These criteria are difficult to meet. Keratab Dump Mix was eventually perfected to display all of these properties. It turned out to be ideal for certain applications in furnace roofs. The biggest application is in feed chutes for submerged arc furnaces. These are subjected to extreme abrasion, mechanical abuse during installation and thermal shock. They are water cooled, and therefore exposed to extreme thermal gradients. Maintaining high strength over the whole temperature range is therefore critical. Vibration casting through the spiral of water pipes is impossible, and only a self-flowing, self-deairing castable can be used. The same applies to water-cooled roof sections. Electrode seals are another major application. The formers are a bit tricky, but have been made. Another application is delta sections. The castings have to be flat on top.
Dump mixes can be used with stainless steel fibres. The piece protruding from the shell of feed chutes and the first 50mm inside the shell is normally reinforced with 3% stainless steel fibres.
Reducing Dump Mix must be discharged directly from the mixer into the mould, and mixes must be made in rapid succession. Dump mixes are fast setting and highly exothermic. Where circumstances require it, slow setting Dump Mixes can be made.
Dump mixes were developed in response to an enquiry for a material to repair the impact areas of ladle floors. They had to be capable of being installed fairly hot, must be self-levelling and self de-airing and develop strength immediately and retain it to high temperatures. They also need good thermal shock resistance.
Description; A dumping mix is a self-levelling castable for discharge directly into the installation. It flows rapidly without any assistance,and de-airs itself. It is based on tabular alumina. It can handle severe thermal shock.
Cold Crushing Strength:
Mixing; Mix with +9% water. It flows for about 20 minutes. It should be discharged directly into the mould, since its flow properties do not allow handling in buckets or wheelbarrows. No vibration is needed. Heat of hydration is high, but delayed. (About 7 hours) Drying should be slow and careful, as the material has very low permeability and a very fine pore size distribution.Packaging; 25kg plastic bags.Shelf life; 12 months in unpunctured bags.Test results are based on single cubes.
Description; A dumping mix is a self-levelling castable for discharge directly into the installation. It flows rapidly without any assistance,and de-airs itself. It has very high mechanical strength at all temperatures. It can handle severe thermal shock.
Density: 2,79g/cm³ = Use 2,79 tons per m³.
Cold Crushing Strength:
Mixing; Mix with +6% water. Can be mixed in 2 minutes in an ordinary concrete mixer. It flows for about 20 minutes. It should be discharged directly into the mould, since its flow properties do not allow handling in buckets or wheelbarrows. No vibration is needed. Heat of hydration is high, but delayed. (About 7 hours) Drying should be slow and careful, as the material has very low permeability and a very fine pore size distribution.
Packaging; 25kg plastic bags.
Shelf life; 12 months in unpunctured bags.
Test results are based on single cubes.
Dump mixes rely on their vast specific surface area for their bond strength and rheological properties. This also results in several other significant properties; Good thermal shock resistance Very strong capillary suction. High surface tension, which makes them stick to buckets rather than falling out. They are not sucked dry by conventional materials if cast against them. Hydraulic bonded materials cast up against them are sucked dry. Therefore Dump mixes cannot be used to repair dump mixes. Interrupted castings will not bond at the joints.
A viscous phosphate bonded mix, Phospatch can be used to repair dump mixes. It is very fast setting and will bond to almost any surface. It can even bond to a surface vertically above it. It has been used to repair the inside of arc furnace roofs by pouring through electrode holes into shuttering under the roof.