New Cementitious Materials Based on Alkali‐Activated Fly Ash: Performance at High Temperatures

Abstract

This paper reports on a comparative study of the mechanical performance at different temperatures of a commercial Portland cement, used as a control, and a new cementitious material made from an 8M-NaOH activated fly ash and containing no OPC. Two types of mechanical tests were conducted: (i) high temperature mechanical tests, to determine the strength and fracture toughness of the two materials between 251 and 6001C, and (ii) post-thermal treatment tests, to evaluate the residual strength after 1 h of exposure to different temperatures (2001, 4001, 6001, 8001, and 10001C). In both cases, the results showed that the new cementitious material performed significantly better at high temperatures than the Portland cement control. Differential thermogravimetry (DTG)/TG, Fourier transform infrared (FTIR), and X-ray diffraction analyses were also conducted to analyze the mineralogical and microstructural variations taking place in the material as a result of high temperature exposure. The results of these tests were correlated with the mechanical behaviour observed.

Mechanical, thermal insulation, thermal resistance and acoustic absorption properties of geopolymer foam concrete

“…F5S0, which is a purely fly ash-based foam and thus contains a solely aluminosilicate gel, maintains its strength at 400°C, and increases by 11 50% after heating to 800°C. The good compressive strength retention up to 400°C (actually slight increase in this study) was also observed in the dense 8 M NaOH-activated fly ash binder [29]; the remarkable strength increase of F5S0 at 800°C is in agreement with these reported results. Rickard et al [30] also showed that the strengths of solid geopolymers increase after exposure to 1000°C, when low iron and low calcium-bearing fly ashes are used.…”

Ceniza de cascarilla de arroz como fuente de sílice en sistemas cementicios de ceniza volante y escoria activados alcalinamente

“…The fact that certain zeolites were, however, would appear to indicate that part of the amorphous gel may have converted into secondary crystalline reaction products such as Na-chabazite, also known as herschelite (R) (NaAlSi 2 O 6 .3H 2 O), and sodalite, otherwise denominated hydroxysodalite (S) (Na 4 Al 3 Si 3 O 12 OH) -. The presence of these compounds, also reported by other authors studying alkali-activated fly ash systems (45)(46)(47)(48), was confirmed by scanning electron microscopy, as shown in Figure 5. While both types of zeolites were found in the two systems, they were more abundant in FA-M3.…”

“…Lógicamente, esta fase no se identificó por DRX, pero sí se detectó la presencia de zeolitas, lo cual parece indicar que parte del gel amorfo se pudo transformar en un producto de reacción secundario cristalino correspondiente a Na-Chabacita o también llamada Herschelita (R) (NaAlSi 2 O 6 .3H 2 O) y sodalita o también llamada Hidroxisodalita (S) (Na 4 Al 3 Si 3 O 12 OH); estos compuestos han sido igualmente reportados por otros autores en sistemas de cenizas volantes activadas alcalinamente (45)(46)(47)(48). La presencia de estas zeolitas se confirma mediante microscopia electrónica de barrido tal como puede observarse en la Figura 5.…”

Effect of NaOH concentration and curing regime on geopolymer

“…There is a synergy between the parameters studied that can be better understand by the mineralogical and microstructural characterization of raw materials and final products [23], which are determined by X-ray diffraction or thermogravimetric analysis [24][25][26]. Most of studies on the geopolymer development report only compressive strength and x-ray diffraction results.…”