Laboratory Study on Improvement of Expansive Soil by Chemically Induced Calcium Carbonate Precipitation
This paper proposes the use of calcium carbonate (CaCO<sub>3</sub>) precipitation induced by the addition of calcium chloride (CaCl<sub>2</sub>) and sodium carbonate (Na<sub>2</sub>CO<sub>3</sub>) solutions as a procedure to stabilize and improve expan...
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doaj-f843bf77cb5841f48d291a583b81c4372021-07-01T00:29:46ZengMDPI AGMaterials1996-19442021-06-01143372337210.3390/ma14123372Laboratory Study on Improvement of Expansive Soil by Chemically Induced Calcium Carbonate PrecipitationShaoyang Han0Baotian Wang1Marte Gutierrez2Yibo Shan3Yijiang Zhang4Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University, 1 Xikang Rd., Nanjing 210098, ChinaKey Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University, 1 Xikang Rd., Nanjing 210098, ChinaDepartment of Civil and Environmental Engineering, Colorado School of Mines, 1500 Illinois St., Golden, CO 80401, USAGeotechnical Engineering Department, Nanjing Hydraulic Research Institute, 34 Hujuguan Rd., Nanjing 210024, ChinaGeotechnical Engineering Department, Nanjing Hydraulic Research Institute, 34 Hujuguan Rd., Nanjing 210024, ChinaThis paper proposes the use of calcium carbonate (CaCO<sub>3</sub>) precipitation induced by the addition of calcium chloride (CaCl<sub>2</sub>) and sodium carbonate (Na<sub>2</sub>CO<sub>3</sub>) solutions as a procedure to stabilize and improve expansive soil. A set of laboratory tests, including the free swell test, unloaded swelling ratio test, unconfined compression test, direct shear test, scanning electron microscopy (SEM) test, cyclic wetting–drying test and laboratory-scale precipitation model test, were performed under various curing periods to evaluate the performance of the CaCO<sub>3</sub> stabilization. It is concluded from the free swell tests and unloaded swelling ratio tests that the addition of CaCl<sub>2</sub> and Na<sub>2</sub>CO<sub>3</sub> can profoundly decrease soil expansion potential. The reduction in expansion parameters is primarily attributed to the strong short-term reactions between clay and stabilizers. In addition, the formed cementation precipitation can decrease the water adsorption capacity of the clay surface and then consequently reduce the expansion potential. The results of unconfined compression tests and direct shear strength tests indicated that the addition of CaCl<sub>2</sub> and Na<sub>2</sub>CO<sub>3</sub> has a major effect on geotechnical behavior of expansive soils. Based on the SEM analyses, new cementing crystalline phases formatted by sequentially mixing CaCl<sub>2</sub> and Na<sub>2</sub>CO<sub>3</sub> solutions into expansive soil were found to appear in the pore space, which results in a much denser microstructure. A laboratory-scale model test was conducted, and results demonstrate the effectiveness of the CaCO<sub>3</sub> precipitation technique in stabilizing the expansive soil procedure. The test results indicated that the concentration of CaCl<sub>2</sub> higher than 22.0% and Na<sub>2</sub>CO<sub>3</sub> higher than 21.2% are needed to satisfactorily stabilize expansive soil. It is proposed to implement the precipitation technique in the field by the sequential permeation of CaCl<sub>2</sub> and Na<sub>2</sub>CO<sub>3</sub> solutions into soils in situ.https://www.mdpi.com/1996-1944/14/12/3372expansive soilprecipitation techniquecalcium carbonatesoil improvement |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Shaoyang Han Baotian Wang Marte Gutierrez Yibo Shan Yijiang Zhang |
spellingShingle |
Shaoyang Han Baotian Wang Marte Gutierrez Yibo Shan Yijiang Zhang Laboratory Study on Improvement of Expansive Soil by Chemically Induced Calcium Carbonate Precipitation Materials expansive soil precipitation technique calcium carbonate soil improvement |
author_facet |
Shaoyang Han Baotian Wang Marte Gutierrez Yibo Shan Yijiang Zhang |
author_sort |
Shaoyang Han |
title |
Laboratory Study on Improvement of Expansive Soil by Chemically Induced Calcium Carbonate Precipitation |
title_short |
Laboratory Study on Improvement of Expansive Soil by Chemically Induced Calcium Carbonate Precipitation |
title_full |
Laboratory Study on Improvement of Expansive Soil by Chemically Induced Calcium Carbonate Precipitation |
title_fullStr |
Laboratory Study on Improvement of Expansive Soil by Chemically Induced Calcium Carbonate Precipitation |
title_full_unstemmed |
Laboratory Study on Improvement of Expansive Soil by Chemically Induced Calcium Carbonate Precipitation |
title_sort |
laboratory study on improvement of expansive soil by chemically induced calcium carbonate precipitation |
publisher |
MDPI AG |
series |
Materials |
issn |
1996-1944 |
publishDate |
2021-06-01 |
description |
This paper proposes the use of calcium carbonate (CaCO<sub>3</sub>) precipitation induced by the addition of calcium chloride (CaCl<sub>2</sub>) and sodium carbonate (Na<sub>2</sub>CO<sub>3</sub>) solutions as a procedure to stabilize and improve expansive soil. A set of laboratory tests, including the free swell test, unloaded swelling ratio test, unconfined compression test, direct shear test, scanning electron microscopy (SEM) test, cyclic wetting–drying test and laboratory-scale precipitation model test, were performed under various curing periods to evaluate the performance of the CaCO<sub>3</sub> stabilization. It is concluded from the free swell tests and unloaded swelling ratio tests that the addition of CaCl<sub>2</sub> and Na<sub>2</sub>CO<sub>3</sub> can profoundly decrease soil expansion potential. The reduction in expansion parameters is primarily attributed to the strong short-term reactions between clay and stabilizers. In addition, the formed cementation precipitation can decrease the water adsorption capacity of the clay surface and then consequently reduce the expansion potential. The results of unconfined compression tests and direct shear strength tests indicated that the addition of CaCl<sub>2</sub> and Na<sub>2</sub>CO<sub>3</sub> has a major effect on geotechnical behavior of expansive soils. Based on the SEM analyses, new cementing crystalline phases formatted by sequentially mixing CaCl<sub>2</sub> and Na<sub>2</sub>CO<sub>3</sub> solutions into expansive soil were found to appear in the pore space, which results in a much denser microstructure. A laboratory-scale model test was conducted, and results demonstrate the effectiveness of the CaCO<sub>3</sub> precipitation technique in stabilizing the expansive soil procedure. The test results indicated that the concentration of CaCl<sub>2</sub> higher than 22.0% and Na<sub>2</sub>CO<sub>3</sub> higher than 21.2% are needed to satisfactorily stabilize expansive soil. It is proposed to implement the precipitation technique in the field by the sequential permeation of CaCl<sub>2</sub> and Na<sub>2</sub>CO<sub>3</sub> solutions into soils in situ. |
topic |
expansive soil precipitation technique calcium carbonate soil improvement |
url |
https://www.mdpi.com/1996-1944/14/12/3372 |
work_keys_str_mv |
AT shaoyanghan laboratorystudyonimprovementofexpansivesoilbychemicallyinducedcalciumcarbonateprecipitation AT baotianwang laboratorystudyonimprovementofexpansivesoilbychemicallyinducedcalciumcarbonateprecipitation AT martegutierrez laboratorystudyonimprovementofexpansivesoilbychemicallyinducedcalciumcarbonateprecipitation AT yiboshan laboratorystudyonimprovementofexpansivesoilbychemicallyinducedcalciumcarbonateprecipitation AT yijiangzhang laboratorystudyonimprovementofexpansivesoilbychemicallyinducedcalciumcarbonateprecipitation |
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