(ShareCast News) - Keller Group posted a rise in first-half pre-tax profit as a recovery in US construction offset challenging conditions in many of its markets, and said it remains confident that results for the full year will be in line with current market expectations.Pre-tax profit grew 6% from the same period last year to £34.6bn and operating profit was up 6% at £37.7m, despite a decline in revenue to £755.8m from £788.2m due to a lower contribution from major projects. The operating margin, meanwhile, came in at 5% from 4.5%.In particular, the company was hit by difficult conditions in Canada and Australia. It said Canadian investment in the resources markets, particularly the oil sands market, was at a very low level. As a result, it has seen increased competition in commercial and infrastructure construction, adversely impacting margins in these areas.In addition, it said the construction market in Australia remains challenging and major projects in the resources industries are scarce, commercial and residential construction remains slow and there is a lull in investment in infrastructure.Still, the engineering specialist, which provides solutions to the construction industry, was able to raise its interim dividend by 5% to 8.8p per share thanks to the growth in profit.Investec, which rates the stock at 'buy', said: "Despite some headwinds in the first half of 2015, today's interims underline the recovery in US construction markets. This rebound, combined with the improvements Keller has implemented, means that the group is trading in line with market expectations for FY15."It said the shares continue to look good value and while there are clearly some near-term challenges in certain markets, the increase in operating profits despite lower revenues is a positive sign. At 12:07, shares were down 0.3% at 1,055p.