Paving lifting - Problem with recycled sand??

Patio flagstones (slabs), concrete flags, stone flags including yorkstone and imported flagstones.
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danielk
Posts: 1
Joined: Thu May 23, 2013 7:17 am
Location: chester

Post: # 90105Post danielk

I'm a builder and on a extension i was working on about a year and half ago a contractor came out to lay an indian stone patio. It was quite a large job in excess of 200sqm. The paving has subsequently started to lift in areas especially along a step and it appears as if the sand has buckled. I know that he used recycled grit sand using a full bed with a full bed at 4:1 mix. There's a minimum of 100mm of well consilidated hardcore with ground below the hardcore being sandstone it can't be due to ground movement. The sand and cement mortar mix just crumbles in your hands. I'm in contact with supplier of the sand with a view to having some chemical tests carried. I was wondering if anyone had come across anything similar before. The paving along the step has raised by approximately 50mm. I'm pretty sure that it's not water collecting under the paving and freezing and pushing the paving up as the sandstone is extremely porous and water drains right through it. We are going to reinstate the paving but need are trying to find out what has caused the problem before starting. Hope someone can help. Thanks Dan
dk
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London Stone Paving
Posts: 2199
Joined: Mon May 10, 2010 1:07 pm
Location: Surrey
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Post: # 90107Post London Stone Paving

What was the time of year when the patio was laid? If he used a 4:1 mix then there is no way that it should be crumbling in your hand, unless:

1. Wasnt mixed properly
2. Was laid in freezing conditions

Steve
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topgrafter2007
Posts: 83
Joined: Tue Feb 10, 2009 4:50 pm
Location: blackpool

Post: # 90374Post topgrafter2007

I started a thread on this on here a few years ago relating to identical problem, we were using recycled 'Fines/sand' as grit sand substitute.
To cut a long story short the problem turned out to be caused by to much soil/non sands in the recycled stuff, this held on to the moisture which was then affected by the freezing temps causing 'heave' which in turn lifted flags and exposed the crumbled bedding layer, ive never used it since after having to relay several drives.

The recycled stuff was popular due to low cost but false economy, very 'tight' area where i live and i just followed everyone else using it. Bit wiser now :)
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