Some ramming products arerendered in wet state

Some examples of plastic refractories are 65-69, 76-80: ü Heat setting super duty fireclay plastic, ü Super duty heat setting plastics with graphite, ü Plastics in the 50 % alumina class, ü Heat setting 60 % alumina class plastics, ü Air setting highalumina plastics in 80 % alumina class, ü Phosphate bonded high alumina plastics with alumina content ranging from 70 % to 90 %, ü Phosphate bonded alumina chrome plastics, ü And silicon carbide based phosphate bonded plastics. c) Ramming mixes Ramming mixes composed essentially of ground refractory aggregates, with a semi-plastic bonding matrix. These refractory materials are like to plastic refractories but are much harder. They need some sort of form to maintenance them when formed. The grain sizes are carefully classified and the final product is usually rendered dry and then mixed with a little content of water just before utilization. Other ramming products arerendered in wet state and are ready for use immediately upon opening. Ramming mixes are placed with pneumatic rammer in layers of 25 mm to 40 mm. Steel making, burner blocks, ports and similar applications used of High purity ramming mixes based on mullite grain. Ramming mixes consist of 80wt. % alumina content have good shrinkage resistance and thermal spalling at high temperatures. Some ramming mixed such as, stabilized high alumina air setting, have good thermal spalling resistance at high temperatures and volume stability up to their temperature limit. Also, phosphate-bonded alumina-chrome ramming mixes typically have very high strength at high temperatures and very good resistance to acid and neutral slags consist of coal ash slags. Alumina-graphite ramming mixes have mixture of high alumina grain and slag inhibitors which give them well slag resistance to acidic and slightly basic slags. In steel making industry, the dry ramming mixes based on high purity MgO and a sintering aid are useful. Magnesite ramming mixes of exceptional purity and stability are used firstly as lining materials forcoreless type induction kilns. Magnesia-Chrome fused 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 grain ramming mixes can create special strength and density 52-60, 64-73. d) Gunning mixes The install method of more monolithic refractories is gunning. The constitution material of gunning mixes are different particles sized of refractory aggregate, a bonding compound, and maycontain plasticizing agent to enhance their stickiness when pneumatically placed onto a kiln surface. These refractory materials are sprayed on application surfaces using a gun device. Usually gunning refractory mixes are supplied dry. In order to application, they are pre-damped in a batch mixer, and then continuously poured into a gundevice. Water is added to the mix at the nozzle to achieve the proper consistency. Typically, Gun mixes are including high alumina, siliceous, fireclay, dead burned magnesite and chrome types. Magnesite and hot gun mixes are not pre-damped and are placed in a batch pressure gun. Gun mixes should provide good coverage in a variety of applications 40-52, 61-68. Some types of gunning mixes are: ü Fireclay gunning mixes of multipurpose hard firedfireclay and standard calcium-aluminate cement compositions. ü Fire clay gunning mixes with high purity calcium-aluminate bonding system. ü Gunning mixes based on vitreous silica. ü High purity alumina mixes which combine high fired alumina aggregate. ü High purity calcium aluminate binder. ü Basic refractory gunning mixes with magnesia content ranging from 60 % to 95 % with or without a phosphate bond. e) Patching refractories These type refractories materials are like to plastic refractories though have a very soft plasticity let them to be casted into place 35-43, 71-76. F) Coating refractories These types of refractories materials are used to maintain refractory linings usually against chemical attack. Coating refractories are usually intended to coat just the working surface of a lining. They tend to be justly thin layers 60-76. g) Mortars Generally, mortars are neither classified as refractory brick nor monolithic refractories. They are very fine refractory materials, 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 which become plastic when mixed with water. These are used to bond the brickwork into solid unit, to provide cushion among the slightly irregular surfaces of the brick, to fill up spaces created by a deformed shell, and to make a wall gastight to prevent penetration of slag into the joints. Mortars should have good water keeping properties and must not foul. In this way, premature penetration of water in the refractory bricks after laying, causing the mortar to dry out, can be avoided. Different types of refractory mortars are consisting of 50-58: Mortars with ceramic bonding (bonding starting at 800 C). Mortars With chemical bonding. Mortars with hydraulic bonding (bonding starting at 20 C). Also, the important properties of the mortars are consisting of: ü Composition and characteristics of the mortar materials, ü Grain size ü Consistency e) Fettling mixes Fettling mixes are also granular refractory materials, with function like to gunning mixes, but are applied by shoveling into the kilns needing patching 43-51. f) Taphole mixes Tap-hole mixes are resin bonded. In these mixes the higher strength which is normally desired for monolithic refractory products, is not that important. Some criteria are necessary for all tap-hole mixes. These criteria are consisting of: correct consistency, setting, and carbonization at the right time, precisely controllable PLC, and above all drilling capability 72-78. 3. Use of Nano technology in refractory industrial: Nano technology is commonly defined by size and consist of the visualization, properties, production and manipulation of structures which are lower than 10 -9 m 89- 90.special mechanical, optical, electrical, and magnetic characterizes which can differ substantially from the properties of the same materials at larger dimensions can show for the structures that the dimensions of which range from 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 100 nm down to approx. 0.1 nm. Hence, Nano technology is a very active research area and has applications in a number of fields. Today, remarkable attention has been paid to the use of nano-technology in the progress of refractories goods 91- 93. Nano technology has been entered to refractories. It has been expressed that the usefulness of the refractories was acutely improved for the well distribution of nano sized grain in the matrix and reaction activity. Some resech have been done by different researchers to enhance characterizes of refractories (bricks and shapeless) by using Nano particles. The use of nano technology is aimed at achieving the special characterizes of brick and shapeless refractories 90-95: these properties consist of: ? High compressive strength, ? Relatively high tensile strength and ductility, ? More efficient cement hydration ? Enhanced aggregate paste bond strength, ? High corrosion resistance ? Control of cracks and self-healing ? High resistance to thermal shock and ? High Abrasion resistance ? High chemical corrosion résistance 4. Use of Nano technology in shapeless refractories: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Based on the above, in this section, the results of carried out activities by different researchers using nano technology in shapeless refractories have been expressed (Table 1). It is showed that the use of Nano technology has been heavily used by researchers in recently. Summary: Recently, Nano technology is used for production to refractory good s and it is a necessary tool included in many activities. Most of researches has been working on the adding of different types of additives in ceramic goods, and some of them have concentrated their investigations on the use of Nano additives, because of the mentioned advantageous of adding nano-particles to the ceramic goods. In this review article, all researches which done to enhance the performance of monolithic refractories is reported and it was concluded that the application of nano-additives has the best results. Results show that recently, researchers have been using nanotechnology and have reached interesting results