Hanson, the UK building materials group, has completed the acquisition of US aggregates company Material Service Corporation for $300m (£160m).

Hanson bought the firm from General Dynamics and it will be integrated with Hanson Aggregates North America. Material Service employs more than 800 people.

Material Service was founded in 1919 by the Crown family and its chairman Lester Crown will remain in the role. It sold more than 20 million tonnes of aggregates in 2005 and is estimated to have about 1.5 billion tonnes of reserves.

Since 1997, it has spent about £1.35bn on more than 50 bolt-on purchases in North America.

Hanson's purchases in the past year have been seen as a defence against acquisition-hungry foreign companies.