Geopolymer concrete: A review of some recent developments

Effect of elevated temperatures on geopolymer paste, mortar and concrete

Fly ash-based geopolymer: clean production, properties and applications

Geopolymer foam concrete: An emerging material for sustainable construction

A new type of geopolymer composite was synthesized from two industrial wastes, red mud (RM) and rice husk ash (RHA), at varying mixing ratios of raw materials and the resulting products characterized by mechanical compression testing, X-ray diffraction, and scanning electron microscopy to assess their mechanical properties, microstructure, and geopolymerization reactions. Prolonged curing significantly increases the compressive strength and Young’s modulus, but reduces the ductility. Higher RHA/RM ratios generally lead to higher strength, stiffness, and ductility, but excessive RHA may cause the opposite effect. The compressive strength ranges from 3.2 to 20.5 MPa for the synthesized geopolymers with nominal Si/Al ratios of 1.68–3.35. Microstructural and compositional analyses showed that the final products are mainly composed of amorphous geopolymer binder with both inherited and neoformed crystalline phases as fillers, rendering the composites very complex composition and highly variable mechanical properties. Uncertainties in the composition, microstructure, the extent of RHA dissolution, and side reactions may be potential barriers for the practical application of the RM–RHA based geopolymers as a construction material.

Synthesis and characterization of red mud and rice husk ash-based geopolymer composites

Comparative performance of geopolymers made with metakaolin and fly ash after exposure to elevated temperatures

This paper presents a study on geopolymers and geopolymer/aggregate composites made with class F fly ash. Samples were heated up to 800 °C to evaluate strength loss due to thermal damage. The geopolymers exhibited strength increases of about 53% after temperature exposure. However, geopolymer/aggregate composites with identical geopolymer binder formulations decreased in strength by up to 65% after the same exposure. Test data from dilatometry measurements of geopolymers and aggregates provides an explanation for this behavior. The tests show that the aggregates steadily expanded with temperature, reaching about 1.5–2.5% expansion at 800 °C. Correspondingly, the geopolymer matrix undergoes contraction of about 1% between 200 °C and 300 °C and a further 0.6% between 700 °C and 800 °C. This apparent incompatibility is concluded to be the cause of the observed strength loss. This study presents the results of 15 different geopolymer combinations (i.e. mixture proportions, curing and age) and four different aggregates.

Damage behavior of geopolymer composites exposed to elevated temperatures

The effects of geopolymer binder systems exposed to elevated temperatures are examined. Geopolymers investigated were synthesized from metakaolin, activated by combinations of sodium/potassium silicate and sodium/potassium hydroxide. The specimens were then exposed to temperatures of 800 °C. The factors studied were: (1) calcining temperatures of kaolin; (2) Si/Al ratio of the geopolymer; (3) activator/metakaolin ratio; (4) curing temperature; and (5) alkali cation type. Altogether 30 geopolymer formulations were studied. The samples were subjected to compressive strength, thermogravimetry, and scanning electron microscopy tests. Results showed that Si/Al ratio has a significant influence on elevated temperature exposure deterioration. Lesser strength loss due to elevated temperature exposures were observed in geopolymer with high Si/Al ratios (>1.5). The geopolymer binders activated by potassium-based activators showed an enhanced post-elevated temperature exposure performance compared to sodium-based systems. The optimum calcining temperature of kaolin and curing temperatures for improved temperature performance are also reported.

Daniel Lean Yew Kong

Papers

Comparative performance of geopolymers made with metakaolin and fly ash after exposure to elevated temperatures

Damage behavior of geopolymer composites exposed to elevated temperatures

Factors affecting the performance of metakaolin geopolymers exposed to elevated temperatures

Effect of aggregate size on spalling of geopolymer and Portland cement concretes subjected to elevated temperatures

Damage due to elevated temperatures in Metakaolinite-based geopolymer pastes