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calcium content. In other words, the finał color of bricks depends mainly on the Chemical composition of raw materia ls, there content, the degree of oxidation and sintering atmosphere. The visual e.\amination of sintered bricks shows that the incorporation of TCPMT in the mixes modifies the reference brick color from red to light yellow (Figurę 5.8). Iron oxide is responsible of the red color in Mo bricks and the yellow color in M40 bricks is attributed to the increased calcium content provided by TCPMT.

brick

brick

Figurę 5.8 Color variation with the addition of 40 wt.° o of TCPMT.

5.3.2.3 Mineralogical characterization

In order to clarify the effect of the addition of TCPMT on sintered brick properties. FTIR and XRD analysis were performed on finely grinded powders of sintered bricks and SEM observations were investigated on fractured bricks. The main crystalline phases formed during the heating process are presented in Figurę 5.9. The XRD spectrum (Figurę 5.8-a) highlights the formation of new crystalline phases in M30 sintered samples such as anhydrite (CaSCfj), magnetite (Fe3CXi) and augite (Ca(Fe.Mg)Si₂06) which do not exist in the reference brick. The formation of augite is the result of the reaction between siliceous and calcium minerals. This finding is