掺灰膨胀土表面吸附试验及吸水性验证

Superficial adsorption experiment and water adsorption corroboration for lime modified expansive soils

利用水蒸气吸附仪对石灰改性膨胀土进行水蒸气吸附试验,得出随着掺灰量的变化,膨胀土的吸水性先减小后增大,且在掺灰量为6%处取得最小值。为了研究引起膨胀土吸水性变化的主要原因,再对改性膨胀土进行氮气吸附试验,从而分析掺灰膨胀土孔隙结构的变化。研究发现,随着掺灰量的增加,BET微孔比表面积呈折线形变化,且在掺灰量为6%时取得最小值;中孔的累积容积随着掺灰量的增大而减小;随着掺灰量的增加,中孔孔径先增大后减小,且在掺灰量为6%处取得最大值。膨胀土的吸水性与中孔孔径的变化成负相关,且膨胀土的最佳掺灰量为6%。

For the lime modified expansive soil, two ：series of tests are carried out. The first ones are water vapor adsorption tests, which are carried out using water vapor adsorption apparatus. The results indicate that with the increasing of lime percentage, the hydroscopicity of expansive soil decreased first then started to increase. And the minimum hydroscopicity is obtained at the point when the content of lime is 6%. In order to study the main reason causing the change of hydroscopicity, the second tests, i.e. the nitrogen adsorption tests, are performed on modified expansive soil. Analysis of the change of porous structure is made. It is found that with the increase of lime percentage, BET microporous specific surface area changes as the fold line; and the minimum value is obtained when the content of lime is 6%. With the increase of lime percentage, accumulating mesoporous volume decreased. With the increase of lime percentage, mesoporous diameter increases first, then decreases, and the maximum value is obtained when the content of lime is 6%. That the hydroscopicity of expansive soils is inversely proportional to the mesoporous diameter is summarized; and the optimal lime percentage is 6%.