Mercury Intrusion Porosimetry Studies with Geopolymers: Fid-Bau Portal

Mercury Intrusion Porosimetry Studies with Geopolymers

Rao, Sudhakar M. / Acharya, Indra Prasad

Abstract The present study examines the role of micro-structure on the compressive strengths of geopolymers using mercury intrusion porosimetry technique. Geopolymers were synthesized from pozzolanas such as, class-F fly ash, kaolinite, metakaolinite, ground granulated blast furnace slag and red soil. Geopolymer reactions were accomplished by alkali activation of the pozzolanas using 10 M NaOH solution at 100 °C for 7-days. The geopolymers exhibited tri-modal nature of pores i.e., macro-pore mode (entrance pore radius: 25–5000 nm), meso-pore mode (entrance pore radius: 1.25–25 nm) and air void mode (entrance pore radius >5000 nm). The micro pores (entrance pore radius <1.25 nm) do not contribute to porosity of the geopolymers. The fly ash geopolymer exhibited largest total intruded volume (0.3908 cm3/g), while the red soil geopolymer exhibited the least intruded volume (0.0416 cm3/g). Interestingly, geopolymers with higher intruded volumes were characterized by larger compressive strengths. The experimental results also indicated that geopolymers with larger air voids + macro pores volume exhibited superior compressive strength; the results imply that geopolymers which develop an open microstructure during polymerization are characterized by larger compressive strength, possibly from stronger bond formation in the silico aluminate structure.