Testing the behavior of nanoalumina as a supplementary material to oil well cement pastes by different dispersive methods under CCS conditions

Abstract

The class G cement behavior after adding n-Al2O3 (0.5 and 1.5 wt%) was investigated using two dispersive methods, solid/liquid (ultrasonic probe sonicator - UPS) and solid/solid (planetary ball mill - PBM), under CCS conditions at 90 °C and 15 MPa for 21 d. The effects of n-Al2O3 and dispersion were evaluated through gas pycnometry, compressive strength, scanning electron microscopy/energy dispersive spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, microtomography, and Vickers microhardness. The unreacted specimens with the added n-Al2O3 exhibited a higher specific density and compressive strength. When the PBM method was used, the cement particle size decreased from 7.30 to 4.20 μm. The UPS dispersive method was more efficient than the PBM method. The CH content decreased, and a higher C–S–H polymerization was observed in the specimens with n-Al2O3. Microtomography results showed that the carbonation mechanism was the same for all specimens, but the UPS method enhanced the matrix densification. The UPS specimens with n-Al2O3 exhibited a smoother and thinner transition zone with a lower Ca/Si ratio. A lower carbonation depth was observed for the UPS specimens with 0.5 wt% of n-Al2O3. An increase in hardness and specific density after CO2 exposure was found in the UPS specimens. The best results in terms of chemical and mechanical properties were obtained using the UPS method for 1.5 wt%.