Abstract

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