Effect of Sintering Temperature and Calcium amount on Compressive Strength of Brushite-Metakaolin Polymer Materials

Abstract

The effect of Ca2+ amount and sintering temperature on mechanical properties of geopolymer-brushite (GPB) binders was investigated. Brushite and raw abandoned kaolinite clay thermally transformed into metakaolin were used for GPB synthesis. The complete phase and structural analyses were performed by X-ray powder diffraction, and Fourier transforms infrared spectroscopy (FT-IR). The pore-filling effect as a consequence of Ca2+ ions incorporation into the hybrid geopolymer networks improved the compressive strength. On the other hand, the chosen biscuit sintering at 800 and 900oC caused the phase transformation of brushite into calcium pyrophosphate, which negatively affected the compressive strength of such materials. The obtained results indicate that the usage of relatively high sintering temperatures is not always the necessary step for producing geopolymer-based types of cement with prominent mechanical properties.

U ovom radu ispitivan je uticaj količine dodatog brušita i temperature sinterovanja na mehanička svojstva geopolimer-brušit veziva. Kao polazni materijali za sintezu korišćeni su kaolinitska glina i sintetisani brušit. Kompletna fazna i strukturna analiza izvršena je difrakcijom rendgenskih zraka na prahu i infracrvenom spektroskopijom sa Furijeovom transformacijom. Efekat dodatka brušita u geopolimernu matricu poboljšao je pritisnu čvrstoću, dok je biskvitno pečenje izazvalo faznu transformaciju brušita u kalcijum pirofosfat što je negativno uticalo na pritisnu čvrstoću takvih materijala. Dobijeni rezultati ukazuju da korišćenje relativno visokih temperatura sinterovanja nije uvek neophodan korak za proizvodnju cementa na bazi geopolimera sa istaknutim mehaničkim svojstvima.