CONCRETE TRIALS soon to start at Stansted Airport could save tens of thousands of cubic metres of pavement quality (PQ) concrete on the Terminal 5 (T5) project, a senior BAA project manager said last week.
The experimental mix - dubbed F8 - could save up to 10% of the 350,000m 3of PQ concrete the project would eventually require.
'The planned introduction of the Airbus A380 superjumbo means the T5 pavements will be among the most heavily loaded in the world, yet they have to be laid on very poor London Clay fill, ' said BAA airside delivery team leader David Harwood.
'We are looking at pavement depths in excess of 600mm, which is well above the accepted maximum for slipforming, ' he told concrete lobby group Britpave's 10th annual seminar.
Since 1997 the Pavement Team - a partnership between BAA and Amec Civil Engineering - has been developing its standard F6 mix which has a target flexural strength of 6N/mm 'We experimented with superplasticisers, fibres and microsilica and found that a superplasticiser enabled us to achieve an F7 mix with a 30% fly ash replacement, ' said Pavement Team head of performance improvement Andy Delchar.
'Recent trials at Stansted proved we could successfully slipform this mix at a depth of 640mm and we are now standardising on F7 for most future projects. But for Terminal 5 the potential savings of an F8 mix are enormous.'
Working with admixture specialist Grace, the team has successfully achieved a mix with a flexural strength of more than 8N/mm 2in laboratory tests.
Trials starting within the next two weeks at Stansted will examine its potential at full scale.
But Delchar said that with a target water/cement ratio of only 0.28, the cost of admixtures may outweigh the potential savings of a 10% reduction in pavement thickness.