High power diode laser-based grout removal process

Due to its inherent versatility and advantageous operating characteristics, the high power diode laser (HPDL) is being recognised as an appropriate tool for many engineering tasks. This work details the characteristics and feasibility of a technique to remove industrial epoxy grout using a 120W HPDL. The highest removal rate was achieved with an O2 process gas owing to the high reactive nature of the gas. A threshold power density of approximately 300 W/cm2 was found to exist below which removal did not occur. Furthermore, the minimum interaction time, below which there was no removal of epoxy tile grout, was found to be approximately 0.5 s. The maximum theoretical removal rate that may be achievable using the HPDL was calculated as being 66 mm2/s. A microstructural analysis revealed significant differences in the epoxy grout surface structure before and after the HPDL radiation. The surface of the HPDL-treated samples exhibited a collection of grouped particles with pores and gaps, whereas the untreated samples displayed a continuous monostructured plane surface. Energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analyses revealed changes in the chemical composition of the epoxy grout after the HPDL radiation. In particular, CaO and CO2 were found in the HPDL treated samples resulting from decomposition of CaCO3 (limestone). In addition, SiO2 that existed in the un-treated epoxy grout material was not detected after HPDL processing due to the compound verification. A thermogravimetric and differential thermal analysis (TG-DTA) identified a sequence of thermal history for the epoxy grout which therefore allowed the prediction of the reactions that occur in the epoxy grout due to HPDL interaction.