepared; the mixes molded at low pressures (30 MPa) make it possible to obtain materials with an initial porosity of 14 -15%. This effect is attained by adding a composite plasticizer (a refractory clay and a complex organomineral thinner) to the mix.Highly concentrated ceramic binding suspensions (HCBS) and HCBS-based plastic (plasticized) mixes are promising in the technology of unshaped refractories [1 -4]. From this standpoint, of special interest are high-alumina mixes.Efficiency of composite additives. It was shown in [5] that a highly dispersed refractory clay and a complex organomineral thinner (COMT) (composed of sodium tripolyphosphate and SB-5 organic plasticizer) when added to the high-alumina chamotte (75% Al 2 O 3 ) HCBS produced an exceptional thinning and plasticizing effect. Relevant illustrative data are shown in Figs. 1 and 2. The difference in porosity of green specimens free of COMT (Fig. 1a, curve 1 ) and containing COMT (curve 2 ) amounts to 2.5%. As the concentration of clay C is raised, the difference tends to increase, and at C = 3%, it reaches 8%. This difference is likewise retained in specimens heat-treated at 1000 and 1300°C ( Fig. 1b and c). The compressive strength of green and heat-treated specimens is likewise controlled by the clay concentration (Fig. 2). In clay-free specimens, the compressive strength s c does not differ much, 20 and 22 MPa (Fig. 2a, curves 1 and 2 ). With increase in C, curves 1 and 2 behave in a different manner; their course is quite clear and does not need detailed comment. Relationships compressive strength versus concentration C for heat-treated specimens are shown in Fig. 2b and c).It was noted in [5] that the high efficiency of the composite additive (COMT + refractory clay) is due to its ability to reduce the amount of kinetically bound liquid in HCBS-based systems.Elastoplastic viscous properties. Introducing highly dispersed refractory clays into "lean" HCBSs provides a route towards plastic mixes with quite satisfactory molding properties at relatively low molding pressure [1, 4]. The concentration of plasticized HCBSs may vary within 35 -45% (by weight) or within 40 -55% (by volume) depending on the HCBS granular composition, molding pressure, etc. In analogy with refractory castables [4,6], the moldability (placeability) of plastic mixes is mainly controlled by rheological properties of the matrix. Therefore it was of interest to explore rheological properties of HCBS in a flow state [5] and in a plastic state which is attained by partial dehydration of precursor HCBS.Our goal in this work was to study in some detail elastoplastic viscosity and structure-mechanical properties of precursor HCBS (free of additives) and HCBS containing additives COMT and refractory clay. Structural and mechanical properties of plastic mixes are typically characterized in terms of the yield limit, elasticity, plasticity, and plastic viscosity [7 -9].

Press-Molding of High-Alumina Ceramic Castables. 1. Compaction and Properties of Matrix Systems Based on Mixed HCBS of Composition: Bauxite, Quartz Glass, and Commercial Alumina

“…4) becomes still more pronounced in materials treated at maximum temperature and extended heating time (a dinas kiln was used for that purpose). 3 The open porosity reduction effect tends to increase in specimens molded at higher pressure p. So, at p = 20 MPa, the open porosity spread is 3.5%; as the pressure is raised to between 75 and 100 MPa, it reaches 6 -7%.…”

“…Based on sedimentation analysis data, the specific surface of bauxite HCBS particles was shown to be S sp = 1.62 m 2 /g, and GÉF particles, S sp = 0.16 m 2 /g. A significant effect of the decreased porosity in HCBSbased high-alumina ceramic castables and a mullitic chamotte filler (at an optimally taken proportion of refractory clay and organomineral thinner) has been reported in [3]. To implement this effect in press powders, plasticizers (LT-1-grade refractory clay, about 40% Al 2 O 3 + TiO 2 ) and thinners (0.1% liquid glass or Castament, an organic deflocculant based on polycarboxylate esters) were used [4].…”

Efficiency of wet mechanoactivation of granite using different milling units

“…By earlier studies [1][2][3] the principal opportunity of NB production was reported using SiO2-and SiO2-Al2O3 bearing rocks of different genesis such as followings: quartz sand, sandstone, quartzite, perlite, zeolitized tuff.…”

High-alumina masses based on plasticized bauxite suspensions

“…Затем [16,17] были рассмотрены структурно-механические и реологические свойства смешанных систем на основе разных суспензий и глин, а также некоторые характеристики материалов на их основе. При добавлении огнеупорного заполнителя эти смеси могут применяться в качестве связки для пластичных огнеупорных масс, что подтверждается результатами использования пластифицированных ИКВ на основе высокоглиноземистого шамота [18,19]. В этой связи цель настоящей работы -разработка и исследование свойств пластичных огнеупорных масс на основе модифицированных ИКВ боксита.…”