Hardening, High-Temperature Resistance and Acid Resistance of One-Part Geopolymers
- In this work, one-part geopolymers were synthesized by mixing solid silica and sodium aluminate with water. Pastes were cured at elevated temperatures (60–90 °C) and relative humidity (r.H.) of 80–98 %. After curing the pastes at 80 °C and 80% r.H for one day, the reaction virtually ceased. Depending on the silica source either geopolymer- zeolite composites or zeolite-free geopolymeric gel forms. The compressive strength of the geopolymer-zeolite composites was lower as the compressive strength of a pure geopolymer, mainly due to a significantly denser and glassy microstructure with less interfaces of the latter one. The major part of the thermal dehydration occurred between 60 °C and 200 °C. Up to 700–800 °C only minor changes of the phase assemblage have been observed for the composites. Depending on the paste composition either ceramic or amorphous phases form during exposure to 1000 °C. Compared to other AAM, very low ambient drying/wetting shrinkage/expansion was observed forIn this work, one-part geopolymers were synthesized by mixing solid silica and sodium aluminate with water. Pastes were cured at elevated temperatures (60–90 °C) and relative humidity (r.H.) of 80–98 %. After curing the pastes at 80 °C and 80% r.H for one day, the reaction virtually ceased. Depending on the silica source either geopolymer- zeolite composites or zeolite-free geopolymeric gel forms. The compressive strength of the geopolymer-zeolite composites was lower as the compressive strength of a pure geopolymer, mainly due to a significantly denser and glassy microstructure with less interfaces of the latter one. The major part of the thermal dehydration occurred between 60 °C and 200 °C. Up to 700–800 °C only minor changes of the phase assemblage have been observed for the composites. Depending on the paste composition either ceramic or amorphous phases form during exposure to 1000 °C. Compared to other AAM, very low ambient drying/wetting shrinkage/expansion was observed for the mortars The mortars furthermore provide very high resistance against sulfuric acid (pH 1). Huge parts of the corroded layer are not dissolved from the specimen and can still provide protection for a potential substrate. In terms of sulfuric acid resistance, above a critical CaO content, the formation of gypsum is introduced. This causes expansion, cracking and the decrease of the sulfuric acid resistance.…