Shares in infrastructure group Balfour Beatty were unwanted on Wednesday, dragging the construction and materials sector lower.The firm said it expects markets to remain tough in the short term as it posted a meagre rise in underlying pre-tax profits and revenues for the half year to 1 July. Underlying pre-tax profits rose to £138m from £133m, while revenues edged up to £5.222bn from £5.16bn.Head of dealing at Prime Markets Richard Curr said, "concerns over the global economy have [...] weighed heavily on the shares, which have now returned to 3-year lows, added to which the half year statement today provides little comfort or visibility, citing the impact of the reduction in government spending on the UK order book and delays and the lack of bank financing in US commercial markets."Meanwhile, the miners were in demand, led by FTSE 100 giant Eurasian Natural Resources Corporation (ENRC).The Kazakhstan-focused miner pointed to continued growth in Kazakhstan's neighbour China and the recovery elsewhere as it posted a sharp rise in profits and revenues in the first half year. Revenues were up by 32% from the same period the previous year at $4.011m while EBITDA (earnings before interest, depreciation and amortisation) climbed by 33% to $1.927bn.Sector peers Fresnillo and Kazkhmys were also higher.BCTop performing sectors so far todayAutomobiles & Parts 4,767.32 +2.77%Food Producers & Processors 5,380.19 +1.73%Health Care Equipment & Services 3,267.80 +1.26%Mining 21,956.61 +1.21%Real Estate Investment & Services 1,517.82 +1.15%Bottom performing sectors so far todayConstruction & Materials 3,145.11 -3.63%Industrial Metals & Mining 5,908.53 -2.37%Financial Services 5,095.54 -1.60%Forestry & Paper 5,536.48 -1.53%Life Insurance 3,839.29 -1.47%