2020-1-19 · Materials. Kaolin clay from Kalabsha quarry in Aswan, Egypt, was provided from Nourmetec Refractories in Wadi Houf, Cairo, Egypt. Kaolin clay (Fig. 1a) was crushed to particle size lower than 20 mm and calcined 3 h in a rotary kiln at 850 °C to get the reactive phase of metakaolin (MK-K). Metakaolin particles were ground and sieved to particle size under 100 μm, to increase its surface area.