Lime-treated Clay Research Articles

Variations in strength of lime-treated soft clays

Strength is often the most significant parameter in measuring the effect of soil improvement in geotechnical engineering practice. In this paper, a primary study is made of the variation in unconfined compressive strength of lime-treated soft clays under various practical conditions. There are three major factors that affect the strength development: lime content, curing time, and curing temperature. The variations in strength with the three factors are analysed and quantified by proposed empirical equations. These equations are verified against experimental data independently. Based on an analysis of the above simulations, a general strength equation is proposed, unifying the influence of all the three factors into a single equation. The capacity of the general equation is demonstrated and it is seen that the proposed strength equations have the potential for predicting the strength of lime-treated clays under various conditions.

Physicochemical Behavior of Cement Kiln Dust–Treated Kaolinite Clay

The physicochemical responses induced in kaolinite clay treated with 25% of a high free lime content cement kiln dust (CKD) were investigated. Atterberg limits, unconfined compressive strength, and stiffness of the compacted, CKD-treated kaolinite were measured as functions of the curing period. These properties were compared with those of the untreated clay and of the clay treated with quicklime, so as to determine the comparative extent of enhancement induced by the CKD treatment. The CKD-treated clay developed significantly higher strength than quicklime-treated clay containing the same amount of lime. The remarkable enhancement in clay properties observed suggests significant potential for use of some CKDs as soil stabilizers. The mineralogi-cal and morphologic changes induced in the clay by the CKD addition were characterized using X-ray diffraction (XRD), scanning electron microscopy, and energy-dispersive X-ray analyses, so as to help provide an understanding of the CKD-clay interaction mechanism. These examinations indicated that the preexisting stacks of kaolinite clay particles were disaggregated and that the individual clay flakes had absorbed calcium hydroxide that had been previously generated by the hydration of quicklime in the CKD. However, direct evidences for production of calcium silicate hydrate (C-S-H) by pozzolanic reaction between the clay and the calcium hydroxide was not found, despite high likelihood that this had occurred. The same basic interaction mechanisms appeared to operate in both the CKD-treated and the lime-treated clays. The 90-day cured specimens were found to be well cemented and not affected by water immersion.

Sulphate Attack in Lime-Treated Marine Clay

ABSTRACT The use of lime to improve the properties of soft clays is not new. Recently the deep lime mixing technique has been extended to coastal regions for improving the behavior of weak marine clays. But lime treatment technique should be approached carefully for clay containing a high percentage of sodium sulphate. The presence of sulphate in lime-treated clays may result in high swelling due to the formation of the expansive mineral, ettringite. A limited study of lime-treated marine clays has shown a need to further explore the formation of ettringite and its stability with time. In this article, a laboratory investigation was carried out to examine the influence of sodium and calcium sulphates on the behavior of lime column treated marine clay. Scanning electron microscopy (SEM) was used to identify the formation of various reaction products, including ettringite. Test results indicate that the formation of ettringite in the lime-sodium sulphate-clay system adversely affects the engineering behavior of the marine clay, whereas the addition of calcium sulphate significantly improves the engineering characteristics of the soil.

Effect of Pollutants on the Physical and Engineering Behavior of Lime-Treated Marine Clay

Effect of Pollutants on the Physical and Engineering Behavior of Lime-Treated Marine Clay

Effect of Pollutants on the Physical and Engineering Behavior of Lime-Treated Marine Clay

Effect of Pollutants on the Physical and Engineering Behavior of Lime-Treated Marine Clay

Effect of Pollutants on the Physical and Engineering Behavior of Lime-Treated Marine Clay

Rapid industrial growth and increasing population has resulted in the discharge of wastes into the ocean, wastes which ultimately reach the seabed and contaminate the marine sediments. The soil-contaminants interaction, and their associated physico chemical properties with sediments control the behavior of marine clays. Marine clay deposits of low strength and high compressibility are located in many coastal and offshore areas. There are several foundation problems encountered in these weak marine clays. In this study, experimental work was carried out in the laboratory to stabilize soft marine clays using the lime column technique. Also the lime-induced effects on the physical and engineering behavior of marine clays in sulfate-contaminated marine environment was investigated. Consolidation tests indicate that compressibility of the lime-treated samples was reduced to 1/2–1/3 of the virgin soil after 45 days treatment. The test results also suggest that the lime column technique can be conveniently used to improve the behavior of contaminated marine clay deposits.

In Situ Monitoring of Lime-Stabilized Road Subgrade

Two refined clay minerals, English China Clay (predominantly kaolinite) and Wyoming Bentonite (predominantly sodium montmorillonite), were used to develop a method for assessing the time-dependent physicochemical behavior of lime-treated clay subgrade. The two clays, representing the extremes of structural negative charge development, were treated with two lime contents. Changes in the physicochemistry of the samples were monitored after three curing periods by performing batch leaching tests and by monitoring changes in undrained shear strength and Atterberg limits. The effects of changing the batch test operating parameters and increasing the curing period were assessed by measuring changes in solution pH and conductivity and by analyzing eight elements in solution. The solidification mechanisms caused by lime addition were found to be different for the two minerals. Pozzolanic reactions involving English China Clay and Wyoming Bentonite occurred because of the dissolution of aluminum and silicon from the respective mineral. Development of the batch leaching test showed that changing the operational parameters had no effect on the observed trends associated with the time-dependent modification and solidification reactions. In addition, it was shown that successful solidification could be monitored using simple conductivity measurements without the need for extensive and complex elemental analysis.

The use of lime-treated British clays in pavement construction. Part 2: The effect of mellowing on the stabilization process

The USA field experiences in the 1960s with lime treatment of marginal materials for pavement layers resulted in the introduction of a ‘mellowing’ period of between 24 and 72 hours, after mixing and prior to final compaction. This period facilitates reaction between the soil and the lime so that pulverization criteria and compact-ability can be achieved. As a result of these early experiences, the ‘mellowing’ period has become an integral part of specifications for lime-treatment processes used globally but it has been based on limited scientific justification. Under the Department of Transport (DoT) Specification for Highway Works (1991 and 1993 amendments) a ‘mellowing’ period of between 24 and 72 hours is mandatory. This period of mellowing is also recommended in volume 4 of the Design Manual for Roads and Bridges HA/74/95. 1 Part 1 of this paper, 2 also presented in Transport, discussed results of a research programme that investigated the effect of mellowing on the modification process of four British soils (Mercia Mudstone, Oxford Clay, Lower Lias and London Clay) treated with quicklime. This second paper presents the findings of the second phase of this research, which investigated the effect of mellowing on the stabilization process of the same four soils discussed in Part 1. Both papers suggest a need to improve the design methods for lime treatment of clays in the international procedures. 3

Leach tests on lime-treated clays : McCallister, L D; Petry, T M Geotech Test JV15, N2, June 1992, P106–114

Leach tests on lime-treated clays : McCallister, L D; Petry, T M Geotech Test JV15, N2, June 1992, P106–114

Techniques for Estimating the Longevity of Lime-Treated Expansive Clays

Abstract Two techniques are presented that investigate the possibility of estimating the longevity of lime-treated expansive clays subjected to leaching. The techniques are based on analyzing calcium concentrations and pH changes within accelerated leached laboratory specimens and their leachates during the leaching process. The accelerated leach times required to produce specific calcium concentrations and pH in the laboratory are converted to actual field leaching (or percolation) times by using developed time scale factors. The techniques are tested for validity by correlating estimated calcium concentrations and pH values of field lime-treated clays to the actual results of field lime-treated clay layers of various known ages. The correlations showed that pH estimations were within an average of 13% of measured values, while estimated calcium concentrations remaining in the soil-lime layers were within an average of 18% of measured values.

Leach Tests on Lime-Treated Clays

Abstract This paper describes the design, use, and results of a multiple leach-cell operation to test the changes in permeability and calcium removal of a lime-treated expansive clay under continuous water leaching. Seventy laboratory-prepared lime-treated clay specimens were subjected to continuous accelerated leaching for periods of 45 and 90 days with varying lime contents and compactive moisture contents. Permeability, leachate pH, and leachate cation changes were continuously recorded during the leach process. Results indicate that lime dramatically increased the soil's permeability, with maximum permeability occurring at the lime modification optimum (LMO). Leachate pH increased as the lime content of the soil increased but decreased linearly during the leach cycle. Calcium concentration in the leachate was lowest in specimens prepared at their LMO but increased as the lime content increased. There is strong evidence to suggest that calcium removal and permeability are in direct correlation to the complex ion interaction within the soil-lime mixture, and therefore the LMO is central in determining leaching effects on lime-treated soils.

Corrélations entre des propriétés mécaniques dynamiques et statiques de sols argileux intacts et traités à la chaux

The use of an ultrasonic accelerometer has led to an empirical correlation between the wave velocity and the static mechanical strength deducted from destructive tests made on intact or lime-treated clays, and to an evaluation of the influence of certain physical soil parameters on wave velocity. The results give a good correlation between the dynamic elastic properties deducted from the shear wave velocity and the static mechanical properties of the intact and the lime-treated clays when measured without confining pressure. The results also confirm that the maximum dynamic shear modulus is proportional to undrained shear strength, independently of soil type. The structure of a lime-treated clay is more favorable to the transmission of shear waves than the same clay in an intact state having the same shear strength; the cause of this difference is associated with the compaction energy and the newly formed minerals resulting from the treatment. Finally, the study of these, treated soils has illustrated the effect of the cementation process on the mechanical behavior of clayey soils. Key words: ultrasonic accelerometer, shear wave velocity, clay, lime treated, cementation, elastic properties, static properties. [Journal translation]