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 ra diative properties of exterior building coatings have considerable eff ect on the energy conservation used to maintain thermal comfort, and t he cement based exterior materials are commonly used as the exterior c oatings of buildings. The surface photographs of various cement based samples taken by scanning electron microscopy (SEM) and formal and sta tistical analysis of the SEM photograph images made by VIDS III equipm ent are presented. The monochromatic absorptance between 0.3-0.8 mum w avelength of the same surfaces has been measured before. The monochrom atic 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 incr ease with the lower water/cement ratio. However, in the case of added Portland cement the monochromatic absorptances remain constant regardl ess of the water/cement ratio because the mixing water has no effect o n the inner structure of this type of cement.