What types of alkali-resistant castables exist and what are their characteristics?

Alkali-resistant castables can withstand alkaline metal oxides such as K2O and Na2O at both medium and high temperatures, acting like regular calcium aluminate cement but composed of alkali-resistant aggregates, powders, adhesives and additives that resist alkaline metal oxides such as K2O and Na2O. Their composition resembles that of ordinary cement: alkaline-resistant aggregates are mixed in with other components similar to regular cement for optimal results.

Based on specific use environments and conditions, alkali-resistant castables can be divided into light castables and heavy castables based on porosity levels of greater than 45% and less than 45% respectively. Heavy alkali-resistant castables may further be divided into medium temperature alkali-resistant castables and high temperature alkali-resistant castables for further classification purposes.

Lightweight alkali-resistant castables contain alkali-resistant aggregates such as alkali-resistant ceramsite, clay porous clinker waste porcelain high strength expanded perlite as the aggregates. Calcium aluminate cement or water glass serves as their binder. Alkali-resistant materials may also be used as high silicon refractories that react with alkali metal oxides at higher temperatures to form high viscosity liquid phases with protective layers containing 33-55% Al2o3 33-55% SiO225%-45% while traditional alkali resistant castables have cement content between 25%-30% while water content between 20%-25%. Results have indicated that when placed medium viscosity ratio results are best achieved at medium thicknesses.

Temperature of 41&800 only causes the cement strength to decrease by 50%. Therefore, ultrafine powder and suitable dispersants may be added, reducing cement usage to 10%-20% while increasing water usage by 15%-20%; typically for alkali resistant castingables: temperature 110, drying for 16h with bulk density 1.5-1.6gcm3, bulk strength between 3-6MPa and compressive strength between 30-40MPa are the physical characteristics. At 1100 degrees sintering will occur for 3h with linear change rates between 0.3%-0.5% before moving back down; at 350 temperatures, thermal conductivity ranges between 0.44-0.5W&40;m*K). These physical properties should provide insight into what makes low cement lightweight alkali resistant castingables: temperature 110, drying for 16h with bulk density 1.5-1.6gcm3, bulk density 1.51.6gcm3, compressive strength 3-6Mpa and compressive strength 30-40MPa are typical low cement lightweight alkali resistant castables may include: 110 and drying for 16hrs: 1.5-1.6gcm3, bulk density 1.51.6gcm3, bulk density 1.51.6gcm3, bulk density 1.5-1.6gcm3, flexural strength 3-6MPa compressive strength between 40 MPa-45MPa with linear change rate after Sintering (0.3%-0.5% after Sintering), linear change rate after Sintering 3h-6.0MPa and compressive strength 30-40 MPa while linear change rate after Sintering is 40-45MPa linear change rate after Sintering (3h), Sintering 3h and 35 temperature (1100, Sintering 3h bulk density 1.5-1.6 1.4- 1.5gcm3, bulk density 1.5g cm3/Gcm3, bulk density 1.5g cm3/ cm3, compressive strength 40 MPa+ 45 MPa compressive Strength 4045MPa), linear change after Sintering after Sintering after Sintering between linear change after Sintering-0.5%40-45 MPa 4045MPa between 45MPa to 45MPa- 45MPa and 45MPa plus 45MPa =0.45%-56%-40MPa= 45 MPa=144 (3h+ 3h = 1.5 GCM3, then 350 thermal Conductivity of 400 > 1.5 and thermal conductivity between 5 GCM3 bulk density of 1.5 and 45mpa and 45MPa 40 MPa with linear change rates after SIN 45MPa 45 MPa compressive Strength, linear change Rate after sintering=45MPa 4045 MPa +45MPa=45 MPa compressive).55M, 45 MPa), compressive Strength of 45MPa-40 MPa), linear change after -0.5% 45MPa-40MPa.45MPa 40 45 MPa; 40 45 MPa 60 45MPa 4045 MPa and 45MPa 40 45MPa40 MPa Linear change Rate post SIN 45 MPa with linear change after -0.3%- 45MPa 40 45MPa 40 45 MPa compressive Strength 4045 MPa with linear change after -45MPa 41 MPa at 1100) 45MPa 45MPa 40 MPa compressive strength40 MPa, linear change Rate post SIN 40MPa compressive 40 45MPa, 4045 MPa 45MPa) linear Change after 0.5%+45MPa Compressive strength 40 45MPa 4045MPa linear change Rate after 0.45% 50MPa comp 40 45MPa 45MPa.45 MPa 45

Heavy alkali-resistant refractory castables utilize aggregates such as bauxite clinker and clay clinker as an aggregate component, with calcium aluminate cement typically serving as the binder material. Chemical composition typically includes Al2O3 at 35%-60% and SiO2 at 235%-60%. Traditional heavy-alkali refractory castables utilize cement of 20% in conjunction with water 10%-15% while low cement heavy-alkali refractory castables use between 5%-15% cement along with 6.5%-7.5% water content. Calcium Aluminate Cement with silica fume is used as the binder in low cement, heavy alkali-resistant refractory castables with good alkali resistance, producing calcium Aluminate cement with silica fume (40); fumed silica fume 41; this additive enhances medium temperature bonding strength by not only adding additional layers but also strengthening medium temperature bonding strength by increasing medium temperature bonding strength to 1000-1200, drying after burning at 110, as well as having good alkali resistance properties. Physical indicators for a typical low cement heavy-alkali castable include the following parameters: temperature 110; 16h of drying; bulk density 2.20-2.59gcm3; flexural strength 4-8Mpa and compressive strength 40-60MPa. At 1100 degrees, 3hrs sintering increases linear change rate from 0.3%-0.4% and linear change rate from 0.4%0.4% linear shock stability 40; 1100-water cooling more than 20 times; temperature 350; thermal conductivity between 1.22-1.33;

What are the characteristics of alkali-resistant castables?

Alkali-resistant castables rely on reacting with alkali metal oxides at high temperatures to form a high viscosity liquid phase that forms a protective glaze layer to keep alkali metal melts from penetrating and erosion.

Which parts are suitable for different alkali-resistant materials?

Heavy alkali-resistant castables are often utilized in roasting alumina rotary kilns and cement rotary kilns as part of the tail, head, preheater, water outlet and tuyere assemblies, while lightweight alkali-resistant refractory castables serve primarily for top covers, cylinders and thermal insulation lining in their preheaters. Alkali corrosion industrial furnaces in steel, nonferrous metals, glass machinery petrochemical industries or any combination thereof also utilize alkali resistant castables in these roles.