International audienceLime treatment is a common technique of improving the workability and geotechnical properties of soils. In this study, the aggregate size effects on the water retention capacity and microstructure of lime-treated soil were investigated. Two soil powders with different maximum aggregate sizes (D max = 0·4 and 5 mm) were prepared and stabilised by 2% lime (by weight of dry soil). Soil samples were prepared by compaction at dry side of optimum water content (w = 17%) with a dry density of 1·65 Mg/m 3. Suction and pore size distribution were determined after different curing periods. The results obtained show that: (a) the treated soil with smaller D max presents relatively smaller modal sizes and lower frequency of macropores (10–330 μm); (b) lime addition effectively improves the soil water retention capacity and decreases both the modal sizes of macro-and micropores gradually over time. Moreover, a higher air entry value and larger water retention capacity were also observed for a smaller D max value, in agreement with the pore size distributions
International audienceAn experimental study was conducted to investigate changes of thermal conductivity, suction and microstructure of a lime-treated silty soil during curing. The soil samples were prepared with 2% lime and compacted dry (17%) and wet (22%) of optimum. The thermal conductivity, total suction and pore size distribution were determined at various curing times. Results show that the thermal conductivity of samples compacted on the dry side decreases slightly with curing time, while the curing time effect on the samples compacted on the wet side is insignificant. The total suction generally increases with curing time even though the soil water content was kept constant. The pore size distribution characteristics are mainly related to its moulding water content. As the samples are compacted on the dry side, the pore size distribution shows typical bi-modal characteristics, with a population of macro-pores and a population of micro-pores. By contrast, as the samples are compacted on the wet side, the pore size distribution shows typical uni-modal characteristics. It is found that the modal size of both the large and small pores decrease with curing time
International audienceBender elements technique has become a popular tool for determining shear wave velocity, V s , hence the small-strain shear modulus of soils, G max , thanks to its simplicity and nondestructive character among other advantages. Several methods were proposed to determine the first arrival of V s. However, none of them can be widely adopted as a standard and there is still an uncertainty on the detection of the first arrival. In this study, bender elements tests were performed on lime-treated soil and both shear wave and compression wave velocities at various frequencies were measured. In-depth analysis showed that the S-wave received signal presents an identical travel time and opposite polarity compared with that of the S-wave components in P-wave received signal, especially at high frequency. From this observation, a novel interpretation method based on the comparison between the S-wave and P-wave received signals at high frequency is proposed. This method enables the determination of the arrival time of the S-wave objectively, avoiding a less reliable first arrival pickup point. Furthermore, the "-point " method and cross-correlation method were also employed and the obtained results agree well with those from the proposed method, indicating the accuracy and reliability of the latter. The effects of frequency on the shear wave velocity are also discussed.La technique avec des éléments piézocéramiques (« bender elements ») est devenue un outil populaire pour la détermination de la vitesse des ondes de cisaillement, Vs, d’où le module de cisaillement à faible déformation des sols, Gmax, grâce à sa simplicité et son caractère non destructif, avec d’autres avantages. Plusieurs méthodes ont été proposées pour déterminer la première arrivée de Vs. Cependant, aucune d’entre elles ne peut être largement adopté comme norme et il y a encore une incertitude concernant la détection de la première arrivée. Dans cette étude, des essais avec des éléments piézocéramiques ont été réalisés sur un sol traité à la chaux et les vitesses des ondes de cisaillement et de compression à différentes fréquences ont été mesurées. Une analyse approfondie a montré que le signal reçu de l’onde-S présente un temps de parcoursidentique et une polarité opposée par rapport au temps de parcours et à la polarité des composants de l’onde-S dans le signal reçu de l’onde-P, en particulier à haute fréquence. De cette observation, une méthode d’interprétation novatrice basée sur la comparaison entre les signaux reçus des ondes-S et des ondes-P à une haute fréquence est proposée. Cette méthode permet de déterminer le moment d’arrivée de l’onde-S objectivement, en évitant une détection moins fiable du premier point d’arrivée. En outre, la méthode « -point » et la méthode de corrélation croisée ont également été utilisées et les résultats obtenus concordent bien avec ceux de la méthode proposée, ce qui indique la précision et la fiabilité de celle-ci. Les effets de la fréquence sur la vitesse des ondes de cisaillement sont également d...
This work aims to investigate the aggregate size effect on changes in mineralogical composition and microstructure of lime-treated compacted soils. Three soil powders with different maximum aggregate sizes (Dmax=5, 1 and 0.4mm) were prepared prior to the treatment with 2% of lime. X-ray diffraction (XRD), environmental scanning electron microscope (Env. SEM) coupled with chemical analysis using energy dispersive X-ray spectrometry (EDX) and mercury intrusion porosimetry (MIP) were used to analyse untreated and treated samples at various curing times. Crystallized C-S-H on tobermorite form was identified in the lime-treated soil prepared with large aggregates after one year curing, and an evident increase in nanopores b0.1 ¼mC-S-H was also observed due to CS-H creation. By contrast, in the case of smaller aggregates, no obvious C-S-H peaks were observed by XRD technique after the same curing time, even though some evidence of such phases are provided by Env. SEM coupled to EDX analysis. But a large amount of undetectable nanopores b6 nm (considering the MIP technical limitation) was supposed to be formed and could be attributed to the creation of nanocrystallized C-S-H or poorly-crystallized C-S-H (that may fill the pores larger than 2 ¼m). Such type of C-S-H phases occurred when lime was coated in thin layer on the large surface associated to lime-treated soil prepared with small aggregates
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.