Molecular Modelling of the Mechanism of Action of Borate Retarders on Hydrating Cements at High Temperature

Bell, I. S.; Coveney, Peter V.

doi:10.1080/08927029808022042

Cited by 26 publications

(10 citation statements)

References 15 publications

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“…The results from this study are in agreement, with a change in consistency and viscosity noted at addition levels around 1-2%. Borate ions react with cement to form calcium borate phases, which are adsorbed onto cement particles to precipitate slightly soluble layers over the cement, thus preventing the usual cement hydration (Atabek et al, 1992;Bell and Coveney, 1998;Bensted et al, 1991;Csetenyi and Glasser, 1995;Demirbas and Karslioglu, 1995;Ramachandran and Lowery, 1998). This coating of particles suggests that the mechanism by which these inorganic compounds retard hydration differs from how organic compounds retard, which is largely based on complexation of calcium from the cement (Taylor, 1997).…”

Section: Discussionmentioning

confidence: 99%

Inorganic anions as retarders for deep borehole disposal grouts

Collier

Balboa

Milestone

et al. 2017

Advances in Cement Research

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Deep borehole disposal (DBD) provides an alternative to comparatively shallow mined repository concepts for many high-level radioactive wastes. Filling the annular space around the waste containers with cement grout will support them during placement and seal against ingress of groundwater. The elevated temperature and pressure ($120°C and 50 MPa) will cause acceleration of grout thickening and setting, so retardation is required. The DBD Research Group at The University of Sheffield has developed grouts based on class G oil well cement that use organic retarders, but their presence may increase the solubility of any radionuclides released from the waste packages. New DBD grout formulations using sodium phosphate and sodium borate as inorganic retarders are reported in this paper. To place the wet grout, the onset of thickening needs to be delayed for at least 4 h. Sodium borate was found to provide this retardation at 90°C (0·75% addition) and nearly retarded sufficiently at 120°C (1% addition). Sodium phosphate did not provide sufficient retardation at either temperature. Neither compounds influenced the phases formed, but may suppress the crystallisation of calcium silicate hydrates. This work demonstrates that the performance of these inorganic materials in this application is inferior to that of organic retarders.

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Section: Discussionmentioning

confidence: 99%

Inorganic anions as retarders for deep borehole disposal grouts

Collier

Balboa

Milestone

et al. 2017

Advances in Cement Research

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show abstract

“…It can be seen in Figure 10(b), a number of spherical, sheet, strip, and block body were appeared in addition to a small amount of whisker group because of the chelation17–20 of PAIN with calcium, the mechanism of chelation was shown in Figure 11. This chelation effectively retard the formation of solid‐phase gel precipitation and growth of Ca(OH) 2 crystal, resulting in the hydration reaction of cement slurry blocked.…”

Section: Resultsmentioning

confidence: 99%

Terpolymerization and performance of 2‐acrylamide‐2‐methyl propane sulfonic acid / itaconic acid / N‐vinyl‐2‐pyrrolidone

Zhang

Zhuang

Liu

et al. 2010

J of Applied Polymer Sci

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Using 2-acrylamide-2-methyl propane sulfonic acid (AMPS), itaconic acid (IA), and N-vinyl-2-pyrrolidone (NVP) as monomers, a new retader terpolymer AMPS/IA/NVP (PAIN) was synthesized by free radical aqueous solution copolymerization and characterized by FTIR and H-NMR. Through the orthogonal experiment, the optimum reaction conditions of copolymerization were obtained: NVP 7.5 wt (mass fraction) %; regulator V 4%; reaction temperature 60 C; initiator 1 wt %. The intrinsic viscosity number of PAIN synthesized with different amount of regulator (isopropanol) was determined, finding that the regulator can change the molecular weight and distribution of PAIN. Through the thickening experiment in high temperature and high pressure, it was found that PAIN had an excellent retardation property in high temperature, and the thickening times of the cement slurries with 1% (BOWC) PAIN were up to 256 min at 110 C and 234 min at 130 C, respectively. The PAIN was even stable when the temperature below 350 C proved by TG-SDTA analysis. Moreover, the retarding mechanism of PAIN was analyzed and discussed.

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“…While the structure of calcium silicate hydration (C–S–H) has garnered the majority of attention by molecular‐scale modelers, presently, the few atomistic studies involving admixtures with cements have primarily focused on set retarder interactions with different cement phases rather than aspects such as admixture‐pore water and air‐water interface behaviors . However, the general study of surfactant assemblies at the air – water interface using molecular modeling is well‐represented .…”

Section: Introductionmentioning

confidence: 99%

Behavior of organic compounds in the pore solution of cement—experimental and molecular dynamics study

2017

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This study summarizes molecular dynamics (MD) simulations and experiments using four ester-based cement shrinkage reducing agents in pure water and simulated cement pore solution. The esters were found to completely dissociate in the alkaline pore solution to form acid and alcohol analogue compounds. The alcohol analogues were further found to be entirely responsible for the surface tension reduction capacity of the parent compounds. In addition, the surface tension reduction capacity of the alcohol analogues are not affected by relevant counterions present in the pore solution. The MD-based analysis show that water molecules form stable hydrogen bonds with head groups of the alcohol analogues and that relevant dissolved ions, K + and Na + , have virtually no effect on hydrogen bond stability. Furthermore, the higher the self-diffusion coefficient of water molecules in the neighborhood of the head groups the lower the resulting surface tension at the air-water interface. K E Y W O R D Satomistic simulation, portland cement, shrinkage

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Molecular Modelling of the Mechanism of Action of Borate Retarders on Hydrating Cements at High Temperature

Cited by 26 publications

References 15 publications

Inorganic anions as retarders for deep borehole disposal grouts

Inorganic anions as retarders for deep borehole disposal grouts

Terpolymerization and performance of 2‐acrylamide‐2‐methyl propane sulfonic acid / itaconic acid / N‐vinyl‐2‐pyrrolidone

Behavior of organic compounds in the pore solution of cement—experimental and molecular dynamics study

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