Homemade concrete blocks - What strength mix do i need?

[chris_h]

I need to replace a few broken concrete blocks (slightly smaller than brick size) on the top of a wall. Can anyone please tell me what ratio of cement to sand to aggregate (or whatever) I should use for the mix?

[lutonlagerlout]

wouldnt it be easier just buying some blocks mate?
LLL

[Tony McC]

Do you remember those screen blocks moulds you could buy from glossy ads in the sunday papers during the 1970s? The number of flimsy, fragile walls they resulted in! I don't think any of them lasted more than about 3 winters.

[matt h]

same as those crazy paving forms... looked ok for a while, then just disintegrated

[lutonlagerlout]

Do you remember those screen blocks moulds you could buy from glossy ads in the sunday papers during the 1970s? The number of flimsy, fragile walls they resulted in! I don't think any of them lasted more than about 3 winters.

i found some in the shed of my old house and tried to make some
just didnt work at all,as soon as i tipped them out of the mould they crumbled
LLL

[Ted]

The makers of my block machine - www.dme.co.za - advocate an intital mix of 1 part cement to 8 parts river sand (coarse sharp).

However if you want to increase the mPa of the blocks you are making you can increase the cement content, introduce larger aggregate such as 10mm pea shingle and incorporate a water reducer.

[Tony McC]

8:1? That's seems weak. What would that generate? Around 12-15 Newtons? I would have expected more for a walling block.

[Ted]

It is to keep costs down!

African building standards are not quite on a par with European ones.



I would advocate at least a 6:1 mix though.

[Ted]

http://www.dainet.org/enterprise/concrete.htm

And this Indian company uses a 1:12-14 mix!

[matt h]

hate to be there in monsoon