Carillion chief executive John McDonough said that the sale of the subsidiary would allow the company to focus on core markets.
He said: "The disposal of Expanded Piling is in line with our strategy for sustainable profitable growth through developing our business services and PPP investment activities."
McDonough added that Carillion was on the hunt for bolt-on acquisitions in health, transport and defence sectors in the UK. The company is also looking to expand its Canadian business.
Expanded Piling, which is based in Grimsby, Lincolnshire, will increase Laing O'Rourke's repertoire of in-house skills, which includes plant, precast concrete, joinery, stonework and steel frames.
Sources close to the deal said last month that O'Rourke was looking to expand its services by purchasing a cladding specialist.