Effect of thermal history on the properties of bentonite

Abstract

The effect of thermal history on the properties of bentonite was studied through a number of experimental tests. The desired thermal history was created on samples of bentonite by keeping them at a fixed temperature (50, 100, 150, 200 and 250 o C) for a specific duration (3, 7, 14 and 30 days). Standard compaction, Atterberg limits, free swelling and swelling pressure tests were carried out on the samples on the dry side of optimum, optimum and wet side of optimum of the compaction curve with desired thermal history. In addition chemical tests were carried out on the flooding water at the end of the swelling test. The results showed that the changes in compaction characteristics were not considerable but the Atterberg limits, free swelling and swelling pressure of the soil were changed due to the thermal history in comparison with the soil without any thermal history. The magnitudes of free swelling and swelling pressure were dependent on the location of prepared sample on the compaction curve. In addition, the changes in Atteberg limits and swelling parameters (amount of free swelling and swelling pressure) were functions of magnitude of temperature and duration of time that the sample experienced the temperature in its temperature history. The effects of temperature and also duration of exposure of the soil to temperature was discussed with the aid of the Diffuse Double Layer (DDL) theory. It was found that the temperature may change the gradation of soil due to cementation of particles as a result of formation of some salts and oxides that help to paste the particles together and change the properties of the soil.

Experimental investigation on the effects of elevated temperature on geotechnical behaviour of tropical residual soils

“…However, the OMCs trend of the current study (Fig. 6) does not support previous researches [25,26,60]. Gadzama et al [25] reported little or no effect of temperature on optimum moisture content (OMC) as their trends were observed to be inconsistent.…”

“…Also, the plastic limit and plasticity index of the current study are consistent with those of Zhang et al [59], who reported that the influence of drying on Atterberg limits of weathered soil is more complex due to interparticle bonding. In accordance with the present results, previous studies have demonstrated the increase in MDD with increase in temperature [25,26,60]. However, the OMCs trend of the current study (Fig.…”

“…Gadzama et al [25] reported little or no effect of temperature on optimum moisture content (OMC) as their trends were observed to be inconsistent. Similarly, Hanuma and Prasad [26] and Estabragh et al [60] reported the decrease in OMC with increase in temperature. It is encouraging to compare Fig.…”

Characterization of Sand and Zeolite Stabilized Expansive Soil as Landfill Liner Material under Environmental and Climatic Effects

“…Swell test results showed that primary swell reduced with the increase of temperature in NS group which is also stated by [23,27,31,32] however, a reverse behavior observed in NZ group. Swelling potential of NZ group increased at elevated temperatures and this behavior can be attributed to the increment of repulsion between clay platelets at micro level due to temperature increase, which can be explained by diffuse double layer (DDL) theory, hence causing increase in swelling capacity [33].…”

Effect of Heating Borehole Spacing on Plasticity of Expansive Soil

“…[5, 6 and 7]. The effect of temperature on Atterberg limits of soil Indicated that any reduction of liquid limit and plastic limit "will cause increasing temperature" [8]. Wang et.…”