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Effect of Heat Treatment on Strength of Clays
Abstract
Thermal treatment alters the physical and mechanical properties of clayey soils. Thermally treated soils have been used since primitive times for making trails for access and bricks for dwellings. In comparison with other soil-improvement methods, thermal stabilization produces immediate results. Thermal treatment of clays alters several material characteristics, such as strength, cohesion, internal friction angle, and resistance to abrasion. Furthermore, thermal treatment causes decrease in cation exchange and compressibility and increase in particle size. Aggregates produced by thermal treatment provide durable and economic substitutes for gravel and crushed rock. These are then used for pavement construction particularly in areas where construction materials have to be imported at excessive costs. Thus, in the Western Beaufort Sea area where large quantities of granular fill for artificial island and undersea-berm construction are required, but not readily available, thermally treated clays may be a solution. Granular material produced from a clayey soil must retain strength when wetted and be durable under wetting and drying conditions. Beyond fusion temperatures of clays, i.e. above 900 C, these conditions are known to be met. However, it is not clear from existing information, if heating below fusion temperatures may also satisfy these requirements. This study examines the relationship between the strength of selected clays and clay mixtures heated from 300 C to 700 C and the factors that influence such a relationship.
... Soil may be subjected to heat for various reasons, which changes soil's physical and mechanical properties (especially in clayey soils). Moreover, these changes may be reversible or irreversible [13][14][15]. Improvement of soil properties through heat has been used in the past, and the effect of heat on soil's engineering properties such as the compressive trength has been observed empirically. These improvements have been used in construction of roads and construction materials [15]. ...
... Improvement of soil properties through heat has been used in the past, and the effect of heat on soil's engineering properties such as the compressive trength has been observed empirically. These improvements have been used in construction of roads and construction materials [15]. ...
... Similar to illite, smectite clays initially form a stable phase where parts of the crystallized structure remain intact. This structure is then entirely destroyed at 800 degrees Celcius [15,25]. ...
Clay soil may be subjected to heat in various applications, such as nuclear waste burial sites and high voltage transmission lines. The impact of heat on clay soil's physical and mechanical properties has been explored in previous studies. However, previous studies have mainly focused on the mechanical properties of clay soil without stabilizers, and the effect of heat on the properties of the stabilized clay soil is scarcely studied. The present paper has analyzed and studied the combined effects of heat and cement on the settlement properties of kaolinite clay soil. To conduct the study, kaolinite clay mixed with various degrees of cement was exposed to a range of 25 to 600 degrees Celcius. The results showed that the coefficient of consolidation gradually decreased by increasing heat up to the dehydroxylation point. An increase in heat up to 200 degrees Celcius resulted in increasing the coefficient of consolidation in the specimens containing cement. In specimens containing 10 percent of the cement at temperatures higher than 200 degrees Celcius, the coefficient of consolidation in room temperature decreased by 73 percent compared to kaolinite. Moreover, the void ratio increased in kaolinite specimens without cement when subjected to heat up to 400 degrees Celcius. By increasing the heat, the void ratio decreased in specimens containing 10 percent cement. © 2022 Materials and Energy Research Center. All rights reserved.
... Soil may be subjected to heat for various reasons, which changes soil's physical and mechanical properties (especially in clayey soils). Moreover, these changes may be reversible or irreversible [13][14][15]. Improvement of soil properties through heat has been used in the past, and the effect of heat on soil's engineering properties such as the compressive trength has been observed empirically. These improvements have been used in construction of roads and construction materials [15]. ...
... Improvement of soil properties through heat has been used in the past, and the effect of heat on soil's engineering properties such as the compressive trength has been observed empirically. These improvements have been used in construction of roads and construction materials [15]. ...
... Similar to illite, smectite clays initially form a stable phase where parts of the crystallized structure remain intact. This structure is then entirely destroyed at 800 degrees Celcius [15,25]. ...
Please cite this article as: M. Hashemi, S. M. Marandi, M. Vahidi, The effect of heat on the settlement properties of cement-stabilized clay soil A B S T R A C T Clay soil may be subjected to heat in various applications, such as nuclear waste burial sites and high voltage transmission lines. The impact of heat on clay soil's physical and mechanical properties has been explored in previous studies. However, previous studies have mainly focused on the mechanical properties of clay soil without stabilizers, and the effect of heat on the properties of the stabilized clay soil is scarcely studied. The present paper has analyzed and studied the combined effects of heat and cement on the settlement properties of kaolinite clay soil. To conduct the study, kaolinite clay mixed with various degrees of cement was exposed to a range of 25 to 600 degrees Celcius. The results showed that the coefficient of consolidation gradually decreased by increasing heat up to the dehydroxylation point. An increase in heat up to 200 degrees Celcius resulted in increasing the coefficient of consolidation in the specimens containing cement. In specimens containing 10 percent of the cement at temperatures higher than 200 degrees Celcius, the coefficient of consolidation in room temperature decreased by 73 percent compared to kaolinite. Moreover, the void ratio increased in kaolinite specimens without cement when subjected to heat up to 400 degrees Celcius. By increasing the heat, the void ratio decreased in specimens containing 10 percent cement.
... High temperature is normally used for stabilizing expansive soils (Joshi et al. 1994, Abu-Zreig et al. 2001, Wang et al. 2008. Joshi et al. (1994) found that as the temperature treatment was increased, shear strength increased particularly between 400-500°C for Kaolinite, between 500-600°C for Kaolinite-Bentonite mixtures, and between 600-700°C for Bentonite. ...
... High temperature is normally used for stabilizing expansive soils (Joshi et al. 1994, Abu-Zreig et al. 2001, Wang et al. 2008. Joshi et al. (1994) found that as the temperature treatment was increased, shear strength increased particularly between 400-500°C for Kaolinite, between 500-600°C for Kaolinite-Bentonite mixtures, and between 600-700°C for Bentonite. This result is related to dehydroxilation (i.e., the loss of structural-hydroxyl groups from clays in the form of water) at temperatures of 300-500°C. ...
... Dramatic decrease in weight loss at 100-200°C is due to dehydration (i.e., the removal of inter-layer water). The weight loss at higher temperature (i.e., 400°C) can be attributed to dehydroxylation (i.e., the loss of structural-hydroxyl groups from clays in the form of water) (Joshi et al. 1994). This process results in unrecognizing montmorillonite mineral in X-ray diffraction test for specimen heated to temperature 400°C. ...
This paper focuses on hydro-mechanical behavior (i.e., suction characteristic and swelling pressure) of thermal treated bentonite. Calcium type bentonite (Calcigel) was used in the experimental study. The specimens were heated to temperatures of 100, 200, 300, 400, and 500°C. Change in minerallogy of specimen was quantified using X-ray diffraction analysis. Chilled-mirror hygrometer technique was used to determine total suction of the pre-heated specimen at room temperature. Swelling pressure was measured applying constant volume swelling pressure method. The results show that the ability of pre-heated specimen to retain water decreases after heating to temperature higher than 100 due to dehydration and dehydroxylation processes. Pre-heated process does not only influence the value of swelling pressure but also the rate of swelling pressure up built during the test.
... Thermal stabilization of expansive soils offers a faster solution compared to other methods, leading to significant changes in their engineering properties. This has been explored in various studies (Beles and Stanculescu, 1958;Mitchel, 1969;Joshi et al., 1994;Abu-Zreig et al., 2001;Tan et al., 2004;Han et al., 2017;Geng and Sun, 2018;Yao et al., 2022). Joshi et al. (1994) demonstrated that heating clay soils beyond the dehydroxylation temperature significantly impacts their mechanical behavior. ...
... This has been explored in various studies (Beles and Stanculescu, 1958;Mitchel, 1969;Joshi et al., 1994;Abu-Zreig et al., 2001;Tan et al., 2004;Han et al., 2017;Geng and Sun, 2018;Yao et al., 2022). Joshi et al. (1994) demonstrated that heating clay soils beyond the dehydroxylation temperature significantly impacts their mechanical behavior. Their study found that heating at approximately 600 • C was adequate to meet construction material standards. ...
This paper explores the effects of heating on the geotechnical and microstructural properties of natural expansive soil found in Sendafa, Ethiopia. Expansive soils, known for their volume changes with moisture variation, pose significant challenges. Traditional methods for improving these soils include using lime, cement, and agricultural wastes. However, this study focuses on heat treatment as an alternative approach to enhance the soil geotechnical behavior. Classified as A7-6 and CH according to the AASHTO and USCS classifications, the soil samples underwent heating in a micro-oven at temperatures of 200°C, 400°C, 600°C, and 800°C for one hour. Notably, the soil index properties showed improvement starting at 400°C. With increased temperatures, dry density rose while optimum moisture content decreased. Furthermore, unconfined compressive strength and swelling pressure dropped as the heating temperature escalated, and the clay minerals composition was reduced due to calcination and dehydration processes. SEM analysis revealed a transformed microstructure, with the soil appearing cinder (scoria)-like, exhibiting a more flocculated, aggregated, and well-integrated layered structure. This study underscores the potential of heat treatment for stabilizing expansive soils, recommending a minimum temperature of 400°C for effective results.
... The removal of OHions from the clay structure in the form of water is called dehydroxylation, which leads to weight loss in the soil [27]. In general, weight loss can be related to the removal of physical and water absorption and the loss of hydroxyl groups from the clay structure and CO 2 emissions as well [38,52]. ...
... As the temperature is increased to 900 ℃, the compressive strength reaches 2.3 MPa. Primary melting of materials and formation of resistant materials is then led to increased compressive strength [27]. ...
... On the other hand, it is well known from the technical burning of ceramics that the resulting changes in the mineralogy of clays (dehydroxylation of clay minerals) cause changes in physical properties such as mechanical strength. Increasing temperatures in clays result in a gradual increase in strength (Joshi et al. 1994;Mbumbia et al. 2000;Milheiro et al. 2005). Since kaolinite and some illte are minor compounds in Cotta type sandstone, the same effect can be expected in micro-scale in pore-filling cements consisting mainly of kaolinite. ...
... The dehydroxylation is connected with mass loss. Moreover, the former clay minerals get mechanically harder with increasing temperature, an effect that is increasing for kaolinitic clays with higher temperatures (Joshi et al. 1994;Mbumbia et al. 2000;Milheiro et al. 2005). Thus, the parts of the structure containing metakaolinite can better withstand the compression strain. ...
Damages due to fire occurred on many monuments and affected building sandstones. Changes in technical properties of heated sandstones are caused by changes in their structure and mineralogy. Therefore, a better knowledge of the changing processes in grain size scale is crucial to understand and assess property changes. The study presents results for the Cotta type Elbe Sandstone, a clay-bearing sandstone that is a widespread material for construction and sculpting. Uniaxial compressive strength and ultrasonic wave velocity as well as changes in colour, structures and mineralogical phases were determined for samples treated at temperatures of 300, 400, 500, 600, 700, 800 and 1250 °C and compared to the untreated material. The results show that minor clay components in the sandstone pores determine the uniaxial compressive strength in dependence of temperature and dry or wet state. Uniaxial compressive strength does not show a decrease even at high temperatures, whereas ultrasonic wave velocity is decreasing continuously with higher temperatures as for many other sandstones. The differing mechanical behaviour of the clay-bearing sandstone can be explained by the phase changes of kaolinite in the pore cement.
... Whether in a transient or steady-state, heat can alter the physical, mechanical, and microstructural properties of soils, particularly the engineering properties of clay soils, and the extent of these changes is a function of the type of mineral constituents, chemical composition, density, and moisture content (Joshi et al., 1994). By affecting the soil microstructure, heating reduces the size of calcite grains and silica and alumina contents, while increasing the silicato-alumina ratio (D'Elia et al., 2018). ...
... than that at 500°C and nearly 100 times higher than the compressive strength of natural soil. This can be attributed to dehydroxylation taking place in this temperature range, as well as the structural changes in the soil and the formation of cement compounds, alite (C 3 S) and belite (C 2 S) (Joshi et al., 1994). ...
Heat alters the engineering behavior of soils. Marl soils are highly-erodible sedimentary deposits composed of clay minerals and calcium carbonate. Clay minerals and calcium carbonate in marl soils considerably influence the engineering behavior of such soils. Soils can be exposed to heat for a variety of reasons leading to changes in the physical, mechanical, and microstructural properties, in particular the engineering properties of marl soils. In the design of geo-environmental projects, the results of soil mechanics, especially the permeability coefficient, directly influence the design outcomes. Accordingly, this study aimed at evaluating the effect of heat treatment on the engineering behavior and permeability coefficient of marl soils from a microstructural perspective. To this end, the marl soil was heated to 25–900°C for 2 h. The changes in the engineering properties of marl soils at different temperatures were studied by macrostructural (gradation, Atterberg limits, loss-on-drying, Unconfined Compressive Strength (UCS) and permeability) and microstructural (XRD and SEM) investigations. The results were suggestive of the considerable effect of heat treatment on the engineering behavior of marl soils, as the compressive strength of marl soils increased by 100 folds, and the permeability coefficient reduced by about 6 times at 700°C.
... Aproximadamente a los 520 °C ocurre la pérdida de agua estructural de la caolinita (Figura 3). Lo anterior, acorde con lo mencionado por autores como (Joshi et al. 1994) e (Isel et al. (2017) quienes indican que la deshidroxilación de este mineral generalmente ocurre entre los 400 °C y 600 °C. ...
... Tal como lo han mencionado autores como (Barranzuela 2014) y (Santos et al. 2009), estos dos componentes son los más importantes en la composición de arcillas y por ende suelen ser los más abundantes en este material, mientras que otros como el hierro, suelen encontrarse en porcentajes más bajos. Para el caso de la composición mineralógica, en la (Figura 4) se observa el difractograma de la arcilla utilizada en la investigación, evidenciando fases mineralógicas características de arcillas como son el cuarzo (SiO 2 ) en ángulos 21,1794°; 26,9496°; 36,8383°; 39,7578°; 42,7379°; 50,4242°; 60,2280° y 68,4041° (código de referencia 01-083-2469 y 00-003-0427), y la caolinita (Al 2 Si 2 O 5 (OH) 4 ) en ángulos 12,6776° y 25,1782° (código de referencia 00-003-0058) (Joshi et al., 1994);(Gonzalez et al., 2014); (Ruge-Guerrero et al., 2016). ...
Cigarette butts are one of the most common waste worldwide. The toxic and non-biodegradable components make cigarette butts a hazardous waste and one of the causes of pollution. This paper presents some of the results of a study on the re-cycling cigarette butts in the manufacture of clay bricks. Four mixtures were made, these include a control clay brick, with a clay content of 100% (LADRICOL 0%) and three additional mixtures incorporating cigarette butts in different percentages by weight (LADRICOL 2.5%, LADRICOL 5.0% and LADRICOL 7.5%). The mixtures were fired at different temperatures and these were tested to determine the physical and mechanical properties of the bricks. The results showed that the samples incorporating 2.5% cigarette butts content and fired at 850 °C are in compliance with the standard normative for this type of product (NTC 4205-2). Furthermore, this brick can improve the environmental quality and can reduce energy consumption during firing, by 19.75%.
... At approximately 520°C, structural water loss from kaolinite occurs (Figure 3). This is in line with authors such as (Joshi et al. 1994) and (Isel et al. (2017), who indicate that the dehydroxylation of this mineral generally occurs between 400 °C and 600 °C. ...
... In the case of the mineralogical composition, (Figure 4) shows the diffractogram of the clay used in the study, evidencing characteristic mineralogical phases of clays such as quartz (SiO 2 ) at angles of 21. 1794°; 26.9496°; 36.8383°; 39.7578°; 42.7379°; 50.4242°; 60.2280° and 68.4041° (reference code 01-083-2469 and 00-003-0427), and kaolinite (Al 2 Si 2 O 5 (OH) 4 ) at angles 12.6776° and 25.1782° (reference code 00-003-0058) (Joshi et al., 1994); (Gonzalez et al., 2014); (Ruge-Guerrero et al., 2016). ...
... Sintering of clayey soil and particle growth result from treatment temperatures beyond 900°C, providing granular material that retains its compressive strength under wetting and drying conditions. It has been suggested as an economic substitute for gravel and crushed rock to avoid importing construction materials at high costs ( Joshi et al. 1994). ...
... 3(b)] and to improve strength compared to nonexpansive clay. This effect is supported by a comparative study on heat treatment of kaolinite and montmorillonite at 100°C to 900°C (Joshi et al. 1994), and may have been the reason for the significantly improved strength in mortar with HP soil, which exceeded the strength of mortar with river sand at 1,000°C. This strength improvement of MP and HP soil was also due to the reduction in water demand with thermal treatment (Fig. 5). ...
In the interest of utilizing high-plasticity excavation soil as a replacement for fine aggregate in cement mortar, a study on the thermal treatment of soils containing 25% and 40% clay fractions was carried out. A range of tests including thermogravimetric analysis (TGA) and X-ray diffraction (XRD) were conducted to examine the transformation of fines (silt+clay) in soil at temperatures ranging from 200°C to 1,000°C. Thermally treated soils were used as fine aggregate in cement mortar, and properties such as water demand, dry density, compressive strength, and drying shrinkage were studied. The experiments were designed with the parameters treatment temperature and duration using central composite design of response surface methodology. From the test results, it was concluded that thermal treatment helps in transforming clayey soil, even high-plasticity soil, to be used as a suitable fine aggregate material in cement mortar. However, the properties of thermally treated soil highly depend on the clay mineralogy present in it.
... Fig. 1 shows typical TGA results. The steep mass loss in the 50-100°C and 400-500°C regions of as-received material corresponded to the well-known emissions of free water and structural hydroxyl water, respectively (Grim, 1968;Odom, 1984;Joshi et al., 1994). To reach the Martian surface soil water content around 2-5 wt% (Boynton et al., 2008), the montmorillonite was dried in a vacuum oven (Carbolite CTF 12/75/700) at 600°C for 10 h and then air cooled; the temperature increase rate was 5°C/min. ...
... The strength of water-bound montmorillonite should deteriorate or remain the same if water-aided hydrogen bonding contributed to the final strength (Joshi et al., 1994;Nichols and Grismer, 1997). Decreasing the flexural strength with increasing pre-compaction drying temperature introduces two possibilities: First, residual water may promote strength development; second, drying at a lower temperature may favor the predominance of hydrogen bonds. ...
The current study discovers that uniaxial compression under ambient condition can directly cause strong bonding in ultra-dry montmorillonite, which is attributed to the secondary molecular interaction other than hydrogen bonding. The strength of so-processed material is sensitive to the lateral confinement condition of loading. Similar compaction pressure produces equally strong solids between quasi-static and impact loading modes. Gas permeability of the compacted solids is comparable to that of dense rocks. These findings shed light on the study of Martian regolith and in-situ resource utilization.
... The scenario where soil comes into contact with elevated temperatures (i.e., the thermal energy field) is frequently encountered in various civil-engineering activities. Some of these situations are the design and execution of the foundations for furnaces [1], boiler units, forging units, brick kilns, rocket launching pads, buried powersupply cables and air-conditioning ducts [2], events like volcanic eruptions and activities such as underground explosions, disposal of high-level radioactive [3] and industrial toxic wastes [4], and ground modification or stabilization techniques with the application of chemicals and thermal energy [5][6][7][8][9][10]. Hence, understanding the influence of elevated temperatures on soil properties becomes necessary. ...
... Alcocer and Chowdhury [6] also employed a thermal treatment as a remedy for soils contaminated with crude oil. Earlier researchers [5,[7][8][9] studied the effect of a heat treatment (300 to 700°C) on clayey bricks. Based on these studies it is clear that the heat treatment of clayey soils (up to 700°C) leads to physical, chemical and microstructural changes, and hence a reduction in their cation-exchange capacity and compressibility. ...
This paper describes details of a study to investigate and demonstrate the changes undergone by soil when it is exposed to elevated temperatures. Such situations are commonly encountered while designing the foundations for the furnaces, boiler units, forging units, brick kilns, rocket launching pads, buried power-supply cables, airconditioning ducts, underground explosions, disposal of high-level radioactive and industrial toxic wastes, ground modifications or soil-stabilization techniques, etc. As such, investigations to establish changes undergone by the soil when it is exposed to elevated temperatures assume some importance. With this in view, individual samples of six soils, with entirely different characteristics, were subjected to temperatures up to 300°C (sequentially in steps of 50°C) and after each step of thermal treatment, these samples were characterized for their physical, chemical and mineralogical properties. Based on a critical synthesis of the results, it has been demonstrated that elevated temperatures cause (i) a change in the color, (ii) an increase in the specific gravity, particle size and weight loss, (iii) a reduction in the specific surface area, cation-exchange capacity and zeta-potential, and (iv) a structural transformation of the soil. Though these changes would affect the engineering properties of the soil to a large extent, the scope of this paper is limited to demonstrating the alterations in physical, chemical and mineralogical changes, only, occurring in the soil when it is exposed to elevated temperatures.
... The scenario where soil comes into contact with elevated temperatures (i.e., the thermal energy field) is frequently encountered in various civil-engineering activities. Some of these situations are the design and execution of the foundations for furnaces [1], boiler units, forging units, brick kilns, rocket launching pads, buried powersupply cables and air-conditioning ducts [2], events like volcanic eruptions and activities such as underground explosions, disposal of high-level radioactive [3] and industrial toxic wastes [4], and ground modification or stabilization techniques with the application of chemicals and thermal energy [5][6][7][8][9][10]. Hence, understanding the influence of elevated temperatures on soil properties becomes necessary. ...
... Alcocer and Chowdhury [6] also employed a thermal treatment as a remedy for soils contaminated with crude oil. Earlier researchers [5,[7][8][9] studied the effect of a heat treatment (300 to 700°C) on clayey bricks. Based on these studies it is clear that the heat treatment of clayey soils (up to 700°C) leads to physical, chemical and microstructural changes, and hence a reduction in their cation-exchange capacity and compressibility. ...
... -Swelling reduced significantly with increased heating time-specific gravity initially rose, then declined-liquid/plastic limits decreased consistently-microwave heating altered particle structure, transitioning from fine to coarse particles and improving soil stability. 3 Joshi et al. [63] -Thermogravimetric analysis, porosimetry, and compressive strength tests-samples were heated at 300 • C, 400 • C, 500 • C, 600 • C, and 700 • C in a muffle furnace to assess pore distribution, void ratio, and strength. ...
The thermal stabilization of expansive soils has emerged as a promising and sustainable alternative to conventional chemical stabilization methods, addressing the long-standing challenges associated with soil swelling and shrinkage. This review critically evaluates the mechanisms, applications, and advancements in thermal stabilization techniques, with a particular focus on both traditional approaches (e.g., kiln heating) and emerging innovations such as microwave heating. This study synthesizes recent research findings to assess how thermal treatment modifies the mineralogical, physical, and mechanical properties of expansive soils, reducing their plasticity and improving their strength characteristics. Comparative analysis highlights the advantages, limitations, and sustainability implications of different thermal methods, considering factors such as energy efficiency, scalability, and environmental impact. While thermal stabilization offers a viable alternative to chemical treatments, key challenges remain regarding cost, field implementation, and long-term performance validation. The integration of thermal treatment with complementary techniques, such as lime stabilization, is explored as a means to enhance soil stability while minimizing environmental impact. By addressing critical research gaps and providing a comprehensive perspective on the future potential of thermal stabilization, this review contributes valuable insights for researchers and engineers seeking innovative and sustainable solutions for managing expansive soils.
... Heat transfer in soil plays a crucial role in the many geotechnical applications such as ground heat exchangers, foundations of power stations, rocket launching pads, underground tunnels, nuclear wastes dump and backfills, etc. It is therefore essential to understand the behavior of soils subjected to variations in temperature so that precautions can be taken to eliminate the risk of unforeseen consequences (Verhoogen 1980, Miller 1985, Stein and Stein 1992, Joshi et al. 1994, Yun 2005, Wang and Qi 2011, Low 2013. Heat transfer in the soil is mainly measured in terms of three main parameters, viz., thermal conductivity, heat capacity and thermal diffusivity (Farouki 1981). ...
In many of the geotechnical applications where transfer of heat takes place such as with ground heat exchangers, rocket launching pads, nuclear waste repositories, backfill of waste liners, etc., soils undergo various physical and chemical changes. It is essential therefore to measure thermal conductivity of soil. A thermal probe is fabricated and calibrated to study the influence of various properties of soils on conductivity. Tests were conducted on seven different soils (fine grained and coarse grained) at various density and water contents. An attempt has been made to study the influence of specific surface area and cation exchange capacity on thermal conductivity of soils by maintaining constant density in dry condition for each soil sample. The obtained results show that mineralogy, grain size, density, water content, SSA and CEC have significant influence on thermal conductivity. These studies are very useful in predicting the thermal response of soils where heat transfer mechanism takes place.
... As shown in Figure 4(a), the modulus of rupture increases by elevating the temperature from 60 o C to 100°C, while it starts to decrease with further increase in temperature. These observations are consistent with reported results in Joshi et al., (1994) that investigated the effect of heat treatment of bentonite clay at 100°C up to the dehydroxylation temperature (i.e., the temperature at which further rewetting of clay cannot revert back to the plastic state). The decrease in flexural strength at higher temperatures can be attributed to the thermally -induced stresses in the clay-regolith mixture. ...
Through the Artemis program, NASA will extensively explore the Moon in preparation for the first human mission to Mars. NASA is planning to return to the Moon in the next few years, to establish a strategic presence at the Lunar south pole. To promote a long-term sustained presence, planetary surface construction technologies are needed to build a variety of supporting structures such as habitats, radiation shields, protective hangars, and launching and landing pads. Construction 3D printing (C3DP) is an autonomous construction technology that employs the principles of additive manufacturing on a structure scale. While C3DP has been mainly used for terrestrial construction, it is also considered a viable robotic construction technology for planetary infrastructure buildup. In this paper, the challenges and possibilities of extrusion-based planetary C3DP will be discussed in detail. Moreover, the results of an ongoing experimental study, as well as future research plans will be presented.
... Dehydration at a high temperature can cause the irreversible collapse of the structure [19]. The clay platelets are bonded electrostatistically. Therefore, dehydration of cation can result in a reduced adsorption ability of the clay [20]. Malo et al [21] studied the effect of heating kaolinite and bentonite and reported gradual increase in the strength of the clays and clay sediments with an increase in heating temperature. ...
The design of wastewater treatment methods is usually based on the need to reduce heavy metals and suspended solid loads to limit pollution of the environment. The quality of treated effluent used in agriculture has a great influence on the operation and performance of the wastewater-soil-plant or aquaculture system. In the case of irrigation, the required quality of effluent is dependent on the crops to be irrigated, the soil conditions and the system of effluent distribution adopted. The present study is aimed to provide a healthy and better environment for both man and aquatic bodies. In this study, Nsu clay was modified by thermal and alkaline process for the removal of heavy metals and organic pollutants from industrial paint effluent. The modified clay was used to purify effluent from paint industry through a process involving coagulation for colour and sorption. The treated effluents were analyzed for the heavy metal concentration such as chromium, potassium, lead, magnesium, manganese, iron, cobalt, sodium, silver, mercury and cadmium. Furthermore, some gross organic pollution indicators such as biological oxygen demand (BOD) and chemical oxygen demand (COD) as well as pH, acidity, alkalinity, turbidity, hardness and total dissolved solids (TDS) of the effluents were studied. It was found that percentage removal was over 60% for all the contaminants. The modified clay exhibited better performance when calcined at 750 o C with 4M NaOH. Application of the simple and low cost modification technique employed in this study makes kaolinite a co-effective adsorbent for removal of many organic and inorganic pollutants from industrial paint effluents.
... Alcocer and Chowdhury [2] applied heat treatment on clayey soils contaminated with crude oil. Joshi et al. [3] studied the effect of the heat treatment on the durability or strength and physical properties of the clays at the temperatures ranging from 300 to 700 jC. Yang and Arouk [4] experimentally investigated the heat conductivity of heat-treated clay bricks. ...
This study examines the effects of heat treatment under laboratory conditions for two types of clay collected
... Clays have been subjected to high temperatures to suit several engineering applications, such as geopolymer cements (Zibouche et al. 2009;Elimbi et al. 2011), bricks for dwellings (Joshi et al. 1994;Abu-Zreig et al. 2001), and ceramic products (Yanti and Pratiwi 2018), and to decontaminate soils from radioactive and toxic substances (Varlakov et al. 1997). In the case of bentonite, its greatest use is as nanoparticle or nanoclay for the modification of asphalts. ...
Clays and clay minerals are widely used as raw materials in different industrial processes due to their abundance. Generally, in road construction projects, clays are considered waste materials because they have some undesirable engineering properties (e.g., plasticity and swelling properties). For this reason, this material is generally discarded in landfills or dumps. However, taking advantage of its abundance , this material could be used as a substitute for natural aggregates of hot mix asphalt (HMA) production as long as their undesirable properties are eliminated. In this study, a bentonite was thermally treated (subjected to high temperatures) in order to be used as replacement for the total filler content of a natural aggregate in HMA. X-ray diffractometry (XRD), X-ray fluorescence (XRF), Atterberg limits, and free swelling index tests were carried out on bentonite (with and without thermal treatment). Marshall, indirect tensile strength (ITS) (under dry and wet conditions), resilient modulus, permanent deformation, resistance to fatigue, and Cantabro tests were carried out on HMA mixtures using thermally treated bentonite (BT) as filler. On all test results an ANOVA test was carried out. When BT replaced the total fraction of the natural filler, its resistance under monotonic load, stiffness under cyclic loading, and resistance to moisture damage increased remarkably. A similar resistance to fatigue and abrasion in the Cantabro test was observed. Based on the results obtained, BT could be considered a technically viable alternative as a substitute material for natural fillers in HMAs.
... This is due to the decreased clogging occurrence and permanent viscosity at higher temperatures (Aldaeef and Rayhani 2014). Aggregates formed by elevated temperature treatment provide economic and durable alternatives for crushed rock which can be used in pavement constructions (Joshi et al. 1994). ...
This paper presents an experimental investigation on the influence of drying marine clay at different temperatures of 27 °C (room temperature air drying), 40 °C, 60 °C, 80 °C, 100 °C and 150 °C (oven drying) on its geotechnical properties. The same soil dried at various temperatures is then rewetted for 7 and 28 days and examined for its variation in the engineering properties. Investigation includes gradation analysis, consistency limits, compaction characteristics, shear strength properties and California bearing ratio. For the level of significance on the drying temperature variation, one-way analysis of variance (ANOVA) is performed using the Microsoft Excel software. Laboratory test results showed a decrease in clay size fractions and an increase in silt and sand size particles with increased drying temperature. Liquid limit and plasticity index decrease with an increase in drying temperature till 100 °C. Improved compaction characteristics, unconfined compressive strength, long-term stress-strain behaviour and California bearing ratio were found upon drying the soil at 100 °C. These results are useful in sample preparation prior to testing, also in specific geotechnical applications of underground storage of radioactive waste, an alternative to crushed rocks in pavement and ground source. Rewetting of the dried soil did not show much variation in gradation, index and compaction properties which are compared with the same properties of soil tested immediately.
... Clays have been subjected to high temperatures to suit several engineering applications, such as geopolymer cements (Zibouche et al. 2009;Elimbi et al. 2011), bricks for dwellings (Joshi et al. 1994;Abu-Zreig et al. 2001), and ceramic products (Yanti and Pratiwi 2018), and to decontaminate soils from radioactive and toxic substances (Varlakov et al. 1997). In the case of bentonite, its greatest use is as nanoparticle or nanoclay for the modification of asphalts. ...
In this study an industrial kaolin was subjected to high temperatures for one and two hours in order to eliminate plasticity and swelling properties. This heat-treated kaolin (HTK) was then evaluated for use as a substitute for natural mineral filler (passing No. 200 sieve; 6% by total mass of aggregate) in a Hot Mix Asphalt (HMA). The Marshall stability and flow test and Indirect Tensile Strength (ITS) test were performed to evaluate responses of HMA mixtures. X-ray diffractometry (XRD) and X-ray fluorescence (XRF) tests were carried out on kaolin (with and without thermal treatment). Effects of temperature and time of exposure on the penetration index (PI) and free swell index (FSI) of the HTK are also presented. Increased resistance under monotonic load and moisture damage was found when the natural mineral filler was completely replaced by the HTK. In contrast, when kaolin (K) that has not been heat-treated is used resistance and damage noticeably decrease especially in the presence of water.
... e matrix of soil can be changed by physically or chemically binding the particles of soil and the reinforced material together [7]. Binding agents include cement or other chemical products [6,8,[9][10][11]; binding processes involve heating or freezing [12,13]. A possible disadvantage of a reinforced soil is that the strengthening effect depends on the orientation of inclusions. ...
Applications of soil improvement have proliferated in recent years. To date, we have limited studies on the quantitative analyses of the autoadaptive material and specifically to model its stress-strain relationship. This paper explored an autoadaptive material, iron-powdered Ottawa sand, which was temporarily solidified by applying an electromagnetic field. A series of compression triaxial tests were carried out with various relative densities of specimens (60% and 80%), in four electromagnetic fields (0 A, 0.5 A, 1 A, and 2 A) and under three confining pressures (103 kPa, 206 kPa, and 310 kPa). The test results indicate that the strength of specimens increased while initial stiffness and brittleness reduced by adding iron powder. Moreover, the strength of the specimens increased by increasing the magnitude of the applied electromagnetic field. The behavior of the iron-powdered sand was described by using a revised Duncan–Chang model. The revised model was evaluated by comparing the simulated results with the corresponding test data. The comparison showed that the revised model can better capture the nonlinear stress-strain behavior of the specimens. With the application of the revised Duncan–Chang model, the standard error of the estimate between the experimental and predicted results is lowered down to 0.39 from 4.7. Future research is geared towards practical applications for temporary solidification of soil.
... Dehydration at a high temperature can cause the irreversible collapse of the structure [19]. The clay platelets are bonded electrostatistically. Therefore, dehydration of cation can result in a reduced adsorption ability of the clay [20]. Malo et al [21] studied the effect of heating kaolinite and bentonite and reported gradual increase in the strength of the clays and clay sediments with an increase in heating temperature. ...
The design of wastewater treatment methods is usually based on the need to reduce heavy metals and suspended solid loads to limit pollution of the environment. The quality of treated effluent used in agriculture has a great influence on the operation and performance of the wastewater-soil-plant or aquaculture system. In the case of irrigation, the required quality of effluent is dependent on the crops to be irrigated, the soil conditions and the system of effluent distribution adopted. The present study is aimed to provide a healthy and better environment for both man and aquatic bodies. In this study, Nsu clay was modified by thermal and alkaline process for the removal of heavy metals and organic pollutants from industrial paint effluent. The modified clay was used to purify effluent from paint industry through a process involving coagulation for colour and sorption. The treated effluents were analyzed for the heavy metal concentration such as chromium, potassium, lead, magnesium, manganese, iron, cobalt, sodium, silver, mercury and cadmium. Furthermore, some gross organic pollution indicators such as biological oxygen demand (BOD) and chemical oxygen demand (COD) as well as pH, acidity, alkalinity, turbidity, hardness and total dissolved solids (TDS) of the effluents were studied. It was found that percentage removal was over 60% for all the contaminants. The modified clay exhibited better performance when calcined at 750oC with 4M NaOH. Application of the simple and low cost modification technique employed in this study makes kaolinite a co-effective adsorbent for removal of many organic and inorganic pollutants from industrial paint effluents.
... The interaction of geomaterials with thermal energy has been an emerging area of research in geoenvironmental engineering because it has an immense scope of application in several real-life situations. Some of these situations are construction of underground storage tanks, installation of buried power cables, remediation of contaminated land by thermal treatment, freezing and thawing of soil mass, provision of foundations in permafrost regions, disposal of nuclear waste, extraction of gas hydrates from subseafloor methane-bearing sediments, and harvesting of shallow geothermal energy, as mentioned by earlier researchers (Stein and Stein 1992;Joshi et al. 1994;Krishnaiah and Singh 2004;Yun 2005;Delage et al. 2010;Yavari et al. 2014;Dao et al. 2015;Di Donna et al. 2016;Faizal et al. 2016;McCartney et al. 2016;Mondal et al. 2017a, b). Needless to say, these situations necessitate an understanding of heat-transfer mechanisms through the soil mass. ...
The heat-transfer phenomenon in dry sands, which is generally looked at from the perspective of conduction, was studied
with the thermal flux method (TFM) proposed in the literature. However, when results from the TFM were compared with
those obtained from the numerical simulation, a substantial disparity was noticed. Through careful analysis of the results, it was
realized that there is a significant contribution from the convective heat and possible ingress of lateral heat into the column,
which would violate the assumption that the heat migration is one-dimensional (conductive). To quantify the ingress of lateral
heat in the column, the TFM was suitably modified, designated as the modified thermal flux method (MTFM). It was found that
the results from the MTFM match quite well with those obtained from the numerical simulation, with adequate boundary conditions.
In short, MTFM facilitates understanding the of the mechanisms of heat transfer in dry sands by conduction and convection,
as demonstrated in this technical note.
... Rapid urbanisation, industrial and infrastructural development in the contemporary civilisation lead to several geo-environmental activities such as disposal of nuclear and industrial wastes (Rao and Singh 1999, Naidu and Singh 2004, Krishnaiah and Singh 2004, Singh and Krishnaiah 2006, construction of crude oil and petroleum storage tanks (Padmakumar 2013), remediation of contaminated land by thermal treatment (Krishnaiah 2003, Kadali et al. 2013, thermal stabilisation of the soil mass, installation of buried power conduits (Singh and Krishnaiah 2006, De Moel et al. 2010, Lee et al. 2010, air-conditioning ducts (Kadali et al. 2013), oil-carrying pipelines (Brandon and Mitchell 1989, Manthena and Singh 2001, Abuel-Naga et al. 2009), extraction of gas hydrates from subseafloor sediments (Verhoogen 1980, Joshi et al. 1994, Yun 2005 and activities related to agriculture and aquaculture (viz. growing crops which need a certain temperature and estimation of the depth of frost penetration) etc. ...
The soil mass is subjected to temperature variation due to several human activities (viz. tanks storing heated fluids, buried cables and pipelines, air-conditioning ducts, disposal of nuclear and thermal power plant wastes etc.), which result in heat-induced migration of the moisture in it. Though several studies have been conducted in the past to investigate the mechanism of heat migration through the soil mass, a methodology for ‘real-time measurement of the variations in temperature, flux and moving moisture front, in tandem, with respect to space' has rarely been attempted. In this context, extensive laboratory investigations were conducted to measure real-time flux and temperature variations in the sandy soils, and the validation of results has been done by employing an equivalent electrical circuit programme, LTspice. Subsequently, a mathematical model PHITMDS (i.e. Prediction of Heat-Induced Temperature and Moisture Distribution in Soil) has been developed and its utility and efficacy, for predicting the depth-wise temperature and heat-induced moisture migration, due to evaporation, in terms of position of moving moisture front in the sandy soil has been critically discussed and demonstrated.
... Marine clay, the most commonly retrieved material from dredging activities, often falls short of this requirement. In this context, attempts made by Joshi et al. (1994) to improve the shear strength of the DS (clays) from Beaufort Sea, Western Beaufort, Canada, are worth mentioning. These authors have recommended usage of the heat-treated (less than 9008C) DS as a granular fill material. ...
Dredged sediments have been extensively used in various parts of the world for applications related to various infrastructural developmental activities, such as land reclamation, building construction, beach replenishment, habitat restoration, and so on. The vicinity of the megacities to the water bodies and shortage of naturally available raw materials for the developmental activities is mostly responsible for such a paradigm shift from the conventional application of natural resources (soils and rock mass). However, utilization of dredged sediments has largely been constrained because of their heterogeneity and also because most of the earlier studies were site specific; hence, these findings cannot be generalized. This calls for a critical analysis of the outcome of the existing studies related to the application of such sediments based on their comprehensive characterization, in infrastructure development, policies adopted in this context, challenges in terms of handling and disposal, and potential of these sediments to contaminate the ecosystem. As highlighted in this paper, such a critical review of the literature would be mandatory for framing the guidelines in establishing the beneficial usages of the dredged sediments as an artificial resource.
... Mitchell (1969) showed that the heat treatment changed some of the physical properties of the clayey soils such as angle of friction, cohesion and strength. Joshi et al. (1994) investigated the effect of the heat treatment on the strength of clayey bricks at temperatures ranging from 300 to 700 o C. And it was found that an increase in strength was accompanied with increase in temperature. ...
... bioresources.com Cheng et al. (2014) ...
Oil heat treatment can effectively improve the dimensional stability and bio-durability of wood. However, the characteristics of high oil uptake (50 percent or higher) and high susceptibility to leaching from wood have an adverse effect on subsequent manufacturing processes of wood product and production costs. A solvent extraction (100% ethanol) process was used to extract the surplus oil from the treated wood. Because the making of powder specimens from high oil uptake wood would result in experimental error, a new method of determination of oil uptake percentage was proposed by two step Soxhlet extraction with ethanol. The oil uptake percentage of oil-heat-treated poplar wood at 180 °C for 2 h with this method was determined to be 113.29%. Additionally, the average oil uptake percentage (OUP) of oil-treated poplar after the oil extraction process for 2 and 6 h was 54.82% and 29.11%, respectively. Moreover, the average oil extraction percentage (OEP) of specimens with the oil extraction process at the first step (wood sticks) in the Soxhlet extractor apparatus was larger than that of oil-heat-treated poplar specimens. Due to the combined effect of chemical changes in the wood at high temperatures and of oil uptake by the wood, the compression strength parallel to the grain changed at different OUP levels.
... In their comprehensive review, Laloui and Cekerevac (2003) indicated that thermal treatment strongly affects the type of free and adsorbed water, which has a considerable influence on clay plasticity, permeability, elastic modulus, etc. According to Joshi et al. (1994), there are three types of water generally attached to clay particles: (1) free-flowing "bulk water", present as moisture in the macro-pores and interlayer; ...
The present research evaluated lanthanide desorption levels from ion-adsorption clays subjected to thermal pre-treatment at various temperatures in the range 100-900 °C. The authors identified macro- and micro-structural changes occurring in the clays during heating and related the observed trends to the water content and rare earth elements (REE) desorption behavior during subsequent ion exchange leaching, in order to gain a better understanding of how temperature and moisture may affect the overall REE recovery, hence impacting the ore processing route. It was found that the total lanthanide extraction from clays pre-heated in the range 100-300 °C increased with the temperature, then decreased drastically, reaching near-zero levels for the range 700-900 °C. This trend was explained in terms of improved clay permeability achieved upon elimination of pore and adsorbed water molecules in the interval 100-300 °C, which facilitated better lixiviant access to the REE adsorption sites. The subsequent decrease in REE extraction in the interval 300-900 °C was related to the loss of hydroxyl groups from the aluminosilicate matrix (dehydroxylation), resulting in irreversible REE fixation to the surface and major structural changes such as layer collapse, loss of crystal structure and vitrification, with the ultimate result of completely blocking lixiviant access to the adsorbed cations.
... Mitchell (1969) showed that the heat treatment changed the physical properties of the clayey soils such as angle of friction, cohesion and strength. Joshi et al. (1994) investigated the effect of the heat treatment on the strength of clayey bricks at temperatures ranging from 300 to 700°C. And it was found that an increase in strength was accompanied with the increase in temperature. ...
This study examined the effects of heat treatment on two types of clays mixed with silica sand under laboratory conditions. Soils were subjected to three varied temperatures, i.e. 100, 250 and 500°C. The soil properties studied were Atterberg's limits, optimum water content and unconfi ned compressive strength. Experimental results showed that the temperature greater than 100°C resulted in a reduction in Atterberg's limits, optimum water content and unconfi ned compressive strength. For illite and silica mixture heating the soils at 500°C, liquid limit, plastic limit, optimum water content and unconfi ned compressive strength were reduced to 12%, 0%, 40% and 0%, and for kaolinite and silica mixture the above characteristics reduced to 18%, 0%, 50% and 0% respectively when matched to soil specimen's properties at ambient temperature. Whereas maximum dry density for illite and kaolinite increased by 5% and 8% respectively for the two clays. ABSTRAK Kajian ini mengkaji rawatan kesan dari rawatan haba ke atas dua jenis tanah liat dicampur dengan pasir silika di bawah keadaan makmal. Tanah melalui tiga suhu berbeza, iaitu 100, 250 dan 500°C. Sifat tanah yang dikaji ialah had Atterberg, kandungan air optimum dan kekuatan mampatan bebas. Hasil eksperimen menunjukkan bahawa suhu melebihi 100 o C mengakibatkan satu penurunan di dalam had Atterberg, kandungan air optimum dan kekuatan mampatan bebas. Untuk campuran ilit dan silica, memanaskan tanah pada suhu 500°C menyebabkan had cecair, had plastik, kandungan air optimum dan kekuatan mampatan bebas dikurangkan kepada 12%, 0%, 40% dan 0%, dan untuk campuran kaolinit dan silica, ciri-ciri di atas mengurang kepada 18%, 0%, 50% dan 0% masing-masing apabila dipadankan dengan ciri-ciri spesimen tanah di suhu ambien. Manakala ketumpatan kering maksimum untuk ilit dan kaolinit dinaikkan sebanyak 5% dan 8% masing-masing untuk dua tanah liat ini. Kata kunci: Tanah liat; rawatan haba; Had Atterberg; kandungan air optimum; kekuatan mampatan bebas
... Incessant industrialisation, urbanisation and infrastructural development activities taking place in modern society necessitate tackling of several real life situations viz., construction of underground storage tanks, installation of buried power cables and pipelines, thermal stabilisation of soil mass, remediation of contaminated land by thermal treatment, freezing and thawing of soil mass, providing foundations in permafrost regions, disposal of nuclear and industrial wastes and extraction of gas hydrates from sub-seafloor sediments, etc. (Verhoogen 1980, Miller 1985, Stein and Stein 1992, Joshi et al. 1994, Yun 2005. In these situations, migration of heat through soil mass becomes a very crucial phenomenon, which is responsible for alteration in its overall properties and moisture content (Radhakrishna et al. 1980, Lawrence and William 1984, Rao and Singh 2010, Kadali et al. 2013. ...
Determination of thermal properties of soils (viz., thermal resistivity, thermal conductivity, thermal diffusivity and heat capacity), which primarily
influence heat migration through the soil mass, is essential in situations where geomaterials are relentlessly subjected to higher temperatures and
temperature variations. These properties of the soil mainly depend upon its type, mineralogy, particle size and gradational characteristics, density and
water content. In this context, earlier researchers have determined thermal conductivity of soils by employing a thermal probe (a line heat source),
which works on the principle of transient method (TM) of heat conduction. However, this methodology cannot be employed for establishing the heat
flow (read thermal regime) through the soil. Hence, development of an alternate technique, which facilitates quantification of temporal and spatial
variation of the heat flux and temperature in the soil mass, becomes essential. With this in mind, a methodology to determine thermal conductivity of
soils by employing the concept of thermal flux measurement (TFM) has been developed and its details are presented in this paper. Results obtained
from the TM and TFM have also been critically evaluated for the sake of validation and generating more confidence in the proposed methodology.
... Mitchell (1969) showed that the heat treatment changed some of the physical properties of the clayey soils such as angle of friction, cohesion and strength. Joshi et al. (1994) investigated the effect of the heat treatment on the strength of clayey bricks at temperatures ranging from 300 to 700 o C. And it was found that an increase in strength was accompanied with increase in temperature. ...
This study examines the effects of heat treatment on two types of clays mixed with silica sand under laboratory conditions. Soils were subjected to three varied temperatures, i.e. 100, 250 and 500 o C. The soil properties studied were Atterberg limits, optimum water content and unconfined compressive strength. Experimental results showed that the temperature greater than 100 o C resulted in a reduction in Atterberg's limits, optimum water content and unconfined compressive strength. For illite and silica mixture heating the soils at 500 o C decreased the liquid limit, plastic limit, optimum water content and unconfined compressive strength reduced to 12%, 0%, 40% and 0%, and for kaolinite and silica mixture the above characteristics reduced to 18%, 0%, 50% and 0% respectively when matched to soil specimen's properties at ambient temperature. Whereas maximum dry density for illite and kaolinite increased by 5% and 8% respectively for the two clays.
... Thermally treated clays have been used since ancient times for making soil stabilization and bricks for construction buildings. Heat treatment changes several material characteristics of clayey soils, such as strength, cohesion, consistency limits, optimum water content, maximum dry density, internal friction angle, particle size, permeability and specific gravity [1][2][3][4][5][6][7][8]. ...
Samples of original and thermally treated bentonite at 650 °C 4 h were characterized with chemical analysis, X-ray diffraction, thermal analysis, mercury porosimetry, differential scanning calorimetry, physisorption measurement and scanning electron microscopy. These consequence of the heating have been found. The chemical analysis shows high silica and alumina contents and small quantities of Fe+3, Ca+2 and Mg+2. XRD analysis shown the presence the main minerals are montmorillonite and opal CT, in the subordinate quantity illite. The result of the heating was the decomposition of clay minerals. Further, the increase in silica and alumina contents. A significant changes in the original pore structure have been found. The changes were characterized by the expressed increase in the content of total porosity caused by the achieved occurence of the pores covering pore radius area over 2000 nm. This effect represents the increased openness of the pore structure which may have the significant role in the intensity of alkali-activation process as a factor contributing to the increase of the contact of alkali activator solution with the activated solid. As a possible consequence of the increased openness could be the acceleration of alkali-activation process resulting, for example, in the acceleration of the strength development of binding system based on the thermally treated bentonite.
... Bentonites, which contain high percentages of smectite, are greatly effected by thermal treatment. For example, physicochemical properties, such as strength, swelling, plasticity, cohesion, compressibility, particle size, cation-exchange capacity (CEC), pore structure, adsorptive properties, and catalytic activity as well as the chemical composition of the particles and the mineralogy can change considerably depending on thermal effects (Bradley and Grim, 1951;Brindley, 1978;Mozas et al., 1980;Reicle, 1985;Ceylan et al., 1993;Sankaya et at., 1993;Joshi et at., 1994). Bentonites are used as industrial raw materials in more than 25 applications (Murray, 1991). ...
A white calcium bentonite (CaB) from the Kutahya region, Turkey, contains 35 wt. % opal-CT and 65 wt. % Ca-rich montmorillonite (CaM). Samples were heated at various temperatures between 100–1300°C for 2 h. Thermal gravimetric (TG), derivative thermal gravimetric (DTG), and differential thermal analysis (DTA) curves were determined. Adsorption and desorption of N2 at liquid N2 temperature for each heat-treated sample was determined. X-ray diffraction (XRD) and cation-exchange capacity (CEC) data were obtained. The change in the d (001) value and the deformation of the crystal structure of CaM depend on temperature. Deformation is defined here as changes of the clay by dehydration, dehydroxylation, recrystallization, shrinkage, fracture, etc. The activation energies related to the dehydration and dehydroxylation of CaB calculated from the thermogravimetric data are 33 and 59 kJ mol−1, respectively. The average deformation enthalpies, in the respective temperature intervals between 200–700°C and 700–900°C, were estimated to be 25 and 205 kJ mol−1 using CEC data and an approach developed in this study. The specific surface area (S) and the specific micropore-mesopore volume (V) calculated from the adsorption and desorption data, respectively, show a “zig zag” variation with increasing temperature to 700°C, but decrease rapidly above this temperature. The S and V values were 43 m2 g−1 and 0.107 cm3 g−1, respectively, for untreated bentonite. They reach a maximum at 500°C and are 89 m2 g−1 and 0.149 cm3 g−1, respectively. The XRD data clearly show that, at 500°C, where the irreversible dehydration is completed without any change in the crystal structure, the porosity of CaM reaches its maximum.
... It is well documented that heat treatment of clays (including bentonite) will result in changes to their properties including cation exchangeability, particle diameter and swelling (van Olphen, 1963;Grim, 1968;Calvet et al., 1970;Pashley, 1981;Joshi et al., 1994;Chorom et al., 1994Chorom et al., , 1995Chorom et al., , 1996Sarmento et al., 2000;Bojemueller et al., 2001). The reduction in cation exchange capacity is not uniform, but varies with the cation present (Grim, 1968). ...
... The main intention of conducting this study is to investigate the influence of thermal energy field (i.e., elevated temperatures) on soils of entirely different characteristics by employing X-ray diffraction (XRD) analysis. Such studies are becoming crucial for: (a) the design and execution of the foundations for furnaces, boiler units, forging units, brick kilns, rocket launching pads, (b) cases where the soil comes in contact with the thermal energy field, viz., coupled phenomenon, wherein heat and moisture migration occurs in the soil mass [1][2][3], buried power supply cables and AC ducts [4], underground explosions, disposal of high level radioactive [5], and industrial toxic wastes [6], and (c) ground modification/stabilization techniques using chemicals and heating [7][8][9][10][11][12]. ...
With an intention to investigate the influence of heat on the soil particles when they get exposed to thermal flux, six soils of entirely different characteristics were subjected to temperatures up to 300 C (this being the maximum temperature associated with the nuclear wastes to be disposed in geoenvironment), in steps of 50 C. After each step of thermal treatment, the residues were characterized for their crystal size, lattice strain, normal stress (tensile and compressive), and shear stress, by X-ray diffraction (XRD) analysis. Based on a critical synthesis of the results, it has been demonstrated that the stresses on the soil particles change from tensile to compressive while the strains are insignificant. It is believed that such a study would be quite useful in predicting the response and engineering properties of soils at elevated temperatures.
... Mitchell (1969) menciona que el calentamiento de arcillas genera cambios en el ángulo de fricción interno, en la cohesión y, por lo tanto, en la resistencia. Joshi et al. (1994), Abu-Zreig, Al-Akhras y Attom (2001) y Tan, Yilmaz y Zaimoğlu (2004) estudiaron el efecto, sobre las propiedades físicas y de resistencia bajo carga monotónica, de aplicar calor a arcillas de 300 a 700 °C, de 100 a 400 °C y de 100 a 1000 °C respectivamente. Por lo general, los estudios mencionados sometieron las muestras de arcilla a altas temperaturas alrededor de un día. ...
Laboratory tests were performed in order to evaluate the effects on the index properties, volumetric behavior and monotonic uniaxial strength of two clays caused by the application of different temperatures (150, 225 and 300 °C) for varying periods of time (1, 7 and 15 days). Additionally, we studied whether the clays recover the mentioned properties after being subjected to high temperatures and being again exposed to room temperature for one week in the laboratory. The mean objective of this research project is to evaluate whether the application of increasing temperatures in clays can be a good stabilization method in the future or if it is possible to produce mineral filler. Results show that the plasticity, expansion potential and monotonic uniaxial strength decrease when the temperature is raised up 150-300 °C on the samples and when the exposure time increased. Additionally, it is reported that the recovery of clay properties is zero when they are subjected to 300 °C for 15 days.
... The present day geotechnical engineering related projects deal with laying of buried power supply cables and air condition ducts (Gangadhara and Singh, 1999), ground modification or stabilization techniques using chemicals and thermal treatment (Ma and Hueckel, 1992;Alcocer and Chowdhury, 1993;Akinmusuru, 1994;Joshi et al., 1994;Yang and Farouk, 1995;Krishnaiah and Singh, 2006), disposal of high level radioactive (Varlakov et al., 1997) and industrial toxic wastes (Farag, 1993), designing foundations for the furnaces (Li et al., 2011), boiler units, forging units, brick kilns, rocket launching pads, volcanic eruptions, underground explosions, etc. In such situations the soil gets exposed to elevated temperatures (about 200°C), which might result in particle breakage and alteration of surface characteristics such as physical (changes in the specific gravity, Yilmaz, 2011; specific surface area and particle size, Utkaeva, 2007), chemical (variation in CEC, pH, EC;Parlak, 2011) and mineralogical (Ghuman and Lal, 1989;Certini, 2005;Hatten et al., 2005). ...
The deep geological disposal has been considered as safe and effective way to dispose high-level radioactive nuclear waste internationally. When nuclear waste is sealed in the repository, it will continue to decay and release a large amount of decay heat, and therefore, the bentonite used as a buffer/backfill layer in the repository will remain in a high temperature state for a long time. After experiencing continuous high temperature, whether the hydro-mechanical behaviour of bentonite will change significantly needs to be resolved. In this paper, the swelling, shrinkage and water retention behaviour of compacted MX80 bentonite experiencing different heating times at temperature of 200 °C were investigated by the swelling pressure, shrinkage and vapour equilibrium technique, together with the thermogravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) tests. The test results show that with increasing the heating time, the swelling and shrinkage indexes (swelling pressure, free swelling rate, shrinkage limit, and shrinkage coefficient) dropped sharply in the first 15–30 days, after that the indexes changed very little. In addition, the total reduction rates in the swelling pressure, free swelling rate, shrinkage limit, and axial shrinkage coefficient of MX80 bentonite experiencing 0 to 120 days heating are 35.4, 45.1, 49.8 and 25.5%, respectively. After experiencing high temperature of 200 °C, the main mineral montmorillonite in the MX80 bentonite was partially transformed into a low-swelling mineral paragonite from the XRD test results. From the TGA test results, the adsorbed water content decreased first and then remained unchanged with increasing the heating time, and the total reduction rates of free water, strong and weak bound waters were 82.5, 68.8 and 96.5%, respectively. From the SEM test results, the high temperature caused the layered structure to shrink and become tighter.
Land used for construction purposes should have large bearing capability and less squeezability. Soft soils such as clayey soil have low bearing capacity and high compressibility which must be converted or treated before the construction process to meet the requirements. The presence of oil and gas pipe lines, buried high voltage cables, fire accidents, storage of high-level waste could limit the use of conventional methods such as deep cement mixing. Hence, alternate methods are required, heat treatment has been considered to be the efficient technique, if the need of enhancement in characteristics are required. This paper discusses the literature available on thermal treatment. The effect of temperature on various properties of soil like Atterberg limits, free swell, porewater pressure, swelling, shear strength, stress strain behavior of soil and mineralogy is included in this paper. This review paper summarizes the effectiveness of thermal treatment on soft soil.
Marly soils can show problematic behaviors such as swelling and dispersion when subjected to water. It can cause problems for various civil constructions, including building foundations, water conveyance canals, highways, and airport runways; so appropriate measurements should be taken to stabilize these soils. In this study, two stabilization methods, including thermal treatment and mixing with coarse-grained particles, were utilized to limit swelling of marly soil samples collected from around the Sonqor city and also to improve their strength properties. The results of experimental tests showed that thermal treatment in high temperatures (after 100 °C) led to a decrease and an increase in liquid and plastic limits, respectively, and subsequently plasticity index decreased. However, after 475 °C, the Atterberg limits were almost unchanged. Also, it was found that with increasing heating levels, the swelling potential of the soil samples decreases as free swelling index values of the samples changed from 13.9% (high swelling potential) at 100 °C to 0.89% (low swelling potential) at 500 °C. Based on the experiments, it was observed that by adding 30% of coarse particles to the marly soil samples, engineering properties such as maximum dry density (γdmax), California bearing ratio, and unconfined compressive strength have been improved up to 10%, 59%, and 30%, respectively. Therefore, the stabilized marly soils could be considered as appropriate construction materials.
This study concerns the determination of the phase composition and physical properties (linear firing shrinkage, apparent porosity and bulk density, ignition loss) as well as mechanical properties of fired products (600-1200°C) of two ferrous clays rich in fluxing minerals from Bakong, a locality in the western part of Cameroon. For temperatures up to 900°C, the products have high values of apparent porosity, which lead to low bulk density ceramics having low mechanical resistance. These results are in agreement with the partial or total dehydroxylation of the lattice water in the clay minerals, where open pores eventually appear. Above 900°C and up to 1200°C, the obtained products show the presence of mullite and cristobalite; the ceramics are dense and have quite high mechanical resistance. These results are in agreement with the fusion of fluxing minerals. These clay materials may be used for the production of terracotta products and also for the formulation of low porosity ceramics.
A white calcium bentonite (CaB) from the Kutahya region, Turkey, contains 35 wt. % opal-CT and 65 wt. % Ca-rich montmorillonite (CaM). Samples were heated at various temperatures between 100-1300°C for 2 h. Thermal gravimetric (TG), derivative thermal gravimetric (DTG), and differential thermal analysis (DTA) curves were determined. Adsorption and desorption of N2 at liquid N2 temperature for each heat-treated sample was determined. X-ray diffraction (XRD) and cation-exchange capacity (CEC) data were obtained. The change in the d(001) value and the deformation of the crystal structure of CaM depend on temperature. Deformation is defined here as changes of the clay by dehydration, dehydroxylation, recrystallization, shrinkage, fracture, etc. The activation energies related to the dehydration and dehydroxylation of CaB calculated from the thermogravimetric data are 33 and 59 kJ mol-1, respectively. The average deformation enthalpies, in the respective temperature intervals between 200-700°C and 700-900°C, were estimated to be 25 and 205 kJ mol-1 using CEC data and an approach developed in this study. The specific surface area (S) and the specific micropore-mesopore volume (V) calculated from the adsorption and desorption data, respectively, show a 'zig zag' variation with increasing temperature to 700°C, but decrease rapidly above this temperature. The S and V values were 43 m2 g-1 and 0.107 cm3 g-1, respectively, for untreated bentonite. They reach a maximum at 500°C and are 89 m2 g-1 and 0.149 cm3 g-1, respectively. The XRD data clearly show that, at 500°C, where the irreversible dehydration is completed without any change in the crystal structure, the porosity of CaM reaches its maximum.
The objective of this work is to determine changes of surface properties of a bentonite after acid activation, using hydrochloric acid solutions (HCl) at room temperature. XRD, FX, FTIR, MEB, and BET analyses of the samples have been carried out to examine the structure of bentonite before and after acid activation. It is found that the raw bentonite is composed of dioctahedral montmorillonite with predominant quantity and certain amounts of quartz, albite and illite, etc. It has an cation exchange capacity (CEC) of 74.32 meq/g which allows it to be characterized as typical sodium bentonite. The changes, at low acid concentrations, are the result from from cation exchange (exchangeable cations with H+ ions). Differences of surface area at high acid concentrations (0.25 - 0.4 M) were caused by structural changes and partial decomposition of the samples. Data of surface area measurements have showed that with increase of concentration of hydrochloric acid, the surface area increased. The maximum value (837.11 m2/g) was reached by the sample activated with 0.4 M HCl. By against, activation with higher concentration (0.6 M) caused a decrease in the surface area.
This study examines the effects of heat treatment under laboratory conditions for mixtures of two types of clay (kaolinite and montmorillonite). Clay samples were burned with different temperatures ranging from . The Atterberg limits such as liquid and plastic limits were influenced with heat treatment. According to the experimental results, the liquid limits slightly decreased between , whereas rapid decreases were observed after . The plastic limits did not show noticeable differences in the interval . But the clay samples showed non plastic behavior at . The amount of NaCl was getting decreased with temperature. It also revealed that the pH values were also influenced with heat treatment, and the cation exchange capacity (C.E.C) values decreased with temperature.
Open burning of waste at dumpsites sites may alter many physical and chemical properties of underlining soil layers including
its ability to retard the migration of potential contaminants, such as lead, through the vadose zone. In this study, lead
sorption onto soil samples from Irbid that were subjected to high temperatures has been investigated. These samples were collected
from ground surface and heated to temperatures of 25, 70, 100, 200, 225, 250, 275, 300, 400, and 550C. Based on these temperatures
the soil was divided into ten different groups. Each group was first characterized by conducting a set of experiments to estimate
the Atterberg limits (liquid limit, plastic limit, and plasticity index), the organic carbon content, and a set of batch experiments
to study lead adsorption. Results indicate that the LL, PL, total organic carbon are slightly affected by high temperatures
less than 200C, show an abrupt change between temperature from 200 and 300C, and then slight change above 300C. Sorption
of lead onto heated samples, however, was not significantly changed. This may be explained by the fact that adsorption of
heavy metals mainly occurs onto the soil mineral parts which are slightly affected by the temperature range used in this study.
A white calcium bentonite (CaB) taken from Çamlıdere (Ankara, Turkey) region was heated at various temperatures between 100
and 1100 °C for 2 h. The mineralogy of the CaB was determined as calcium smectite (CaS), metahalloysite (MH), opal-A (OA),
opal-CT (OCT), quartz (Q), feldspar (F), and calcite (C) using the X-ray diffraction patterns of the natural CaB and its heated
samples. Besides the XRD patterns, the thermogravimetry, differential thermal analysis, and low-temperature nitrogen adsorption
(N2-AD) data show that the CaS lose adsorbed and hydration water up to 300 °C, dehydroxylation takes place between 300 and 750 °C,
and then the 2:1 layer structure completely collapses above 900 °C. The activation energies for the dehydration and dehydroxylation
were calculated as 7636 and 48838 J mol−1, respectively, from the TG data using Coats and Redfern method. The specific surface area (S) and specific micro–mesopore volume (V) obtained from N2-AD data were 44 m2 g−1 and 0.100 cm3 g−1 for the natural CaB. S and V reach their maxima of 105 m2 g−1 and 0.155 cm3 g−1, respectively, at 300 °C, remain approximately constant as the temperature increases up to 700 °C and then decrease almost
in parallel with each other, reaching their minima at 900 °C. This indicates that the S and V values increase gradually during dehydration and dehydroxylation of the CaS.
Significant aspects of contributed papers presented at Int Conference held at Washington, DC, Jan 16, 1969 are summarized and appraised; relevant supplementary data and analyses are introduced for illustration of points under discussion; topics discussed eal with volume change phenomena, pore pressure effects, compressibility, strength, elasticity, creep and stress relaxation and salt heave of soils; effects of preliminary heat treatment, fusion of soils, and ice barriers; temperature effects in pavement subgrades.
Sensitive soils, in general, are prone to mechanical disturbances while sampling, handling, and testing. This necessitates the prediction of true field behavior. The compressibility response of such soils is typical of having three zones, mechanistically explained as nonparticulate, transitional, and particulate. Such zoning has enabled the development of a simple method to predict the field compressibility response of the sample. The field compression curve with σct as the most probable yield stress is considered to reflect 0% disturbance. By a comparison of experimentally determined σc and σct, it is possible to estimate the degree of sample disturbance. When the value of σc is closer to σct, the sampling disturbance approaches zero. As the value of σc reduces, the degree of sampling disturbance increases. The possibility of using this degree of sample disturbance from compressibility data to obtain other true properties from laboratory results of the sampled specimens has been examined.
Thermal stabilization of soils
- D E Day
Effect of temperature on some engineering properties of clay soils
- Laguros J. G.
The swelling of a montmorillonitic clay at elevated temperatures
- Yong R. N.