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Detecting the Water-soluble Chloride Distribution of Cement Paste in a High-precision Way
Published on: November 21, 2017
Study on performance and environmental benefits of oil well cement modified by alkali-activated fly ash and eggshell
Shaojun Zheng1, Guoliang Zhu1, Mingsheng Chen1
1Unconventional Cementing and Special Reinforcement Laboratory, China University of Geosciences, Wuhan 430074, China; Faculty of Engineering, China University of Geosciences, Wuhan 430074, China.
Abstract:
Traditional oil well cement production imposes a significant environmental burden due to its high energy consumption and considerable carbon emissions, making the development of low-carbon alternatives increasingly urgent. This study explores the use of alkali-activated fly ash (FA) and eggshell powder (ESP) as partial cement replacements for G-grade oil well cement (GOWC) to create more sustainable cementitious composites. Three blends: FA30 (30 wt% FA replacing GOWC), ESP30 (30 wt% ESP replacing GOWC), and FA15ESP15 (15 wt% each of FA and ESP) were prepared and cured hydrothermally at 25-80 °C for 7 days. Rheological tests showed pronounced shear-thinning behavior in all slurries, well described by the Power-law model (R2 > 0.98). ESP increased the consistency index K, while the FA15ESP15 blend exhibited balanced rheology with favorable pumpability. Among the three blends, FA15ESP15 showed the highest compressive strength (34.52 MPa at 80 °C, 7 d), exceeding FA30 (27.68 MPa) and ESP30 (23.49 MPa). Its porosity was also the lowest (18.96%) after 7 days of water bath curing at 50 °C, indicating a denser matrix. Microstructural analysis via thermogravimetric-differential thermal analysis (TG-DTG), X-ray diffraction (XRD), scanning electron microscope with energy-dispersive X-ray spectroscopy (SEM-EDS), and computed Tomography (CT) showed enhanced C-A-S-H formation, AFt-to-AFm conversion and 10.81 % Ca(OH)2 at 80 °C, confirming pozzolanic and hydration-promoting reactions. Carbon emission analysis revealed a substantial reduction (46.37 kg CO2/MPa), highlighting the synergy of performance, durability, and sustainability. These results suggest FA-ESP blends are a promising sustainable option for oil well cementing, contining better mechanical properties with a lower carbon footprint.
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