Physicochemical properties of the Portland cement-based mortar exposed to deep seafloor conditions at a depth of 1680 m

Kobayashi, Mari; Takahashi, Kohshin; Kawabata, Yuichiro

doi:10.1016/j.cemconres.2020.106335

Cited by 27 publications

(30 citation statements)

References 37 publications

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“…These results indicate that damages and dimensional changes at submillimeter to submicron scales as was reported in our previous study (Kobayashi et al 2021) do not appear due to the action of short-term hydraulic pressure.…”

Section: Resultssupporting

confidence: 87%

“…As already reported in Kobayashi et al (2021), specimens salvaged from the deep seafloor with a depth of 1680 m at Tarama Knoll were severely damaged as shown in Fig. 2.…”

Section: Effects Of Short-term Hydraulic Pressure On a Laboratory Scale -The First Step For Verifying Mechanical Damages On The Mortar Spsupporting

confidence: 70%

“…1700 m in depth) by measuring with X-ray microtomography scanning (X-μCT), and by measuring the strain in the mortar specimen while under hydraulic pressure and the changes in material properties provoked by pressurization and depressurization. Disintegration of the mortar specimen observed in our previous study (Kobayashi et al 2021) is verified from the aspect of hydraulic pressure on a laboratory scale.…”

Section: Introductionsupporting

confidence: 70%

“…Such specific environments have impacts on the durability of cement-based materials. The authors have reported that significant deterioration was observed in a Portland cement mortar exposed 608 days to a seafloor environment at a depth of 1680 m at Tarama Knoll and interpreted that a key influencing factor for the disintegration of the mortar specimen could be extremely low temperature (Kobayashi et al 2021). Although the effect of high hydraulic pressure has been rarely addressed in our previous paper, hydraulic pressure could be another key influencing factor that can affect the durability of the mortar under the deep-sea environment.…”

Section: Introductionmentioning

confidence: 99%

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Action of Hydraulic Pressure on Portland Cement Mortars - Current Understanding and Related Progress of the First-Ever In-Situ Deep Sea Tests at a 3515 m Depth

Takahashi

Kawabata

Kobayashi

et al. 2021

ACT

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In order to realize the utilization of cement-based materials in the special extreme environment, the deep sea, the authors have launched a project targeted at creating a technology platform with in-situ methods and systems for monitoring and evaluating cement-based materials located at deep ocean bottom sites. The first in-situ test in the world with a view to investigating the time-dependence of the volumetric stability and microstructure of Portland cement mortar following its long-term exposure to deep-sea conditions is currently underway at a 3515-m depth in the Nankai Trough. This paper reviews previous studies about the influences of deep-sea hydraulic pressure on cement-based materials, verifies the action of short-term hydraulic pressure using Portland cement mortars on a laboratory scale, and introduces the ongoing progress of in-situ deep-sea tests. Results from laboratory tests indicate that dimensional changes were provoked by liquid water infiltration and confinement while under short-term hydraulic pressure, however, time-dependent behavior under stresses such as creep has not appeared. Weight gain, changes in pore-size distribution, compressive strength and bending strength of the cement mortar were monitored after pressurization and depressurization processes.

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Section: Resultssupporting

confidence: 87%

“…As already reported in Kobayashi et al (2021), specimens salvaged from the deep seafloor with a depth of 1680 m at Tarama Knoll were severely damaged as shown in Fig. 2.…”

Section: Effects Of Short-term Hydraulic Pressure On a Laboratory Scale -The First Step For Verifying Mechanical Damages On The Mortar Spsupporting

confidence: 70%

Section: Introductionsupporting

confidence: 70%

Section: Introductionmentioning

confidence: 99%

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Action of Hydraulic Pressure on Portland Cement Mortars - Current Understanding and Related Progress of the First-Ever In-Situ Deep Sea Tests at a 3515 m Depth

Takahashi

Kawabata

Kobayashi

et al. 2021

ACT

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“…Cement-based materials are also adopted to construct offshore structures using underwater concreting. Several kinds of research investigated the properties of cement-based materials in deep-sea conditions and showed the results of the deterioration mechanism due to the microstructural changes with pressurization [18,19] The authors invented an environment-friendly underwater mining method that aims to control the dispersion of seabed surface sediments and fill the extracted areas by sealing a submerged mine site with anti-washout cement-based sealants. That is to say, sealants can restrain suspension by covering the mining area in advance.…”

Section: Introductionmentioning

confidence: 99%

Study on Deformation Behavior of Sediments and Applicability of Sealants in Seabed Mining

Sasaoka¹,

Hashikawa²,

Hamanaka³

et al. 2021

Adv. sci. technol. eng. syst. j.

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The importance of rare earth resources is increasing and a lot of investigations are conducting all over the world. As a result, it was discovered that abundant deep-sea mud contained rare-earth elements on the deep-sea floor. The suction mining method can be one of the effective seabed mining methods to recover these seafloor sediments. However, it is required to evaluate the deformation behavior of the sediments in seabed mining in terms of environmental evaluation. For this reason, this study investigates the deformation behavior of sediments with different water contents by a laboratory suction test. In the test, the sediments filled in a box whose size is 155 mm× 50 mm×180 mm are vacuumed with a suction pump. The suction pressure of the pump is adjusted to 4.0 kPa, the diameter of the suction pump is 10 mm, and the duration of suction is 8 seconds. The results show that suction volume increases with an increase of water content/liquid limit ratio. In addition, the deformation behavior can be categorized as three shapes based on water content/liquid limit ratio; sharp, cone-shaped, and gentle circular arc when the ratio of water content/liquid limit is under 1.3, from 1.3 to 1.6, and over 1.6, respectively. Furthermore, the application of sealants on the sediment surface is effective to reduce the environmental disturbance although its density has to be the same level as the density of sediments to inhibit sinking the sealants.

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Physicochemical Properties of Portland Cement/Calcium Aluminate Cement/Calcium Sulfate Ternary Binder Exposed to Deep Seafloor

Kobayashi,

Takahashi,

Kawabata

et al. 2023

ce papers

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Cementitious materials employed in deep‐sea marine engineering must have excellent durability. In this study, the durability of a ternary binder‐based paste composed of Portland cement, calcium aluminate cement, and anhydrite was investigated after deep‐sea exposure at a depth of 3515 m for 438 days. The recovered paste specimen showed significant expansion. However, the hydrate phases in the ternary binder exhibited no changes with the exception of the formation of Friedel's and Kuzel's salts. One reason for this was the transformation from unstable monosulfate to stable ettringite under low‐temperature seawater conditions. However, the additional ettringite formation could lead to significant expansion of the paste specimen.

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Physicochemical properties of the Portland cement-based mortar exposed to deep seafloor conditions at a depth of 1680 m

Cited by 27 publications

References 37 publications

Action of Hydraulic Pressure on Portland Cement Mortars - Current Understanding and Related Progress of the First-Ever In-Situ Deep Sea Tests at a 3515 m Depth

Action of Hydraulic Pressure on Portland Cement Mortars - Current Understanding and Related Progress of the First-Ever In-Situ Deep Sea Tests at a 3515 m Depth

Study on Deformation Behavior of Sediments and Applicability of Sealants in Seabed Mining

Physicochemical Properties of Portland Cement/Calcium Aluminate Cement/Calcium Sulfate Ternary Binder Exposed to Deep Seafloor

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