Brickies Grey for Concrete Pad?

[alexi82]

Hi Guys

I have an opportunity to buy bags of brickies grey for 4 bucks a bag, which is a good deal in my mind. I need to lay about a cubic metre of concrete for a pad for an outdoor kitchen...so low stress application. Brickies grey is 50/50 cement/hylime.

Do you think it would work ok as concrete if i mix with sand/aggregate in the normal ratios?

Cheers!
Alexi

[Gulf]

Re: Brickies Grey for Concrete Pad?

No, it will not have the same strengths. Since you mentioned having the sand and gravel, I would go ahead and get portland cement.

[alexi82]

Re: Brickies Grey for Concrete Pad?

hey thanks for the reply. I dont already have the sand/aggregate as yet...i just saw the good price for the grey and was hoping to use it.

it may not be as strong, but would it necessarily be a poor pad? as in would it still do the job i guess is my question...

[david s]

Re: Brickies Grey for Concrete Pad?

Lime in the mix tends to retard hydration, so to boost strength by adding more Portland you have to double your quantity. At your $4 price you aren't gaining much. Portland is $10/20kg where I come from.

[Tscarborough]

Re: Brickies Grey for Concrete Pad?

It will be about 800 psi at a 50/50 ratio, a little higher with stone aggregate, so it will work, but you should add enough portland to get it to a ratio of 75/25 if possible.

[alexi82]

Re: Brickies Grey for Concrete Pad?

Ok cool, 800 would probably suffice.

If it is reinforced with steel bar, that would increase the PSI yea? i have a heap of that as well lying around.

[Tscarborough]

Re: Brickies Grey for Concrete Pad?

Rebar doesn't affect the compressive strength, just the tensile strength.

[alexi82]

Re: Brickies Grey for Concrete Pad?

Yea true....didn't think that one through.

so what compressive strength would suffice for a pizza oven....if a house pad is between 3000-5000 psi, surely 800-1000 would suffice for oven?

[Gulf]

Re: Brickies Grey for Concrete Pad?

Yea true....didn't think that one through.

so what compressive strength would suffice for a pizza oven....if a house pad is between 3000-5000 psi, surely 800-1000 would suffice for oven?

You should reach for, at least, the same as your house. Your oven will exert more pounds per square inch than the middle of your living room. Save the good deal on the mortar mix for the decorative brick or for making home brew.

Just Sayin'

[alexi82]

Re: Brickies Grey for Concrete Pad?

You should reach for, at least, the same as your house. Your oven will exert more pounds per square inch than the middle of your living room. Save the good deal on the mortar mix for the decorative brick or for making home brew.

Just Sayin'

Fair point i'll still get the cheap brickies grey coz its a good deal and i'll use it for mortar anyway....

Thanks!

[Tscarborough]

Re: Brickies Grey for Concrete Pad?

Actually, if you do the calculations, your basic dirt has enough compressive strength to hold an oven. What it doesn't have is the tensile strength to allow for movement via the shrinkage and swelling of the soil through the various seasons.

WAG it out at 10,000 pounds (that is outrageously high) for the stand and the oven, and the bearing surface of the stand at 2304 square inches (24 linear foot of 8" CMU grouted solid). 10,000/2304=4.302PSI. As you can see, the compressive strength is not really important. What you need is tensile strength, which is provided by rebar, and if you are a worrier, micro-fibers.

[alexi82]

Re: Brickies Grey for Concrete Pad?

cool...

So lets say i use the brickies grey, which will have lower compressive strength, and use 6mm rebar for tensile strength, will that suffice? i mean, i coudl stick in two layers of rebar if it helps...

[Tscarborough]

Re: Brickies Grey for Concrete Pad?

If the rebar mat does not have enough concrete coverage, it does no good. One layer should be fine, concentrate on getting it into the center of the pad, and make sure you have a good gradation of aggregate.

[alexi82]

Re: Brickies Grey for Concrete Pad?

goodo.

I mean I am happy to buy normal cement but if i can get this brickies grey for the price, and with the right size slab and reinforcement it does the job then im happy...

and it sounds like with the rebar in the middle of the pad it will...?

thanks everyone