Effects of red mud and Alkali-Activated Slag Cement on efflorescence in cement mortar

Kang, Suk-Pyo,Kwon, Seung-Jun Elsevier 2017 Construction & building materials Vol.133 No.-

<P><B>Abstract</B></P> <P>Recently AASC (Alkali Activated Slag Cement) is utilized for construction materials in order to reduce environmental load like abundant CO<SUB>2</SUB> emission. Red mud which is a byproduct from Bauxite ores process has a strong alkali component containing 10.0–15.0% of Na<SUB>2</SUB>O, so that it can be used for an alkali activator or retarder for cement hydration. This work presents an evaluation of efflorescence characteristics in cement mortar with AASC and red mud. For the work, OPC (Ordinary Portland Cement) and AASC are used as matrix binder, and varying replacement ratios of red mud (0.0–30%) are prepared. In order to evaluate the efflorescence characteristics in the binders with red mud, analysis of water absorption and porosity are performed. The changing efflorescence areas with weight loss are also measured. The compounds in efflorescence are quantitatively analyzed through various techniques such as EDS, XRD, SEM, TGA, and alkali leaching test. In the work, the accelerated efflorescence mechanism and its characteristics are quantitatively evaluated considering the effects of binder types and red mud replacement ratios.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Quantitative evaluation of red mud effect on efflorescence. </LI> <LI> Various micro observation test results like EDA, XRD, SEM, and TGA. </LI> <LI> The relationship between efflorescence and the results (ion concentration, porosity). </LI> <LI> Verification of efflorescence mechanism through micro observation test. </LI> <LI> Mechanical and durability performance evaluation. </LI> </UL> </P>

초분광 카메라를 이용한 콘크리트 백화 평가에 관한 연구

김병현,김대명,조수진 한국안전학회 2017 한국안전학회지 Vol.32 No.6

In Korea, the guideline for the bridge safety inspection requests to assess surface degradation, including crack, efflorescence, spalling, and so on, for the rating of concrete bridges. Currently, the assessment of efflorescence is performed based on the visual inspection of expertized engineers, which may result in subjective inspection result. In this study, a novel method using a hyperspectral camera is proposed for objective and accurate assessment of concrete efflorescence. The hyperspectral camera acquires the light intensity for a number of continuous spectral bands of light for each pixel in an image, which makes the hyperspectral imaging technique provides more detailed information than a color camera that collects intensity for only three bands corresponding to RGB (red, green, and blue) colors. A stepwise assessment algorithm is proposed based on the spectral features to decompose efflorescence area from the inspected concrete area. The algorithm is tested in the laboratory test using two concrete specimens, one of which is dark colored with efflorescence on a surface while the other is bright concrete without efflorescence. The test shows high accuracy and applicability of the proposed efflorescence assessment using a hyperspectral camera.

콘크리트 벽돌 및 속 빈 콘크리트 블록 제품의 백화시험 평가

이상현 ( Lee Sang-hyun ),기전도 ( Ki Jun-do ),조홍범 ( Cho Hong-bum ),김영선 ( Kim Young-sun ),전현수 ( Jeon Hyun-soo ),문형재 ( Moon Hyung-jae ) 한국건축시공학회 2023 한국건축시공학회 학술발표대회 논문집 Vol.23 No.2

Concrete bricks and hollow concrete block products manufactured using ordinary portland cement react with salt and carbon dioxide absorbed from the soil and atmosphere in the use environment, causing contamination such as efflorescence. This is due to the reaction between calcium hydroxide, a cement hydration product, and carbon dioxide, producing and eluting calcium carbonate. This study was a preliminary study to compare and evaluate the reduction of efflorescence in concrete bricks and hollow concrete block products manufactured using carbon dioxide reaction hardening cement. The purpose was to evaluate the efflorescence occurrence in products using ordinary Portland cement.

레드머드 대체율에 따른 알칼리활성화 슬래그-레드머드 시멘트 모르타르의 기공 및 백화특성

강석표 ( Kang Suk-pyo ),강혜주 ( Kang Hye-ju ) 한국건축시공학회 2017 한국건축시공학회지 Vol.17 No.3

본 연구에서는 레드머드 대체율에 따른 알칼리활성화 슬래그-레드머드 시멘트 모르타르의 압축강도, 기공특성, 흡수율, 용출특성 및 백화 특성을 검토하여 알칼리활성화 슬래그 시멘트에 나트륨계 자극제인 레드머드를 사용함으로서 발생될 수 있는 백화특성을 확인하였다. 알칼리활성화 슬래그-레드머드 시멘트에서 레드머드 대체율이 높아질수록 10∼100nm 직경의 기공은 증가하였으며 백화면적이 증가하는 것으로 나타났다. 알칼리활성화 슬래그-레드머드 시멘트의 백화물질은 Na₂SO₄가 가장 많이 생성되며 다음으로 Na₂CO₃로 백화의 발생원인은 레드머드에서 공급되는 Na+인 것으로 판단된다. Red mud is an inorganic by-product obtained from the mineral processing of alumina from Bauxite ores. A highly alkali inorganic waste product with a pH level over 11, red mud in its original state negatively impacts the ecosystem, so appropriate treatment is necessary. The development of alkali activated slag-red mud cement can be a representative study aimed at recycling the strong alkali of the red mud as a construction material. However, Alkali-activated binders that use sodium activators have been reported to be more vulnerable to efflorescence. Therefore, in this study, the compressive strength, pore characteristics, water absorption, elution characteristics, and efflorescence properties of alkali-activated slag cement mortar were assessed according to their red mud substitution ratio.

익산 미륵사지 석탑의 백화현상과 제어를 위한 용출실험

이동식,이찬희,김사덕 한국문화재보존과학회 2006 보존과학회지 Vol.19 No.-

익산 미륵사지 석탑은 백제 무왕대에 창건되어 몇 차례 수리 및 개축작업을 하면서 현 상태를 유지해 왔으나 최근에 구조적인 불균형이 심화되어 탑의 원형에 따른 보존과학적 수복을 위해 해체중이다. 이 탑의 원형은 평면방형탑으로 9층으로 추정되나 최근까지 일부 6층까지만 남아 있었다. 붕괴되어 망실된 부분은 1915년 일본인들이 콘크리트를 이용하여 불안전 탑의 형태를 고정시켜 놓았다. 현재 암석의 표면에는 침전물질이 피각되어 백화현상을 유발하였고 이로 인해 원암의 조직과 색상이 훼손되어 있다. 따라서 표면에 피각된 이차적 무기 오염물질의 종류와 산출상태 및 오염종을 정량 분석하였다. 또한 용해실험을 통해 가용성 오염종을 규명하고 이에 대한 오염물질을 세정하는데 필요한 조건을 제시하였다. 이 결과는 석조문화재 표면의 무기오염종을 정량적으로 규명할 수 있는 자료를 제공할 것이며, 백화현상을 제어 할 수 있는 표면 세정제의 보존과학적 적용에 기여할 것이다. The Mireuksaji stone pagoda of the Iksan was built in Muwang King of Baekjae Kingdom and has maintained its present status through several rebuilding process. Recently, the structural unbalance of the pagoda has worsened, so for scientific maintenance recovery of its original pagoda form, the pagoda is under dismantling process. The original form of this pagoda is being presumed to be a plane square pagoda of nine stories, though only a portion of six stories remains until today. The destroyed part from collapse was liked in insecure pagoda form by Japanese in year of 1915. On the surface of the stone which has gone through the present time, efflorescence appeared as precipitation substance over crusted and due to this phenomenon, the structure and color of thee original stone haven't been preserved. Therefore, quantitative analysis on its kind, emitted status and contamination type of secondary inorganic contamination substance of the over crusted surface were analyzed. Also through reaction experiments, contamination type was defined and tests have been applied to find the requirements that will wash out the contaminants. The result of this study will provide the base of quantitative analysis on the kind of inorganic contamination of the surface of stone assets, and it shall also contribute to the application of scientific maintenance recovery of surface cleaner for efflorescence.

무시멘트 결합재를 사용한 콘크리트 보도블록의 특성

이원규 ( Lee Won-gyu ),조은석 ( Jo Eun-seok ),이상수 ( Lee Sang-soo ),송하영 ( Song Ha-young ) 한국건축시공학회 2018 한국건축시공학회 학술발표대회 논문집 Vol.18 No.2

Korea has many problems due to the asphalt pavement or impermeable pavement. Many methods are being implemented to improve water circulation. Among them, permeable packaging materials are used. However, existing permeable packaging materials have a problem of causing efflorescence and clogging the pores. The pores of the permeable packing material are clogged and the permeability is lost. This leads to economic problems and product problems. The purpose of this study was to develop a block to prevent efflorescence.

Efflorescence assessment using hyperspectral imaging for concrete structures

Byunghyun Kim,Soojin Cho 국제구조공학회 2018 Smart Structures and Systems, An International Jou Vol.22 No.2

Efflorescence is a phenomenon primarily caused by a carbonation process in concrete structures. Efflorescence can cause concrete degradation in the long term; therefore, it must be accurately assessed by proper inspection. Currently, the assessment is performed on the basis of visual inspection or image-based inspection, which may result in the subjective assessment by the inspectors. In this paper, a novel approach is proposed for the objective and quantitative assessment of concrete efflorescence using hyperspectral imaging (HSI). HSI acquires the full electromagnetic spectrum of light reflected from a material, which enables the identification of materials in the image on the basis of spectrum. Spectral angle mapper (SAM) that calculates the similarity of a test spectrum in the hyperspectral image to a reference spectrum is used to assess efflorescence, and the reference spectral profiles of efflorescence are obtained from theUSGS spectral library. Field tests were carried out in a real building and a bridge. For each experiment, efflorescence assessed by the proposed approach was compared with that assessed by image-based approach mimicking conventional visual inspection. Performance measures such as accuracy, precision, and recall were calculated to check the performance of the proposed approach. Performance-related issues are discussed for further enhancement of the proposed approach.

Effect of Red Mud Content on Strength and Efflorescence in Pavement using Alkali-Activated Slag Cement

Kim Hyeok-Jung,Suk-Pyo Kang,Gyeong-Cheol Choe 한국콘크리트학회 2018 International Journal of Concrete Structures and M Vol.12 No.2

Efflorescence which severely occurs in alkali-activated slag cement can cause reduction of strength and durability due to calcium leaching. In the work, efflorescence characteristics in pavement containing red mud which can be affected by strong alkaline were investigated through various tests such as compressive strength, porosity, absorption, efflorescence area, alkali leaching content, and properties of the efflorescence compound. The compressive strength of pavement was evaluated to be higher over 15.0 MPa in all cases regardless of replacement ratio of red-mud and binder type, which can provide a reasonable strength for walking and bike lanes. The pavement with red mud was applicable to parking lots only when the replacement ratio of red-mud is within 10%. The efflorescence area increased with a higher replacement ratio of red mud and its propagation appeared though the efflorescence was removed through evaporation of moisture. However, the area of efflorescence gradually decreased with the repetition of the test.

Efflorescence assessment using hyperspectral imaging for concrete structures

Kim, Byunghyun,Cho, Soojin Techno-Press 2018 Smart Structures and Systems, An International Jou Vol.22 No.2

Efflorescence is a phenomenon primarily caused by a carbonation process in concrete structures. Efflorescence can cause concrete degradation in the long term; therefore, it must be accurately assessed by proper inspection. Currently, the assessment is performed on the basis of visual inspection or image-based inspection, which may result in the subjective assessment by the inspectors. In this paper, a novel approach is proposed for the objective and quantitative assessment of concrete efflorescence using hyperspectral imaging (HSI). HSI acquires the full electromagnetic spectrum of light reflected from a material, which enables the identification of materials in the image on the basis of spectrum. Spectral angle mapper (SAM) that calculates the similarity of a test spectrum in the hyperspectral image to a reference spectrum is used to assess efflorescence, and the reference spectral profiles of efflorescence are obtained from theUSGS spectral library. Field tests were carried out in a real building and a bridge. For each experiment, efflorescence assessed by the proposed approach was compared with that assessed by image-based approach mimicking conventional visual inspection. Performance measures such as accuracy, precision, and recall were calculated to check the performance of the proposed approach. Performance-related issues are discussed for further enhancement of the proposed approach.

세라믹소지에 생성되는 석회에 의한 백화현상분석

이기강,Lee, Ki-Gang 한국결정성장학회 2006 韓國結晶成長學會誌 Vol.16 No.3

The efflorescence mechanism of ceramic bodies with different sintering temperature was studied by quantitative analysis for the effect of various metal ions and anions. SEM and EDS characterization for efflorescence formed on the surface of the ceramic body showed that the main components of the efflorescence were Ca and S atoms. Leaching concentrations of various metal ions and anions for the ceramic bodies prepared by wet mixing with pH 7 and pH 10 were evaluated by ICP and IC analysis. The results of leaching test showed that the concentration of Ca ion at pH 7 body was eight times more than that of pH 10 body. Ca-rich efflorescence was not formed on the surface of ceramic body which prepared at pH 10 and sintered over $1100^{\circ}C$. 세라믹소지에 발생하는 온도별 백화생성기구를 백화를 형성하는 양이온과 음이온을 분석하여 규명하였다. 백화가 발생된 세라믹 소지의 표면을 SEM과 EDS 분석을 하여 백화의 주 성분은 Ca와 S임을 확인하였다. 세라믹소지를 pH 7과 pH 10에서 각기 습식혼합 하였으며, 이때 여과된 액을 ICP와 IC 분석을 하여, 양이온 및 음이온 농도분석을 하였다. pH 7에서 제조된 세라믹 소지의 Ca 이온농도는 pH 10에서 제조된 세라믹소지의 Ca 이온농도의 8배 값을 보였으며, pH 10에서 제조된 세라믹소지는 $1100^{\circ}C$ 이상으로 소결된 소지에서도 백화가 발견되지 않았다.