C30 Concrete

[MarkSmith]

Hi all,

I have had a cellar support designed by an engineer, and it specifies, amongst other things, "C30" concrete (which defines its resistance to crushing, I think). I need about 0.6m3 of if, about 0.15m3 at a time (days or weeks in between), so it's just not worth getting readymix or similar.

How can I achieve a C30 mix? I just rang Readymix for advice and was told there was no way to do it myself - the only way, he said, was to buy it in. I find that hard to believe.

I have found websites specifying other mixes - C20 for example. Just can't find C30.

Thanks!
-Mark

[alastairreid]

have a read at this.

[Chukka63]

im sure 4:2:1 will suffice

[MarkSmith]

Thanks both.

According to alastairreid's link it's 300kg cement, 0.5m3 sand, 0.75m3 aggregate, which is a straight answer but still a bit awkward as two of those quantities are volume and the third one mass - which doesn't lend itself to how much of each I put into the mixer.

It also refers to that as a 6:1 mix, which is think is by volume (?). That would suggest 300kg cement has a volume of 0.2m3.

The ratio in the document doesn't work out as exactly 1:2:4 - it works out as 1:2.4:3.6. Would I be right to assume the ratio of sand:aggregate is less important than the ratio of cement:(sand+aggregate)?

Thanks,
Mark

[Chukka63]

if youre using ballast make it a 5:1 mix

[Chukka63]

i wouldnt worry about being too precise .when the cube guys come out to site they get there concrete then we add loads of water so its all bulls**t anyway.

[MarkSmith]

Chukka63 wrote:

if youre using ballast [...]

As opposed to what?

Ta,
Mark

[Chukka63]

sand and stone seperately

[Shytalkz]

Chukka63 wrote:

i wouldnt worry about being too precise .when the cube guys come out to site they get there concrete then we add loads of water so its all bulls**t anyway.

And you are probably exactly the self-same person who whinges and moans that things seem over-designed - which they are, of course, due to inbuilt safety factors that are there to cater for prats like you.

[Deluks]

Shytalkz wrote:

And you are probably exactly the self-same person who whinges and moans that things seem over-designed - which they are, of course, due to inbuilt safety factors that are there to cater for prats like you.

[Chukka63]

Shytalkz wrote:

Chukka63 wrote: i wouldnt worry about being too precise .when the cube guys come out to site they get there concrete then we add loads of water so its all bulls**t anyway. And you are probably exactly the self-same person who whinges and moans that things seem over-designed - which they are, of course, due to inbuilt safety factors that are there to cater for prats like you.

as an engineer im sure youve been on site on many occasions and seen such things being done,so you know this happens and build in the safety factor.

so whats the correct self mix quantites ???

[stuart45]

Shame on you Chukka, adding water after the cube mans gone.

[Chukka63]

well when you order a 60mm slump and the truck turns up and the concrete wont even come down the chute you dont have much choice.also,we all know it isnt 60mm slump, so its been delivered wrong in the first place.

[stuart45]

Most of the groundworkers I know usually put enough in to self level.

[hotrod]

stuart45 wrote:

Most of the groundworkers I know usually put enough in to self level.

LMFAO .

Without exception, every single groundworker subbie I have had working on one of my sites has been a sub-human neanderthal. Most of them have been nice lads, but I wouldn't want to go drinking with any of them.