Diminishing The Swelling Ratios Of Black Cotton Soil And Its Application In Preparation Of Adsorption Materials And Lightweight

Black Cotton Soil?BCS?is composed of 2:1 layered structure of montmorillonite,and the high content of clay as high as 70%,which has characteristics of water swelling and drying shrinkage.Meanwhile,it has excellent properties,such as the high cation exchange capacity?CEC?and excellent adsorption properties for organic compounds,etc.Also,the BCS is widely distributed and rich in reserves,but there are few researches on its application.The swelling property gives rise to serious problems in civil engineering when it was directly used,such as subgrade/dam collapse.This paper attached to the problem caused by BCS in road construction in Kenya,silane was used to modify BCS,which effectively reduced free swell index?FSI?;and solved the expansibility problem of BCS and extended the high value application of BCS,which included the application of BCS as adsorption material and lightweight building materials.Firstly,based on the study of mineral and chemical composition of BCS,BCS was pretreated by using H₂SO₄ or Na₂CO₃ for the test results.And we designed a method of diminishing the FSI of BCS.In this paper,silane was dissolved in the mixed solvent of ethanol and water,then BCS or BCS pretreated?H₂SO₄ or Na₂CO₃?was added into the mixed solvent,BCS was modified with the condition of constant temperature water bath to diminish the hydrophilicity.When BCS was treated with 7.5%H₂SO₄ and silane,the FSI of BCS decreased from 160%to 15%,and the expansion grade reduced from high to low?GB50112-2013?.According to the results of XRD before and after modification,which shows the?001?diffraction peaks of the modified BCS were left-shifted in XRD patterns,indicating silane molecules entered into the montmorillonite layer,which resulted from crystal plane spacing enlarged.Accordingly,the intensity of-OH peaks were decreased or even disappeared in FTIR in modified BCS,indicating that montmorillonite could be grafted by silane,hydrophilic group of the silane molecules was reacted with broken bond of interlamellar hydroxyl group,causing the hydroxyl bonds to weaken or disappear.After reaction,the hydrophobic group is exposed to the outside,changed the hydrophilicity and reduced the FSI of BCS.Secondly,BCS was used as adsorption material for large specific surface area and high CEC.In this paper,BCS and treated with H₂SO₄ as adsorptive materials were studied,various factors such as amount of BCS and MB,adsorption time were investigated.The experimental results shows The initial concentration of the solution is 500 mg/L,and the solid-liquid ratio is 2 g/L,the removal rate could be close to 100%.The removal of MB by BCS was interpreted by the Langmuir isotherm,and maximum uptake capacity of BCS for MB was 104.6 mg/g and 99.7mg/g.The adsorption efficiency of original BCS was better than that of sulfuric acid treated BCS.Kinetic fitting results showed that the adsorption process of BCS for MB was more consistent with the second-order kinetic model,illustrating that the adsorption rate of reaction is controlled by the chemical adsorption mechanism.Lastly,using BCS as raw material and pozzolanic ash?VA?as aggregate to make lightweight building material-fired hollow clay bricks.The process conditions are optimized by experiments,when the bricks fired with BCS/VA ratio of 7:3-8:2 at temperatures of 1000-1050oC were found to exhibit brilliant unconfined compressive strength over 60 MPa,the linear shrinkage is less than9%,apparent porosity is 30%.The measured physical-mechanical parameters meet the criteria of MU10.0 of GB/T 13545-2014.In this paper,we diminish the FSI of BCS,and studied mechanization,BCS was studied as adsorbent,and light building materials were also prepared as raw materials.Its application in engineering was expanded,which has certain practical and theoretical significance.