The paper is focused on the assessment of laser-treated cementitious surfaces. It forms part of the larger study on laser cleaning process and its effect on modification of geometrical microstructure of cementitious composites. The great variation in absorptivity of highly developed surfaces of cementitious materials results in substantial differences in their responses to laser irradiation. Even though lasers can be successfully used to remove dirt from mortar surfaces, there are always some residual surface alterations associated with the removal of mortar, formation of cracks and glazing (melted mortar). Comprehensive understanding of surface processes resulting from laser interaction with substrate is essential in further industrial commercialisation of the technology. In order to address the problem a wide range of laser-treated samples with different internal microstructures, surface roughness and moisture content were studied. The characteristic features of all laser-cleaned areas included removal of mortar, formation of cracks and glassy patches. Systematic analysis of surface modifications resulting from laser cleaning confirmed a strong relationship between initial roughness of surfaces and their end conditions. An increase in initial surface roughness leads to more pronounced alterations in roughness and reduced tendency towards crack formation.
Cementitious surfaces, crack propagation, laser cleaning, porosity, surface roughness
 Cooper, M., Laser Cleaning in Conservation, an Introduction, Bath Press, UK, 1998.
 Costel, A., Garcia-Moreno, I., Gomez, C., Caballero, O. & Sastre, R., Cleaning graffi tion urban building by use of second and third harmonic wavelength of a Nd:YAG laser:A comparative study. Applied Surface Science, 202, pp 86–99, 2003. doi: http://dx.doi.org/10.1016/S0169-4332(02)01241-2
 Matsui, I., Nagai, K., Yuasa, N. & Ishigami, Y., Removing graffi ti on concrete surface by laser, Nihon University, Taisei corporation Japan. Proc. of the Int. Conference, Dundee, Scotland: UK, 2002.
 Liu K. & Garmire, E., Paint removal using lasers. Applied Optics, Optical Society of America, 34(21), 1995.
 Rozniakowski, K., P. Klemm, P. & Klemm, A.J., Some experimental result of laser beam interaction with surface layer of brick. Building and Environment, 36, pp. 485–491, 2001. doi: http://dx.doi.org/10.1016/S0360-1323(00)00012-3
 Li, L., Steen, W.M., Modern P.J. & Spencer, J.T., Laser removal of surface embedded contaminations on/in building structures. Proc. SPIE 2246, Laser Materials
Processing and Machining, 84, 1994: doi:10.1117/12.193126. doi: http://dx.doi.org/10.1117/12.193126
 Schmidt, M.J.J., Li, L. & Spencer, J.T., An investigation into the feasibility and characteristics of using a 2.5k W high power diode laser for paint stripping. Journal of Materials Processing Technology, 138, pp. 109–115, 2003. doi: http://dx.doi.org/10.1016/S0924-0136(03)00057-8
 Sanjeevan, P., Klemm, A.J. & Klemm, P., Removal of graffi ti from the mortar by using Q-switched Nd:YAG laser. Applied Surface Science, 253(20), pp. 8543–8553, 2007. doi: http://dx.doi.org/10.1016/j.apsusc.2007.04.030
 Sanjeevan, P., Klemm, A.J. & Klemm, P., The effects of microstructural features of mortars on the laser cleaning process. Eighth International Symposium On Brittle Matrix Composites, Warsaw, Poland, 2006. doi: http://dx.doi.org/10.1533/9780857093080.45
 McStay, D., Wakefi eld, R., Murray M. & Houston, H., Laser stone cleaning in Scotland, Historic Scotland, Edinburgh, 2005.
 Sanjeevan, P., The Effects of Geometrical Microstructure of Cementitious Composites on Laser Cleaning Process, PhD Thesis, Glasgow Caledonian University, UK, 2007.
 Hertz, K.D., Limits of spalling of fi re-exposed concrete. Fire Safety Journal, 38(2), pp. 103–116, 2003. doi: http://dx.doi.org/10.1016/S0379-7112(02)00051-6
 Khan, M.I., Factors affecting the thermal properties of concrete and applicability of its prediction models. Building and Environment 37, pp 607–614, 2002. doi: http://dx.doi.org/10.1016/S0360-1323(01)00061-0