The use of recycled materials, such as the fine recycled aggregate made from concrete waste and carbon fiber (CF) product of industrial waste, for the manufacture of conductive recycled mortars (CRM), transforms the mortar base cement normally made with cement:sand in a sustainable multifunctional material, conferring satisfactory mechanical and electrical properties for non-structural uses. This action provides ecological benefits, reducing the use of natural fine aggregates from rivers and the amount of concrete waste deposited in landfills resulting from construction waste. In this investigation the effect of the addition of CF on electrical properties in hardened, wet and dry state, electric percolation in dry state and fluidity of the wet mixture of a cement based CRM was evaluated: fine recycled aggregate: graphite powder, CRM specimens with dimensions of 4 × 4 × 16 cm. were manufactured for 3, 7 and 28 days of age and sand/cement ratios = 1.00, graphite/cement = 1.00, water/cement = 0.60 and CF = 0.1, 0.3, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0% compared to the weight of cement. The results demonstrated the effect of the addition of CF in CRM, reducing fluidity of the mixtures due to the opposition generated by its physical interaction of CF with recycled sand or recycled fine aggregate and graphite powder (GP), in its case, placing the electric percolation percolation at 0.30% and 0.45% of CF for CRM with and without GP, respectively. Increases in electrical conductivity (EC) without the presence of GP are defined by the contact between the CF and the conductive paths formed. In contrast, with the presence of GP, the EC is defined by the contact between the CF and the GP simultaneously, forming conductive routes with greater performance in its EC.

3D 프린팅의 적층제조를 위한 시멘트 모르타르의 이용은 시멘트의 유동 특성을 개질하기 위한 시멘트 혼화용 폴리 머의 혼입이 필수적이다. 시멘트 모르타르는 점성이 높고 수축이 크기 때문에 적층제조를 위해서는 유동성, 경화속도, 시공성 및 적층특성의 개선이 필요하다. 시멘트 혼화용 폴리머 디스퍼젼을 혼입한 시멘트 모르타르는 시멘트 수화물과 공극 사이에 폴 리머 필름이 상호 형성되어 인장강도와 취성이 개선되며 우수한 접착성, 기밀성, 내약품성을 보인다. 최근, 사용편리성이 우수한 Ethylene-vinyl acetate 재유화형 분말수지가 널리 사용된다. 하지만 화재와 같은 고온에서는 재유화형 분말수지를 혼입한 경우에 는 성능저하가 더 크다. 재유화형 분말수지가 시멘트 수화물과 공극에 폴리머 필름을 형성하고 충전하지만 고온에 의해 열분해 되기 때문이다. 본 연구에서는 3D 프린팅의 적층제조를 위해 내열성이 개선된 Ethylene-vinyl chloride 재유화형 분말수지의 혼입률을 달리하여 고온에서의 특성과 열분해에 따른 공극특성을 검토하였다. 연구결과, EVCL 재유화형 분말수지를 혼입한 경우 고온에서 약간의 성능개선을 보였지만 열분해하여 공극률이 커지며, 밀도, 강도가 감소한다. 따라서, 사용조건에 적합한 배합조절 등이 필요하다.

본 연구는 시멘트 노출에 따른 어류 조직의 형태 생리적 변화를 분석하여 용해된 시멘트 분말이 어류에 미치는 영향을 조사하고자 하였다. 용해된 시멘트 분말에 노출된 아가미는 일차새변의 두께가 두꺼워지고, 염세포와 점액세포도 두드러지게 활성이 증가되고 있으며, 이차새변의 새엽에서는 상피세포의 증식과 박리 및 곤봉화 현상도 관찰되었다. 신장 조직에서는 보우만 주머니 공간이 넓게 관찰되었고, 표피 조직은 표피층의 두께가 감소하며 진피층의 배열이 불규칙해지는 것으로 관찰되었다. 항산화효소와 LDH의 활성은 조직 및 노출 기간에 따라 활성에 차이가 있는 것으로 나타났다. 표피 조직에서 용해된 시멘트 분말에 의해 발현이 증가되는 단백질은 해당과정과 에너지 대사과정에 관여하는 단백질로 확인되었고 발현이 저하된 단백질들은 근수축에 관여하는 근섬유 구성 단백질로 조사되었다. 이러한 결과로 보아 용해된 시멘트 분말은 붕어 조직의 형태적 변형과 생리적 기능의 약화를 초래하여 어류의 생존에 커다란 위협이 될 요인으로 작용할 수 있을 것으로 사료된다.

PURPOSES : This study is to investigate the fundamental properties of limestone added cement concrete for application of pavement. METHODS : As the production of Portland cement causes environmental problems, engineers have sought more environment-friendly concrete construction materials. Limestone powder can be used for concrete as a partial replacement of Portland cement. One of the great applications of limestone powder added cement concrete might be a cement concrete pavement since the concrete pavement consumes massive quantity of Portland cement. Experimental variables were different replacement level of limestone powder by 0% to 25% with 5% increment. Before hardening of fresh concrete, setting time and plastic shrinkage characteristics were investigated in addition to other basic properties. Properties of hardened concrete included compressive, tensile and flexural strength as well as drying shrinkage. RESULTS : The addition of limestone powder did not significantly affect the properties of fresh concrete. Strength deceased as the replacement ratio increased and when the replacement ratio was greater than 10% decrease rate increased. CONCLUSIONS : It was found that the partial replacement of the limestone powder to cement in pavement materials can be positively considered as its mechanical properties show comparable performance to those normal concrete.

Geopolymer materials are attractive as inorganic binders due to their superior mechanical and eco-friendly properties. In the current study, geopolymer-based cement was prepared using aluminosilicate minerals from fly-ash with KOH as an alkaline-activator and Na2SiO3 as liquid glass. Then, calcium carbonate powder from a clam shell was mixed with the geopolymer and the mixture was coated on a concrete surface to provide points of attachment for environmental organisms to grow on the geopolymers. We investigated the effect of the shell powder grain size on the microstructure and bonding property of the geopolymers. A homogeneous geopolymer layer coated well on the concrete surface via aluminosilicate bonding, but the adhesiveness of the shell powder on the geopolymer cement was dependent on the grain size of the shell powder. Superior adhesive characteristics were shown in the shell powder of large grain size due to the deep penetration into the geopolymer by their large weight. This kind of coating can be applied to the adhesiveness of eco-materials on the surface of seaside or riverside blocks.

This research is to investigate the effect of borosilicate glass powder on neutron shielding capability of cement mortar. The average particle size of the borosilicate glass powder was 13 μm. It was found that the addition of borosilicate glass powder increased 28 day compressive strength. In addition, neutron shielding capability of cement mortar also increased by the addition of borosilicate glass powder. Considering our earlier findings on enhanced thermal neutron shielding of cement mortar by borosilicate glass powder, the use of borosilicate glass powder was found to be effective to shield neutron when the cement mortar was exposed to the neutron radiation. It can be concluded that borosilicate glass powder is a good alternative material for neutron shielding purposes.

본 연구는 PVA(polyvinyl alcohol) 섬유와 VAE(vinyl acetate ethylene) 분말 폴리머를 사용한 시멘트복합체의 압축·휨강도 와 온도변화에 따른 충격파괴거동을 연구하였다. 충격시험은 -35℃, 0℃ 및 35℃의 선정된 온도조건에서 실시하였다. 본 실험에서는 시멘트 복합체와 일반 모르타르에 대한 충격파괴 에너지와 변위, 시간을 얻기 위해 낙하 충격시험기(Ceast 9350)를 사용하여 충격시험을 수행하였다. 강도 시험결과, PVA 섬유와 VAE 분말 폴리머의 휨강도는 모두 증가하였다. PVA 섬유보강 시멘트복합체의 경우 재령 28일에서의 압축강도는 약간 감소하였으나, 휨강도는 일반 모르타르 강도보다 24.4% 증가하였다. 낙하 충격시험 결과, PVA 섬유보강 시멘트복합체 시편은 섬유의 가교역할로 인한 균열발생의 억제와 에너지 분산에 의한 미세균열이 발생하였으며, 충격에 의한 배면파괴와 관통에 대하여 억제되었다. 반면 VAE 분말 폴리머 시멘트복합체와 일반 모르타르의 시편은 대부분 큰 균열이나 관통파괴 되었다. 충격하중을 받는 시멘트복합체와 일반 모르타르의 시편은 대부분 국부적인 취성파괴거동을 보이며, PVA 섬유보강에 의한 휨성능 증진으로 인해 충격에 대한 저항성능이 크게 향상되었다.

The influence of different amount of SiO2 powder on the mechanical properties of cement-quartz composite cementitious material was discussed through the measurement of the compressive strength of the paste with the water/binder ratio of 0.5 and 0.2 where the SiO2 powder with different proportion to replace the Portland cement(PC). The compressive strength test shows that adding SiO2 powder to the concrete with low water-binder ratio can reduce the use of cement.

The study investigated the fluidity and compressive strength properties of cement paste containing Ferro-Nickel slag powder by different curing conditions to estimate the applicability of Ferro-Nickel slag powder for cement replacement materials.

This paper was evaluated manufacturing properties for core material of self-healing capsules using cement powder, it was found that coagulants for coagulation of core materials were important factors in manufacturing core materials.

This paper was evaluated manufacturing properties for core material of self-healing capsules using cement powder, it was found that coagulants for coagulation of core materials were important factors in manufacturing core materials.

This study was aimed to investigate the effect of blending cement with crushed aggregate powder on the setting time. crushed aggregate powder was incorporated with the ratio of 0~30 wt.% of cement. The experimental results presented that there was little influence on the intial setting time, whereas the final setting time decreased by blending with higher amount of crushed aggregate powder.

This study examines the strength properties use of talc as a substitute for OPC-GGBFS cement. The test was carried out by replacing the plain mix(OPC : GGBFS = 50 : 50) with talc at the rate of 0~100%. The OPC contents was constant in all mixtures. The mixtures replaced GGBFS with talc. The results showed that the compressive strength and bending strength decreases with an increase in talc contents.

Based on the study of chloride migration coefficient and hydration heat evolution, it was found that the use of ternary blended cement was effective to achieve desired service life and minimum crack index. On the other hand, a high level of compressive strength is required for marine concrete mix design.

The purpose of this study is to examine whether cementitious powder separated from waste concrete can be used as the alternative raw material for limestone and reducing the usage of natural resource (limestone) and CO2emission based on recycling cementitious powder from waste concrete. Therefore, to reduce waste and CO2 emission in the cement industry and develop recycled cement, mix design was deducted by multi-objective optimization.

In this study, manufactured of cement mortar using high early strength cement(10 ~ 50 wt%) and blast furnace slag powder(50 ~ 90 wt%), according to compressive strength and flexural strength of hardened cement mortar. XRD and SEM were evaluated utilizing the initial cement hydration properties.

본 연구에서는 CaO-SiO2-Al2O3가 다량 함유된 산업폐기물과 산업부산물을 소성하여 개발한 분말형 속경성 분말을 초기강도의 향상을 위해 기능성 분쇄조제로 처리하여 분쇄한 속경성 미분말을 제조하였다. 이렇게 제조된 미분말을 BFS 분말과 일정비율로 혼합한 후, 시멘트에 첨가하여 모르타르 압축강도 실험을 실시하였다. 그 결과 BFS 조기강도 향상 실험 (Series I)에서는 클링커 분쇄시 기능성 분쇄조제가 첨가되어 분쇄된 속경재가 혼합된 BFS의 초기강도 발현이 우수하며 OPC 조기강도 향상 실험 (Series II)에서는 Clinker-C에 본 실험의 기능성 분쇄조제가 첨가되어 분쇄된 속경성의 분말형 자극제가 첨가된 경우에 가장 압축강도가 높은 사실을 알 수 있었다.

Waste stone sludge generated during the collection of crushed aggregate is difficult to use due to high moisture content. Production of 1 ton aggregate generates approximately 0.25 tons of waste stone sludge. Considering the total crushed aggregate collection in 2012 of about 100 million tons, it can be estimated that 25 million tons of waste stone sludge is generated annually. Recycling of waste stone sludge is made difficult by the high moisture content of 30%. Therefore, to make recycling this process must be a drying process, which makes a fine powder of even better quality that can use as an additive. The purpose of this study is to analyze the changes in physical properties caused by the use of dried waste stone sludge as an additive in the extrusion of cement. A test specimen was made, substituting 50% of the silica with waste stone sludge, and physical performance evaluation was performed. Results showed that 50% substitution of silica resulted in no difference in moldability, but a slight increase in the water content required for the same workability was found. Flexural strength and drying shrinkage were found to be 97% of normal levels, but satisfied the specified performance in the KS F 4735 standard.

Limestone powder can be used for concrete as a partial replacement of Portland cement so that concrete becomes more environment-friendly construction material. One of the great applications of limestone powder added cement concrete might be a cement concrete pavement since the concrete pavement consumes massive quantity of Portland cement. However, it has been reported recently that Alkali-Silica Reaction (ASR) occurs on the cement concrete pavement causing a serious damage. This study investigates the resistance of limestone powder added cement mortar to ASR. The mortar used very high reactive silicious aggregate for accelerated ASR. Experimental procedures followed ASTM C 1260 and variables included different replacement levels of limestone powder in the mortar mix.