THE PROPERTIES OF HARDENED MPC MORTAR AND CONCRETE RELEVANT TO THE REQUIREMENTS OF RAPID REPAIR OF CONCRETE PAVEMENTS

There is an increasing need for new materials and methods for rapid but durable repair of concrete pavements where the closure time is in hours rather than days. The author outlines the main properties and reports on some aspects of durability derived from laboratory investigation and field experience. Magnesia phosphate cement (mpc) based materials provide a workable mix setting within 15 minutes at normal temperature and harden to sufficient strength within one hour. Unlike most fast setting, early strength materials, mpc mortar can be considered dimensionally stable. Its coefficient of thermal expansion falls within the range of that of conventional mortar and concrete and its modulus of elasticity is similar to that of high strength concrete when tested under identical conditions. Pull-out tests show a satisfactory strength of bond with steel. Although mpc material has a low permeability it allows water vapour to diffuse through the matrix. Experience has shown that fuels, engine oils, urea and other de-icing materials have no effect on mpc repair patches. Details are given of successful applications on roads, motorways, bridge decks, airfields and industrial floors. (TRRL)