• Advances in concrete construction
• /
• 제8권1호
• /
• pp.65-76
• /
• 2019

This paper investigates the effect of recycled glass powder (RGP) on flowing properties of self-compacting mortars (SCMs) containing different ratios of fillers and superplasticizer dosages. Fly ash (FA), nano-silica (NS), micro-silica (MS), metakaolin (MK) and rice husk ash (RHA) are used as fillers and their synergistic effect with RFP is studied. The effects of fillers and high-range water reducer (HRWR) on flowing ability of mortars are primarily determined by slump flow and V-funnel flow time tests. The results showed that for composites with a higher RGP content, the mortar flowing ability increased but tended to decrease when the composites containing 10% MK or 5% RHA. However, the flowing ability of samples incorporating 5% RGP and 10% SF or 25% FA showed an opposite result that their slump flow spread decreased and then increased with increasing RGP content. For specimens with 3% NS, the influence of RGP content on flowing properties was not significant. Except RHA and MS, the fillers studied in this paper could reduce the dosage of HRWR required for achieving the same followability. Also, the mixture parameters were determined and indicated that the flowability of mixtures was also affected by the content of sand and specific surface area of cement materials. It is believed that excess fine particles provided ball-bearing effect, which could facilitate the movement of coarse particles and alleviate the interlocking action among particles. Also, it can be concluded that using fillers in conjunction with RGP as cementitious materials can reduce the material costs of SCM significantly.

• 한국건축시공학회지
• /
• 제19권5호
• /
• pp.391-399
• /
• 2019

본 연구는 국내에 새롭게 도입하고자 시운전중인 석탄가스화복합발전(IGCC)에서 발생하는 석탄가스화 용융슬래그(CGS)를 국내의 부족한 골재자원으로 재활용 가능성을 검토하였다. 즉, 부족한 골재자원확보를 위해 IGCC에서 발생하는 CGS를 빈배합 모르타르인 콘크리트 2차제품용 잔골재로 활용하고자 국내 건설산업에서 가장 많이 사용되고 있는 석산의 부순 잔골재로 양호한 품질의 CSa 및 굵은 입자로 표준입도를 벗어난 CSb와 해사인 SS를 혼합한 혼합잔골재에 CGS를 0~100 % 범위에서 치환하는 것을 검토하였다. 연구결과, CSa 혹은 CSb+SS에 CGS를 25~50% 정도 치환할 경우 골재의 입도측면 및 시멘트 모르타르의 유동성 및 압축강도 측면에서 양호한 결과가 얻어져 활용가능함을 확인할 수 있었다.

• Computers and Concrete
• /
• 제27권3호
• /
• pp.241-252
• /
• 2021

An experimental program was conducted to investigate the fresh properties, mechanical properties and durability characteristics of the self-compacting mortars (SCM) produced with pumice powder and Artificial Lightweight Fine Aggregate (aLWFA). aLWFA was produced by using fly ash. A total of 16 different mixtures were designed with a constant water-binder ratio of 0.37, in which natural sands were partially replaced with aLWFA and pumice powder at different volume fractions of 5%, 10% and 15%. The artificial lightweight aggregates used in this study were manufactured through cold bonding pelletisation of 90% of class-F fly ash and 10% of Portland cement in a tilted pan with an ambient temperature and moisture content. Flowability tests were conducted on the fresh mortar mixtures beforehand, to determine the self-compacting characteristics on the basis of EFNARC. To determine the conformity of the fresh mortar characteristics with the standards, mini-slump and mini-V-funnel tests were carried out. Hardened state tests were conducted after 7, 28 and 56 days to determine the flexural strength and axial compressive strength respectively. Durability, sorptivity, permeability and density tests were conducted at the end of 28 days of curing time. The test results showed that the pumice powder replacement improved both the fresh state and the hardened state characteristics of the mortar and the optimum mixture ratio was determined as 15%, considering other studies in the literature. In the aLWFA mixtures used, the mechanical and durability characteristics of the modified compositions were very close to the control mixture. It is concluded in this study that mixtures with pumice powder replacement eliminated the negative effects of the aLWFA in the mortars and made a positive contribution.

• 한국지진공학회논문집
• /
• 제26권3호
• /
• pp.137-147
• /
• 2022

This study investigated the seismic performance of reinforced concrete (RC) wall-slab frames with masonry infills. Four RC wall-slab frames with or without masonry infill were tested under cyclic loading. The RC frames were composed of in-plane and out-of-plane walls and top and bottom slabs. For masonry infill walls, cement bricks were stacked applying mortar paste only at the bed joints, and, at the top, a gap of 50 mm was intentionally left between the masonry wall and top RC slab. Both sides of the masonry walls were finished by applying ordinary or fiber-reinforced mortars. The tests showed that despite the gap on top of the masonry walls, the strength and stiffness of the infilled frames were significantly increased and were different depending on the direction of loading and the finishing mortars. During repeated loading, the masonry walls underwent horizontal and diagonal cracking and corner crushing/spalling, showing a rocking mode inside the RC wall-slab frame. Interestingly, this rocking mode delayed loss of strength, and as a result, the ductility of the infilled frames increased to the same level as the bare frame. The interaction of masonry infill and adjacent RC walls, depending on the direction of loading, was further investigated based on test observations.

• 한국건설순환자원학회논문집
• /
• 제10권4호
• /
• pp.514-522
• /
• 2022

본 연구에서는 시멘트 복합체에 시멘트계 재료로 구성된 자기치유 캡슐을 적용하여 콘크리트 구조물의 자기치유 성능을 향상시키기 위한 연구의 일환으로 PCC(Powder Compacted Capsule) 크기 및 혼입율에 따른 모르타르의 공학적 특성을 비교ㆍ분석하였다. 이를 위해 PCC 크기 및 혼입율에 따른 모르타르의 유동성, 압축강도, 하중재부하 시험, 탄산화, 초음파속도, 투수 특성 등을 측정하였다. 측정 결과, PCC의 혼입율이 증가할수록 유동성과 압축강도가 증가하였으며, 치유특성 검토를 위해 진행한 하중재부하 시험의 경우 03PC 배합에서 PCC 혼입율이 증가할수록 치유율이 증가하였다. 정수위투수 시험의 경우 PCC를 사용할 경우 유출수량 감소율이 Plain 배합에 비해 최대 35 % 높은것으로 나타났으며, 크기 0.3~0.6 mm의 PCC를 15 % 혼입할 시 모르타르의 균열 치유율 향상에 효과적인 것으로 나타났다.

• Computers and Concrete
• /
• 제30권2호
• /
• pp.99-111
• /
• 2022

In this study, deep learning and k-Nearest Neighbor (kNN) models were used to estimate the sorptivity and freeze-thaw resistance of self-compacting mortars (SCMs) having binary and ternary blends of mineral admixtures. Twenty-five environment-friendly SCMs were designed as binary and ternary blends of fly ash (FA) and silica fume (SF) except for control mixture with only Portland cement (PC). The capillary water absorption and freeze-thaw resistance tests were conducted for 91 days. It was found that the use of SF with FA as ternary blends reduced sorptivity coefficient values compared to the use of FA as binary blends while the presence of FA with SF improved freeze-thaw resistance of SCMs with ternary blends. The input variables used the models for the estimation of sorptivity were defined as PC content, SF content, FA content, sand content, HRWRA, water/cementitious materials (W/C) and freeze-thaw cycles. The input variables used the models for the estimation of sorptivity were selected as PC content, SF content, FA content, sand content, HRWRA, W/C and predefined intervals of the sample in water. The deep learning and k-NN models estimated the durability factor of SCM with 94.43% and 92.55% accuracy and the sorptivity of SCM was estimated with 97.87% and 86.14% accuracy, respectively. This study found that deep learning model estimated the sorptivity and durability factor of SCMs having binary and ternary blends of mineral admixtures higher accuracy than k-NN model.

• 한국건설순환자원학회논문집
• /
• 제10권1호
• /
• pp.74-79
• /
• 2022

본 연구에서는 고강도 콘크리트 및 시멘트 복합체의 밀실한 내부 구조로 인한 급격한 내부 습도 저하 및 수화도 저하 등의 영향을 파악하고자 하였다. 내부 Si 수화도 변화 검증을 위해 폐유리발포비드를 경량골재로 사용하였으며, 중장기에 걸쳐 내부 미반응 수화물의 저감 및 수화물 형성 경향을 파악하였다. 폐유리발포비드는 5, 10, 20 % 혼입되었으며 프리웨팅하여 사용하였다. 폐유리발포비드의 혼입률이 증가함에 따라 강도는 감소하는 경향을 보였다. 이와 함께 XRD 분석, TGA 분석 및 Si NMR 분석을 통해 프리웨팅된 폐유리발포비드의 혼입량이 내부에 증가할 때, 페이스트에 수분이 공급되는 것으로 내부 Si의 수화 정도는 달라지는 것으로 판단된다.

• 한국건축시공학회지
• /
• 제23권3호
• /
• pp.261-272
• /
• 2023

본 연구는 현재 늘어나고 있는 수소 충전소 및 ESS 시설 등에서 예상치 못한 사고로 발생할 수 있는 폭발 위험과 이로 인한 구조물 방호 기술의 중요성에 초점을 맞추고 있다. 시멘트 복합체의 보강 방법에 따른 내충격 특성을 평가하여 구조물의 방호 설계를 위한 기초 데이터를 제시하였다. 실험결과 가장 기본적 구조재료인 철근콘크리트는 내충격 성능에 미치는 보강효과가 무근 콘크리트에 비해 약 20% 향상되는 것으로 나타났으며, 고속충격과 같은 빠른 하중에 대해서는 국부적 보강보다는 섬유와 같이 매트릭스 전체를 보강하는 방법이 효과적인 것으로 확인되었다.

• 한국농촌건축학회논문집
• /
• 제24권4호
• /
• pp.59-66
• /
• 2022

This study is to investigate the old buildings that have been built more than 50 years ago, targeting the areas of Seongan and Jungang-dong, the historic urban area of Cheongju. Their types and distribution characteristics are as follows. 1) First, the old buildings existing in downtown Cheongju account for 21.4% of 1,070 out of the total 5,000 buildings. Among them, wooden buildings before the 1950s accounted for 60% of them, resulting in severe aging. 2) Second, by use, 728 detached houses and 276 neighborhood living facilities account for 93.8% of the total, with 16 offices and 12 religious facilities. By structure, there are wood 65%, masonry 30%, and reinforced concrete 5% (54 buildings). By number of floors, the first floor 90%, the second floor 7.3%, and the third floor or higher 2.7% (30 buildings). The roof material is 51.6% of earthenware, followed by slate, cement, and slab. 3) Third, the old buildings are scattered all over the streets, and are concentrated in Namju-dong, Nammun-ro 1-ga-dong, Seoun-dong, and Sudong at the foot of Uamsan Mountain, a former refugee village. Also old buildings are distributed in Seoun-dong and Seokgyo-dong where hanok(korean traditional houses) are concentrated, in Namju and Nammunro 1 ga-dong blocks connected by alleys, and in cul-de-sac all over the place.

• 자원리싸이클링
• /
• 제32권6호
• /
• pp.18-24
• /
• 2023

본 연구에서는 염소 바이패스 분진을 광물 탄산화하여 시멘트의 원료 및 콘크리트 혼화재로 적용하기 위한 초기 연구를 수행하였다. 염소 바이패스 분진의 물리적·화학적 특성을 확인하기 위해 수세 처리 유무 및 수세 횟수에 따른 XRD, XRF, 입도분포 분석을 수행하였으며 그에 따른 특성 변화를 확인하였다. 분진의 종류, 교반 온도, 시간 경과에 따른 염소 바이패스 분진의 광물 탄산화 결과 수세 미처리 샘플은 최대 24%이었으며 수세 처리 샘플은 27%이었으나 실험 조건에 따라 광물 탄산화의 속도 및 정도는 상이하였다. 수세 처리된 분진이 수세 미처리 분진에 비해 더 많은 광물 탄산화가 일어난 이유는 칼슘 함량이 더 높았기 때문이라고 판단되었다. 또한, 더 높은 교반 온도는 초기 광물 탄산화를 더 촉진시키지만 분진의 종류 및 시간 경과에 따라 상이한 결과가 도출되었다.