M and natural Z were used in this experiment as two different additives. M was obtained from Panzhihua City, Sichuan Province, China and Z was obtained from Yueyang City, Hunan Province, China. The two natural minerals were prepared by crushing and sieving until they turned into powders with particle sizes between 0.5 mm and 1.0 mm. The powders were washed with deionized water and then dried at 105 °C for 12 h in the oven. Atomic absorption spectroscopy was used in detecting the chemical compositions of the minerals (Hitachi-Z 5000, Japan