Lime Modification at Minworth WWTW

Buckingham Group Contracting

Minworth Waste Water Treatment Works



The site at Minworth was the old sludge lagoons for the adjacent Minworth WwTW. The sludge cake was between 20 and 40 years old and could not be removed from the site. It was to be utilised as treated fill beneath areas of lightly loaded external pavings and had to have a bearing capacity of CBR3%.

How Combined Soil Stabilisation Helped

The Main Contractor asked CSSL to suggest ways in which this could be done using modification or stabilisation techniques.

CSSL proposed that a two-powder binder be used, lime and PFA to give the strength with the sludge acting as a bulking material. UKQAA (The ash people) were consulted which resulted in a conditioned PFA being used.

Site trials were undertaken and a method of working devised. The moisture content of the sludge, variable across the site, dictated the amount of lime to be used. A ratio of 1 lime : 5 PFA was used thus the mass of PFA per unit area could be calculated. A mass of PFA was tipped from lorries and spread at an appropriate depth across a defined area, this was the rotivated into the sludge. The lime was then added either by spreader-cart of integrated mixer and the sludge/pfa/lime re-mixed.

It was found that a combination of the winter rain and a large, flat site resulted in some areas having to be re-worked with lime or, in critical areas, lime and cement (CEM1).

Study Project Date  
Soil Stabilisation at Hinkley Point 'C' Nuclear Power Station 23/01/2015
Combined Soil Stabilisation at Jaguar Landrover, Solihull 07/01/2013
Lime Modification for Tesco Superstore, Hattersley 01/08/2011
Soil Stabilisation at Stublach Gas Storage, Northwich 01/06/2011
Soil Stabilisation at Tesco Store, Great Harwood 01/06/2011
Soil Stabilisation at Northwood Recycling, Matlock 01/04/2011
Lime Modification at Hameldon College, Burnley 01/03/2011
Cement Stabilisation at Loch Ryan Port, Stranraer 01/01/2011
Lime Modification at Sir John Thursby College, Burnley 01/12/2007
Lime Modification at Minworth WWTW 01/07/2007
Soil Stabilisation at BAE, Chadderton 01/06/2007
Soil Stabilisation at Eaves Green Link Road, Chorley 01/02/2007
Cement Stabilisation at Clydebank Towpath, Glasgow 01/11/2006
Soil Stabilisation, Leeds Bradford Airport 01/10/2005

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