How to Select Refractory Binder?
The mechanical strength (structural strength) of refractory products, especially unburned refractory products and unshaped refractory materials, mainly depends on the binder. However, there are many kinds of binders used in refractories, and the bonding mechanism is also different. Therefore, in the actual production and use, the appropriate binder should be selected according to the refractory material, forming or construction methods and service conditions. The selection principles are as follows.
① The properties of the binder must be compatible with the properties of the bonded refractory. Acidic, neutral or weakly alkaline binders can be selected for acidic and neutral refractories. Alkaline refractories can only use neutral or alkaline binders instead of acid binders. If used under reducing conditions, organic binders with high carbon residue can also be selected.
② The selected binder shall be suitable for the forming method or operation performance (construction performance) of the material. Temporary binders (such as lignin sulfonic acid, hydrochloric acid, etc.) are generally used for fired refractory products, while chemical binders (such as aluminum dihydrogen phosphate, sodium silicate, etc.) are generally used for non fired refractory products;
For pouring refractory materials, the binder that can produce condensation and hardening at room temperature shall be selected, such as hydration bonded or chemical bonded (with hardener), or coagulation bonded (with coagulant).
The ramming materials and plastics can be bonded, chemically bonded or ceramic bonded;
For the sprayed refractory, the binder similar to the cast refractory can be selected.
③ The selected binder must be compatible with the high temperature performance of the material. The high temperature structural strength, corrosion resistance and slag permeability of the material shall not be reduced. For high alumina or clay castables, ordinary calcium aluminate cement or bonded clay can be used as binder, while corundum or corundum spinel castables shall use pure calcium aluminate cement or reactive alumina as binder.