Nano-chemo-mechanical signature of conventional oil-well cement systems: Effects of elevated temperature and curing time

Krakowiak, Konrad J.; Thomas, Jeffrey J.; Musso, Simone; James, Simon; Akono, Ange-Thérèse; Ulm, Franz Josef

doi:10.1016/j.cemconres.2014.08.008

Cited by 125 publications

(55 citation statements)

References 57 publications

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“…The addition of silica flour (S1-S3) with 3.25 -63.13 µm median particle sizes effectively mitigates the strength This result means that silica flour has participated in the pozzolanic reaction and likely changed the composition of hydrated phases [25]. In the previous literature, 35 % BWOC was recommended as the optimal incorporation of silica flour, suggesting that values above this one lead to worse strength degradation-combating effects, which is consistent with the results of the samples with silica flour S1 and S3 incorporation but not with those of the sample modified with silica flour S2 [26,27]. To further evaluate the abnormal phenomena, we prolonged the curing time to 28 days for samples with 67 % BWOC silica flour S2 incorporation.…”

Section: Compressive Strengthsupporting

confidence: 83%

“…Comparing the compressive strengths of the samples in Figures 3c and 3b subjected to 260 °C and 21 MPa between 28 days and 7 days, the strengths of the samples with 43 % BWOC silica flour S1, S2 and S3 incorporation decrease 4.8 %, 11.6 % and 22.6 %, respectively. This result indicates that the optimal particle size of silica flour should be 63.13 µm (median particle size of S1), which is coarser than the universally adopted 325 mesh (45 µm) [1,8,26,27], suggesting that very fine silica flour may not be a good choice for the anti-retrogression performance of cement slurry in the HTHP environment. The samples with 43 % and 67 % BWOC silica flour S2 incorporation show 11.6 % and 31.8 % compressive strength loss after curing at HTHP from 7 to 28 days because the higher silica flour amounts exceed the amount required for the reaction [28].…”

Section: Compressive Strengthmentioning

confidence: 95%

See 1 more Smart Citation

Influence of the Particle Size Distribution of Silica Flour on the Mechanical and Microstructural Properties of Oil Well Cement Paste Exposed to HTHP Conditions

Xie¹

2019

Ceramics - Silikaty

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Silica flour is used to mitigate the strength retrogression and microstructure degradation problems of oil well cement paste in high temperature wells. This study investigates the effects of the particle size distribution of silica flour on the thermal stability of cement paste. After 7 days of hydrothermal curing at 80 °C, the cement paste was exposed to further aging for 7 or 28 days under high temperature and high pressure (HTHP) conditions in a sealed chamber at 260 °C (500 °F) and 21 MPa (2900 psi). The results show that 43% silica flour by weight of cement (BWOC) mitigates the strength degradation of silica-stabilized Portland cement (SSPC), and course silica flour (63.13 and 48.25 µm) maintains the strength stability of SSPC better than fine silica flour (3.25 µm). The transformation of C-S-H gel to xonotlite in SSPC was influenced by the silica particle size. The relatively fine silica flour (d 50 = 3.25 µm) accelerates the consumption of calcium hydroxide during the pozzolanic reaction, resulting in a poorer strength stability of SSPC than the courser silica flour (d 50 = 63.13 and 48.25 µm). The silica flour with an average particle size of 48.25 µm is more conducive to crystallization of xonotlite on the crystal plane corresponding to a diffraction angle of 25.5° than the other size silica flour.

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Section: Compressive Strengthsupporting

confidence: 83%

Section: Compressive Strengthmentioning

confidence: 95%

Influence of the Particle Size Distribution of Silica Flour on the Mechanical and Microstructural Properties of Oil Well Cement Paste Exposed to HTHP Conditions

Xie¹

2019

Ceramics - Silikaty

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“…2A, we plot the scattering intensity computed from the simulation data (Materials and Methods) for η = 0.33 and η = 0.52 and the SANS data from ref. 28. Apart from the lowest wave vectors (where the simulations data are limited by the system size), the curves can be readily compared, having considered that the calculations are in real physical units but that the signals are not expected to match exactly because of the presence of other hydration products in the experiments (e.g., ettringite, Portlandite, etc.)…”

Section: Resultsmentioning

confidence: 99%

Mesoscale texture of cement hydrates

Ioannidou

Krakowiak

Bauchy

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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206

146

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Strength and other mechanical properties of cement and concrete rely upon the formation of calcium-silicate-hydrates (C-S-H) during cement hydration. Controlling structure and properties of the C-S-H phase is a challenge, due to the complexity of this hydration product and of the mechanisms that drive its precipitation from the ionic solution upon dissolution of cement grains in water.Departing from traditional models mostly focused on length scales above the micrometer, recent research addressed the molecular structure of C-S-H. However, small-angle neutron scattering, electron-microscopy imaging, and nanoindentation experiments suggest that its mesoscale organization, extending over hundreds of nanometers, may be more important. Here we unveil the C-S-H mesoscale texture, a crucial step to connect the fundamental scales to the macroscale of engineering properties. We use simulations that combine information of the nanoscale building units of C-S-H and their effective interactions, obtained from atomistic simulations and experiments, into a statistical physics framework for aggregating nanoparticles. We compute small-angle scattering intensities, pore size distributions, specific surface area, local densities, indentation modulus, and hardness of the material, providing quantitative understanding of different experimental investigations. Our results provide insight into how the heterogeneities developed during the early stages of hydration persist in the structure of C-S-H and impact the mechanical performance of the hardened cement paste. Unraveling such links in cement hydrates can be groundbreaking and controlling them can be the key to smarter mix designs of cementitious materials.U pon dissolution of cement powder in water, calcium-silicate-hydrates (C-S-H) precipitate and assemble into a cohesive gel that fills the pore space in the cement paste over hundreds of nanometers and binds the different components of concrete together (1). The mechanics and microstructure are key to concrete performance and durability, but the level of understanding needed to design new, more performant cements and have an impact on the CO 2 footprint of the material is far from being reached (2).Most of the experimental characterization and models used to predict and design cement performance have been developed at a macroscopic level and hardly include any material heterogeneity over length scales smaller than micrometers (3). However, EM imaging, nanoindentation tests, X-rays and neutron scattering, and NMR analysis as well as atomistic simulations have now elucidated several structural and mechanical features concentrated within a few nanometers (4-8). The hygrothermal behavior of cement suggests a hierarchical and complex pore structure that develops during hydration and continues to evolve (1, 9-11). NMR and small-angle neutron scattering (SANS) studies of hardened C-S-H identified distinctive features of the complex pore network and detected significant structural heterogeneities spanning length scales between tens and hu...

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“…As an established chemical strategy, fine crystalline silica stabilizer is added to avert the strength deterioration of Portland cement when exposed to ultra-high temperature [12]. Portland cement has calcium oxide to silicon dioxide (C/S) ratio close to 3.1 but upon addition of extra quantity of silica (typical dosage~35% bwoc) [13,14] decreases the ratio close to 1.0, desirable for the stable formation of non-retrogressing stronger cement at temperature above~230 F (110 C).…”

Section: Introductionmentioning

confidence: 99%