Influence of calcium aluminate cement on geopolymerization of natural pozzolan

• Pozzolan geopolymer mixtures were designed adding CAC up to 24% of total binder.
• CAC enhances compressive strength development under hydrothermal curing condition.
• Workability and setting time reduced with increase of CAC.

This paper presents a study on the influence of calcium aluminate cement (CAC) on the geopolymerization of natural pozzolan. CAC was incorporated at 0, 8, 16 and 24% replacement by weight of pozzolan and aqueous solutions of NaOH and sodium silicate with different SiO2/Na2O ratios (MS) and Na2O contents were used as alkali activators. The setting time, workability, compressive strength, (SiO2 + Al2O3)reactive content and free alkali content of cured cement samples were determined. Complementary studies using semi-adiabatic calorimetry, FTIR spectroscopy and XRD were also performed. According to the results, incorporation of CAC increases the reactive Al of the binder, accelerates the dissolution of reactive contents and facilitates the progress of the polycondensation reactions. These improvements in the geopolymerization reactions result in the formation of a more cross-linked aluminosilicate network that exhibits higher compressive strength.