Cementing a new path for remediation

According to geo-environmental specialist Mike Southall, of Castle Cement,

the UK is currently on the verge of change in the way it deals with contaminated

sites. He adds that stabilisation solidification technology is set to become

one of the most ideal means of remediating contaminated land in answer to UK

policy, environmental needs and the new EU landfill directive.

Dr Colin Hills, senior research fellow at the University of Greenwich, who

has headed a two-year investigation into stabilisation solidification technology,

said that the new method was a ‘more obvious choice’ to deal with certain types

of contamination.

He is currently finalising a draft report on the new technique which is due

to go before the Environment Agency in the summer.

As well as treating hazardous waste on site there was a potential to re-use

the treated product in a wide variety of engineering uses which made it cost-effective,

he added.

Mr Southall explained that the solidification stabilisation procedure can effectively

manage a wide range of contaminants including organic and inorganic matter.

It involves mixing cement and other hydraulic binders into contaminated waste

to physically solidify and chemically stabilise it. The cement mixture modifies

the physical properties of contaminants while triggering a chemical reaction,

rendering them chemically stable and immobile.

Physical bond

During solidification, cement mixed into soil reacts with water forming a physical

bond which immobilises contaminants. Solidification lowers the permeability

of treated material, inhibiting water movement and preventing leaching.

During stabilisation, hazardous constituents are chemically changed. Cement,

when added to contaminated soil, forms less soluble and more stable hydration

products with the contaminants.

“Each contaminated site is different and therefore the remedial solution

is bespoke. The solution is designed to take into account site conditions and

characteristics of the contamination, using a combination of laboratory tests,

field trials and on going monitoring works as the remediation works are implemented,”

says Mr Southall.