As we all know, the self-flowing refractory castable is a castable refractory material that can flow and degas without vibration. Its characteristic is that under the condition of not reducing or not significantly reducing the performance of the castable, it can be cast into various shapes of construction bodies without vibration by adding water appropriately. So, why does the self-flowing castable have such fluidity? Why self-retained castables are suitable for construction in parts that are not easy to vibrate?
Why is Self-Flowing Castable Fluid?
Self-flowing amorphous refractory castable is a kind of refractory castable with fluidity, filling, and stability, which can form dense lining by self-flowing.
The so-called fluidity is to rely on the self-weight of the castable to overcome the resistance and realize the flow. Fillability means that the castable can pass through the gap without plug flow. Stability means that the castable does not segregate or bleed. In addition, self-flowing castables should also have good after-burning properties. In general, the self-flow rate of the self-flowing material is controlled between 50% and 100%. If the self-flow value is too small, the fluidity of the material is poor, and the castable cannot fill the model during construction, making it difficult to form a dense lining. If the self-flow value is too large, the material may segregate during construction.
self-flowing realization. The fluidity of the self-flowing material depends on the particle size composition and liquid phase properties, that is, the friction between the aggregates, as well as the viscosity and yield stress of the slurry. Once the gravity-induced shear stress exceeds the yield stress, the castable will flow. Self-flowing materials require medium to low viscosity. If the viscosity is too high, the slurry cannot flow. If the viscosity is too small, segregation may occur again.
Why is Self-Flowing Castable Suitable for Construction in Parts that are Not Easy to Vibrate?
In order to obtain good fluidity, the powder content of the self-flowing castable is increased, and a large amount of fine powder and additives are used. Thus, the cost is significantly increased. On the other hand, self-flowing materials still cannot completely solve the problems of large water demand, high porosity, low bulk density and strength, and strong sintering ability. The performance comparison of high-alumina self-flowing castables and similar low-cement castables was found. The self-flowing castable has a large amount of water, a small bulk density, and a large apparent porosity. Self-flowing castables have low strength after treatment at 105°C and 1400°C, but high strength at 1600°C. Self-flowing castables have good fluidity and can flow in spaces with complex shapes or narrow dimensions, and can be molded by self-weight to obtain dense integral linings. Therefore, self-flowing castables are suitable for special parts where construction is inconvenient or where it is difficult to obtain dense linings by other molding methods.
Comparison of Self-Flowing Monolithic Refractory Castable and Low Cement Castable
In the castable, firstly the powder is mixed with water to become a clean slurry; then the fine aggregate is suspended in the clean slurry to become a mortar; finally, the coarse aggregate is suspended in the mortar to become a castable.
In low-cement castables, the proportion of aggregate is relatively large, and there are many direct contact points between aggregates, which hinder the flow of materials. Thus, vibration is required to make the castable flow. On the contrary, self-flowing castables contain less aggregate and more matrix. In this way, there is little direct contact between the aggregate particles, and the fine powder and water form a continuous fluid. Materials can flow under the action of gravity.
In order to have a certain resistance to segregation, there must be enough fine aggregate in the self-flowing castable. In this way, it helps to increase the density and viscosity of the mortar. As the density of the mortar increases, the buoyancy of the mortar also increases, which offsets part of the gravity of the coarse aggregate and is beneficial to delay the sinking of the coarse aggregate. The increased viscosity of the mortar makes it easier for the mortar to flow with the coarse aggregate and also helps reduce segregation.
In order to maintain good fluidity, self-flowing castables are mixed with more fine powder and fine powder. In this way, after curing, drying and calcination, the self-flowing material is prone to greater shrinkage or “porcelainization”. Therefore, self-flowing castables need to add expansive substances such as “three stones” to offset the shrinkage of firing. It is also necessary to control the proportion of micro powder, control the composition and formation process of the bonding phase, and suppress over-densification after firing. If controlled properly, self-flowing refractory castables can obtain physical and chemical properties close to low-cement castables.
Rongsheng Self-Flowing Unshaped Refractory Castable Manufacturer
Rongsheng Refractory Material Manufacturer is a manufacturer of refractory lining materials with rich experience in production, sales, and after-sales. We not only have advanced refractory brick production lines, but also our newly established environmentally friendly fully automatic monolithic refractory production lines are also outstanding. The annual output is 80,000 tons. Our refractory products have been sold to more than 70 countries and regions all over the world. For example, South Africa, Philippines, Chile, Malaysia, Indonesia, Vietnam, Kuwait, Turkey, Zambia, Peru, Mexico, Qatar, Egypt, Russia, Kazakhstan, etc. If you need to buy refractory products for high-temperature kilns, please contact us and get samples for free. If you encounter a difficult problem with your refractory lining, we can also provide a solution for free. In a word, Rongsheng welcomes you and looks forward to cooperating with you.