# A bit of fun maths for you in the morning!

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• 12th August 2011, 09:55 AM
MK-2
A bit of fun maths for you in the morning!
I know there will be someone here who works this out.
We are ripping up our current patio to lay a new one. We need to order a skip to get rid of the slabs, but obviously don't want to overfill the skip in terms of weight so want to work out how much the slabs weigh.
they are 600mx600m slabs (approx 2" thick) and we have about 40 to get rid of.
Is there a sort of general weight of concrete that can be applied to this?

I think the 8yard skip can take up to 8 tonnes but obviously if i could get away with a smaller skip and smaller weight limit it would lower the cost
• 12th August 2011, 10:01 AM
MK-2
Not sure if I found an answer just after posting. Just wanted to see if this makes sense to anyone?

Paving Expert - AJ McCormack and Son - Pre Cast Concrete BS Flags <-- that site at the bottom says that a 600mx600m (2" thick) slab will weigh approx 41kg each.
So 41kg * 40 = 1640kg which equates to 1.64tonnes? Does that sound about right, 40 patio slabs weighing just over a tonne and a half?
• 12th August 2011, 10:01 AM
Steve21
Quote:

Originally Posted by MK-2
they are 600mx600m slabs (approx 2" thick) and we have about 40 to get rid of.

Well under the assumption that's 600mm, not meters? :P Unless I worked something out wrong, 0.6*0.6*0.05*40 is 0.72~ barely 1m3

Norm concrete 2.5~ tonnes per m3, so say 2 tonnes. (Assuming slabs not normal though) Unless i did somethign wrong, nowhere near 8tonnes. (Might want to double check the maths but hey :P)

Steve
• 12th August 2011, 10:07 AM
MK-2
yeah sorry 600mm, thats me typing in haste!

these are the sort of slabs, 600mm by 600mm and 2 inch thick. they weigh a fair bit each, but once you are loading stuff into a skip its hard to just say "yep thats about 2 tonne in there" so wanted to check first
Attachment 10996

so you're saying 40 slabs would work out approx 2 tonne?
• 12th August 2011, 10:07 AM
TechMonkey
Concrete has a density of around 150lbs per cubic foot (so I've heard I don't have that off the top of my head!!), 600mm is about 2ft so 2*2*(1/6)*150 = 100lbs. 2000 pounds in a ton so you should be able to 160 in that skip ((2000*8)/100).

Hope my workings out are correct now!
• 12th August 2011, 10:09 AM
Steve21
Quote:

Originally Posted by MK-2
yeah sorry 600mm, thats me typing in haste!

these are the sort of slabs, 600mm by 600mm and 2 inch thick. they weigh a fair bit each, but once you are loading stuff into a skip its hard to just say "yep thats about 2 tonne in there" so wanted to check first
Attachment 10996

so you're saying 40 slabs would work out approx 2 tonne?

Well it's less I'd say nearer what you said, 0.72 x 2.4k is roughly 1.728~ but just rounding it a bit :) That's basing it on "standard concrete" weight anyway. Unless we both worked something out majorly wrong that is :D

Steve
• 12th August 2011, 10:11 AM
Hightower
Quote:

Originally Posted by MK-2

Oh, those are nasty. My brother has some of those in his garden from when he bought the house. He keeps saying he's dying to get rid of them, but it's been 8 months now and they are still there - I think he secretly likes them! :)
• 12th August 2011, 10:12 AM
MK-2
just so we're all clear, if the skip buckles under these slabs im holding you all personally responsible :p
• 12th August 2011, 10:14 AM
MK-2
Quote:

Originally Posted by Hightower
Oh, those are nasty. My brother has some of those in his garden from when he bought the house. He keeps saying he's dying to get rid of them, but it's been 8 months now and they are still there - I think he secretly likes them! :)

thats just a pic off that site, but ours are a bit similar. just uploading a pic from my phone as ive been taking in progress pics all the way, so you can see the state of ours.

we've been in the place about 10 months and decided its time ours went too!! definitely dont like them. plus they aren't laid properly, the hardcore under isn't compacted well enough.

these are ours:
Attachment 10997
• 12th August 2011, 10:22 AM
Hightower
Don't forget to include the cat when calculating weight for the skip. I think it'll take about 0.004 tonnes per cat. Wouldn't want you going over the limit, that's all ;)
• 12th August 2011, 10:24 AM
MK-2
thats not even our cat, its next doors. she sat and watched us moving loads of stuff last night.

anyway why am i even listening to you, you're working out the weight of a lion, not a house cat :p
• 12th August 2011, 10:30 AM
Hightower
Quote:

Originally Posted by MK-2
thats not even our cat, its next doors. she sat and watched us moving loads of stuff last night.

anyway why am i even listening to you, you're working out the weight of a lion, not a house cat :p

Let me google that for you

And I only said 4 kilos because a) to take into account really big cats b) because I look at cats like those naughty rioters and each cat is sure to have a few electrical goods in their coats and c) because I'm not a cat person in the slightest and don't know what they weight and d) because it's really hard to judge a cats weight just by kicking them ;)
• 12th August 2011, 10:31 AM
mac_shinobi
or you could just pull one slab up, get all the mud and stuff off and weigh one and * by 40 ?
• 12th August 2011, 10:32 AM
SYNACK
Quote:

Originally Posted by MK-2
just so we're all clear, if the skip buckles under these slabs im holding you all personally responsible :p

Not to spoil this beautiful thought exercise but if you want assurance what is stopping you from simply ripping one up, weighing it and multiplying that weight by 41. I know its rather dull but would get you a reasonably accurate figure without involving a bunch of (reasonably accurate) assumptions.
• 12th August 2011, 10:39 AM
MK-2
Quote:

Originally Posted by SYNACK
Not to spoil this beautiful thought exercise but if you want assurance what is stopping you from simply ripping one up, weighing it and multiplying that weight by 41. I know its rather dull but would get you a reasonably accurate figure without involving a bunch of (reasonably accurate) assumptions.

i don't think our kitchen weighing scales go up that far (and we don't have bathroom scales) :p
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