Swelling behavior of kaolinitic clays contaminated with alkali solutions

Applied Clay Science 135 (2017) 575–582

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Research paper

Swelling behavior of kaolinitic clays contaminated with alkali solutions: A micro-level study Rama Vara Prasad Chavali, Sai Kumar Vindula, Hari Prasad Reddy P ⁎, Ambili Babu, Rakesh J Pillai Department of Civil Engineering, National Institute of Technology, Warangal, India

a r t i c l e

i n f o

Article history: Received 10 August 2016 Received in revised form 24 October 2016 Accepted 30 October 2016 Available online 3 November 2016 Keywords: Alkali Kaolinitic clays Swelling XRD SEM

a b s t r a c t Alkali contamination of soils results in repeated structural failure when exposed. Though the effects of alkali on different soils have been investigated in recent years, a systematic research approach aimed at establishing swell behavior in non-swelling kaolinitic clays when exposed continuously with varying concentrations of alkali solution as pore fluid and its micro-level investigation is not well documented. Series of one-dimensional free swell tests and micro-level studies (XRD, SEM) have been carried out to investigate the alkali induced swell in nonswelling kaolinitic clays. Naturally available red earth and two commercial clays, namely ball clay and china clay, which predominantly contains kaolinite mineral are selected for the study. The swell test results showed that all three clays exhibited high swelling with alkali solutions (0.1 N, 1 N, 4 N, 8 N) when compared with water. The magnitude of swell observed in clays interacted with alkali solution ranged from a minimum of 8% to maximum of 56% depending upon the concentrations exposed. China clay showed a minimum swell of 8% with 8 N alkali solution to a maximum swell of 22% with 4 N alkali solution and red earth showed a minimum swell of 18% with 8 N alkali solution to a maximum of 27% with 0.1 N alkali solution. Whereas, ball clay showed a minimum swell of 12% with 0.1 N alkali solution and maximum swell of 56% with 8 N alkali solution. The resulted magnitude of alkali induced swell in clays is attributed to dispersion of clay particles and new mineral formations. To explore the formation of new minerals and morphological transformations a micro-level investigation is carried out on representative samples collected at the end of free swell tests. The formation of zeolite minerals viz. sodalite and cancrinite were evidenced from XRD results and rosette type structures were observed from SEM studies. © 2016 Elsevier B.V. All rights reserved.

1. Introduction Soil contamination can occur due to leakage of a variety of contaminants from underground or above ground storage tanks and accidental spills. It has long been recognized that soil contamination has a significant effect on the volume change behavior of soil, which in turn can have direct bearing on their geotechnical properties and can affect the stability of structures built on them (Sokolovich and Troitskii 1976; Sibley and Vadgama 1986; Chunikhin et al., 1988; Rao and Rao 1994). Volume changes in soils generally occur as a result of settlements due to compression, heave due to expansion and deformations caused by the shear stresses. Large volume changes in soils results in extensive damage to superstructures, which often reflects as progressive failures. The knowledge of soil contamination is thus necessary to understand the mechanism and to control the related heave or differential settlements. Soil contaminants can be divided into two groups, organic and

⁎ Corresponding author at: Department of Civil Engineering, National Institute of Technology, Warangal 506004, India.

http://dx.doi.org/10.1016/j.clay.2016.10.045 0169-1317/© 2016 Elsevier B.V. All rights reserved.

inorganic contaminants (Estarbagh et al. 2014). Most of the research has focused on the effect of organic contaminants on the volume change behavior of soil (Meegoda and Ratnaveera, 1994; Singh et al. 2008; Moavenian and Yasrobi 2008; Olgun and Yildiz 2010; Khosravi et al. 2013), it was not until recently that Assa'ad (1998), Maltsev (1998), Sivapullaiah et al. (2006), Sunil et al. (2006), Sivapullaiah and Manju (2007), Yukselen-Aksoy et al. (2008), Reddy and Sivapullaiah (2010) performed systematic studies aimed at determining the influence of inorganic contaminants on the swelling and mineralogical transformations of soils. One important aspect that can have considerable effect is the alkali contamination of the soil. Alkali solutions are released into the soil environment from varies industries such as paint and dyes, paper and pulp industries, cotton mills and aluminium industries and so on. Sokolovich and Troitskii (1976) reported the heaving of sand due to leakage of NaOH, NH4Cl, and soda solutions into the subsoil for 5 year period of the Krasnopresensk sugar refinery in Moscow. The soil samples extracted at foundation base level showed that the sandy soil is completely filled with alkali-salt crystal hydrate formations, which lead to deformations of the superstructure. Kabanov et al. (1977) investigated the swelling and deformations of soils in various

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Table 1 Physical properties of clays used. Properties

Red earth

China clay

Ball clay

Specific gravity Liquid limit (LL), % Plastic limit (PL), % Plasticity index (PI), % Free swell index (ml/g) Max. Dry unit weight (kN/m3) Optimum water content (%) Clay content (%) Silt content (%) Fine sand content (%) Cation exchange capacity (meq/100 g)

2.63 24.8 13.1 11.7 1.0 17.9 17.1 26 38 36 9.39

2.54 51.8 26.7 30.2 1.1 15.7 25.5 32 68 – 5.62

2.6 58.6 29.4 24.9 1.2 16.6 24.5 36 64 – 6.43

aluminium plants in Uralsk due to leakage of alkali solutions. Based on the studies conducted on the soils collected from different plants, the swelling process of clayey soils is divided into three periods. In the first, swelling takes place by accumulation of osmotic and adsorbed moisture in the soils. The second is characterized by relative stabilization of the soil, when chemical reaction between the clay fraction of the soil and the alkali begins. This continues until the concentration of authigenic material reaches a certain value. Higher the concentration of alkali solution, shorter the duration of the second period. In the third period, the rate of forming new salt compounds increases, and this causes intensified swelling of the soil. Rao and Rao (1994) reported the cause of ground heave of sub soil containing non-swelling kaolinite due to prolonged spillage of concentrated (40% by weight of solution) solution of caustic soda. Loss of cementitious iron oxide coatings of the soil aggregates in the alkaline environment which releases or disperses the soil particles held in the aggregates coupled with the negative charge imparted to the soil particles by the seepage of the caustic soda solution has been attributed as a cause for the observed heaving. Sinha et al. (2003) reported the results of investigations on the effect of seepage of caustic soda, due to spillage of liquid caustic soda during operation of an alumina plant, on the bearing capacity of foundation rock. Plate load tests were carried out on contaminated as well as uncontaminated locations and it was noticed that safe bearing capacity of contaminated site is lower by about 33% compared to uncontaminated location. When highly alkaline solutions contact clay minerals, mineral dissolution and precipitation may occur. The effect of alkaline solutions on the transformation of clay minerals has been the subject of many studies (Cuadros and Linares 1996; Bauer and Berger 1998; Bauer and Velde 1999; Taubald et al. 2000; Elert et al. 2008; Jiang et al. 2008; Aslhaaer, 2013; Elert et al. 2015; Boussen et al. 2015). The mineral transformations depend on the nature and chemical composition of the reacting alkaline solutions and the nature of the reacting mineral. In particular, Kaolinitic soils which are known as non-swelling soils can exhibit swelling due to alkali contamination (Rao and Rao 1994; Sinha et al. 2003; Sivapullaiah et al. 2004; Sivapullaiah and Manju, 2007). However, no attempts were made so far to understand the influence of (i) the amount of kaolinite mineral present in clays and (ii) the concentration of alkali solution, on the swell behaivour of clay and the mechanism involved. Hence, in the present study, a comprehensive experimental program is carried out on the swelling behavior of kaolinitic clays (red earth, ball clay and china clay) with varying concentrations of alkali solution.

Fig. 1. Percent swell in red earth inundated with water and with alkali solutions.

2. Experimental program 2.1. Clays and solutions used Three Kaolinitic clays from India, namely red earth, ball clay and china clay, were examined in this work. Naturally available red earth was collected from Warangal, India by open excavation, from a depth of 1 m from ground level. Whereas, commercially available ball clay and china clay are purchased from Godavari Mines and Minerals, Visakhapatnam, Andhra Pradesh, India. The major difference between ball clay and china clay is that the ball clay contains a large portion of silica in addition to kaolinite. All the clays are oven dried and sieved through no.40 (425 μ) sieve prior to usage. The physical properties of clays are summarized in Table 1. All the physical properties tests were performed as per ASTM standards. The chemical composition of clays is presented in Table 2. Mulyukov (2008) reported that even a concentration of 0.1 N (0.4%) alkali solutions promote activation of swelling in soils. Thus, in this study 0.1, 1, 4 and 8 N NaOH solutions were considered for experimental investigation. The alkali solutions were prepared by dissolving the required amount of Analar Grade sodium hydroxide pellets in distilled water. 2.2. One-dimensional free swell test The one-dimensional free swell test measures the amount of swelling in the vertical direction of a confined specimen (Puppala et al. 2005). Special teflon oedometer cells were fabricated, which were entirely non-reactive to alkali. Clay samples sieved through no. 40 (425 μ) sieve were used for the test. Clay was initially dried in an oven at 110 °C. Oven-dried clay once cooled in a desiccator was spread over a plane glass sheet and mixed with water at optimum moisture content. The mixed specimens were placed in a sealed plastic bag and then kept in a desiccator for 24 h so as to attain uniform moisture content. Silicon

Table 2 Chemical composition of clays used. Clay

SiO2

Al2O3

Fe2O3

MgO

CaO

Na2O

K2O

TiO2

P2O5

MnO

SO3

Red earth China clay Ball clay

36.6 34.5 44.4

22.9 49.0 35.3

26.8 6.5 11.8

4.6 2.3 2.1

4.5 5.3 2.7

0.079 0.034 0.039

0.74 0.17 0.41

2.0 1.22 1.97

0.22 0.15 0.31

0.75 0.17 0.21

0.125 0.11 0.19


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Hatched portion shows the first phase of swelling and dark portion shows the second phase

Fig. 2. Percent swell in ball clay inundated with water and with alkali solutions.

Fig. 4. Swelling variation in three kaolinitic clays inundated with water and with alkali solutions.

grease was applied on the inner surface of the oedometer ring to reduce the friction during compaction. Clay specimens were then compacted (static compaction) in three layers to their maximum dry density and optimum moisture content in the rigid teflon cell (6 cm in diameter and 2 cm in height) to a height of 1.4 cm. Porous stones were placed at the top and bottom of the specimens, which facilitate the movement of fluid to the clay specimen. The specimens were inundated with varying concentrations of alkali solution as pore fluid and allowed to swell under free loading condition. The volume of the pore fluid used for all specimens was about 500 ml and testing was carried out at room temperature of 27 °C. For reference, clay specimens were also tested using distilled water as a pore fluid. The swell displacement readings were measured using dial gauges until no significant changes in displacements were observed. The final swell displacements along with the original heights of the specimen were used to calculate percentage swell in the vertical direction. Reproducibility of the test results was enhanced by keeping two samples for a minimum period of 21 days. One sample was terminated if both samples replicate values were generally within 3% of another. Representative clay samples were collected at the completion of the long term free swell tests and were analyzed using x-

Fig. 3. Percent swell in china clay inundated with water and with alkali solutions.

Fig. 5. X-ray diffraction patterns of red earth inundated with alkali solutions.

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3. Results and discussions 3.1. Free swell tests results The results of free swell tests on kaolinitic clays inundated with water and different concentrations of alkali solutions are presented in Figs. 1–3. It is evident from the figures that all three clays exhibited high swelling with alkali solutions when compared with water. The time-swelling curve of red earth inundated with water shows a maximum swelling of about 1%. Whereas, ball clay and china clay inundated with water exhibited a maximum swelling of about 3%. It is observed that the red earth has considerable sand content, so also lower swelling. The presence of high amounts of clay contents resulted in moderately high swelling and free swell index values of ball clay and china clay in comparsion with red earth though the CEC value is high for red earth. Further, presence of iron oxide in red earth and calcite in china clay (shown in XRD analysis) binds the particles which results in less swelling compared to ball clay. The small number of exchangeable cations present at the edges of sheets of the kaolinite structure does not allow the clay to swell which leads to low swelling in red earth, ball clay and china clay with water (Foster, 1954). All the three kaolinitic clays experienced swelling to different levels when inundated with different concentrations of alkali solutions. The variations in swelling in kaolinitic clays under alkaline conditions can be explained by two possible

Fig. 6. X-ray diffraction patterns of ball clay inundated with alkali solutions.

ray diffraction analysis and scanning electron microscopy tests to identify the chemico-mineralogical and morphological changes that may have occurred.

2.3. X-ray diffraction studies X-ray diffraction was accomplished with PANanalytical X-ray diffractometer to determine changes in mineralogical composition of clays. The representative samples collected at the end of swell tests were air dried for 24 h. The dried samples were pulverized manually to pass through the No. 200 sieve (75 μm). The X-Ray Tube was operated at 60 kV and 55 mA using an X'Celerator ultra fast detector. The samples were scanned between two theta values of 6° to 70° with a step size of 0.02°. X'pert high score plus software based on PCPDFWIN database was used for qualitative identification of minerals.

2.4. Scanning electron microscopy studies Morphological studies on samples were performed using TESCAN VEGA 3LMU scanning electron microscope with conventional tungsten heated cathode having live stereoscopic imaging using 3D beam technology. The samples were coated with gold using a sputter coater prior to scanning.

Fig. 7. X-ray diffraction patterns of china clay inundated with alkali solutions.


mechanisms: (1) dispersion of structure due to changes in the charge on the edges of clay particles and (2) formation of new minerals. It has long been recognized that kaolinite is a highly pH dependent mineral. At high pH (alkaline) conditions the charge on the edges become increasingly negative due to the adsorption of OH¯ ions. This leads to face-toface (F-F) associations (dispersion) of clay particles which results in an increase in swelling (Mitchell, 1993). It is also well known that under alkali environment dissolution processes affect mineral structures to a lesser extent, though formation of new mineral phases is a frequent phenomenon (Jozefaciuk, 2002). Thus, swelling caused by new mineral formations was considered a strong possibility in view of XRD results. In case of red earth, the variations in swelling with an increase in concentrations is very less as can be seen from Fig. 1. Though at higher concentrations (4 N and 8 N), loss of cementitious iron oxide (Hematite) coatings and new mineral formations (to a lesser extent) can be evidenced by XRD results, at lower concentrations only red earth exhibited maximum swell potential. However, in case of ball clay, the swell potential increased with increase in alkali concentrations and also exhibited a high swelling potential of 56% among the three kaolinitic clays (Fig. 2). This high swelling is mainly associated with the formation of zeolite minerals (Sodalite) with high intensity at high concentrations. The formation of zeolite minerals at highly alkaline conditions which lead to volume changes were even highlighted by Sivapullaiah and Manju (2006). In contrast to red earth and ball clay, china clay exhibited high swelling upto 4 N concentration thereafter the swelling reduced. Even with china clay, severe zeolite mineral formations (with 4 N concentration mineral transformations are very intense) only resulted in a rise in swelling (Fig. 3). These mineralogical and morphological changes are discussed in XRD and SEM results in detail. The varations in swelling patterns of three kaolinitic clays with different concentrations of alkali solutions are summarized in Fig.4. From figure it can be clearly observed that clays contaminated with 0.1 N NaOH solution exhibited swelling in single phase which is mainly due to particle dispersion. Whereas with 1, 4 and 8 N NaOH solutions, clays exhibited swelling in two phases: first phase is due to particle dispersion and the second phase is attributed to zeolite mineral formations.

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3.2. X-ray diffraction (XRD) studies X-ray diffraction tests have been performed on alkali contaminated kaolinitic clays to identify new mineral formations which can seriously influence the swelling behavior of clays. The minerals are identified by matching the d-spacing values. The results of XRD tests on red earth treated with water and alkali solutions are shown in Fig. 5. X-ray diffraction pattern of red earth inundated with water shows that the natural red earth primarily consists of quartz (major peaks at 4.25, 3.34, 1.82 and 1.37 [Å]). Relatively less intense peaks pertaining to kaolinite (Major peaks at 7.12, 4.41, 3.56, 2.32 [Å]) and hematite (Peak at 2.52 [Å]) were also observed. XRD analysis of red earth inundated with 0.1 N and 1 N NaOH solutions showed no changes in XRD pattern compared with that of water. However, red earth inundated with 0.1 N and 1 N showed high swelling. This indicates that the swelling in red earth with 0.1 N and 1 N is mainly controlled by particle dispersion. XRD patterns of red earth with 4 N NaOH showed new peaks pertaining to sodalite (major peaks 6.34, 3.66 and 2.59 [Å]), which is sodium aluminium silicate hydroxide hydrate, and trona (major peaks at 3.19 and 2.64 [Å]), which is sodium hydrogen carbonate hydrate. Sodalite which belongs to zeolite mineral group is formed due to precipitation of dissolved silica and alumina combined with sodium hydroxide. Trona is formed over time as the results of carbonation of alkali solution. Due to the crystallization of these two minerals volume increases. Similar set of peaks with same relative intensity as observed for samples inundated with 4 N NaOH solution were also observed in the case of 8 N NaOH. However the peak pertaining to trona transformed into cancrinite (peaks at 3.24, 3.07 [Å]), which is a sodium aluminium silicate calcium carbonate hydrate. Thus, as inferred earlier, the nature and magnitude of swell in red earth at higher concentrations are attributed to these mineral formations. Fig. 6 shows the X-ray diffraction patterns of ball clay samples collected after free swell tests with different concentrations of alkali solution. X-ray diffraction pattern of ball clay show primarily quartz (peaks at 4.25, 3.34, 1.82 and 1.37 [Å]) along with kaolinite (major peaks at 7.14, 4.45, 3.57, 2.55 and 2.38 [Å]) as their major minerals. No changes were observed in the XRD patterns of clay inundated with 0.1 N alkali solutions. However, an increase in swell is observed, which is mainly due to dispersed nature of clay under alkaline

Fig. 8. SEM images of red earth after swell test with a) water b) 0.1N NaOH, c) 1N NaOH, d) 4N NaOH and e) 8N NaOH.

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Fig. 9. SEM images of ball clay after swell test with a) water b) 0.1N NaOH, c) 1N NaOH, d) 4N NaOH and e) 8N NaOH.

environment. X-ray diffraction pattern of clay with 1 N NaOH showed substantial decline in the intensities of kaolinite peak and formation of new peaks. These new peaks at 6.34, 3.66 and 2.82 [Å] can be attributed to sodalites (sodium aluminium silicates nitrate), which are formed due to precipitation of dissolved silica and alumina reacted with sodium hydroxide. Further, the relatively less intense peak pertaining to cancrinite (peaks at 3.64 [Å]) was also observed. These two minerals play the major role in the amount of swelling (16%) observed in 1 N NaOH (Fig. 2). XRD analysis of samples inundated with 4 N NaOH show the presence of kaolinite mineral with a single peak, which indicates dissolution releasing silica and alumina. These silica and alumina combine with sodium hydroxide to from sodium aluminium silicate nitrate called sodalites. More intense peaks related to sodalites and cancrinite (sodium aluminium silicate calcium carbonate hydrate) are clearly

observed from XRD pattern (Fig. 6). This observation from XRD analysis substantiate the high swelling (31%) observed in the case of 4 N NaOH (Fig. 2). XRD pattern of ball clay with 8 N NaOH reflects that all the sodalite peaks which are present in the case with 4 N NaOH solution are completely absent and the number of cancrinite peaks has been increased. This confirms the very high swelling (55%) observed from ball clay sample inundated with 8 N NaOH (Fig. 6). Similar observations were made by Zhao et al. (2004) on the transformation of kaolinite to sodalite and cancrinite, when treated with caustic solutions. Two major chemical processes are involved in the reactions viz. dissolution of kaolinite and precipitation of cancrinite and sodalite. X-ray diffraction pattern of china clay with respect to water shows that it primarily contains kaolinite (major peaks at 7.20, 4.45, 3.57 and 2.34 [Å]) as their major mineral with relatively less intense quartz

Fig. 10. SEM images of china clay after swell test with a) water b) 0.1N NaOH, c) 1N NaOH, d) 4N NaOH and e) 8N NaOH.


peaks (peak at 3.34 [Å]). Peak pertaining to calcium carbonate called calcite (3.03 [Å]) can also be seen (Fig. 7). Though no changes were observed in the XRD pattern of china clay inundated with 0.1 N NaOH solution, an increase in swell which was observed is mainly due to the dispersed nature of china clay under alkaline environment. XRD pattern of china clay with 1 N NaOH showed new peaks pertaining to sodalite (6.33 [Å]). The reduced intensity of kaolinite peak in the presence of 1 N NaOH solution shows the dissolution of the mineral, releasing silica and alumina required for the formation of sodalite. In 4 N and 8 N NaOH solutions, similar set of new peaks pertaining to sodalite were observed. However the intensity of new peaks increased with increase in concentration of alkali solution. Though severe mineralogical changes occurred in both 4 N and 8 N NaOH solution, the swelling behavior of china clay at higher concentrations is not clear. 3.3. Scanning electron microscope (SEM) studies The scanning electron microscopy tests have been performed to examine the significant role of morphological changes in the swell behavior of alkali contaminated clays. The SEM images shown in the study were selected from numerous images taken at different magnifications of the samples. The micrographs shown are those with the magnifications that best demonstrate the distinctive microstructure of the clay. The microstructural behavior of alkali contaminated red earth after swelling is presented in Fig. 8. The weathering of the alkali contaminated red earth was clearly evident from the figure. The SEM image of red earth with water indicates an unusual fibrous like microstructure of soil particles. It can be observed that the soil particles dispersed nature in the presence of alkali solution when compared with original particles and the degree of dispersion increased with increase in concentration of alkali solution. Red earth inundated with 0.1 N and 1 N NaOH solutions shows little change in morphology, whereas with 4 N there is considerable change in morphology due to the formation of new minerals like sodalite and trona. In case of 4 N NaOH solution a rosette morphology can be observed due to the formation of sodalite. The morphological change in 8 N NaOH solution supports the formation of sodalite, trona and cancrinite, showing rosette morphology and chip structure. In Fig. 9, the microstructures of ball clay contaminated with water and alkali solutions are shown. The micrograph of ball clay with water is similar to that of red earth, which shows more fibrous microstructure. It is clear that there is no morphological change in case of ball clay contaminated with 0.1 N NaOH solution (Fig. 9b). Conspicuous morphological changes are there in the cases of samples inundated with 1 N, 4 N and 8 N NaOH solutions. Spherical formations along with pores are observed in case of 1 N and 4 N NaOH solutions, indicating the dissolution of kaolinite mineral and formation of sodalite (Figs. 9(c) & 9(d)). Discrete prismatic particles are observed in case of 8 N NaOH solution indicating the formation of cancrinite and severe dispersion of clay particles. The SEM patterns of china clay contaminated with water and alkali solutions are presented in Fig. 10. The microstructure of china clay with water shows highly loose fibrous nature. There is no clear change in morphology (with little dipersion) in the case of china clay contaminated with 0.1 N NaOH solution is observed. Fig. 10(c) shows the formation of spherical structure on the crystalline structure showing evidence for the precipitation of sodalite. With an increase in concentration, i.e. 4 N for the same interaction period, this spherical structures further increase in number, indicating more precipitation of sodalite (Fig. 10d). In case of 8 N, the size of this sodalite particles increase to more than 2 μm (Fig. 10d). These morphological studies also clearly supporting the swelling behavior of kaolinitic clays. 4. Conclusions Based on the swell tests, XRD and SEM analysis carried out on the three kaolinitic clays inundated with different concentrations of NaOH solutions, the following conclusions can be drawn.

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1. The mineralogical studies conducted on the three kaolinitic clays indicated that china clay consists of a high amount of kaolinite mineral followed by ball clay and red earth. 2. The low amount of swelling in all clays attributed to the small number of exchangeable cations present at the edges of sheets of the kaolinite structure does not allow the clay to swell. 3. The magnitude of swelling is as high as 56% in case of ball clay contaminated with alkali and 27% & 22% for red earth and china clay respectively. The swelling potential of kaolinitic clays was attributed to particle dispersion and zeolite mineral transformations. 4. The zeolite group mineral, sodalite, formations was evidenced in three clays along with trona in case of red earth, cancrinite in case of both ball clay and china clay. 5. The rosette type structures at higher concentration of alkali in three clays explains severe disintegration of morphology. Acknowledgments This research was financially supported by Department of Science and Technology (DST), SERB, India, under Fast Track Scheme for Young Scientist (Award No·SR/FTP/ETA-10/2012). References Alshaaer, M., 2013. Two-phase geopolymerization of kaolinite-based geopolymer. Appl. Clay Sci. 86, 162–168. Assa'ad, A., 1998. Differential upheaval of phosphoric acid storage tanks in Aqaba, Jordan. J. Perform. Constr. Facil. 12 (2), 71–76. Bauer, A., Berger, G., 1998. Kaolinite and smectite dissolution rate in high molar KOH solutions at 35° and 80 °C. Appl. Geochem. 13, 905–916. Bauer, A., Velde, B., 1999. Smectite transformation in high molar KOH solutions. Clay Miner. 34, 259–273. Boussen, S., Sghaier, D., Chaabani, F., Jamoussi, B., Messaoud, S.B., Bennour, 2015. The rheological, mineralogical and chemical characteristic of the original and the Na2CO3 – activated Tunisian swelling clay (Aleg formation) and their utilization as drilling mud. Appl. Clay Sci. 118, 344–353. Chunikhin, V.G., Mavrodi, V.K., Kramarenko, O.A., Dobromil'skaya, N.G., 1988. Effect of leakage of industrial alkali solutions on the construction properties of soils. Soil Mech. Found. Eng. 25 (6), 559–561. Cuadros, J., Linares, J., 1996. Experimentalkinetic study of the smectite-to-illite transformation. Geochim. Cosmochim. Acta 60, 439–453. Elert, K., Sebastian, E., Valverde, I., Rodriguez-Navarro, C., 2008. Alkaline treatment of clay minerals from the Alhambra formation: implications for the conservation of earthen architecture. Appl. Clay Sci. 39, 122–132. Elert, K., Pardo, E.S., Rodriguez-Navarro, C., 2015. Influence of organic matter on the reactivity of clay minerals in highly alkaline environments. Appl. Clay Sci. 111, 2–36. Estabragh, A.R., Beiytolahpour, I., Moradi, M., Javadi, A.A., 2014. Consolidation behavior of two fine-grained soils contaminated by glycerol and ethanol. Eng. Geol. http://dx.doi. org/10.1016/j.enggeo.2014.05.017. Foster, M.D., 1954. The relation between composition and swelling in clays. Clay Clay Miner. 3, 205–220. Jiang, T., Li, G., Qui, G., Fan, X., Huang, Z., 2008. Thermal activation and alkali dissolution of silicon from illite. Appl. Clay Sci. 40, 81–89. Jozefaciuk, G., 2002. Effect of acid and alkali treatments on surface charge properties of selected minerals. Clay Clay Miner. 50 (5), 647–656. Kabanov, V.M., Lebedeva, G.A., Finkel'shtein, L.I., Tkachenko, G.P., Shenin, O.S., 1977. Swelling of soils due to wetting with alkali solutions. Soil Mech. Found. Eng. 14 (5), 338–339. Khosravi, E., Ghasemzadeh, H., Sabour, M.R., Yazdani, H., 2013. Geotechnical properties of gas oil-contaminated kaolinite. Eng. Geol. 166, 11–16. Mal'tsev, A.V., 1998. Theoretical and experimental investigations of the effect of aggressive wetting on various types of bed soils. Soil Mech. Found. Eng. 35 (3), 83–86. Meegoda, N.J., Ratnaweera, P., 1994. Compressibility of contaminated fine grained soils. Geotech. Test. J. 17 (1), 101–112. Mitchell, J.K., 1993. Fundamentals of soil behavior. 2nd edn. Wiley, New York, NY. Moavenian, M.H., Yasrobi, S.S., 2008. Volume change behavior of compacted clay due to organic liquids as permeant. Appl. Clay Sci. 39, 60–71. Mulyukov, E.I., 2008. Alkaline swelling and consequences of alkalization of clayey bed soils. Soil Mech. Found. Eng. 45 (5), 182–185. Olgun, M., Yildiz, M., 2010. Effect of organic fluids on the geotechnical behavior of a highly plastic clayey soil. Appl. Clay Sci. 48, 615–621. Puppala, A.J., Napat, I., Rajan, K.V., 2005. Experimental studies on ettringite-induced heaving in soils. J. Geotech. Geoenviron. 131 (3), 325–337. Rao, S.M., Rao, K.S.S., 1994. Ground heaving from caustic soda solution spillage - a case study. Soils Found. 34 (2), 13–18. Reddy, P.H.P., Sivapullaiah, P.V., 2010. Effect of alkali solutions on the swell behavior of soils with different mineralogy. GeoFlorida 2010: advances in analysis, modeling and design, Florida, GSP199. ASCE 2692–2701.

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