High power diode laser surface glazing of concrete

This present work describes the utilisation of the relatively novel high power diode laser\ud(HPDL) to generate a surface glaze on the ordinary Portland cement (OPC) surface of\udconcrete. The value of such an investigation would be to facilitate the hitherto impossible\udtask of generating a durable and long-lasting surface seal on the concrete, thereby extending\udthe life and applications base of the concrete. The basic process phenomena are investigated\udand the laser effects in terms of glaze morphology, composition and microstructure\udare presented. Also, the resultant heat affects are analysed and described, as well as\udthe effects of the shield gases, O2 and Ar, during laser processing. HPDL glazing of OPC\udwas successfully demonstrated with power densities as low as 750 W cm-2 and at scanning\udrates up to 480 mm min-1. The work showed that the generation of the surface glaze resulted\udin improved mechanical and chemical properties over the untreated OPC surface of concrete.\udBoth untreated and HPDL glazed OPC were tested for pull-off strength, rupture strength,\udwater absorption, wear resistance and corrosion resistance. The OPC laser glaze exhibited\udclear improvements in wear, water sorptivity, and resistance (up to 80% concentration) to\udnitric acid, sodium hydroxide and detergent. Life assessment testing revealed that the OPC\udlaser glaze had an increase in actual wear life of 1.3 to 14.8 times over the untreated OPC\udsurface of concrete, depending upon the corrosive environment