White and Coloured Cements

Country/cement producer Fe Oj content, % FeO content, % Degree of whiteness 

Due to the absence of Ca(OH)2 in the calcium aluminate cement paste a higher durabiUty of glass fibers was expected in fiber reinforced composites. Majumdar [26] proved that the calcium aluminate cement composites had much better mechanical properties, but only the case of alkali resistant glass. 

The color of cement is the result of Ught absorption in the visible part of spectrum, due to the presence of transition metal ions. 

Teoreanu [27] reminds that the Ti02 admixture improves the whiteness because the Tf + ions displace Fe ions from tetrahedral positions, causing to occupy by them the positions with octahedral coordination. The similar positive effect has vanadium. 

Cobalt and chromium, in spite of the changing the Fe + ions coordination to the octahedral, reduce the whiteness, because they absorb the light stronger than the iron (III) ions [27, 30]. 

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