Thermal Shock-resistant Cement

Technical Report · Wed Feb 01 04:00:00 EST 2012

DOI:https://doi.org/10.2172/1091187· OSTI ID:1091187

Sugama, T. ^[1]; Pyatina, T. ^[1]; Gill, S. ^[1]

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1. Brookhaven National Laboratory (BNL), Upton, NY (United States)

We studied the effectiveness of sodium silicate-activated Class F fly ash in improving the thermal shock resistance and in extending the onset of hydration of Secar #80 refractory cement. When the dry mix cement, consisting of Secar #80, Class F fly ash, and sodium silicate, came in contact with water, NaOH derived from the dissolution of sodium silicate preferentially reacted with Class F fly ash, rather than the #80, to dissociate silicate anions from Class F fly ash. Then, these dissociated silicate ions delayed significantly the hydration of #80 possessing a rapid setting behavior. We undertook a multiple heating -water cooling quenching-cycle test to evaluate the cement’s resistance to thermal shock. In one cycle, we heated the 200°C-autoclaved cement at 500°C for 24 hours, and then the heated cement was rapidly immersed in water at 25°C. This cycle was repeated five times. The phase composition of the autoclaved #80/Class F fly ash blend cements comprised four crystalline hydration products, boehmite, katoite, hydrogrossular, and hydroxysodalite, responsible for strengthening cement. After a test of 5- cycle heat-water quenching, we observed three crystalline phase-transformations in this autoclaved cement: boehmite → γ-Al₂O₃, katoite → calcite, and hydroxysodalite → carbonated sodalite. Among those, the hydroxysodalite → carbonated sodalite transformation not only played a pivotal role in densifying the cementitious structure and in sustaining the original compressive strength developed after autoclaving, but also offered an improved resistance of the #80 cement to thermal shock. In contrast, autoclaved Class G well cement with and without Class F fly ash and quartz flour failed this cycle test, generating multiple cracks in the cement. The major reason for such impairment was the hydration of lime derived from the dehydroxylation of portlandite formed in the autoclaved cement, causing its volume to expand.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 1091187
• Report Number(s): BNL--101087-2012-IR; EB4005020
• Country of Publication: United States
• Language: English

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