Sulphate-based activation of a binary and ternary hybrid cement with portland cement and different pozzolans

Abstract

The purpose of this study was the development of a hybrid cement based on ordinary Portland cement (OPC) and different sulfate-based alkaline activated pozzolans using the one-part method dosed in binary and ternary mixtures. The factors evaluated were the percentage and type of pozzolan between fly ash, tepojal and volcanic sand and the use of alkaline activators between sodium and potassium sulfate. The amount of cement in conjunction with the use of alkaline activators benefits the reaction of the pozzolans, reducing the setting time according to isothermal calorimetry due to the consumption of portlandite when reacting with the pozzolans, which can be observed with the derivative of thermogravimetry at approximately 450°C. The shift of the main peaks in FTIR implies the reaction of the cementitious compounds towards the thermodynamically stable phase of C-A-S-H. The ternary mixture of OPC-Fly Ash-Tepojal/Volcanic Sand activated with 4% sodium sulfate are presented as the dosages with the best mechanical performance based on compressive strength due to a synergy effect between pozzolans. Tepojal and volcanic sand are chemically and physically presented as an eco-efficient alternative to natural pozzolan for use as cementitious material.