Sanral, the government-owned roads agency, plans to sue the biggest construction companies this month for colluding over highway improvement projects. It is suing builders, including Murray&Roberts and Aveng, following an investigation by the Competition Commission two years ago.The commission fined 15 construction companies a combined R1.46-billion for collusion over contracts, including those for building stadiums for the 2010 Soccer World Cup.Sanral's claim would include all the companies mentioned by the Competition Tribunal, the road agency's CEO, Nazir Alli, said.The amount of damages it was suing for had not been determined, he said."We are going to have a civil claim against them, we hope by the end of this month," Alli said.Ed Jardim, a spokesman for Murray & Roberts - the second-biggest construction company in South Africa - said it was aware of the Sanral action."We have on a few occasions in 2014 been in contact with Sanral regarding competition matters specifically and will continue to co-operate."Aveng, the country's biggest builder by revenue, said it could not comment "on the potential of civil litigation", and Basil Read Holdings was "not aware" of Sanral's decision to file claims for civil damages, according to spokesman Andiswa Ndoni.Murray& Roberts gained 1% to R13.80 on the JSE yesterday afternoon, paring the year's decline to 35%. Aveng fell by 0.9%...