A Study on Soil Cementation and Calcite Precipitation with Clay as a Medium

Sung-Sik Park; Eun-Hee Suh; Kyung-Hyeon Chae; Sang-Kyu Jang; Jin-Ho Kim

doi:10.7843/kgs.2015.31.12.17

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2015 Vol.31, Issue 12 Preview Page Next Page

A Study on Soil Cementation and Calcite Precipitation with Clay as a Medium 점토를 매개체로 한 탄산칼슘 석출 및 흙의 고결에 관한 연구

31 December 2015. pp. 17-27

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Abstract

TIn this study, we tried to precipitate calcium carbonate with carbonate ions decomposed from urea by plant extract and calcium ions dissolved in water. The clay particles carry a net negative charge on their surfaces. Such clay mineral was additionally mixed as a medium to improve soil strength and durability with environmentally-friendly way. The 1st solution (plant extracts and urea) and the 2nd solution (calcium chloride and clay) were mixed together with clean Nakdong River sand. Then, this mixed soil was compacted into a small cylindrical specimen and then air cured for 7 days in laboratory. The molar concentration of urea and calcium chloride was tested for three different conditions, 1, 5, and 7 mol. Three different clay contents (0, 1, and 3% per total weight) were mixed with sand. For each specimen, a series of unconfined compression test, a durability test, SEM, EDX and XRD analyses were carried out to evaluate its cementation and structure. As the molar concentration of the solution and clay content increased, the unconfined compressive strength and durability increased. The results of SEM, EDX and XRD analyses showed that calcite was precipitated around clay mineral. The thermogravimetry analysis indicated that calcium carbonate precipitated about 1～2% per total weight of the sample.

Keywords

Cementation

Plant extracts

Urea

Calcium Carbonate

Unconfined compressive strength

본 연구에서는 식물추출액을 이용하여 요소를 분해한 다음 이로부터 분해된 탄산이온과 수용액 상태의 칼슘이온이 음전하를 띄는 점토를 매개체로 하여 탄산칼슘을 석출시켜 친환경적으로 흙을 고결시키면서 내구성도 향상시키는 연구를 수행하였다. 식물추출액과 요소가 혼합된 제1용액과 칼슘원(염화칼슘)이 용해된 용액에 소량의 점토가 혼합된 제2용액을 깨끗한 낙동강모래에 섞어서 비빈 다음 다짐방법으로 소형 공시체를 제작하였다. 요소와 염화칼슘의 몰농도를 세 종류(1, 5, 7몰)로 달리하였으며, 각 공시체에 점토를 전체중량의 0%, 1%, 3%의 세가지 비율로 혼합하여 공시체를 제작한 다음 실내에서 7일 동안 양생하였다. 양생이 완료된 공시체에 대해 일축압축시험, 내구성시험, SEM, EDX 및 XRD 분석, 그리고 열중량 분석을 실시하여 사질토의 고결 정도와 구조를 분석하였다. 요소와 염화칼슘의 몰농도가 높을수록 점토 함유량이 증가할수록 일축압축강도와 내구성이 증가하는 경향을 보였다. SEM, EDX 및 XRD 분석을 통하여 점토광물 주변에 탄산칼슘(calcite)이 석출되는 것을 확인하였으며, 열중량 분석으로부터 시료 내에 중량대비 탄산칼슘이 1-2% 정도 석출되었다.

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Information

Publisher :The Korean Geotechnical Society
Publisher(Ko) :한국지반공학회
Journal Title :Journal of the Korean Geotechnical Society
Journal Title(Ko) :한국지반공학회 논문집
Volume : 31
No :12
Pages :17-27
Received Date : 2015-08-03
Revised Date : 2015-10-10
Accepted Date : 2015-11-20
DOI :https://doi.org/10.7843/kgs.2015.31.12.17

Journal of the Korean Geotechnical Society ISSN:1229-2427(Print) 2288-646X(Online) 한국지반공학회 논문집

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