Effets de cycles de gel–dégel sur les propriétés d'une argile sensible

1995 ◽  
Vol 32 (4) ◽  
pp. 725-740 ◽  
Author(s):  
M. Roy ◽  
P. La Rochelle ◽  
S. Leroueil ◽  
J.M. Konrad ◽  
G. Bergeron
Keyword(s):  
Laboratory Study ◽  
Structure Change ◽  
Triaxial Tests ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Mercury Porosimeter ◽  
Sensitive Clay ◽  
High Suction ◽  
Scanning Electron

A laboratory study of the evolution of the behaviour of a sensitive clay under many freeze–thaw cycles is presented; it follows the laboratory study of Leroueil et al. (1991) and the field study of Roy et al. (1992). The physical properties of the clay have been followed by means of consistency and permeability tests after each freeze–thaw cycle, and the mechanical behaviour has been assessed by means of falling cone, oedometer, and consolidated isotropically undrained triaxial tests. The changes in internal structure have been observed by means of the scanning electron microscope and the mercury porosimeter. The results show that the changes in properties are significant during the first three freeze–thaw cycles and hardly significant during the following cycles. The structure change can be explained by the high suction that develops during the generation of ice lenses behind the frost front. Key words : clay, freeze–thaw, shear strength, permeability, heaving, settlements. [Journal translation]

scholarly journals Study on Strength Characteristics of Solidified Contaminated Soil under Freeze-Thaw Cycle Conditions

2018 ◽  
Vol 2018 ◽  
pp. 1-5 ◽  
Author(s):  
Qiang Wang ◽  
Jinyang Cui
Keyword(s):  
Electron Microscopy ◽  
Compressive Strength ◽  
Contaminated Soils ◽  
Unconfined Compressive Strength ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Strength Tests ◽  
Freeze Thaw Cycle ◽  
Microcosmic Mechanism ◽  
Scanning Electron

Cement solidification/stabilization is a commonly used method for the remediation of contaminated soils. The stability characteristics of solidified/stabilized contaminated soils under freeze-thaw cycle are very important. A series of tests, which include unconfined compressive strength tests, freeze-thaw cycle tests, and scanning electron microscopy (SEM) tests, are performed to study the variation law of strength characteristics and microstructure. It aims at revealing the microcosmic mechanism of solidified/stabilized Pb2+ contaminated soils with cement under freeze-thaw cycle. The results show that the unconfined compressive strength of the contaminated soils significantly improved with the increase of the cement content. The unconfined compressive strength of stabilized contaminated soils first increases with the increase of times of freeze-thaw cycle, and after reaching the peak, it decreases with the increase of times of freeze-thaw cycle. The results of the scanning electron microscopy tests are consistent with those of the unconfined compressive strength tests. This paper also reveals the microcosmic mechanism of the changes in engineering of the stabilized contaminated soils under freeze-thaw cycle.

Experiment Study on the Effect of GGBFS on Frost Resistance of Concrete

2014 ◽  
Vol 629-630 ◽  
pp. 207-212 ◽  
Author(s):  
Shi Yi Zhang ◽  
Ying Fang Fan ◽  
Qi Wang
Keyword(s):  
Electron Microscopy ◽  
High Performance ◽  
Plain Concrete ◽  
Industrial Wastes ◽  
X Ray Diffraction ◽  
X Ray ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Scanning Electron

High volume utilization of industrial wastes and by products is the solution for high disposal coast. The anti-frost of high performance concrete is a key factor for safe utilization of concrete structure containing industrial wastes under severe environment. In this paper, to understand the property on anti-frost of high performance containing ground granulated blast furnace slag (GGBFS) under cold marine environment. Some comparison studies were conducted on plain concrete by rapid freeze-thaw cycle test. During the rapid freeze-thaw cycle test, the mass loss and relative elastic modulus were measured regularly at the prescribed conditioning ages. The development of microstructure in concrete was analyzed through scanning electron microscopy (SEM) and X-ray diffraction (XRD). The rapid freeze-thaw cycle test results show that the plain concrete was destroyed severely at 150 freeze-thaw cycles. After 225 freeze-thaw cycles, the mass loss and the relative dynamic modulus of elasticity of GGBFS concrete decrease 1.3% and 26.11%, respectively, that indicates that GGBFS significantly improve the anti-frost performance of concrete; The addition of GGBFS can accelerate the cement hydration reaction, promote more Ca (OH)2 crystals shift to C-S-H gel and help to increase the density of the micro-structure of concrete, which can prevent the formation of micro-cracks and suppress the propagation of cracks and thus effectively improve the durability of concrete. KEY WORDS: GGBFS; freeze-thaw durability; microstructure; scanning electron microscopy; X-ray diffraction.

scholarly journals Dynamic Characteristics and Mechanism of the Saturated Compacted Loess under Freeze-Thaw Cycles

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Qian Wang ◽  
Fuqiang Liu ◽  
Xiumei Zhong ◽  
Zhongnan Gao ◽  
Shouyun Liang ◽  
...  
Keyword(s):  
Dynamic Stability ◽  
Dynamic Characteristics ◽  
Saturated Soil ◽  
Evolution Process ◽  
Dynamic Strain ◽  
Triaxial Tests ◽  
Strengthening Effect ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle

To study the dynamic characteristics and mechanism of saturated loess after freeze-thaw cycles, a series of laboratory tests including freeze-thaw cycle tests, dynamic triaxial tests, and scanning electron microscope tests of the saturated remolded loess was conducted. The characteristics of the dynamic parameters of the saturated loess after different freeze-thaw cycles were discussed. The characteristics of the microstructure parameters changes were analyzed. The evolution process and mechanism of the microstructure of the remolded loess under freeze-thaw cycles were proposed. The results show that after different freeze-thaw cycles, the dynamic stress-dynamic strain curves of the saturated remolded loess conform to the hyperbolic model; however, the freeze-thaw cycle has a significant effect on the model parameter b . With the increase of freeze-thaw cycles, the dynamic shear modulus of saturated remolded loess first decreases and then increases, while the damping ratio is opposite. When saturated remolded loess experiences freeze-thaw cycles greater than four, its dynamic stability is better than that of saturated soil without freeze-thaw cycles. The dynamic stability reaches its peak after seven freeze-thaw cycles and is equivalent to that of saturated soil without freeze-thaw cycles after forty cycles. Combined with the results of the quantitative analysis of microstructure images, with the increase of the freeze-thaw cycles, the number of large and medium particles in the soil reduces, and the number of micros and small particles increases. The particle size tends to be uniform. The apparent porosity increases rapidly and then decreases sharply and tends to be stable after 4 freeze-thaw cycles. The pore and particle fractal dimensions continue to decrease. The probability of entropy increases first and then decreases. It is illustrated that the saturated loess has mainly experienced three steps under freeze-thaw cycles: (1) fracture and expansion of original skeleton cementation, (2) damage, crushing and aggregation of the particle, and (3) compaction and reorganization of soil structure. Besides, the saturation condition significantly accelerates the evolution process of the internal structure of the soil under freeze-thaw cycles. These lead to the strengthening effect of soil dynamic stiffness under long-term freeze-thaw cycles.

A laboratory study of soil conditions affecting emissions of nitrous oxide from packed cores subjected to freezing and thawing

2011 ◽  
Vol 91 (2) ◽  
pp. 223-233 ◽  
Author(s):  
Mario Tenuta ◽  
Brad Sparling
Keyword(s):  
Nitrous Oxide ◽  
Laboratory Study ◽  
Surface Soil ◽  
Microbial Biomass C ◽  
Soil Conditions ◽  
Freezing And Thawing ◽  
Treated Soil ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle

Tenuta, M. and Sparling, B. 2011. A laboratory study of soil conditions affecting emissions of nitrous oxide from packed cores subjected to freezing and thawing. Can. J. Soil Sci. 91: 223–233. A series of laboratory experiments using a packed core soil assay was carried out to test several soil conditions affecting the emission of N2O (nitrous oxide) during thawing of soil. The assay consisted of a sandy loam soil packed to 1.1 Mg m−3, moistened to 80% water-filled pore space, and temperature treated to 4 or −20°C for 2.5 d; the emissions from thawing soil were then determined as the differences in N2O release rates of the temperature-treated soils when placed at 15°C. Nitrate addition to surface soil (0–10 cm) enhanced thaw emission. Thaw emissions, averaged for deeper collected soil (10–30 and 30–60 cm), was 0.3% with NO3− treatment and 1.2% without NO3− treatment of that for surface soil treated similarly. Higher thaw emission for surface soil was related to greater organic matter and microbial biomass C contents and denitrifying enzyme activity than deeper collections of soil. Increasing the bulk density of soil from 1.1, 1.2, and 1.25 Mg m−3 decreased thaw emission. A second freeze-thaw cycle of the highest compaction treatment resulted in an emission of 2.3% of the first freeze-thaw cycle. Acetylene increased thaw emission of N2O and more so for NO3− untreated than treated soil. Using the acetylene inhibition method, the N2O:N2 ratio of gas produced was higher for frozen (0.17) than cold (0.07) treated soil, respectively, without the addition of NO3−. The addition of NO3− increased the N2O:N2 ratio of gas produced with the ratio being 2.45 and 0.53 for frozen and cold-treated soil. The results are consistent with biological denitrification being a source of N2O with conditions promoting N2O production rather than consumption enhancing thaw emissions.

scholarly journals Petrographically Quantifying the Damage to Field and Lab-cast Mortars Subject to Freeze-thaw Cycles and Deicer Applications

2021 ◽  
Author(s):  
CHUNYU QIAO ◽  
Nima Hosseinzadeh Nanehkaran ◽  
Prannoy Suraneni ◽  
Sihang Wei ◽  
David Rothstein
Keyword(s):  
Crack Density ◽  
Cementitious Materials ◽  
X Ray ◽  
Freeze Thaw ◽  
Friedel’S Salt ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Sand Particles ◽  
Portland Cement Paste ◽  
Scanning Electron

Abstract Although calcium oxychloride (Ca-Oxy) is known to damage cementitious materials exposed to calcium chloride (CaCl2) deicers, there is little direct observation of Ca-Oxy in the field due to its instability. This paper uses optical microscopy (OM) and scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM-EDX) to detect the formed Ca-Oxy and quantify its associated damage in a field mortar subject to freeze-thaw cycles and deicer applications. The characterized damage in the field mortar is compared to that in lab-cast portland cement paste and mortar which are submerged in a CaCl2 solution of 25 wt. % under freeze-thaw cycles (-8 to 25 °C). The field and lab-cast mortars show similar cracking patterns that are parallel to the exposure surface with a variation of 30-45° in the preferred orientation due to the constraints of sand particles. During each lab-controlled freeze-thaw cycle, the high CaCl2 concentration of 25 wt. % stabilizes the formed Ca-Oxy, which continually damages the mortar and eventually results in 3-4 times higher crack density compared to that in the field mortar. SEM-EDX analysis confirms the presence of secondary deposits including Friedel’s salt, ettringite and Ca-Oxy. Image analysis on thin section photomicrographs shows a reduction of 86.4% in calcium hydroxide (Ca(OH)2) content in the damaged field mortar compared to the undamaged field mortar, suggesting significant leaching of Ca(OH)2 to form Ca-Oxy due to the deicer application.

scholarly journals Dynamic Behavior of Geosynthetic-Reinforced Expansive Soil under Freeze-Thaw Cycles

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Zhongnian Yang ◽  
Xuesen Liu ◽  
Liang Zhang ◽  
Fujun Niu ◽  
Xianzhang Ling ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Expansive Soil ◽  
Soil Samples ◽  
Reinforced Soil ◽  
Frost Heave ◽  
Triaxial Tests ◽  
Foundation Engineering ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle

Expansive soil has a significant impact on the stability of many key construction projects in cold regions. To study the physical and mechanical properties of expanded soil under the condition of freeze-thaw cycle, cryogenic cyclic triaxial tests were conducted on the dynamic and the displacement characteristics of geosynthetic-reinforced expansive soil subjected to the freeze-thaw cycles. Compared with the unreinforced expansive soil samples, the effects of freeze-thaw cycles on the soil dynamics were discussed. The dynamic shear modulus (Gd) and damping ratio (λ) of the expansive soil samples are improved by reinforcement. Reinforced soil can inhibit the axial compression of the sample and restrain the frost heave deformation of the sample during the freezing process. Meanwhile, it can delay the structural damage effect caused by frost heave and reduce the rate of change of the Gd and the λ with the freeze-thaw cycle. At the same time, reinforced soil can inhibit the axial expansion, reduce the rate of reduction of the Gd, stabilize it with a higher rate, and reduce the influence of the freeze-thaw cycles on the λ of the expansive soil sample. Finally, the change of mechanical properties of expansive soil under the condition of reinforcement is obtained. The main conclusions of this paper can be used to reinforce the roadbed and foundation engineering of frozen soil in a cold region and provide support for the fiber reinforcement method of expansive soil.

scholarly journals Petrographically quantifying the damage to field and lab-cast mortars subject to freeze-thaw cycles and deicer application

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Chunyu Qiao ◽  
Nima Hosseinzadeh ◽  
Prannoy Suraneni ◽  
Sihang Wei ◽  
David Rothstein
Keyword(s):  
Crack Density ◽  
Cementitious Materials ◽  
X Ray ◽  
Freeze Thaw ◽  
Friedel’S Salt ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Sand Particles ◽  
Portland Cement Paste ◽  
Scanning Electron

AbstractAlthough calcium oxychloride (Ca-Oxy) is known to damage cementitious materials exposed to calcium chloride (CaCl2) deicers, there is little direct observation of Ca-Oxy in the field due to its instability. This paper uses optical microscopy (OM) and scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM-EDX) to detect the formed Ca-Oxy and quantify its associated damage in a field mortar subject to freeze-thaw cycles and deicer application. The characterized damage in the field mortar is compared to that in lab-cast portland cement paste and mortar which are submerged in a CaCl2 solution of 25 wt.% under freeze-thaw cycles (− 8 to 25 °C). The field and lab-cast mortars show similar cracking patterns that are parallel to the exposure surface with a variation of 30–45° in the preferred orientation due to the constraints of sand particles. During each lab-controlled freeze-thaw cycle, the high CaCl2 concentration of 25 wt.% stabilizes the formed Ca-Oxy, which continually damages the mortar and eventually results in 3–4 times higher crack density compared to that in the field mortar. SEM-EDX analysis confirms the presence of secondary deposits including Friedel’s salt, ettringite and Ca-Oxy. Image analysis on thin section photomicrographs shows a reduction of 86.4% in calcium hydroxide (Ca(OH)2) content in the damaged field mortar compared to the undamaged field mortar, suggesting significant leaching of Ca(OH)2 to form Ca-Oxy due to the deicer application.

scholarly journals Effect of freeze–thaw cycle on physical and mechanical properties and damage characteristics of sandstone

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Longxiao Chen ◽  
Kesheng Li ◽  
Guilei Song ◽  
Deng Zhang ◽  
Chuanxiao Liu
Keyword(s):  
Mechanical Properties ◽  
Shear Failure ◽  
Triaxial Compression ◽  
Physical And Mechanical Properties ◽  
Freeze Thaw ◽  
Damage Characteristics ◽  
Large Pore ◽  
Natural Rock ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle

AbstractRock deterioration under freeze–thaw cycles is a concern for in-service tunnel in cold regions. Previous studies focused on the change of rock mechanical properties under unidirectional stress, but the natural rock mass is under three dimensional stresses. This paper investigates influences of the number of freeze–thaw cycle on sandstone under low confining pressure. Twelve sandstone samples were tested subjected to triaxial compression. Additionally, the damage characteristics of sandstone internal microstructure were obtained by using acoustic emission (AE) and mercury intrusion porosimetry. Results indicated that the mechanical properties of sandstone were significantly reduced by freeze–thaw effect. Sandstone’ peak strength and elastic modulus were 7.28–37.96% and 6.38–40.87% less than for the control, respectively. The proportion of super-large pore and large pore in sandstone increased by 19.53–81.19%. We attributed the reduced sandstone’ mechanical properties to the degenerated sandstone microstructure, which, in turn, was associated with increased sandstone macropores. The macroscopic failure pattern of sandstone changed from splitting failure to shear failure with an increasing of freeze–thaw cycles. Moreover, the activity of AE signal increased at each stage, and the cumulative ringing count also showed upward trend with the increase of freeze–thaw number.

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