The effect of the inner structure on the absorptance of cement based exterior coatings

The relationship between the inner structure and the surface radiative properties of cement based exterior coatings has been studied. The radiative properties of exterior building coatings have considerable effect on the energy conservation used to maintain thermal comfort, and the cement based exterior materials are commonly used as the exterior coatings of buildings. The surface photographs of various cement based samples taken by scanning electron microscopy (SEM) and formal and statistical analysis of the SEM photograph images made by VIDS III equipment are presented. The monochromatic absorptance between 0.3–0.8 μm wavelength of the same surfaces has been measured before. The monochromatic absorptance of white Portland cement surfaces decreases when the water/cement ratio of the mixture increases since the inner structure of this cement has more crystalline content and the crystallites increase with the lower water/cement ratio. However, in the case of added Portland cement the monochromatic absorptances remain constant regardless of the water/cement ratio because the mixing water has no effect on the inner structure of this type of cement.