Preparation and properties of hexafluorosilicic acid series accelerators

Abstract

Shotcrete technology has been widely used in tunnel engineering, road repair, underground engineering, and other scenarios due to its advantages of simple construction and fast progress. Liquid alkali-free accelerator is a necessary additive used in sprayed concrete, which can quickly set the concrete in a short period of time. Therefore, the development of alkali-free liquid accelerator is of great significance. The purpose of this research is to obtain low-cost and high-performance accelerator products and explore the influence of aluminum sulfate, hexafluorosilicic acid, and other raw materials on performance and stability. The main research results are as follows: (1) The accelerator product with low cost and high performance has been prepared. Its aluminum sulfate content is about 43%, hexafluorosilicic acid content is about 17%, sodium aluminate content is about 21%, the initial setting time is 1′ 15″, the final setting time is 2′ 05″, and the 1-day compressive strength is 9.5 MPa. (2) F ion plays a solubilizing role in the solution, and the appropriate ratio of aluminum sulfate and fluorine ion can greatly enhance the stability of accelerator solution. (3) Under the same cost condition, the influence of aluminum sulfate on the condensation performance is far greater than that of hexafluorosilicic acid and sodium metaaluminate. Subsequent research and development should focus on how to effectively increase the solubility of aluminum sulfate.