Porous basalt aggregate is commonly used in roadbed engineering, but its application in concrete has rarely been studied. This paper studies the application of porous basalt in concrete. Porous basalt aggregate is assessed for its effects on mechanical strength and durability of prepared C50 concrete; because it has a hole structure, porous basalt aggregate is known for its porosity, and porous basalt aggregates can be made full of water through changing the content of saturated basalt; after full-water condition is achieved in porous basalt aggregate mixture of C50 concrete, we discuss its mechanical properties and durability. The effects of C50 concrete prepared with basalt aggregate on the compressive strength, water absorption, and electric flux of concrete specimens of different ages were studied through experiments, and the effects of different replacement rates of saturated porous basalt aggregate on the properties of concrete were also studied. The results show that porous basalt aggregate can be prepared as C50 concrete. For early saturated porous basalt aggregate concrete, its compressive strength decreases with the increase of the replacement rate of saturated aggregate; this occurs up to concrete curing at 28 d, when the replacement rate of saturated basalt aggregate is greater than or equal to 40 %. The compressive strength of concrete increases with the increase of the replacement rate of saturated aggregate. The 28 d electric flux decreases with the increase of the replacement rate of saturated aggregate, indicating that saturated porous basalt aggregate can improve the chloride ion permeability resistance of concrete in later stages.

본 연구는 이러한 단점을 보완하기 위해 철근을 대체하여 내산화성과 전기저항이 높은 GFRP 보강근을 적용한 도상슬래브의 최적 변수해석을 수행하였다. 철도 궤도슬래브에 적용되는 철근은 열차 운행 중 신호전류의 손실을 일으켜 열차의 안정성을 저해하며, 철 근의 부식으로 내구성이 저하될 수 있다. GFRP 보강근의 직경 및 배근 개수 변화가 전체 콘크리트 도상슬래브의 휨강도 및 균열제어 에 미치는 영향을 유한요소 변수해석을 통하여 상세분석하였다. 해석 결과, GFRP 보강근의 직경 및 배근을 합리화하여 제안하였으며 이러한 경우 기존 배근보다 더욱 경제적인 단면을 도출할 수 있음을 알 수 있었다. 본 연구로부터 도출된 결과는 향후 GFRP 보강근을 적용하여 도상슬래브를 설계하는 경우 보다 합리적이고 경제적인 단면을 산정할 수 있는 가이드라인이 될 수 있을 것으로 기대된다.

PURPOSES : Given that large-scale repair works of expressway bridge pavements have high maintenance cost and long traffic blocking time, the thin overlay method that maintains the existing pavement is attracting attention. In this study, because the bridge thin overlay has not been introduced in Korea yet, the basic physical properties of the epoxy thin overlay, which is mainly used for the bridge thin overlay, were investigated, and the skid resistance and bond performance were analyzed. METHODS : Basic physical property tests were performed on each of the epoxy binders, aggregates, and mixtures used in epoxy thin overlay. They were also compared and reviewed against foreign standards. The epoxy binders were tested for viscosity, gel time, and thermal compatibility. The aggregates were tested in terms of water absorption, specific gravity, and gradation. The compressive and flexural strengths of the mixtures were investigated. The epoxy thin overlay has the possibility of detachment of aggregates, so the skid resistance was tested according to the paving phase. In addition, to investigate the bond performance, which is the most important performance of the epoxy thin overlay, the bond strength test was performed by varying the moisture condition and treatment condition of the existing layer surface. RESULTS : The basic physical properties of the materials used in the epoxy thin overlays satisfied foreign standards except for the gradation of aggregates. The skid resistance did not satisfy the standard when the epoxy was exposed, whereas the skid resistance did satisfy the standard when the aggregates were exposed, even after the abrasion test. The bond strength of the epoxy thin overlay satisfied the standard in all cases. The bond strength was the highest when the relative humidity of the existing layer surface was 60%. CONCLUSIONS : The materials of epoxy thin overlay that could be obtained in Korea satisfied the basic physical property standards except for aggregate gradation. Given that the aggregate gradation could be adjusted, it can be concluded that the epoxy thin overlay could be introduced in Korea. In addition, it was confirmed that the skid resistance and bond strength of the epoxy thin overlay were high enough to be used in general road conditions. It was determined that the existing layer surface should maintain an optimal relative humidity of approximately 60% because the moisture condition affects the bond strength.

최근 건축물의 보수보강 및 리모델링 시 구조부재를 부착하거나 고정하는 데 있어서 시공의 유연성 및 용이성으로 후설치 확장앵커의 사용량이 점점 증가하고 있는 실정이다. 본 연구에서는 현장에서 비교적 용이하게 시공할 수 있는 후설치 확장앵커를 대상으로 비균열 무근콘크리트에 매입한 확장앵커의 연단거리 및 앵커간격를 변수로 한 전단실험을 통하여 확장앵 커의 전단내력과 하중-변위관계를 분석하였다. 실험결과 연단거리 및 앵커간격에 비례하여 일정비율로 전단내력이 상승하였으며, 파괴모드는 강재앵커 파괴 및 콘크리트 파괴로 각각 나타났다. 그리고 실험결과를 ACI318-19 및 CCD설계기준과 비교분석 하였으며, 향후 보다 합리적인 후설치 확장앵커의 최적설계를 위한 기초자료를 제시하고자 한다.

PURPOSES : The purpose of this study was to investigate the performance of additives that affect internal curing in order to reduce the damage occurring in concrete pavements. METHODS : SAP was used as an additive to reduce internal curing in concrete pavements. SAP is an additive that has a very high absorption rate which prevents concrete wrappers from externally draining water. To evaluate the internal curing performance according to the ratio of SAP, we identified the number of cracks and amount of abrasion reduction. RESULTS : Plastic shrinkage and durability of a concrete mixture with added SAP were evaluated. The following results were obtained: (1) SAP showed a tendency to reduce slumps due to absorption of the concrete mixture. (2) It was possible to verify that concrete condensation did not occur during the penetration resistance test and that the initial curing did not lead to reactions within the mixture. (3) Adding more than 0.6% of SAP for dry curing resulted in greater compressive strength at all ages than OPC, with the highest compression strength of 0.9% after 56 days. (4) Regarding abrasion resistance, it was found that adding SAP was 30~50% better than adding the OPC mixture, and at 0.9% compression strength, abrasion resistance showed the best performance. (5) In the chlorine ion immersion resistance experiment, the passing charge of the OPC mixture was rated “high,” but it was rated “normal” in SAP. The results showed that the addition of SAP improved the water density of concrete due to internal curing effects, and that it showed the greatest chlorine ion penetration resistance for a compressive strength of 0.9%. (6) Regarding plastic shrinkage resistance, cracks did not occur on the surface until the end of the experiment, but the plastic shrinkage rate upon addition of SAP was relatively low compared to that of the OPC mixture. CONCLUSIONS : Recent studies have shown that internal curing techniques can be applied using SAP to prevent shrinkage due to the loss of water and to decrease the effects of hydration. If internal curing effects are expressed using SAP, it is thought that contraction due to a loss of moisture and reduction in sign language reaction can be prevented.

Concrete masonry prisms are strengthened with steel fiber-reinforced mortar (SFRM) overlay and tested for compressive and diagonal tension strength. Masonry prisms are produced in poor condition considering standard workmanship for masonry buildings in Korea. Amorphous steel fibers are adopted for SFRM, and appropriate mixing ratios of SFRM are derived considering constructability and strength. Masonry prisms are strengthened with different fiber volume ratios, while numerous strengthened faces and additional reinforcing meshes are produced for compression and diagonal tension tests. Compression and diagonal tension strength are increased by up to 122% and 856%, respectively, and the enhancement effect for diagonal tension strength was superior compared to compression strength. Finally, the test results and strength prediction equations based on existing literature and regression analysis are compared.

건축 및 토목 구조물의 대표 재료인 콘크리트의 핵심지표인 구조 성능을 개선하기 위해 많은 연구가 진행되고 있다. 아울러 구조물의 크기가 커질수록 강도가 높은 고기능 콘크리트의 필요성이 높아지고 있으며, 특히 내구성과 내후성이 우수한 콘크리트 재료의 개발이 필요한 실정이다. 따라서, 본 연구에서는 강섬유와 함께 파라-아라미드 원사를 이용하여 피복 및 꼬임, 원사 데니어 및 섬유 길이에 대한 차별화된 원사가공을 적용한 복합재료인 슈퍼섬유를 콘크리트에 혼입하여 구조적인 성능을 평가하고자 하였다. 본 연구를 통해 최적화된 슈퍼 섬유로 보강된 슈퍼 콘크리트는 도로, 교량, 상수도 및 하수도 등 기존 SOC 의 수리 및 보강에 적용될 유망한 성장 기술 분야가 될 것으로 예상된다.

최근 국내에서 토목 및 건축구조물의 노후화 및 성능저하에 따른 사회적인 우려가 발생하고 있다. 일반적으로 노후 구조물의 보수보강 방법으로는 외부 부착공법이 가장 많이 사용되고 있으며 시공 용이성을 위하여 GFRP나 CFRP Sheet나 Plate를 활용한 부착 보강방법이 활발히 적용되고 있다. 그러나 이들 방법은 온도에 취약하며 탄소섬유의 경우 경제성이 낮다는 우려가 발생한다. 본 연구에서는 친환경적이고 내열성이 상대적으로 우수한 현무암 섬유(BFRP)를 활용하여 온도변화 및 콘크리트 표면 내 균열발생에 따른 BFRP-콘크리트의 인장 부착성능 및 파괴 패턴을 실험적으로 평가하였다. 그 결과 구조물의 온도가 상승함에 따라 BFRP-콘크리트 계면의 부착성능은 약 30%정도 감소하는 것으로 나타났으며 내열성 수지를 사용한 보강재의 경우 일반 함침용 에폭시 수지보다 부착성능이 다소 우수한 것으로 평가되었다. 콘크리트 표면 내 균열 발생된 경우 균열의 폭이 증가함에 따라 부착 성능은 약 20%씩 감소하는 것으로 나타났다. 하지만 균열보수제로 보강 후 계면에서의 부착성능의 경우, 보강 전 대비 약 30% 정도의 개선효과를 나타내었다.