Low Cement & Ultra Low Cement Refractory Castable Performance and Characteristics

July 07, 2018

Low cement and ultra low cement castable refractory refer to castable refractory materials with a calcium aluminate cement addition less than 8%. According to American Standard ASTM, CaO in the low cement castable refractory (LLC) is less than 2.5%, generally between 1.0~2.5, and when CaO content less than 1%,it becomes ultra low cement castable(ULCC). Unlike conventional castable refractory, some or most of calcium aluminate cement in the low cement and ultra low cement castable is replaced by the same or approximate superfine powder as the chemical composition. At the same time, an appropriate amount of water reducing agent and a certain amount of retarding coagulant are added.

Since the partial calcium aluminate cement is replaced by ultrafine powder, the refractory castable has the following characteristics:

1. The low content of CaO in castable can reduce the formation of low eutectic phase in the material, thus improving the refractoriness , high temperature strength and slag resistance.

2. The mixing water consumption of the conventional castable refractory is only 1/2 to 1/3 (about 4% to 6%), resulting in low porosity and high bulk density.

3. The cement hydreate formed after curing is less, and there is no decrease in the medium temperature caused by a large number of hydration bonds,but gradually sintering with the increase of heat treatment temperature,and the strength is gradually improved.

Low cemen and ultra low cement castables are made of clay, high alumina, mullite, corundum, carbon and silicon carbide. Its ingredients are: refractory aggregate, refractory powder, proper amount of superfine powder,proper amount and a small amount of calcium aluminate cement( as a retarding agent) and a small amount dispersing agent (high efficiency debonding agent). Generally, multi-stage ingredients are used, which are divided into 5~3mm, 3~1mm, 1~0.2mm, 0.2~0.074mm,0.074~0.044mm, and less than 1 micron.

Compared with the conventional castable refractory, low cement and ultra low cement refractory castable have better physical properties, and the slag penetration resistance and slag corrosion resistance are better. 

Low cement and ultra low cement castable refractory have been applied to industrial furnaces in metallurgy, petrochemical, mechanical manufacturing and building materials and have achieved better use and economic benefits.

Clay and high alumina refractory low cement castable can be used as lining for reheating furnace, soaking furnaces, heat treatment furnace and rotary kiln.

The mullite low cement castables can be used as a lining of various high temperature burners and the lining of the water cooling tube of the reheating furnace.The corundum and chrome low cement refractory castable can be used as lining of some parts of the refining equipment, such as the spray metallurgical spray gun liner, RH and DH vaccum degasser and dip tube liner, the industrial frequency induction furnace lining, high temperature wear-resistant lining of petrochemical catalytic cracking reactor etc. 

The Al2O3-SiC-C low cement castable is used as a lining for the blast furnace tapping, runner, the iron casting through the iron furnace, and the integral spray gun for hot metal pretreatment. A low cement castable refractory of MgO-Al2O3 or Al2O3-MgO.Al2O3 is used for as a lining for ladle and runner.