how much does MOT compact ?
sm_jamieson
(BCO agreed).
First floor slab I've done.
To what depth should I rake it out before compaction to end up with
100mm ?
In other words, how much should I expect it to compact ?
Thanks,
Simon.
Tim S
I don't know about MOT 1, but I can tell you for a fact that reclaimed
washed railway ballast compacts from 8" as shovelled and raked out to 6" of
solid mass under several runs with a standard single-person vibroplate
compacting machine. I learnt this little fact after 3 of us busted a gut
moving the damn stuff to help a mate make his new crossover and drive.
Said ballast consisted of rock lumps typically about 1.5" across, no fines
and not much below 1". If that's similar to type 1 MOT, then I would expect
similar compaction ratios.
HTH
Tim
Bruce
That depends how you are compacting it, and what with.
I assume that you are using crushed limestone with a relative density
of around 2.7 t/m3. Loose, it is about 1.3 t/m3. Compacted
systematically with mechanical plant at the material's optimum
moisture content, and it can go as high as 2.1 t/m3. Depending on how
you compact it, and how meticulous you are, it could be anywhere
between 1.6 and 2.0 t/m3 (tonnes per cubic metre).
If you wanted me to take a stab at a rough nominal thickness to start
with, I would suggest 140mm for a final thickness of 100mm. But that
is just a very rough guess. All depends on the method of compaction.
Bruce
The two materials couldn't be more different.
Railway ballast is a single size material, typically 2" to 1" - the
maximum size being no more than twice the minimum size is what defines
a single size material. It is usually made of granite but can be made
of other strong rocks.
MOT Type 1 is a fully graded material, with everything from 3" (75mm)
down to dust, and all intermediate sizes present. It must be made of
crushed limestone.
With MOT Type 1, the small particles fill the gaps between the larger
particles, reducing the overall void ratio (the ratio of empty spaces,
or voids, to the total volume) to 20% or less. Railway ballast has
about twice the percentage of voids.
Tim S
Interesting. Presumably with MOT 1, there's less risk of the soil base
working its way into the hardcore, resulting in the lab and hardcore
sinking?
Cheers
Tim
sm_jamieson
From builders merchant, "MOT roadstone" it is.
A whacker plate I will use.
Simon.
The Natural Philosopher
i'd guess at 30% if well smashed down.
andrew
> MOT Type 1 is a fully graded material, with everything from 3" (75mm)
> down to dust, and all intermediate sizes present. It must be made of
> crushed limestone.
I've got the spec somewhere but MOT type one is just a strength and size
assortment, quite a loose one at that, plus the material needs to be
angular, not round. It does not specify limestone and many quarry
waste "crusher runs" will fit the spec.
I know this because I had to find and inert (pH 7 or lower) sub base for a
car park on a sensitive acid heath and it's actually quite difficult to
find an alternative to limestone scalpings for type 1, but they are
available. In fact a granite type one is available but this too has a pH
>7.
In my searching I very nearly decided to have some local pebbles (rejects)
crushed to mix my own type one.
The very fact that the spec is the correct assortment for no voids suggests
it shouldn't compact much.
AJH
The Natural Philosopher
It doesn't pour without airgaps tho.
AND if you dont mix it thoroughly, you find all the larger lumps end up
on top..or at one end...;-(
> AJH
>
Bruce
Phil L
Put a nominal 125m and whack down - it will go down about an inch, depending
on moisture content, the wetter it is, the tighter it packs down, although
it does make a bit of a mess, it makes for a better job, but saying that,
under a floor slab, it isn't really that important - under a drive, it is.
Bruce
Only up to a point. If it gets too wet, you cannot compact it.
It should be moist, but never wet.
sm_jamieson
Oh. So what happens if it has been raining ?
I can't imagine real groundworkers waiting for it to dry out !
Simon.
Phil L
I think Bruce means if it gets waterlogged.
The chances of this happening are extremely slim considering it's mostly
stone, but even if it does, when it dries out it's akin to a weak concrete.
Bruce
>On 20 Jul, 14:46, Bruce <n...@nospam.net> wrote:
>> "Phil L" <neverchec...@hotmail.com> wrote:
>>
>> >the wetter it is, the tighter it packs down
>>
>> Only up to a point. If it gets too wet, you cannot compact it.
>>
>> It should be moist, but never wet.
>
>Oh. So what happens if it has been raining ?
That depends how heavy the rain is.
>I can't imagine real groundworkers waiting for it to dry out!
Just because you cannot imagine it doesn't mean that it doesn't
happen.
You're welcome.
Tim S
> Tim S <t...@dionic.net> wrote:
>
> The two materials couldn't be more different.
>
> Railway ballast is a single size material, typically 2" to 1" - the
> maximum size being no more than twice the minimum size is what defines
> a single size material. It is usually made of granite but can be made
> of other strong rocks.
>
> MOT Type 1 is a fully graded material, with everything from 3" (75mm)
> down to dust, and all intermediate sizes present. It must be made of
> crushed limestone.
>
> With MOT Type 1, the small particles fill the gaps between the larger
> particles, reducing the overall void ratio (the ratio of empty spaces,
> or voids, to the total volume) to 20% or less. Railway ballast has
> about twice the percentage of voids.
On a tangential, but related note, which type of hardcore is best under a
concrete house floor (just floor, not structural raft, though it might
carry the weight of some brick internal walls, non load bearing)?
Thanks,
Tim
Bruce
MOT Type 1.
It cannot be beaten, because apart from spreading the loads into the
ground like other granular materials, it has significant strength of
its own.
Tim S
Cheers Bruce. that's the answer in advance to another bit of work...
sm_jamieson
I just had an image of lots of burly blokes sitting on deck chairs and
anxiously glancing at the sky !
Simon.
Bruce
You're welcome.
I have long been a "fan" of unbound macadams, which are granular
materials that exhibit a surprisingly high strength when compacted,
simply because of the careful grading of the various sizes of material
used. In contrast, bound materials gain their strength mainly from
being held together with a binder such as cement (as in concrete) or
bitumen (as in bitumen macadam), although some of their strength still
comes from the interlocking of the aggregate.
It comes from the 1970s when I wrote specifications for civil
engineering projects such as airports and roads. I did an extensive
literature survey of a vast range of bound and unbound materials, and
developed a library of standard specifications which could be
incorporated into the contract documents for each specific project.
Coupled with extensive site experience on road and airport projects, I
became a specialist in construction materials, something which I
thoroughly enjoyed, and which paid my mortgage for 30+ years.
The Natural Philosopher
However in the context of using random hardcore to make a subfloor base,
I think the relevant issues are that almost any stuff will do, provided
its graded right..i.e. big lumps with concrete poured over are not as
good as smashed up stuff with a good amount of particle size variation,
with added sand and ballast to fill in the sizes that smashing wont deliver.
Plus the fact that if you have e.g. old footings and bricks lying about,
its cheaper to use them - mixed with MOT or some other substance, and
well whacked with a sledge hammer - than paying to bring in new MOT and
paying to take away the scrap.
And if a load bearaing wall is to be inserted, its advisable to use a
proper strip foundation under it as well. i.e a proper possibly
reinforced, cocrete filled trench of at least 600mm deep, and maybe a
lot more in tree root filled soil.
Bruce
>
>However in the context of using random hardcore to make a subfloor base,
>I think the relevant issues are that almost any stuff will do, provided
>its graded right..i.e. big lumps with concrete poured over are not as
>good as smashed up stuff with a good amount of particle size variation,
>with added sand and ballast to fill in the sizes that smashing wont deliver.
>
>Plus the fact that if you have e.g. old footings and bricks lying about,
>its cheaper to use them - mixed with MOT or some other substance, and
>well whacked with a sledge hammer - than paying to bring in new MOT and
>paying to take away the scrap.
>
>reinforced, cocrete filled trench of at least 600mm deep, and maybe a
>lot more in tree root filled soil.
I don't disagree with any of those general principles, however my
reply was intended to address the OP's specific question.
bosn...@hotmail.com
Rod Speed
<bosn...@hotmail.com> wrote in message
news:4f554412-dc03-4b8d...@googlegroups.com...
Graham.
NNTP-Posting-Host: 41.86.8.70
Whois puts that in Liberia.
Perhaps he's using a re-mailer, otherwise he knows rather a lot about
our aggregates for a foreigner ;-)
--
Graham.
%Profound_observation%
Tim Watts
> bosn...@hotmail.com
> NNTP-Posting-Host: 41.86.8.70
> Whois puts that in Liberia.
>
Rod Speed
"Graham." <m...@privicy.net> wrote in message
news:3v5daals241gchg4r...@4ax.com...
polygonum
they didn't mostly have various forms of smartphone. Now what they can
connect to is another matter...
--
Rod
bejena...@gmail.com
Thank you.
Brian Gaff
Brian
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<bejena...@gmail.com> wrote in message
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Rod Speed
"Brian Gaff" <bri...@blueyonder.co.uk> wrote in message
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Peeler
Speed blabbered, again:
> Just a response to an ancient post back in 2015
HILARIOUS! LOL
--
Bill Wright to Rot Speed:
"That confirms my opinion that you are a despicable little shit."
MID: <pjqpo3$1la0$1...@gioia.aioe.org>
Roger Hayter
> Huh?
> Brian
Apparently someone answered a question about hardcore compaction in
2008. This was a belated appreciation of the answer, by someone on
Google groups who doesn't know how to quote.
--
Roger Hayter
Brian Gaff
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