PURPOSES : This study describes the experimental findings on the mechanical properties of calcium aluminate cement (CAC)-based repair mortars with or without natural cellulose fiber (NCF). Additionally, the effect of adding NCF to the reduction of fugitive dust in the CAC powder was examined. METHODS : To produce mortar, four different levels of NCF (0.0.5, 1.0, and 2.0% by binder weight) were adopted, and the water-binder ratio was fixed at 0.485. The flow, strength characteristics, absorption, and surface electrical resistivity of the mortars were measured at predetermined periods. Additionally, SEM observations were performed to examine the microstructural changes and hydrates formed on the 28 day-mortar samples. RESULTS : The addition of NCF led to a decrease in fugitive dust. Regarding the mechanical properties of the mortars, that with 0.5% NCF exhibited a better performance in terms of strength development and surface electric resistivity compared to those of other mortars. However, the addition of NCF was less effective in the enhancement of the absorption of mortars. Further, we discovered that the microstructures of the mortars with additional NCF were comparatively dense compared to those without NCF. CONCLUSIONS : The appropriate addition of NCF can enhance the performance of CAC-based repair materials. However, further studies on the durability of CAC with the addition of NCF are needed to determine the optimal mixture.

PURPOSES : Experimental findings pertaining to the mechanical properties of calcium aluminate cement (CAC)-based repair mortars incorporated with anhydrite gypsum (AG) are described herein. METHODS : To prepare the mortars, three different levels of AG were adopted and the ratio of water–cementitious materials was fixed at 0.50. For comparison, mortar composed of ordinary Portland cement was prepared. The fluidity, setting time, compressive and bond strengths, absorption and surface electric resistivity of the mortars were measured at predetermined periods. RESULTS : The incorporation of AG increases the fluidity but decreases the setting time of the CAC-based repair material system. However, the AG in the CAC mixes does not effectively enhance the compressive strength of the mortars owing to the decreased formation of CA hydrates, such as CAH10 and C2AH8. Meanwhile, the mortar with 10% AG shows excellence absorption. CONCLUSIONS : The mechanical properties of CAC based-mortars rely significantly on the amount of AG incorporated. However, further studies regarding the microstructure and durability of CAC-AG repair mortars must be conducted to obtain the optimal mixture.

PURPOSES : Recently, the generation of industrial by-products has been increased owing to the increase in electrical power consumption. This experimental study investigated a special mortar development using outstanding benefits of porous structures in heavy oil fly ash (HOFA) and bottom ash (BA) to reduce heat transfer and weight of tunnel repair mortar. METHODS : Based on the concept of materials usable for this objective being porous and light, the physical and chemical properties of heavy oil fly ash and bottom ash were analyzed to determine the application possibility for tunnel repair mortar. In addition to satisfying this primary requirement, the research aimed at determining the relationships between the characteristics of porous structures and effectiveness of reducing weight and thermal conductivity. This study was undertaken on the use of bottom ash as fine aggregate and heavy oil ash as filler in mortar mix proportion. Four different levels of bottom ash (25%, 50%, 75%, 100%, and 5%), and 10%, 15%, and 20% of heavy oil fly ash were investigated to determine the proper replacement amount within the designed specification. According to the analytic results on the effectiveness of both by-products and chemical additives, the repair mortar with optimum mixture proportion was investigated using various tests including thermal conductivity and porosity. RESULTS : The use of porous by-products increased the demand for mixing water in obtaining the required flowability, but the compressive strength did not decrease significantly in proportion by adding an amount of bottom ash. Based on the results, bottom ash can be replaced with aggregate as much as 50%, but adding an amount of heavy oil ash is suggested as below 10% in formulation. CONCLUSIONS : The optimized repair mortar, which was produced by conclusive formulation, was evaluated as a high-performance material to repair tunnels with the effectiveness of porous and remarkable physical properties.

초고성능 콘크리트(UHPC)는 낮은 물-결합재비(W/B), 고성능 감수제(SP), 혼화재 및 강섬유(Steel Fiber)의 혼입으로 일반 콘크리트보다 유동성, 강도 등에서 월등히 우수한 성능을 지닌 건설 재료이다. 본 연구에서는 진동밀로 분쇄하여 시멘트의 분말도를 6000cm2/g급 까지 높여 최적의 초고성능 모르타르를 제작하였다. 또한, UHPC의 특성상 시멘트, 혼화재뿐만 아니라 화학 혼화제 혼입량에 따라 물성에 많은 차이를 나타내기 때문에 최적의 화학 혼화제를 도출하기 위하여 고성능 혼화제에 따른 물성 평가 실험도 수행하였다. 분쇄된 시멘트를 활용한 초고성능 모르타르의 유동성, 강도 등 물성 테스트를 진행하였으며, 경제성을 고려하여 강섬유와 기타 혼화재를 혼입하지 않고 목표 물성을 달성하고자 하였다. 실험결과, 모든배합에서 플로우 값은 목표치 180±10mm를 확보하였으며, W/B 20%, SP 0.8%에서 최대 압축강도 90MPa, 휨강도 16.8MPa까지 나타났다.

PURPOSES: The objective of this study is to evaluate the durable performance of combined organic and inorganic hybrid mortar as repair material (HRM mortar) for concrete road facilities via comparison with that of cement repair materials (IRM mortar). METHODS : To produce HRM mortars, inorganic materials as binder and 2 mineral fillers were adopted. The ratio of main resin versus hardener was fixed at 1:2. For comparison, IRM mortars made with cement repair materials were also manufactured. Compressive, flexural, and bonding strengths were measured at predetermined periods. For durability assessment, the scaling resistance, freezing & thawing resistance, rapid chloride penetration resistance, and acid attack resistance of those mortars were experimentally monitored. RESULTS: The durability performances of HRM mortars, especially with respect to freezing & thawing, rapid chloride penetration and acid attack, were identified to be much better than those of IRM mortars. This result implies that HRM is a highly promising and versatile material because of its excellent durability. CONCLUSIONS: It is concluded that the application of the combined organic and inorganic hybrid mortars is possibly an option for the repair of concrete road facilities exposed to aggressive environments.

PURPOSES : The objective of this study is to evaluate the performance of combined organic and inorganic hybrid mortar used as repair materials (UM mortar) for concrete road facilities by comparison with cement repair materials (RM mortar). METHODS: In order to produce UM mortar, four different levels of inorganic materials were adopted and the ratio of main resin to hardener was fixed at 1:2. For comparison, RM mortar made with cement repair materials was also produced. Fluidity, strength characteristics, length change, and freezing-thawing resistance of the mortars were measured at the predetermined periods. In addition, the microstructures of the mortars was performed on the 28-day mortar samples to examine the properties of the interfacial transition zone (ITZ). RESULTS : It was observed that the mechanical properties, except for compressive strength, and freezing-thawing resistance of UM mortars were much better than those of RM mortar. Furthermore, showing a densified ITZ properties on the UM mortars from the microstructural observation, the usage of UM mortars exhibited a beneficial effect on the enhancement of mortar properties. CONCLUSIONS: It is concluded that the application of combined organic and inorganic hybrid mortars is a possible option for the repair of deteriorated concrete road facilities.

현대 섬유 기술의 발전으로 박리에 의한 복합체 파괴 가능성을 줄일 수 있고, 복합체의 전단강도를 향상시킬 수 있는 있는 3차원 직물섬유를 제작할 수 있게 되었다. 본 연구에서는 3D 직물섬유의 시멘트 기반 복합체 적용 가능성을 살펴보기 위해 3D 직물섬유의 종류, 매트릭스의 종류, 보 부재 높이를 변수로 한 3D 직물섬유 보강 모르타르 보 시험체를 제작하고 휨실험을 수행하였다. 휨실험 결과, 3D 직물섬유 보강 모르타르 부재는 전형적인 직물섬유 보강 콘크리트의 휨거동과 유사한 결과를 나타내었다. 3D 직물섬유 보강을 통해 보 부재의 휨강성 및 휨인성이 향상되었고, 6mm 스페이서를 가진 직물섬유 보강 시험체가 4mm 스페이서를 가진 직물섬유 보강 시험체 보다 더 높은 휨강도 및 휨인성을 보였다. 3D 직물섬유 보강 모르타르의 휨강도 및 휨인성을 보다 향상시키기 위해서는 높은 인장강도와 탄성계수를 가지는 섬유의 적용, 섬유량의 증가, 인장단에 가까운 섬유의 배치가 필요하다.

This study was to investigate the firing method of limestone in Joseon Dynasty, and analyze the physical·chemical properties of lime mortars in Joseon Dynasty. This study was to manufacture and evaluate the firing experiment and mortar of Limestone by each sort in order to reproduce the traditional lime mortars in Joseon Dynasty, and investigate the behavior to improve physical properties according to the firing method of Limestone. This study has found out that there were screening criteria and standard of appropriate firing temperature about the Limestone in Joseon Dynasty. Accordingly, this study was to improve its strength through various additives and mixture. In particular, in case of Limestone, the black and blue Limestone were preferred, and most of domestic Limestones were low grade Limestone including the clay and took ivory white or blue with low whiteness. This study has shown that the low grade Limestone was mined by the surface mining compared with the high grade Limestone as underground mining method, and could be used because it was easy to mine relatively and there was possibility that Natural Hydraulic Lime(NHL) was used with the traditional lime mortars in Joseon Dynasty.

본 연구에서는 실험을 통하여 자기치유 재료 혼입 모르타르 보의 자기치유 성능을 평가하였다. 실험에는 일반 모르타르 보 실험체와 자기치유 모르타르 보 실험체가 사용되었으며, 모르타르의 압축강도, 내력 및 균열의 자기치유 효과를 비교하여 자기치유 성능을 평가하였다. 실험결과 자기치유 재료를 혼입한 모르타르의 압축강도가 일반 모르타르의 압축강도보다 작았지만 28일 압축강도에 대한 118일 압축강도 비율은 동일하게 나타났다. 실험체의 내력은 재령일이 길어질수록 증가하는 경향을 나타냈다. 일반 모르타르 실험체는 균열이 발생할 경우 재령일이 증가하여도 하중은 회복되지 않았으나 자기치유 모르타르 실험체의 경우 반응 생성물의 영향으로 내력이 다소 회복되는 경향을 나타냈다. 균열폭은 두 종류의 실험체 모두 치유기간이 지난 후 감소하는 경향을 보였으나 자기치유 모르타르 실험체에서만 반응 생성물이 관찰되었다.

In this study, the mechanical property and durability of improved bond performance mortar shotcrete was investigated. Mortar shotcrete was prepared by replacing coarse aggregate with 100% fine aggregate in the shotcrete mixture proportion proposed in the road construction standard specification. OPC, GGBFS and anhydrite were used as binders, and polymer powder was substituted for 1% and 2% of binder for improving bond property. From the experimental results, it was found that the compressive strength decreased with increasing polymer addition, but the bond strength increased. The addition of polymer to mortar shotcrete also reduced the drying shrinkage and improved the resistance to carbonation. Initial hydration heat of mortar shotcrete decreased with the addition of polymer, and it was judged that the initial compressive strength decreased.

This study was evaluated the chloride penetration resistance performance of Surface Protection Material(SPM). SPM was applied 0.25 and 0.51 kg/㎡ to the surface of the mortar and immersed aging of the chloride solution 7, 14, and 28 days. As a results, In the case of SPM was applied, chloride did not penetrate until the 28th day.

This paper evaluates the seismic performance of reinforced concrete(RC) frame strengthed with expansive mortar and steel frame. For this purpose, cyclic loading test was conducted, load-displacement relationship and energy dissipation capacity were evaluated. As a results, RC frame retrofitted with steel frame was increased maximum strength and energy dissipation capacity than conventional RC frame.

In the case of VOCs, it is known that the removal can be realized through the use of titanium dioxide (TiO2) photocatalyst. The experimental results reveal that VOCs removal efficiency for Mortar with Photocatalyst powder was effective and It was different depending on the Photocatalyst types.

The study was conducted to evaluate the latent heat properties of cement mortar with different contents of phase change material (PCM). The paraffin PCM with melting point of 44℃ used in this study. PCM was added in the mixture with contents ranged from 0 to 30%. Test results indicated that the heat storage performances of cement mortar were improved with increasing the content of PCM.

In this study, Early compressive strength analysis of low carbon mortar using industrial byproducts and describes relationships between strength property and CO2 indices to evaluate eco-efficient of low carbon binder mortar. Based on the results, this study is to give fundamental data for ability of eco-efficient low carbon binder.

In this study, Early compressive strength analysis of low carbon mortar using industrial byproducts and describes relationships between strength property and CO2 indices to evaluate eco-efficient of low carbon binder mortar. Based on the results, this study is to give fundamental data for ability of eco-efficient low carbon binder.

본 논문은 바탕면의 함수조건에 따른 보수재료로서 MKPC의 인발 부착강도, 전단 부착강도, 계면 부착강도를 폴리머 시멘트 모르 타르, 에폭시 모르타르와 비교 분석하였다. 그 결과 MKPC는 PC 및 MKPC와 비교하여 바탕면 함수조건에 따른 부착성능의 변화가 상대적으 로 작은 것으로 나타났다. 또한 MKPC의 경우 절건 바탕면에서의 부착성능은 무기계 보수재료인 폴리머 시멘트 모르타르와 비교하여 우수한 특성을 지니고 있으며, 습윤 바탕면에서의 부착성능은 폴리머 시멘트 모르타르와 유사한 수준을 보이고 있으나 에폭시 모르타르와 비교하여 우수한 특성을 지니는 것으로 나타났다.

본 연구에서는 칼슘알루미네이트 시멘트(CAC) 모르타르의 수화생성물, 강도, 흡수율, 표면전기 저항성 및 염소이온 침투저항성을 실험적으로 고찰하였다. CAC 모르타르의 성능은 보통포틀랜드 시멘트(OPC) 모르타르의 성능과 상호 비교되었다. 실험 결과에 따르면, CAC 모르타르의 주요 수화생성물은 C2AH8 및 CAH10으로 조사되었으며, 압축 및 부착강도는 OPC 모르타르에 비하여 우수하게 나타났다. 뿐만 아 니라, 표면전기 저항성 및 염소이온 침투저항성도 대체적으로 좋은 결과를 나타냄으로서, CAC의 우수한 성능도 확인하였다. 그러나, CAC 모 르타르의 흡수율은 초기재령부터 OPC 모르타르에 비하여 다소 크게 나타남으로써, CAC 경화체의 표면흡수 성능을 개선하기 위한 연구가 더 필요할 것으로 판단된다. 반면, CAC 및 OPC 혼용배합 모르타르의 역학적 성능은 CAC 모르타르에 비하여 대체적으로 다소 떨어지는 것으로 조사됨으로써, CAC계 경화체 제조시 주의가 요구된다.