Refractory mortar is the fine-grained material that bonds refractory brick into a continuous, gas-tight lining. It is supplied as a dry powder and mixed with water at the bricklayer's station, and it is used in joints of only 1-3 mm. Its chemistry, expansion and temperature limit must match the...
Refractory mortar is the fine-grained material that bonds refractory brick into a continuous, gas-tight lining. It is supplied as a dry powder and mixed with water at the bricklayer's station, and it is used in joints of only 1–3 mm. Its chemistry, expansion and temperature limit must match the brick it joins, because a mismatched mortar fails before the brick it was meant to protect.
XZK Group supplies mortars across the alumina range, including the ZKM series for clay and high alumina brickwork. This page covers how a refractory mortar is matched to the brick and applied.
Mortar is a thin, fine-grained mix applied between brick faces. It is not a structural material and it does not fill gaps; its function is to hold the brick in a continuous, closed joint and to keep that joint closed as the lining heats and cools. Because the joint is thin, its volume in the lining is small, and the properties that matter are bond strength and temperature compatibility rather than density or refractoriness on their own. Selection is therefore a question of matching the mortar to the brick.
Different brick families call for different mortars, and the match is chemical as well as thermal. Fireclay and low-porosity clay bricks are laid with a clay-based mortar of the same alumina class. High alumina, mullite and sillimanite bricks call for a high-alumina or mullite mortar that expands and softens at a rate close to the brick. Silica bricks are laid with a silica mortar, because a clay mortar would introduce alumina and lower the melting point of the joint. In every case the mortar must be able to reach the service temperature of the brick it bonds.
Application decides as much as the formulation. The joint should be 1–3 mm, the mortar grain size should suit the joint width, and the water addition should be the minimum that gives a workable consistency, since excess water shrinks out and leaves a porous joint. Each brick should be fully bedded to avoid voids, and the bond is largely heat-setting: strength develops as the lining comes up to temperature and the raw materials react to form a ceramic bond. The dry-out schedule must suit both the mortar and the brick.
| Index | Corundum Mortar | Corundum - Mullite Mortar | Zircon - Mullite y Mortar | Zirconite Mortar | Sillimanite Mortar | Mullite Mortar | ZKM -1 | ZKM -2 |
| Al₂O₃ /% | ≥ 95 | ≥ 80 | ≥ 60 | ≥ 60 | ≥ 60 | ≥ 70 | 46 | 60 |
| Fe₂O₃ /% | ≤ 0.5 | ≤ 0.5 | ≤ 0.5 | ≤ 0.5 | ≤ 0.7 | ≤ 0.5 | 1.0 | 0.7 |
| ZrO₂ /% | / | / | ≥ 20 | ≥ 63 | / | / | / | / |
| Refractoriness /℃ | 1790 | 1790 | 1790 | 1790 | 1750 | 1790 | 1300 | 1500 |
| Maximum Particle Size /mm | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 |
| Moisture /% | 20 - 24 | 20 - 25 | 20 - 23 | 19 - 22 | 19 - 23 | 20 - 25 | / | / |
Test methods follow GB/T and ISO practice; ASTM equivalents and full certificates of analysis are issued with every shipment.
Mortar grades are chosen by the brick they bond. A clay mortar is used with fireclay and low-porosity clay bricks; a high-alumina mortar with high alumina bricks; and a mullite mortar with mullite and sillimanite bricks. Where the alumina content of the mortar differs sharply from the brick, the two expand and soften differently and the joint opens under cycling. The temperature limit of the mortar should always be at least that of the brick.
The ZKM series is a ready-mixed example of this matching: ZKM1 for clay brickwork up to 1300°C and ZKM2 for high alumina and mullite brickwork up to 1500°C, with flexural bond strengths of 3.8 and 4.5 MPa. The binder behind both is described under refractory cement, and cast linings that replace brickwork use high alumina castable instead.
Refractory mortar is indispensable in the construction, maintenance, and repair of high-temperature industrial furnaces and equipment. Its main applications include:
Refractory mortar is used in the brickwork of every part of a glass furnace:
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 mortar is supplied with the brick it bonds, including high alumina bricks, low porosity fire clay bricks, mullite bricks and zircon bricks. See also ZKM series refractory mortar, refractory cement and all refractory products.
Al₂O₃:46%-60%;
Fe₂O₃: 0.7%-1.0%;
Operating Temp:1300-1500℃;
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