Alkali-reinforced hydrothermal synthesis of lathy tobermorite fibers using mixture of coal fly ash and lime

The hydrothermal synthesis of tobermorite fibers was explored using mixture of coal fly ash (CFA) and slaked lime. Only tiny tobermorite fibers with 2-3 mu m in length and 0.01-0.5 lm in diameter could be obtained at 220 degrees C for 3-7 h. In the presence of 20 g/L NaOH, the dissolution of silicon- and aluminum-bearing constituents in CFA was accelerated, and well-crystalline tobermorite fibers with 5-10 mu m in length and 0.01-0.5 mu m in diameter were synthesized at 220 degrees C for 1 h. Tobermorite fibers were aggregated into porous spherical constructions, making the synthetics potential for production of energy-saving building materials. (C) 2019 Elsevier Ltd. All rights reserved.