An intensifying multi-year infrastructure construction boom is cementing the best business conditions on record, leaving some of the nation's biggest companies struggling to keep up with a surge in demand that has buoyed Reserve Bank of Australia confidence in a wages rebound.

As Boral chief executive Mike Kane warned of becoming "stretched" by soaring demand for concrete and asphalt, a top Reserve Bank official said that falling unemployment would eventually lift wages, easing the burden on households that remain the economy's chief risk.