For the synthesis of CaO–Ca12Al14O33 the procedure
suggested from Li et al [25] was followed. 28.4 g of aluminum nitrate enneahydrate (Al(NO3)3 Æ 9H2O) and
26.2 g of calcined calcium hydroxide (Ca(OH)2) was added
into a mixture of 150 ml 2-propanol and 750 ml distilled
water so that the weight ratios of CaO to Ca12Al14O33 to
be 75/25. The solution was stirred for 1 h at 75 C and
dried at 120 C overnight. The sample was calcined at
500 C for 3 h in the presence of air. After calcination, distilled
water was added to the mixture and the obtained
paste was dried at 120 C overnight and then calcined at
900 C for 1.5 h.