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Slag can be used for a few things:-

Basic slag was ground and used to top-dress pastures to replenish lost minerals in high-rainfall areas.

It can be remelted and made into 'mineral wool' for insulation.

It can be ground and added to the raw materials when making cement; a lot of the slag from the Dunkerque steel works is used for this.

It can be used as aggregate for road-building etc; a lot (about 2 million tonnes)of the remaining slag from Llanwern was used to 'make' ground on Cardiff Docklands

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Ground granulated blast furnace slag (GGBS) is an important constituent part of blended cement and concrete. Sadly with the demise of the SSI blast furnaces at Lackenby, the U.K. Will again soon be facing a shortage.

 

I'm not aware of any rail flows of this to / from cement works though so assume it goes by road.

Not in the UK, but in France, Europorte handle slag from Dunkerque. Some goes by rail to Le Havre, the rest by ship to Bordeaux, then rail.
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There are a number of former steelworks slag tips that can be reclaimed, about 15 years ago the one at Port Clarence was dug up by Fearndale Aggregates and about 5 years ago a one at Cargo Fleet was dug up!

 

There is also the large slag bank at Workington that could be reclaimed?

 

The ending of Coal burning at power stations means that Pulverised Fuel Ash will no longer be readily available for construction and as a cement additive!

 

Mark Saunders

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Huge slag banks here too.

 

At one time, most of it was tipped from up to 6 slag ladles at once. Not for nothing was Scunthorpe's town motto:

 

"Refulget Labores Nostros Coelum", or "The skies reflect our labours".

When they tipped, and remember that we once had THREE steelworks here, the sky glowed red for ten minutes.

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Slightly off topic. When I worked in the IT department of the country's 2nd largest (at that time) cement manufacturers a lot of blast furnace slag was used with cement clinker in the manufacture of cement products. I was in a meeting once with some external software suppliers when a colleague put his head around the door and asked another colleague in all innocence "Has that slag arrived from Glasgow yet?". You can imagine the look on our visitors' faces!

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The approach embankments carrying the M6 over the Manchester Ship Canal are largely made of steelworks slag. Handily, the Lancashire Steel Corporations slag tip had been built up on the north bank of the Ship Canal just a mile or so to the east. Some of it is still there forty years after steelmaking ceased.

 

 

It's specifically steel making slag which is used as a fertiliser as it is high in phosphorous, sold as Basic Slag Fertiliser (basic in the chemical sense).

 

Blast furnace slag, produced in considerably larger amounts, is what is used as an aggregate, in cement making, aerated to make light building blocks and blown to make slag wool.

 

Is it still used as a railway ballast?

 

This is Clugstons Appleby Frodingham operation in the 60's/70's.

 

 

post-6861-0-65237100-1452972454.jpeg

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Those hoppers look a tad overloaded!  Or is slag lighter than I'm imagining?

 

Some very interesting answers here, its not something I'd ever really considered, but interesting to read.  Thanks to those who've posted.

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Those hoppers look a tad overloaded!  Or is slag lighter than I'm imagining?

 

Some very interesting answers here, its not something I'd ever really considered, but interesting to read.  Thanks to those who've posted.

 

Slag is what is termed Lightweight Aggregagate, and when used as Ballast was known as Aero ballast by Railwaymen, hence the size of the Procor built for Brag Lightweight Aggregates!

 

Mark Saunders

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As Mark says, some of it develops an aero like texture, i.e. it contains little air holes. It depends on how it is cooled, it can be air cooled or water sprayed and that can be controlled so that the gasses liberated both crack the slag and form air pockets. When ground up it has a rough surface texture. This makes it relatively light and the rough surfaces 'lock' together so it binds well as a ballast.

 

Another use for it is as a medium in sewage works filter beds. The bed is filled with slag which chemically is very stable and, because of it's rough and bubbly texture, it allows space for the foul water to percolate down. The large surface area supports a very large colony of bacteria which essentially digest the muck and the water filtering out of the bottom is clean.

 

post-6861-0-73780900-1453031480.png

 

The UK was producing about 3 million tons per year of blast furnace slag, the closure at Redcar will have cut that to about 2 million and 75% of it is used in cement making.

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Those hoppers will have been filled with what was called "foamed slag", since it had bubbles in it like foam.

 

As for ground slag, the two things you didn't want blowing into your eyes on the works were that stuff and sinter.

 

As an aside, I remember watching a rake of half a dozen loaded slag ladles making their way over an internal road crossing from Appleby-Frodingham blast furnaces to the slag banks, when one suddenly sort of burped, and shot about half a hundred-weight of molten slag skywards.

 

The fitter I was with was unmoved, he reckoned it was a regular, and we shouldn't worry unless the whole lot landed on us. We were always taught to stand still for molten metal and slag ejections, and that if we did, chances are it would bounce off. if we were backing away, it would stick.

Dunno how much truth is in that?

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Slag sticks, molten metal tends to splash off, in modest quantities of course. At the Irlam soaking pits an ingot would occasionally slip from the grasp of the drawing crane and drop back into the pit, the bottom of which contained a pool of liquid slag. The pit walls prevented lateral splashing but a fountain of the stuff shot upwards, dropping down in the near vicinity. If you saw an ingot slip, you legged it.

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