High temperature exposure of alkali-activated coal fly ashes

Creative Commons License

Seyedian Choubi S., Meral Akgul Ç.

JOURNAL OF BUILDING ENGINEERING, cilt.59, 2022 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 59
  • Basım Tarihi: 2022
  • Doi Numarası: 10.1016/j.jobe.2022.105081
  • Dergi Adı: JOURNAL OF BUILDING ENGINEERING
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Compendex, INSPEC
  • Anahtar Kelimeler: Thermal exposure, Alkali-activated fly ash, Thermal conductivity, Mechanical performance, Microstructure, CALCIUM-CARBONATE CALCITE, A-S-H, THERMAL-DECOMPOSITION, PART I, GEOPOLYMERS, PERFORMANCE, BEHAVIOR, RESISTANCE, CERAMICS, MICROSTRUCTURE
  • Orta Doğu Teknik Üniversitesi Adresli: Evet

Özet

This study systematically investigates the impact of heat exposure on the performance of a wide range of alkali-activated coal fly ashes (AAF). Three low-Ca and three high-Ca coal fly ashes (CFAs) were activated with 10 M NaOH at an activator-to-CFA ratio of 0.5. Prepared pastes were cast into 5 x 5 x 5 cm cubes (for mechanical tests) and phi 6 x 4 cm cylinders (for thermal constant tests), cured at 80 ? for 24 h, and then stored in the fog room for 28 days. Samples were then exposed to 400, 700, and 1000 ? for 1 h and cooled in the furnace. The morphological and mineralogical changes due to heat exposure were studied through X-ray diffraction (XRD), thermogravimetric analysis (TGA/DTA), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR). The performances of the AAF samples before and after heat exposure were evaluated by measuring thermal conductivity (lambda), volumetric specific capacity (c(vol)) and compressive strength. Mechanical performance varied considerably after exposure to elevated temperatures depending on the exposure temperature and intrinsic properties of the activated CFA, low-Ca AAFs being more stable than high-Ca AAFs, whereas exposure significantly reduced lambda and c(vol) values for all AAFs.