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Experimental Study on Low-pH, Anti-washing Grouts Incorporating Gypsum for Reinforcement of Underwater Cavities

수중 공동보강용 석고 활용 저 pH형 수중불분리 그라우트에 대한 실험적 연구

  • 김영상 (전남대학교 토목공학과) ;
  • 백정진 (조선대학교 건축학부 (건축공학전공)) ;
  • 김형기 (조선대학교 건축학부 (건축공학전공))
  • Received : 2018.09.17
  • Accepted : 2018.11.16
  • Published : 2018.12.28

Abstract

A series of experiment was conducted to evaluate basic performances of low-pH, anti-washing grouts incorporating gypsum which applied for reinforcing underwater cavities in limestone- grounds. Various types of mix proportions were designed and the fluidity, strength and environmental impact of these mixtures were evaluated. The flowability was evaluated under two conditions, i.e., flows without and with pressing, respectively. Strength was measured for the hardened mixtures fabricated under conditions of air and water injections. The environmental impacts including the pH of the suspension and the suspended solids concentration for the mixtures were evaluated. The low pH of fresh mixture suspension, below than 10, was achieved by incorporation of gypsum. The mix proportions of cement-quartz powder-gypsum binders and chemical agents resulted in mortar natural flow 7-10 cm and uniaxial compressive strength 4 MPa were derived.

석회암 기반 지반 등에 존재하는 수중공동의 보강을 위해 사용할 수 있는 석고 혼입 저 pH형 수중불분리 그라우트에 대한 기초 실험을 수행하였다. 다양한 종류의 배합을 설계하였으며 이 배합들의 유동성, 강도, 환경영향성을 평가하였다. 유동성은 자연유하, 가압유하의 두 가지 조건에 대해 평가하였다. 강도는 기중 및 수중 주입의 경우에 대해 각각 측정하였다. 환경영향성은 현탁액의 pH 및 현탁물질 농도 두가지로 평가되었다. 석고혼입을 통해 pH를 10 이하로 감소시켰으며, 포틀랜드 시멘트-규사-석고 간의 배합비 및 수중불분리제-유동화제 혼입량의 변화을 통해 모르타르 자유흐름량 7-10 cm, 압축강도 4 MPa 이상의 수중불분리 그라우트 배합을 찾아내었다.

Keywords

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Fig. 1. Flow diameter of fresh mortar grout.

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Fig. 2. Penetration resistance of hardening grout.

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Fig. 3. Uniaxial compressive strength (UCS) of hardened grout.

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Fig. 4. pH of suspension from fresh grout.

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Fig. 5. Concentration of suspended solid in suspension from fresh grout.

Table 1. Mix proportion (weight ratio)

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Table 2. Specified limitation of compressive strength of cement fill14)

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