Basic cement/ ballast Q

[zoothorn]

4 hours ago, dpmiller said:

so you don't have any data?

 

dpm what I have, is a 2.3m square (& crest H) log cabin/ shed, plus a chap whose day-to-day job is structures like this but on a much bigger scale. If he outlines the footings & the base on which it'll go, & says once all that's done you could park a car on it.. I trust that I've at the least we've gone overkill on my footings: getting an SE involved for a heavy shed & trawling data- seriously? (& this is wales- you just crack on with things here).

 

I think the thing is my photos don't give a good idea of how big/ massive these are. 3/4 of a ton of ballast in each of these lower footings, & that's plus concrete/ water. theyre a full metre high.

[zoothorn]

@Onoff how could I find my 2.3m points for my upper 2 corners? just thought with the ~1m drop to lower ones.. getting a reference line from A to B isn't so simple.

[Onoff]

1 hour ago, zoothorn said:

@Onoff how could I find my 2.3m points for my upper 2 corners? just thought with the ~1m drop to lower ones.. getting a reference line from A to B isn't so simple.

 

1m tall bits of wood with a base plate  nailed to the bottom. Sit it on the lower plinths. Weight down with bricks. Two bits of string, where the arcs meet...or one big of string and a knot at the intersection. Tie other ends around nail in centre of 1m high posts, pull tight, knot marks centre of up slope plinths.

 

 

2300x2300 square? Diagonal bit of string will be 3252mm.

 

Edited August 30, 2019 by Onoff

[zoothorn]

Hi @Onoff many thanks for your pics/ it gets me all geared up seeing an Onoff sketch again!

 

Ok done upright wood bits. But not getting the arcs. I read of this 3,4,5 rule.. to for a perfect R-angle. Is this where your 3252mm fig comes from, being the '5' as it were? I don't get how you establish the '4' or the '5' from just knowing the '3' (which I assume is 2300 here, or is it '4'?)

 

I can see how an arc is used @ 2300mm, from this LHS stream foot..  but not getting the 'intersection' of two arcs/ where this other arc is from (it looks like there's another arc originating from way down in the stream out of pic LH edge in your 2nd sketch ^).

[Declan52]

Ok you have a basic sq that each corner is 2.3m  from the other points. You know the distance from points a to b and a to c is both 2.3m. then you use Pythagoras to work out the other distance c to b.

A²& B² = C²

2.3² & 2.3²= 10.58

√10.58 = 3.252m

 

[zoothorn]

Ooh pythagoras.. I like him! thanks Declan. Ok but if I only have two cnr points known, to find the 3rd cnr do I use the 3252mm & the 2300mm arc intersections? then go on to find the 4th easily enough.. if so Ive got my other 2 feet positions marked.

 

Digging tmrw.. urgh/ but only 40cm deep or so in my 47cm or so high tubes, as I've got only 2/3rds of a ton of ballast left to do these two footings.

 

Is there any way of calculating the volume of 'concrete needed' (& specifically how much mixed ballast), for a cylinder with known diameter + height?

 

 

Edited August 31, 2019 by zoothorn

[Declan52]

If you call the other point d, you know b to d(2.3m),c to d (2.3m) and even a to d( 3.252m) so it's just using a tape and a level and mark on the ground roughly where these points all meet. It will be much easier if you have 2 tapes going at the same time. 

In the grand scheme of things due to the size of the pads even if your 50mm out it there won't be an issue.

Once you put the frame on it it will be much easier to move it slightly to get it spot on. Once you have it square then you can fix it to the pads and it will never move.

[andyscotland]

11 minutes ago, zoothorn said:

Is there any way of calculating the volume of 'concrete needed' (& specifically how much mixed ballast), for a cylinder with known diameter + height?

For the overall volume, start with the area of the circle forming the cylinder - π X (radius squared). Then multiply by the height.

 

To get from the overall volume to the ballast qty depends on the concrete mix you're doing.

[Onoff]

29 minutes ago, zoothorn said:

Ooh pythagoras.. I like him! thanks Declan. Ok but if I only have two cnr points known, to find the 3rd cnr do I use the 3252mm & the 2300mm arc intersections? then go on to find the 4th easily enough.. if so Ive got my other 2 feet positions marked.

 

You have two existing plinths that are "down" the slope.

 

You want to put two more plinths further up the slope.

 

If I'm correct each side measures 2300mm.

 

Standing down by the stream, looking up the slope:

 

1) From your existing left hand, lower plinth, strike an arc 2300mm. From your existing right hand, lower plinth strike an arc 3252mm. Where the two arcs meet is the centre of your left hand plinth further up the slope.

 

2) From your existing right hand, lower plinth, strike an arc 2300mm. From your left hand, lower, existing plinth strike an arc 3252mm. Where the two arcs meet is the centre of your right hand plinth further up the slope.

 

 

 

 

 

 

 

[zoothorn]

1 minute ago, Onoff said:

 

You have two existing plinths that are "down" the slope..

 

Cheers Onoff- then I've done just as you outlined. Just wanted to double-check. Yes thankfully I do have wiggle room being big wide pads.

 

Ok next thing is once my tubes in place, is the mix. My pro chap was winging 1/3rd of a bag of cement into mixer already with water + splash of stuff in.. then as I was labouring ballast continuosly (from tip top of my slope, brought down steeply- hard graft) I couldn't observe exactly the no. of buckets went in too.  But I can't wing it. So what's the best method of measuring my ratio?

 

Also as I maybe slightly on the short side re. ballast.. I wonder if I can safely do it with just a wee bit less ballast-per-mix?

[Onoff]

Do these up slope plinths are 2' or 600mm dia and 500mm high?

 

Is that correct?

 

That's pretty much bang on 0.25m3. So 0.5m3 concrete required to do both plinths.

 

EDIT: ABOVE CALCS ARE WRONG!!!

 

 

 

Edited August 31, 2019 by Onoff

[zoothorn]

2 minutes ago, Onoff said:

Do these up slope plinths are 2' or 600mm dia and 500mm high?

 

Is that correct?

 

That's pretty much bang on 0.25m3. So 0.5m3 concrete required to do both plinths.

 

 

 

 

 

Yes, well 600mm wide x 480mm high to be exact. But they're not cubes.. but cylinders: was that taken into account for your 0.5m3 figure?

[Onoff]

15 minutes ago, zoothorn said:

 

Yes, well 600mm wide x 480mm high to be exact. But they're not cubes.. but cylinders: was that taken into account for your 0.5m3 figure?

 

Sorry. My mistake, blinding headache here and waiting for pills to kick in! 

 

It's actually 0.14m3 for each plinth. So 0.28m3 for both.

 

 

 

 

[Oz07]

Sorry have flicked thru thread but shouldn't rebar have cover all around rather than hammer into earth. Not to say I'd be worried seems OTT as said

[zoothorn]

Sympathies @Onoff on headaches.. I get them too/ debilitating. 0.14m3 per cylinder seems an oddly small ammount. I was thinking 0.5m3 was about right actually.

 

Hang on. If it were 500mm x 500m x (500mm H), so lets say square instead of a cylinder.. this equates to 0.5m3 does it not? how come your figures of 600x 600mm (wxd as you innitially thought ) x 500mm H = 0.25m3?

 

Surely it was 0.5m3 per plinth, so 1m3 to do both.

[PeterW]

A 500mm cube only contains 0.125 cubic metres - think about it ... its half the width, half the length and half the height, so is one eighth of the volume 

[Onoff]

If you stacked 8 cubes each 500x500x500 they would make 1m3. So each one is 1/8 of a cubic metre or 0.125m3.

[Declan52]

Just keep mixing till they are full. If you need to buy another few bags of sand and cement then buy them, finish this part and move onto the next task.

[zoothorn]

37 minutes ago, PeterW said:

A 500mm cube only contains 0.125 cubic metres - think about it ... its half the width, half the length and half the height, so is one eighth of the volume 

 

I just don't get it. Its probably bc it was done in school 37 yrs ago..

 

0.5m x 0.5m x 0.5m is less than 0.5 x 0.5. My head can't cope as it doesnt make sense. The more I multiply 0.5 the smaller the number gets. But its not a negative number, its a positive number. So how come it gets smaller? its all nuts. maths sucks.

[Onoff]

 

Have a read of this:

 

056-How-to-make-concrete.pdf

Edited August 31, 2019 by Onoff

[zoothorn]

13 minutes ago, Declan52 said:

Just keep mixing till they are full. If you need to buy another few bags of sand and cement then buy them, finish this part and move onto the next task.

 

 

Ok what I wanted to establish, before the 0.125m3 figure emerged & fried my noggin, was whether my remaining bag of ballast (2/3rds of a ton).. will be enough once mixed into concrete, to fill my two 0.5m x 600mm dia tubes.

 

Sand? my ingredients have been mixed ballast, concrete, water, splash of gubbins. No sand. I thought sand + concrete = mortar?

[Onoff]

19 minutes ago, zoothorn said:

 

 

Ok what I wanted to establish, before the 0.125m3 figure emerged & fried my noggin, was whether my remaining bag of ballast (2/3rds of a ton).. will be enough once mixed into concrete, to fill my two 0.5m x 600mm dia tubes.

 

Sand? my ingredients have been mixed ballast, concrete, water, splash of gubbins. No sand. I thought sand + concrete = mortar?

 

@Declan52 quoted sand wrongly, no biggie, we knew what he meant.

 

You are using what's known as "all in one ballast". It's a mixture of aggregate up to 20mm in size and sand. 

 

What mix are you using, 4:1?

 

 

[Declan52]

Mixed ballast is a mixture of usually sharp sand and gravel from 10mm to 20mm depending on what you need it for.

You really didn't notice the sand in it when you where shoveling it into the mixer???

I should have said buy another few bags of ballast like these.

https://www.diy.com/departments/diall-all-in-ballast-large-bag/35702_BQ.prd

[zoothorn]

4 minutes ago, Onoff said:

 

@Declan52 quoted sand wrongly, no biggie, we knew what he meant.

 

You are using what's known as "all in one ballast". It's a mixture of aggregate up to 20mm in size and sand. 

 

What mix are you using, 4:1?

 

 

 

Aha. now I know what the word 'mixed' means then. I assumed it was various sizes of gravel mixed together.. but its one size of gravel plus sharp sand mixed together. I thought it looked quite 'beachy' but thought english pig here just got lumped with last few bags off the huge heap!!

 

I believe 4:1 yes. I've just tried the concrete calculator.. & cannot understand a flamin thing now. All this maths stuff just beats me.. I hate it. It worked before, gave me my 15 bags of cement + 1.54 tons of mixed ballast but now its giving me sand bags, cement bags, & ballast/ or ballast I can't tell what.

 

I need to go back a step & clear my head- this 0.125m3 figure has fried my brain.

 

Ok can anyone help & use this calculator to determine my 2 ingredients, cement no.of 25kg bags & mixed ballast no.of tons: how many needed for my figure of 0.28m3?

 

thanks- zoot

[zoothorn]

18 minutes ago, Declan52 said:

Mixed ballast is a mixture of usually sharp sand and gravel from 10mm to 20mm depending on what you need it for.

You really didn't notice the sand in it when you where shoveling it into the mixer???

I should have said buy another few bags of ballast like these.

https://www.diy.com/departments/diall-all-in-ballast-large-bag/35702_BQ.prd

 

Yup did notice the sand. reminded me of crap holidays as a kid. but honestly just thought it was the 'crumbs' from the bigger bits. tbh I shovelled so many buckets I was thinking rather too much on the consistancy reminding me of my hobnob packet I ate that day. whole lot all in one go, & quite an abundance of crumbs at the btm too; the crumbs you see kind of remained in my brain, & took the place of the sand.