cheapest concrete

[Jimk]

PFA is an example of "a" pozzolan.....others exist...

[FMurtz]

Probably different costs to here in Australia, but what would the cheapest stuff to use for concrete aggregate for non important garden shed floor? In grandfathers day they used to use some sort of ash (fly ash?)or was it crushed slag/

[David]

Most of the UK has sand and gravel quarries fairly close, so ballast (a mixture of sand and gravel) is as cheap as anything else.

Possibly false economy, but then again I think you have more coal fired power stations than we do.

Fly ash is very fine (not like an aggregate). I assume that you need the lumps for strength.

I remember it being packed down beside a concrete gully under a dual carriageway because it was very light and could be compacted to exert very little side pressure on the concrete.

Also at one time proposed for spreading on marine oil spills to clump up the oil.

As far as I know modern power stations grind the coal up very fine to make it burn more efficiently so you probably don't get slag any more.

Cheers

Dave R

[tabbypurr]

Plastic pallets are free here, and don't rot. As for cheapest agg, just ask your suppliers.

NT

[Cynic]

Dave R wrote-

Most of the UK has sand and gravel quarries fairly close, so ballast (a  mixture of sand and gravel) is as cheap as anything else. 

Possibly false economy, but then again I think you have more coal fired  power stations than we do. 

Fly ash is very fine (not like an aggregate). I assume that you need the  lumps for strength. 

I remember it being packed down beside a concrete gully under a dual  carriageway because it was very light and could be compacted to exert very  little side pressure on the concrete. 

Also at one time proposed for spreading on marine oil spills to clump up  the oil. 

As far as I know modern power stations grind the coal up very fine to make  it burn more efficiently so you probably don't get slag any more. 

Cheers 

Very few pulverized fuel (ground coal) fired stations now running in the UK due to being sacrificed on the altar of greentardery. Those that were best for concrete quality pulverized fuel ash or PFA (eggborough, Fiddlers Ferry, West Burton, Ironbridge and Longannet) required at least 3 days under baseload for the combustion to settle down and yield low carbon clean pale ash which could be used as a Pozzolan in the mix. Some of the ash particles in the flame would clump together and fuse then fall to the bottom of the furnace. This was Furnce Bottom Ash or FBA colloquially known as Clinker. Used in Breeze blocks and roads. Adding pozzolan to concrete had many technical advantages. Thousands of tons were included in the Thames barrier and motorway bridges in the South West where alkali silicate reaction in mixes using local aggregate caused failure (concrete cancer).

[Brian Gaff (Sofa)]

A local clay quarry has a housing estate built over it and it was filled by that black klinker slag stuff then concreted over. I note its starting to sink now after 50 years.. Oops. Brian

[FMurtz]

Used them for one shed but a nuisance if not filled with ballast.