The news came as Keller unveiled a sharp rise in pre-tax profit for the first half of 2013.
Interim results for six months to June 30 show pre-tax profits hit £26.8m from £11m last time as turnover ticked-up to £644.6m from £613.8m.
Justin Atkinson, Keller Chief Executive said: “This is a much improved first-half performance, with three out of four of the Group’s divisions significantly more profitable than in the same period last year.
“We expect revenue in the second half to be broadly flat year on year, after adjusting for the effect of acquisitions.
“However, through careful contract selection and further benefit from our business improvement initiatives, we also expect to report an improved margin, taking us closer towards our 6% target.
“Accordingly, the Group’s results for the full year are expected to be towards the top end of current market expectations.”