Use of the Algerian natural pozzolan for the production of a geopolymer as a complete cement replacement

Abstract

This paper investigates the use of the Algerian Beni Saf natural Pozzolan (BSP) to produce a geopolymer (GP) as a complete replacement material for the traditional binder of OPC. No such study has been carried out on using the Algerian BSP for GP synthesis, especially as the latter’s properties have a high dependency on the precursor material characteristics. The research sets to establish the optimal combination of alkaline activators that corresponds to the BSP, sand content, and curing temperature. A series of experiments were carried out on BSP-based GP mortars in fresh and hardened states to investigate properties such workability, CS, and FS at 3, 7, 28, and 90 days. Selected GP samples were subjected to microstructure characterization experiments, including FTIR and SEM-EDS. The results have shown that workability is greatly affected by the studied parameters. The optimal values of CS and FS at 28 days were 38 and 12 MPa, respectively. These were obtained for sand/pozzolan ratio, Si/Al, Si/Na, and temperature equal to 2.5, 6.1, 2, and 80 °C respectively. The microstructure analyses also revealed a considerable change in the microstructure GP samples.