Refractory cement is the hydraulic binder used to make castables and refractory mortars, not a jointing material in its own right. It is a calcium aluminate cement, made by fusing or sintering limestone with bauxite, and it sets by hydration rather than by drying. Its alumina content, typically...
Refractory cement is the hydraulic binder used to make castables and refractory mortars, not a jointing material in its own right. It is a calcium aluminate cement, made by fusing or sintering limestone with bauxite, and it sets by hydration rather than by drying. Its alumina content, typically from about 50% up to 80%, sets how refractory the castable or mortar made from it will be.
XZK Group supplies refractory cement as part of its castable and mortar systems and as a stand-alone binder for customers who mix their own. It should not be confused with Portland cement, which has a far lower refractoriness.
Calcium aluminate cement is produced from limestone and bauxite, either fused in an electric furnace or sintered in a rotary kiln, then ground fine. Its main phases, calcium monoaluminate, calcium dialuminate and C12A7, hydrate when mixed with water and give the castable its green strength before firing. The higher the alumina content, the more of the refractory calcium dialuminate phase and the fewer low-melting phases, so a CA-70 or CA-80 cement is used where the lining must reach a higher service temperature.
The cement is also the source of the lime that limits a castable's refractoriness. Every percent of cement brings CaO into the body, and CaO forms low-melting phases with silica and alumina at high temperature. This is why low-cement and ultra-low-cement castables exist: by cutting cement content to 5–8% or 2–4% and replacing some of it with silica fume and reactive alumina, the same refractoriness is reached with less lime, at the cost of tighter water control and a slower heat-up. Cement level also drives water demand, and more water means more porosity after drying.
Handling is straightforward but strict. The cement is stored dry and used within its shelf life, because it takes up moisture from the air and loses strength. The water addition is measured, not judged, and the heat-up schedule is written to suit the cement level, since the hydrated phases dehydrate over a range of temperatures and release water as they do. Selecting a cement is therefore a question of matching its alumina content and setting behaviour to the castable or mortar that will be made from it.
| Item/Grade | A600 | A700 | A900 | |
| Chemical Composition | ω (SiO2) ≤/% | 7.8 | 7.5 | 5.5 |
| ω (Al2O3) ≥/% | 50.0 | 51.0 | 53.5 | |
| ω (Fe2O3) ≤/% | 2.5 | 2.5 | 2.5 | |
| ω (R2O) ≤/% | 0.4 | 0.4 | 0.4 | |
| ω (S) ≤/% | 0.1 | 0.1 | 0.1 | |
| ω (Cl) ≤/% | 0.1 | 0.1 | 0.1 | |
| 325M ≤/% | 15 | 12 | 8 | |
| Specific Surface Areas ≥/ (㎡/kg) | 300 | 320 | 350 | |
| Setting Time | Initial Setting Time ≥/ (min) | 45 | 60 | 90 |
| Final Setting Time ≤/ (min) | 6 | 6 | 6 | |
| Flexural Strength ≥/Mpa | 6h | / | / | / |
| 24h | 6.0 | 6.5 | 8.0 | |
| 72h | 7.0 | 7.5 | 10.0 | |
| Compressive Strength ≥/Mpa | 6h | / | / | / |
| 24h | 45 | 55 | 72 | |
| 72h | 55 | 65 | 82 | |
| Item/Grade | CA70 | CA70W | CA70S | CA71 | ||
| Chemical Composition | ω (SiO2) ≤/% | 0.5 | 0.5 | 0.5 | 0.5 | |
| ω (Al2O3) ≥/% | 68.5-70.5 | 68.5-70.5 | 68.5-70.5 | 69.5-71.5 | ||
| ω (Fe2O3) ≤/% | 0.2 | 0.2 | 0.2 | 0.2 | ||
| ω (CaO)/% | 28.5-30.5 | 28.5-30.5 | 28.5-30.5 | 27.5-29.5 | ||
| ω (MgO) ≤/% | 0.4 | 0.4 | 0.4 | 0.4 | ||
| ω (R2O) ≤/% | 0.4 | 0.4 | 0.4 | 0.4 | ||
| Fineness | d50/μm | 11-4 | 8-11 | 6-9 | 10-13 | |
| -45μm ≤/% | 8.0 | 5.0 | 5.0 | 8.0 | ||
| Setting Time | Initial Setting Time (min) | 120-180 | 30-90 | 180-240 | 150-210 | |
| Final Setting Time (min) | 150-240 | 90-180 | 240-330 | 210-300 | ||
| Strength (ISO) | Flexural Strength/Mpa | 24h | 7.5-10.0 | 8.0-10.5 | 8.0-10.5 | 8.5-11.0 |
| 72h | 10.0-12.0 | 10.5-12.5 | 10.5-12.5 | 11.0-12.5 | ||
| Compressive Strength/Mpa | 24h | 40-50 | 45-55 | 45-55 | 50-60 | |
| 72h | 45-55 | 50-60 | 50-60 | 55-65 | ||
| Item/Grade | CA80 | CA80S | ||
| Chemical Composition | ω (SiO2) ≤/% | 0.5 | 0.5 | |
| ω (Al2O3) ≥/% | 78.0-81.0 | 78.0-81.0 | ||
| ω (Fe2O3) ≤/% | 0.2 | 0.2 | ||
| ω (CaO)/% | 17.5-20.5 | 17.5-20.5 | ||
| ω (MgO) ≤/% | 0.4 | 0.4 | ||
| ω (R2O) ≤/% | 0.4 | 0.4 | ||
| Fineness | d50/μm | 5-8 | 5-8 | |
| -45μm ≤/% | 5.0 | 5.0 | ||
| Setting Time | Initial Setting Time (min) | 30-90 | 90-150 | |
| Final Setting Time (min) | 90-180 | 270-360 | ||
| Strength (ISO) | Flexural Strength/Mpa | 24h | 5.0-7.5 | 5.0-7.5 |
| 72h | 6.0-8.5 | 6.0-8.5 | ||
| Compressive strength/Mpa | 24h | 30-40 | 30-40 | |
| 72h | 40-50 | 40-50 | ||
Grades are commonly described by their alumina content, for example CA-50, CA-70 and CA-80. A lower-alumina cement sets the refractoriness of a general-purpose castable or mortar at the lower end of the range; a CA-70 or CA-80 cement is chosen when the castable must reach the higher service temperatures or when the cement level is being reduced to make a low-cement body. The right choice is the lowest-alumina cement that still meets the duty, because higher alumina raises cost.
The cement is normally supplied as part of a complete castable or mortar system rather than on its own. Its job in the lining is described under high alumina castable and refractory mortar, and the matching of mortar to brick is set out in the ZKM series. The full monolithic refractory range covers the castables and mortars built on it.
Refractory cement is used as the binder in the cast and bonded parts of a glass furnace lining:
Manufacturing is controlled from raw material through to finished brick. Four automatic batching lines feed 20 CNC presses ranging from 630 to 2000 tonnes, so density is set by press force rather than operator judgement, and firing runs through four 108-metre fully automatic tunnel kilns and five ultra-high-temperature shuttle kilns for a uniform soak.
Every batch is tested for bulk density, apparent porosity, cold crushing strength and refractoriness under load, and ships with a certificate of analysis. XZK Group holds ISO 9001, ISO 14001, ISO 45001 and ISO 50001 certification and operates the Henan Provincial Engineering Technology Research Center for Sintered Refractories for Glass Furnaces.
Refractory cement is supplied alongside high alumina castable, insulating castable, silicon carbide castable, lightweight mullite castable and refractory mortar. Browse all refractory products or the monolithic range.
Al₂O₃:46%-60%;
Fe₂O₃: 0.7%-1.0%;
Operating Temp:1300-1500℃;
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