Boosted by £21m from the sale of its Avonmouth facility, Keller made a pre-tax profit of £55.2m for the six months to 30th June 2017 (2016 H1: £25.0m) on revenue up 17% to £991.1m (2016 H1: £849.7m).
Underlying pre-tax profit was up 30% to £39.3m.
With contract awards continuing in the first half of 2017, the order book is up 20% on a year ago.
However, the results were marred by the death of 18 employees in South Africa when a heavy truck ran head on into two buses transporting employees and contractors from Keller company Franki Africa to work at the Nkomati Mine on 4th July.
Chief executive Alain Michaelis said: "We have all been immensely saddened by the recent road traffic accident in South Africa, in which 18 Keller employees lost their lives and a further 15 were injured. Our deepest sympathies go out to the victims and their families, friends and colleagues. Our priority is providing support to them during this difficult time.
"From a financial perspective, our results show significant overall profit growth and we have ended the half year with a record order book. As a result, the board is confident that the group's full year 2017 results will be in line with its expectations."