Block paving on a clay soil

[BlueDragon]

Hi,

I am new to the forum and have found it really useful so far. However can someone please advise me on a specific question.

I am currently having a parking area completed and the contractor has found pockets of soft clay. He has advised that if he backfills this with type 1 it will still move about however much he compacts it and there will be a chance of it sinking in the future?

He has recommended that he use a pre mix of some fine type scalpings and cement and compact this as it will provide the strength and stability to lay the blocks on top with much less chance of future sinkage.

I am posting as I dont know if this is a good or bad idea, plus it it is adding significant cost to the job?

To qualify, as a contractor he comes highly recommended by numerous partys and has 20 years of experience as a paver.

Can anyone help?

[SelectPaving]

Everything sounds fine to me, if he was to backfill with crusher to a certain depth that was too much then there will be a chance of settling! I have 18 years experience of paving, this should not add a great deal of money to the job though!:D

[Tony McC]

The contractor should use a geo-textile or geo-grid to stiffen the sub-base after removing as much of the soft clay as is feasible. It may be necessary to use a capping or improvement layer which could use, say 75mm crusher run, before finishing with a 150mm layer of Type 1.

The right geo-textile/geo-grid can have a truly dramatic impact on even the crappest of sub-grades.