Deterioration of swelling pressure of compacted Gaomiaozi bentonite induced by heat combined with hyperalkaline conditions

AbstractMicrolevel properties such as mineralogical and chemical compositions greatly control the macro behaviour of expansive soils. In this paper, the combined effect of mineral (i.e. montmorillonite, MMC) and chemical contents (i.e. Ca and Na in their total (T), leachable (L) and exchangeable form (CEC)) on swelling behaviour is investigated in a comprehensive way. Several 3-dimensional (3D) graphs correlating MMC and Ca/Na ratio, together, with swelling property (swelling potential, Sa, and swelling pressure, Sp) are developed. 3D plots, in general, portrayed a non-linear relationship of Sa and Sp with MMC and Ca/Na ratio, together. It is hypothesized that swelling initially is triggered by chemical parameters due to their quick and rapid ionization capability, but the overall swelling phenomenon is largely controlled by MMC. It is importantly found that expansive soils are dominant with divalent Ca++ ions up to MMC of 67% and beyond this percentage, monovalent Na+ ions are prevalent. From the interpretation of results, the maximum Sa of 18% and Sp of 93 kPa is measured at MMC of 43%, (Ca/Na)T of 10–14 and (Ca/Na)L of 2–7. It is concluded from study that total CEC + MMC for determining Sa and (Ca/Na)T + MMC for determining Sp are superior parameters to be considered. The findings of the study also excellently endorsed the results of Foster32, who stated that ionization of Na or Ca depends on the constituent mineral contents. The findings presented herein are unique, interesting and bear very practical significance, as no earlier research work reported such findings by accounting for chemical and mineralogical parameters impact, in tandem, on swelling properties.

Download Full-text

Swelling Properties and Permeability of GMZ Bentonite-Sand Mixtures during Different Solutions Infiltration

Sustainability ◽

10.3390/su13041622 ◽

2021 ◽

Vol 13 (4) ◽

pp. 1622

Author(s):

Yu-Ping Wang ◽

Zhe Wang ◽

Yu Zhao ◽

Fa-Cheng Yi ◽

Bao-Long Zhu

Keyword(s):

Swelling Pressure ◽

Development Stage ◽

Gmz Bentonite ◽

Test Results ◽

X Ray Diffraction ◽

Swelling Properties ◽

Swelling Capacity ◽

Slow Expansion ◽

Expansion Stage ◽

Chemical Solutions

In China, Gaomiaozi (GMZ) bentonite is recognized as a barrier material for isolating nuclear waste. Different chemical solutions may change the hydraulic conductivity and swelling capacity of bentonite. Consequently, a series of swelling pressure and permeability experiments was carried out on bentonite-sand mixtures with various dry densities and infiltrating solutions. X-ray diffraction (XRD) and the field emission scanning electron microscope (FESEM) were carried out on the samples experiencing the tests to identify the influence of chemistry pore solutions upon the mineralogical and microstructure changes. The results show that the swelling pressure experienced rapid swelling, slow expansion, and the stable expansion stage for the specimens of infiltrating solutions except for NaOH. For the specimens infiltrated with NaOH solutions, the swelling pressure experienced rapid increases, slow decreases, and a stable development stage. With hyper-alkaline and hyper-salinity infiltration, the swelling pressure decreased, and the permeability increased. In addition, swelling pressure attained stability more quickly on contact with hyper-alkaline and hyper-salinity solutions. Comparing the test results, the results indicate that the influence of NaOH on the expansion and permeability was higher than NaCl-Na2SO4 at the same concentration.

Download Full-text

Swelling pressure and microstructure of an activated swelling clay with temperature

Clay Minerals ◽

10.1180/000985598545615 ◽

1998 ◽

Vol 33 (2) ◽

pp. 255-267 ◽

Cited By ~ 20

Author(s):

D. Tessier ◽

M. Dardaine ◽

A. Beaumont ◽

A. M. Jaunet

Keyword(s):

Room Temperature ◽

Swelling Pressure ◽

Radioactive Waste Disposal ◽

Basic Medium ◽

Hydraulic Pressure ◽

Swelling Behaviour ◽

Transmission Electron ◽

Ca Ions ◽

Na Ions ◽

Marked Drop

AbstractClay from Fourges has been selected by the Commissariat à l'Energie Atomique as a support in radioactive waste disposal studies. This material was activated by adding Na2CO3, then compacted at 60 MPa. Subsequently, its swelling behaviour was monitored at 90°C and 145°C for 330 days and at the end of this period the samples were examined by transmission electron microscopy (TEM). For this, they were embedded in a resin then sectioned with an ultramicrotome for mineralogical and chemical analyses. The initial material is essentially composed of kaolinite and smectite. Addition of Na2CO3 at room temperature induces a replacement of Ca ions by Na ions and the precipitation of finely divided carbonates on the surface of the constituents. At the end of 330 days at 90°C under a hydraulic pressure of 1 MPa, the initial particles combine and the material exerts a swelling pressure of 20 MPa. A complete reorganisation of the clay crystallites is observed without significant dissolution of the solid phases. After the same time at 145°C under a hydraulic pressure of 10 MPa, in a basic medium, the combined conditions are such that a high proportion of the clay is dissolved with formation of amorphous aluminosilicates correlated with a marked drop in the swelling pressure to 5 MPa. This work establishes the advantages of following the macroscopic properties in parallel with the microstructure variations for understanding the changes in the properties of clays.

Download Full-text

Finite Element Modeling of Osmotic Swelling in Tissue-Engineered Cartilage

ASME 2008 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2008-192368 ◽

2008 ◽

Author(s):

Liming Bian ◽

Terri Ann N. Kelly ◽

Eric G. Lima ◽

Gerard A. Ateshian ◽

Clark T. Hung

Keyword(s):

Articular Cartilage ◽

Potential Role ◽

Swelling Pressure ◽

Type Ii Collagen ◽

Type Ii ◽

Osmotic Swelling ◽

Fixed Charges ◽

Central Regions ◽

Significant Research ◽

Engineered Cartilage

Proteoglycans and Type II collagen represent the two major biochemical constituents of articular cartilage. Collagen fibrils in cartilage resist the swelling pressure that arises from the fixed charges of the glycosaminoglycans (GAGs), and together they give rise to the tissue’s unique load bearing properties. As articular cartilage exhibits a poor intrinsic healing capacity, there is significant research in the development of cell-based therapies for cartilage repair. In some of our tissue engineering studies, we have observed a phenomenon where chondrocyte-seeded hydrogel constructs display cracking in their central regions after significant GAG content has been elaborated in culture. A theoretical analysis was performed to gain greater insights into the potential role that the spatial distribution of proteoglycan and collagen may play in this observed response.

Download Full-text

Laboratory instrument for measuring lateral soil pressure and swelling pressure

International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts ◽

10.1016/0148-9062(83)91685-6 ◽

1983 ◽

Vol 20 (1) ◽

pp. A9

Author(s):

Z. Ofer

Keyword(s):

Swelling Pressure ◽

Soil Pressure ◽

Laboratory Instrument

Download Full-text

A Low-Range Drift-Free Bio-compatible Pressure Sensor Based on P(VDF-TrFE) Piezoelectric Thin Film

MRS Proceedings ◽

10.1557/proc-1222-dd05-29 ◽

2009 ◽

Vol 1222 ◽

Cited By ~ 1

Author(s):

Xiaoyang Li ◽

Timothy Reissman ◽

Fan Yu ◽

Edwin C. Kan

Keyword(s):

Thin Film ◽

Blood Pressure ◽

Pressure Sensor ◽

Equivalent Circuit Model ◽

Swelling Pressure ◽

Pressure Monitoring ◽

Sensing Element ◽

Piezoelectric Resonance ◽

Piezoelectric Thin Film

AbstractA low-range pressure sensor (0-100kPa) based on the P(VDF-TrFE) piezoelectric thin film is proposed, where the long-term drift is eliminated by operating near the piezoelectric resonance. The pressure sensor is designed for blood pressure and tissue swelling pressure monitoring. The poled 50μm±1μm P(VDF-TrFE) copolymer film is used as the sensing element, with all fabrication and assembly materials biocompatible. A modified Butterworth-Van Dyke (BVD) [1] equivalent circuit model is used to characterize the sensor behavior. The pressure sensor exhibits negligible drift in weeks of operation. The device shows a sensitivity of 0.038MHz/kPa resonance frequency shift under stress, which leads to a maximum readout change of 1.1%/kPa in the present setup.

Download Full-text