I need to make some concrete (approx 4-2-1) and I have a large amount of MOT (crushed limestone I guess). I only need about 0.1 m^3 of concrete. Can I use the MOT as ballast, instead of going to B&Q and grabbing bags of gravel and sand etc ? Thanks, Simon.
you'll still need sand but I expect yes go for it (unless mission critical but that quantity and mix ratio I doubt it will be a prob)
what's going to be doing?
cheers JimK
It is some lumps of concrete to buttress an internal loadbearing wall whose foundation I have to dig down next to in one place for a toilet connection. It will be sitting mostly under the ground. Simon.
ah yes - I remember now!
Yeah go for it - get some sand in there though, maybe 1:1:5? see how it feels on mixing up (there won't be enough fines in the MOT as it digs at least)
Cheers JimK
I would not use it without checking with an expert first. Concrete ballast is graded to leave gaps for the sand and cement to fill, MOT may be graded to not have the voids (MOT type 2 has no voids IIRC, MOT type 3 has 30% voids IIRC).
Umm. Its got two not very nice properties. Its bloody WEAK and it sucks up moisture.
If you just want bulk with a smooth surfcee, add extra waterr, and OK.
IF its go to take serious loads, be bloody careful.
I understand its sometimes used cement stabilised to form road surfaces, where bitumen isnt as available.
NT
Personally, I would get the usual sand and gravel and do it properly.
The proportion of fines in MOT Type 1 is far too high to make a decent concrete. There is no chance of coating all the particles with cement paste.
For that small quantity, if you have a 5mm sieve, I suppose you could sieve away anything less than 5mm and use what remains as ballast, adding some sand. But I have no idea what the results would be.
erm....
WEAK as compared to .........?? gravel?
sucks up moisture.... how much ?
it's rock after all? go see malham!!
Cheers JimK
No, it isn't. For cement bound macadam you need a very different grading to MOT Type 1 sub-base - fewer fines.
So you think that chalk is as strong as granite?
Rock is a generic term.
Rock is VERY variable.
Evening Bruce.
Bollox!
I have had several tons of MOT over the years to dress our trackways and i would 100% say it does not have as many fines as from sand in a
1:2:4 concrete mix.Remember the "4" in the 1:2:4 refers to 20mm gravel, the"2" to sand - in MOT you have many differnet sizes of grain all the way from say
40mm to dust.... the porportion of those sizes is the moot point. If there were "too many" fines in MOT it would just behave like a "slurry with lumps in" when used on tracks like ours ..... it doesn't, it binds together esp. after vehiclular use - that is it's best property which implies a decent spread of grain sizes to knit together.Comparing to "all in ballast" aka "2:4" it *is* short on fines - hence my recommendation to add sand to the mix.
Cheers JimK
you get granite in your ballast then??
JimK
Well, I'm off to get some all-in ballast bags from B&Q. Better be safe than sorry. Strange how wickes is exactly the same price. =A31.58 Simon.
I would agree.
I would also agree, but I repeat my point: no way is limestone as strong as flint or granite.
MOT aint called 'crush and go' for nothing!
Its brilliant at load bearing once it HAS been crushed, but use unsmashed in concrete it will not be nearly as good in compression as proper ballast.
Can do in some parts of the country. Ours is mainly flint. Calcium silicate IIRC.
Limestone is calcium carbonate IIRC.
ballast and gravel are sedimentary deposits of alluvial or glacial spoil. Essentially smashed up rocks of whatever was upstream.
The big stuff we call gravel, the small stuff we call sand. The very small stuff we call clay, and the carbonates usually wash away and end up in the sea.
A walk on any beach or any river bed thats currently dry-ish will reveal almost no limestone or chalk of any description. Its flints, the odd bits of sandstone, and granitic type materials.
Anything thats weak gets turned into fine and fine gets carried further. Nature does a good job of grading gravel beds for us to use.
mmm fascinating... if well known.
Even though OP has already decided to buy a few bags of all in ballast (for the one mixerful of concrete) let's look closer:-
Density Granite 2700 kg/m3 Limestone 2700 kg/m3
Modulus of rigidity (m) Granite 24 GPa Limestone 24 GPa
Unconfined compressive strength Granite 100-250 MPa Limestone 30-250 MPa
Shear strength Granite 14-50 MPa Limestone 10-50 MPa
Tensile strength Granite 7-25 MPa Limestone 5-25 MPa
You have to agree it would not have been a bad second to your granite/ flint/whatever in a mix - especially considering it was already kicking around at the OPs...
I'll let you know if my road melts anytime soon (have you been to Malham? noticed any major changes recently?)
Cheers JimK
Limestone isn't physically weak. Chemically, yes, but that's not necessarily a problem.
^^^^^^^^^^^^^^^^^^^^^^^^^^ This is the killer though.
Limestone covers everything from chalk to the sort of jurassic limestones, that are really hard. Almost marbles.
But what goes in MOT is NOT jurassic limestone, or even thr scraps left over from making nice stone building blocks.
Its deliberately selected for its ability to compress and break under pressure to form a nice compacted, yet still permeable substrate for roads.
So my contention that is way worse than granite under compressive loads is correct. It could be up to 8 times weaker, and even if you take the average, its considerably worse.
Let me know when you see a road with limestone chippings applied as a wear surface as well.
Ive only ever seen flint or granite..
It is physically weak.
Or what's in MOT is. You can smash it easily with hammer in a way that is not possible with flint. Flint shatters under a sharp knock. MOT crushes under a heavy load.
If uyou lay a road with pure MOT and run a few 30 tonners over it, it doesn't settle like granite or flint gravels do, it turns into a continuous surface of crushed particles filling the gaps between the larger lumps, and ends up quite smooth. I know, because I have done just that before covering it in gravel.
The whole POINT of MOT type 1 is to BE physically weak in order that it CAN end up as a stable free draining load spreading base although it starts as lumps with gaps.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.