The Brew Cabin

Is it ok to use this as sub base material for a paved area that will only have foot traffic ?

Yep, as long as it's crushed reasoably fine. With the progressive taxation on Primary Aggregates and Landfill, many aggregate companies are now crushing concrete and grading it as a low-cost DTp1 or DTp2. Because it is a recycled material, it escapes the PrimaryAggs tax and is therefore cheaper than, say, a limestone or gritstone equivalent.

I am a novice wrt paving a drive, although I have done a garden patio. I am thinking of laying a block paved drive in place of a drive of tarmac on concrete. In a similar vein can I use the concrete I dig out as base material. How fine should it be broken up and how would this be done, given that I am a diyer with limited money. Would it be cheaper/better to skip this and buy in aggregate?

If you want to 'recycle' the concrete as a sub-base material, then it really needs to be broken up into pieces no bigger than 40mm. However, that is not the end of the story, because you need a good proportion of 'fines' to fill the gaps in between the 'lumps', something like 50% of the concrete needs to be reduced to a size of 10mm or less.

Just how you do this is up to you. Ideally, you'd have an onsite crusher that simply swallowed the big chunks of concrete and spewed out a well-graded crushed aggregate, but, if you don't have such a piece of kit, then you're more or less stuck with using a sledge hammer and then it becomes a battle of wills - who will crumble first: you or the concrete?

It's probably easiest to break up the concrete to reasonably small pieces, scatter them as a 'blinding' over the excavated sub-grade, and then top up with a "real" sub-base material, although even this is a lot of hard work.

Compare and contrast with the cost of skipping the broken out concrete and bringing in sub-base material. If you reckon that a skip costs 130 quid, then each cubic metre of concrete broken out and dumped is costing around 32.50 to dispose, and each cubic metre of DTp1 (or similar) brought in as replacement costs roughly 40 quid - that's 70-odd quid per cubic metre (roughly 10 square metres). Think of this when your back and arms begin to scream with pain as you raise the sledge hammer for yet another blow.

If it were me, I'd cart the concrete/bitmac off-site and let the waste transfer station deal with it while I brought in a ready-crushed concrete to use as a sub-base. There's not many tasks that are more soul-destroying than "breaking rocks under a hot sun" - that's why it was such a popular pastime for recidivists. ;)

Thanks Tony,

I take your point. Although I had to look up recidivists in the dictionary :)

Cracking site.

Not only do you learn all about paving, but you get an expanded vocabulary as well!