Refractory Mortar for Fireclay, High-Alumina, Corundum, Silica, Magnesia, Carbon and SiC Brickwork

Refractory mortar is the cheapest line on a lining bill and the most frequent cause of a lining that fails at the joints rather than in the brick. It has one job: bond the courses, seal the joint against hot gas and slag, and stay intact while the furnace heats and cools. When it does that badly, the working lining is finished long before the brick is worn.

There is no such thing as a general-purpose refractory mortar, because the joint has to match the brick it joins. XZK supplies every mortar family used in iron- and steelmaking — fireclay, high-alumina, andalusite, corundum, silica, magnesia, magnesia–spinel, carbon, silicon carbide and corundum–silicon carbide — in heat-setting, air-setting and phosphate-bonded systems. Send us the brick schedule and we grade the mortar to it.

Why Joints Fail Before the Brick Does

Three failure modes account for most mortar problems in service, and all three are specification or installation issues rather than a question of material cost.

• Chemistry mismatched to the brick. A high-alumina mortar against silica brick, or an aluminosilicate mortar against basic brick, reacts at temperature and either fluxes the brick face or loses its own bond. Chemistry compatibility is not negotiable, and it is the first thing we confirm.
• Joint thickness outside the design range. Mortar is a bonding layer, not a levelling compound. Joints much beyond 2–3 mm become a porous, weakly bonded layer with poor slag resistance; joints below about 1 mm cannot seal reliably. Both end the same way — a hot spot behind the brick face.
• Excess mixing water. Water beyond what the grade requires raises porosity and drying shrinkage, which is the opposite of what a joint needs. It is the single most common installation error and it happens on every continent.

Three Bond Systems, Three Behaviours

Bond type decides when the joint develops strength, and therefore how the lining must be handled before it goes into service.

• Heat-setting (ceramic bond). Strength develops when the furnace is fired. Once sintered, the joint is strong and slag-resistant, but the green bond is weak — the lining depends on good brick fit and correct geometry during construction. This is the traditional system for fireclay and high-alumina brickwork.
• Air-setting (phosphate or silicate bond). Gains handling strength at ambient temperature through a chemical bond. The practical advantage is that a lining can be built weeks ahead of commissioning without the courses shifting, and courses that brick geometry cannot hold are secured by the mortar itself.
• Hydraulic (calcium aluminate). Sets by hydration, giving predictable early strength independent of furnace heat. Used where the joint must develop strength quickly, and in castables and gunning mixes as much as in brickwork.

Where a lining will be fired promptly and brick fit is good, a heat-setting grade gives the better in-service result. Where the schedule is uncertain, air-setting is the difference between a sound lining and a loose one. We grade to the schedule you actually have, not the ideal one.

What We Ask Before Recommending a Grade

• The brick being laid — chemistry, alumina or magnesia content, and whether it is dense or insulating.
• Service conditions — maximum temperature, slag chemistry and basicity, atmosphere (oxidising or reducing) and thermal cycling pattern.
• The construction schedule — whether the lining is commissioned immediately or stands before firing, which decides heat-setting versus air-setting.
• Design joint thickness — grain size and consistency are graded to it.

A drawing or a brick schedule answers most of this. Where it does not, we will ask rather than assume, because the cost of asking is a day and the cost of assuming is a reline.

Where Mortar Is Used in a Steel Plant

• Hot blast stoves — low-creep andalusite, sillimanite and high-alumina mortar for shaft, dome and burner brickwork, where creep resistance matters as much as raw strength.
• Torpedo ladles and casthouse runners — high-alumina and corundum–SiC mortars where joints must survive thermal cycling and iron & slag erosion.
• Blast furnace hearth and stack — carbon mortar for carbon brickwork and silicon-carbide mortar for stack and bosh grades, matched to the reducing atmosphere and alkali load.
• Ladles and converters — magnesia and magnesia–spinel mortar for basic brickwork in slag-line, metal-zone and transition courses.
• Tundishes and ladle bottoms — corundum and corundum–spinel mortars behind the working face, and wherever carbon pickup has to be avoided.
• Furnace and stove crowns — silica mortar where silica brick is used, because aluminosilicate mortar is incompatible with silica brick at temperature.

Joint Thickness and Mixing Guidance

Every grade ships with written guidance covering the mixing water for that specific grade, the joint thickness range, trowel or dipping method, and the brick sequence it assumes. Two points we will state plainly, because they are where linings most often go wrong: use only the water the grade requires, and never re-temper mortar that has begun to set. Adding water to a stiffened mix changes both the bond and the shrinkage, and the joint will fail even though the material supplied was correct.

Supply

Minimum order 5 metric tons, shipped in 7–14 days. Grades are produced to order, so confirm chemistry and bond type when ordering. Every batch is tested for chemistry, grain size and bonding strength after firing at the service temperature, with a Certificate of Analysis on every shipment and third-party inspection (SGS / BV / TüV) available on request. If a lining has failed at the joints, send us the mortar, the joint thickness and the mixing practice together — the cause is usually one specific thing rather than a change of supplier.