The composition of phosphate refractory castable is similar to that of general refractory castable. Aluminum phosphate, phosphoric acid, and neutral and acidic aggregates only react slowly at room temperature. In order to give the castables hardening properties at room temperature, a hardener must be used. Hardeners include active aluminum hydroxide, talc, ammonium fluoride, magnesium oxide, alkaline aluminum chloride, pure calcium aluminate cement, etc. Magnesium oxide is a commonly used hardener with a good hardening effect, but the magnesium phosphate produced by the reaction has poor heat resistance, resulting in a decrease in thermal strength. When magnesium oxide is used as a hardener, the hardening time varies significantly with different temperatures.

The hardening mechanism of phosphoric acid refractory castables and the chemical changes during heating have been analyzed in previous articles. According to the conclusions of the analysis, the preparation of phosphoric acid refractory castables uses clinker or bauxite clinker as refractory aggregate and Powder, the dosage is 65~74% and 24~35% respectively. The commonly used mix ratios in actual production are shown in Table 1. The refractory aggregate is a solid material with a particle size of less than 15mm, and the particle gradation is determined to be 15~5mm50%, 5~2.5mm24%, and less than 2.5mm26%. The fineness of refractory powder is less than 0.09mm and more than 80%. The coagulant is 525# high alumina cement, the amount of which depends on the construction conditions and the strength requirements at room temperature. The general dosage is about 2%. When the ambient temperature is low, the dosage should be appropriately increased. When the strength at room temperature is not required, no or less high alumina cement can be added.