Combustion synthesis has been used to study the combustion characteristics and microstructure in the TiB2-CaO-Al2O3-SiO2 system. Both the combustion temperature and wave velocity decreased with an increase in the amount of silica. The reacted product consisted of solid crystalline TiB2 phase and CaO-Al2O3-SiO2 matrix. No significant reaction between the TiB2 and the matrix was observed. It was found that the binary calcium aluminate matrix (Ca12Al7O33 and CaAl2O4 compounds) could form amorphous phase (glass) at a high cooling rate. Under a normal cooling rate, significant formation of glass in the matrix was found possible only by adding another glass-former, e.g., silica NOD. The addition of SiO2 led to the formation of Gehelenite, to the reduction of the other crystal phases and to an increase in the glass phase in the matrix. A pure glass matrix was obtained for all compositions in the composition range from Ca12Al7O33 to CaAl2O4 compounds provided that an adequate amount of SiO2 was added. The resulting glass matrix can be expressed by the formula Ca-2(SixAl1-x)(3)O, where x = 0.32-0.58, depending on the composition. Effects of the TiB2 phase on the combustion synthesis process and on the microstructure are also discussed. TiB2 increased the reactivity and led to the formation of the molten matrix which was critical for glass formation. However, its effects on the vitrification of the matrix was considered to be minimum. The mechanism of glass formation in the matrix is discussed using the Zachariasen-Warren network theory.