Making bricks from slag

22/10/1898 – St Andrews Citizens – The utilisation of slag – A German brick making patent. An official German report, just published, contains particulars of a new process of making building bricks from furnace slag. Hitherto many attempts have been made to utilise the slag, but all have been more or less a failure, and the result has been that ironmasters have had to procure ground in the neighbourhood of their works, often at enormous cost, on which to store the useless material. In Middlesbrough brick-making from slag has been going on for many years, the brick being principally used for street-paving purposes, its permeability rendering it almost useless for building. The new process is said to overcome this difficulty. The slag is first broken up and then passed through water. This causes disintegration, the silica being separated in a soluble condition, and as such, hardens in the air and combines readily with caustic lime. The slag grains are next compressed with the silica, and by the addition of about 10 per cent, of burned or slaked lime, the subsequent hardening is facilitated, six or eight days being sufficient. The quality of the brick thus produced is said to be very much superior to the ordinary burned clay brick. The strength is seven times greater, and it has a much higher resistance to heat. Although it is five times as permeable as the ordinary burned brick, it does not absorb water so readily. In a test burned brick filled its pores with water in twelve hours, while a slag brick required 190 hours. The best kind of slag for the new brick is that produced in the making of forge, Thomas and Bessemer pig-iron, and of those kinds of slag, there are thousands of tons in the neighbourhood of all the Scottish ironworks, which can be had at present practically for the taking away. If the process is successful and there is good demand for the bricks, ironmasters might turn their attention to the new industry, but it would have practically no effect on the price of pig-iron.

Below – 19/11/1898 – The Scotsman – Eugene Langen. Friedrichs Wilhem mine, Siegberg, Westphalia.






1921 – 1941 – Numerous references of bricks being manufactured from slag by the Slag Brickmaking Plant, Shotts Ironworks

1940 – 1961 – Numerous references of bricks being manufactured from slag by David Colville and Sons, iron and steel makers, Motherwell, North Lanarkshire in partnership with Messrs. Clugston Cawood. Ltd.

28/10/1940 – The Scotsman – Brickmaking from slag. Alongside suggestions which have been made that blast furnace slag, should be used in the manufacture of cement, proposals have been put forward to utilise slag for brick-making. As with blast furnace slag cement, the production of slag bricks is an old story in Scotland. The Shotts Iron Co ., Ltd ., has long turned out blast furnace slag bricks, though it does not engage in cement manufacture. The basis is granulated slag, the gravel-like material produced by running the molten slag from the blast furnace into a stream of water. In brick-making, the granulated slag is pressed in steam-heated moulds, without the kiln burning, which is a feature of ordinary brick production. After weathering for several months, the bricks are ready for use. The whole process is, of course not quite so simple as all that, as care has to be taken in getting the right quality of slag and recent changes in the types of ores used in the blast furnaces have posed certain problems. Though they have been the butt of many criticisms in past years, the Scottish blast furnace operators have in fact pioneered many forms of by-product utilisation. When they introduced methods of recovering by-products from splint coal-fed blast furnaces in the early seventies of last century, they showed the way for the development of by-product coke ovens. In essence, the full utilisation of by-products depends on local conditions, and especially on the raw materials available. No universal rule can be laid down as to what can and what cannot be recovered. Certain slags may be quite useless for cement or brick-making it all depends on the compound nature of the material; for instance, the proportion of lime, silica, or alumina.


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