Geopolymer

About: Geopolymer is a research topic. Over the lifetime, 6776 publications have been published within this topic receiving 157991 citations. The topic is also known as: geopolymers.

Factors affecting the performance of metakaolin geopolymers exposed to elevated temperatures

Abstract: 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.

Influence of Slag as Additive on Compressive Strength of Fly Ash-Based Geopolymer

Abstract: Slag was utilized as an additive for fly ash-based geopolymers in this study. It was found that the incorporation of slag could significantly increase the compressive strength of the geopolymer. The compressive strength of geopolymer with 4.0% slag reached 50 and 70 MPa when cured for 14 days at 30 and 70°C , respectively. The mechanism of slag as additive on the enhancement of compressive strength of geopolymer was investigated using X-ray diffractometer (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and mercury intrusion porosimetry (MIP). The XRD and FTIR results showed that the addition of slag could generate more amorphous products and accelerate the reaction rate of raw materials. From XPS results, the decrease of binding energy and a broadening of peaks were observed for Si 2p , Al 2p , and O 1s elements due to the Ca2+ provided by slag. The decrease in binding energy was more favorable to zeolite formation. The results of MIP suggested that the 4% sl...

Silica fume as porogent agent in geo-materials at low temperature

Abstract: The synthesis of geopolymers based on alkaline polysialate was achieved at low temperature (∼25–80 °C) by the alkaline activation of raw minerals and silica fume. The materials were prepared from a solution containing dehydroxylated kaolinite and alkaline hydroxide pellets dissolved in potassium silicate. Then the mixture was transferred to a polyethylene mold sealed with a top and placed in an oven at 70 °C for 24 h. For all geopolymer materials, following dissolution of the raw materials, a polycondensation reaction was used to form the amorphous solid, which was studied by FTIR-ATR spectroscopy. The in situ inorganic foam based on silica fume was synthesized from the in situ gaseous production of dihydrogen due to oxidation of free silicon (content in the silica fume) by water in alkaline medium, which was confirmed via TGA-MS experiments. This foam has potential as an insulating material for applications in building materials since the thermal measurement has a value of 0.22 W m−1 K−1.