Characterisation and control of cementitious mixes with colour pigment admixtures

Cement is the most widely used and adaptable material in the construction industry due to its numerous good properties. On the other hand, it contributes to the emission of carbon dioxide and has a dull grey appearance. To remedy this, a new type of cementitious product is now being researched: architectural concrete. One way to improve the aesthetics of cementitious products is to incorporate colour pigment admixtures. The addition of admixtures, such as pigments might affect the mix properties. Therefore, the double aim of this study is (1) to characterise pigmented mortar in terms of physical, chemical and mechanical properties to assess how different types of pigment affect their properties, and (2) to propose a method to control the performance of these mixes adapting the maturity method. Then, samples were produced with three different pigments: red (iron (III) oxide), blue (cobaltous aluminate) and green (chromium (III) oxide) considering four different percentage: 0, 1, 5 and 10 % and two types of cement, CEM I-42.5 N and CEM II/A-M(S-V)-42.5 N. The characterisation used in this study allowed spotting major problems, which were not observed previously in the literature, with the usage of green pigment. Making the characterization of mixes an essential requirement before its final use in construction. Finally, the study proposed an equation which is more versatile than Plowman's equation that enables estimating the compressive strength of both reference and pigmented mixes