PURPOSES : Experimental findings pertaining to the mechanical properties and microstructures of calcium sulfo-aluminate (CSA) cement and amorphous calcium aluminate (ACA) cement based-repair mortars incorporated with anhydrite gypsum (AG) are described herein. METHODS : To prepare the mortars, the CSA or ACA as binders were adopted and the ratio of water–binder was fixed at 0.57. For comparison, mortar made of Type I ordinary Portland cement (OPC) was prepared. The fluidity, setting time, compressive and bond strengths and absorption of the mortars were measured at predetermined periods. In addition, the microstructures of paste samples using OPC, CSA or ACA were visually examined through SEM observation. RESULTS : The ACA-based mortars showed the increases in the fluidity, and the acceleration of the setting time. Furthermore, the ACAbased binder effectively enhanced the compressive and bond strengths of the mortars owing to amount of formation of C2AH8 hydrates. Meanwhile, the mortar with ACA showed an excellence absorption. CONCLUSIONS : Comparing with those of CSA-based mortars, the mechanical properties of ACA based-mortars were more remarkable. However, further studies regarding the durability of repair mortars using aluminate-based binders must be conducted to obtain the optimal mixture.

PURPOSES : In this experimental study, the resistance of blended cement concrete containing air-cooled slag (AS) and water-cooled slag (WS) to freeze–thaw action was investigated. For comparison, the durable performance of ordinary Portland cement (OPC) concrete exposed to a similar damage environment was also evaluated. METHODS : Based on the ASTM C 666 standard, the relative dynamic modulus of elasticity, mass ratio, surface electric resistivity, and compressive strength of blended cement concrete specimens were periodically measured and compared with those of OPC concrete to evaluate the durability of concrete exposed to the freezing-thawing environment. In addition, microstructural characteristics of deteriorated concrete parts were evaluated using scanning electron microscopy (SEM) and energy dispersive spectroscopy techniques to detect products formed by freeze–thaw action. RESULTS : It was found that the resistance of blended cement concrete containing AS and WS to freeze–thaw action was significantly better than that of OPC concrete. Furthermore, the SEM results revealed the frost damage of OPC concrete, owing to the formation of thaumasite. CONCLUSIONS : The application of AS in concrete can effectively improve the durability of concrete, particularly in freeze–thaw environments.

PURPOSES : It is necessary to clarify the rheological properties of cement paste as a basic research in the development of mechanistic concrete mix design. The rheological properties of cement paste with different binder types, mix propositions, and with/without high range water reducers have been analyzed. METHODS: In this study, ordinary Portland cement, fly-ash, blast furnace slag, silica fume, and limestone powder were used as binders. The range of water-binder ratio was 0.3-0.5, and a total of 30 different mixes have been tested. The slump flow test, V-funnel test, and Dynamic Shear Rheometer (DSR) test were performed to analyze the rheological properties of cement paste. RESULTS : As a result of the slump flow test, it was found that the composition ratio of the binder contents greatly affected the paste flow when the high range water reducers were added. The results of V-funnel test showed that when the water-binder ratio was decreased without high range water reducers, the binder composition ratio had a large effect on the passing time of the V-funnel tester, but with high range water reducers the impact of the binder composition ratio was decreased. The slump flow and V-funnel have a certain relationship with the rheological factors (yield stress and plastic viscosity), but the correlation was not significant. Finally, we proposed the M-value considering the density and specific surface area of the binder. The correlation between rheological factors and M-value were better demonstrated than experimental values, but there is still a limit to predict the rheological factor in general mix design. CONCLUSIONS: In this study, the rheological properties of cement paste were analyzed. The binder type, composition ratio of binder, and with/without high range water reducers have combined to provide the complex effects on the rheological properties of cement paste. The correlation between the proposed M-value and rheological factor was found to be better than experimental results, but needs to be improved in the future.

The demand for environmental consideration is on the increase in civil engineering. This study focuses on the development of technology to reduce the use of carbonate cement and improve its performance by using a silicate mineral and hardening agents, and presents the test results for the demonstrative evaluation of the properties of the raw material. Highly active feldspar was used as a binder to augment the bonding of the carbonate cement, and their change in strength was observed after test piece construction with the addition of soluble hardening agent. The uniaxial compression strength of the test piece of the general Portland cement with the addition of 0.5% soluble hardening agent, showed an increase by 33% and that of the test piece of cement with the addition of 70% substituted with feldspar increased by 28%. The strength of viscous soil; classified as soft ground, showed an increase of a maximum of 1.7 times when it was mixed with cement and solidifier depending on the curing period. These tests confirmed that a soluble solidifier is effective for improving the strength of a cement binder and that the highly active feldspar can be used as a binder.

PURPOSES : This study is to evaluate ASR(alkali silica reactivity) resistance of ternary blended binder adding ultra fine mineral admixture. METHODS : This study analyzes ASR expansion using ASTM C 1260 and 1567. RESULTS : This study showed that the fineness of mineral admixture had no effect on ASR expansion. The expansion of ternary blended binder(UFFA 20%+FGGBS 10%) were below 0.1%, and this binder met the ASR standard. Also when adding the CSA expansion agent, ASR expansion slightly decreased. The expansion of latex modified mixture increased by 80% comparing plain mixture. CONCLUSIONS : Ternary blended binder met the ASR standard, and this binder is available in concrete bridge deck overlay.

PURPOSES : This study deals with the working life of polymer concrete, which is typically used as a repair or overlay material for portland cement concrete pavements. METHODS : In the scope of this study, laboratory testing was conducted on fresh MMA modified UP polymer concrete, which uses an MMA monomer for viscosity adjustment and strength improvement of UP resin. The experimental variables were temperature (-20 to +20℃) and binder components (MMA, MEKPO, and DMA). RESULTS : The result showed that the optimum binder ratios for polymer concrete production were 12, 11, and 10 wt.% when the MMA contents were 20, 30, and 40 wt.%, respectively. The working life of polymer concrete depending on temperature and binder components could be expressed by a logarithmic functional formula. The coefficient of variation for each binder component was the highest for DMA content while the lowest for MEKPO content. Also, the contents of each binder component for ensuring the working life of 60 minutes were proposed. CONCLUSIONS : Ultimately, the present study derived a linear regression equation estimating 60 minutes working life based on the setting times of each binder component.

The microstructure and hardness of (W,Ti)C cemented carbides with a different metallic binder composition of Ni and Co fabricated by powder technology were investigated. The densifications of the prepared materials were accomplished by using vacuum sintering at . Nearly full dense (W,Ti)C cemented carbides were obtained with a relative density of up to 99.7% with 30 wt.% Co and 99.9% with 30 wt.% Ni as a metallic binder. The average grain size of the (W,Ti)C-Co and the (W,Ti)C-Ni was decreased by increasing the metallic binder content. The hardness of the dense (W,Ti)C-15 wt%Co and (W,Ti)C-15 wt%Ni, was greater than that of the other related cemented carbides; in addition, the cobalt-based cemented carbides had greater hardness values than the nickel-based cemented carbides.

본 연구에서는 아스팔트 바인더의 절대점도, 동점도, 침입도, 연화점, PG 고온등급을 이용하여 샌드아스팔트 흔합물의 고속 직접인장강도(DTS1), 저속 직접인장강도(DTS2), 간접인장강도(ITS), 회복탄성계수(MR), 강성지수(SI)를 추정하기 위한 연구를 수행하였다. 여러 가지 혼합물의 특성 중 DTS2가 가장 상관성이 높게 나타났으며 그 다음이 DTS1, ITS, SI, MR 순인 것으로 나타났다. 바인더 성질 중에는 PG 등급이 DTS2와 가장 높은 상관 관계를 보여 PG 고온등급이 높은 바인더를 사용하면 직접인장강도가 어느 정도 우수한 혼합물을 얻을 수 있음을 알 수 있었다. 하지만 각각의 물리적 성질만으로는 신뢰도가 낮아 종합적으로 여러 물성을 이용하여 상관성을 분석하였다. 그 결과 직접 및 간접인장강도는 결정계수가 0.99 이상인 모델을 얻을 수 있었다. 그리고 MR, SI 값의 추정치 모델도 R2이 0.91 및 0.93 이상이어서 상당한 신뢰성을 가지고 물성으로부터 역학적 특성을 추정할 수 있음을 보여준다.

본 연구에서는 아스팔트 바인더의 절대점도, 동점도, 침입도, 연화점, PG 고온등급을 이용하여 샌드아스팔트 흔합물의 고속 직접인장강도(DTS1), 저속 직접인장강도(DTS2), 간접인장강도(ITS), 회복탄성계수(MR), 강성지수(SI)를 추정하기 위한 연구를 수행하였다. 여러 가지 혼합물의 특성 중 DTS2가 가장 상관성이 높게 나타났으며 그 다음이 DTS1, ITS, SI, MR 순인 것으로 나타났다. 바인더 성질 중에는 PG 등급이 DTS2와 가장 높은 상관 관계를 보여 PG 고온등급이 높은 바인더를 사용하면 직접인장강도가 어느 정도 우수한 혼합물을 얻을 수 있음을 알 수 있었다. 하지만 각각의 물리적 성질만으로는 신뢰도가 낮아 종합적으로 여러 물성을 이용하여 상관성을 분석하였다. 그 결과 직접 및 간접인장강도는 결정계수가 0.99 이상인 모델을 얻을 수 있었다. 그리고 MR, SI 값의 추정치 모델도 R2이 0.91 및 0.93 이상이어서 상당한 신뢰성을 가지고 물성으로부터 역학적 특성을 추정할 수 있음을 보여준다.

본 연구에서는 원료 석탄 핏치와 흑연화성이 우수한 THF 가용성분만을 추출한 핏치 결합재에 8H/Satin woven fabric 프리프레그 및 고탄성 및 고강도계 연속 탄소섬유 등을 보강하여 가압열성형법으로 green body 를 제조한 다음 탄화, 함침, 재탄화 및 흑연화 공정을 거쳐 열적 미 기계적물성이 우수한 CFRC를 제조하였으며, 주사전자현미경, 편광현미경, X선회절분석,열중량분석, 굴곡강도, 굴곡탄성률, 충간전단강도 등을 시험하였다. THFSP결합재를 2300˚C까지 열처리 한 다음 X선회절분석을 한 결과, 결정성이 가장 우수하여 (002) 면에서 C0/2인 값이 3.380Å였으며, 2θ값도 26.276˚로 천연흑연의 Bragg angle에 거의 접근하였으며 공기산화 반응특성을 시험하기 위하여 등온 열중량분석을 한 결과 2300˚C까지 흑연화 한 THFSP결합재가 산화에 대하여 가장 우수한 저항성을 나타내었다. 섬유용적률이 증가됨에 따라 65~70%까지는 기계적 물성이 중가하는 경향을 보였지만 그이상 섬유가 보강된 CFRC는 결합재의 부족으로 인하여 오히려 기계적 물성이 감소하였다. 또한 굴곡강도 시험후 주사전자현미경으로 파괴 단면을 관찰한 결과 THFSP결합재가 흑연화성이 우수하여 파괴시 결합재가 외력에 대한 흡수가 양호하여 보강재의 파괴를 억제했기 때문에 기계적 물성도 우수하게 나타났다.

본 연구는 건설 디지털 제조를 위한 3D 프린팅 기술 개발을 위하여, 플라이애시 및 고로슬래그 미분말 등의 알칼리 활성화 결합재를 Binder Jetting 3D 프린팅 방식으로 출력하고, 후처리 방법을 통해 출력물의 압축강도를 증진하는 것이다. 진공 펌프 및 규산나트륨-수산화나트륨 복합 수용액을 적용하여 후처리 방법을 검토하였으며, 후처리 용액에 침지한 후 -0.1 MPa 진공 압력으로 처리한 공시체의 압축강도는 11.04 MPa 로써 강도 증진을 확인하였다.

본 연구에서는 저탄소 친환경 콘크리트의 일반적인 원재료로 널리 알려져 있는 플라이애시, 고로슬래그미분말을 혼합하여 알칼리 활성화 결합재를 제작한 후, 양생 조건에 따른 내구성을 파악하고자, 탈형한 시험체를 15 및 25°C의 해수에 양생 시켜 재령 91일까지의 내구 특성을 살펴보았다. 플라이애시와 고로슬래그미분말의 혼합비에 대해서 일부 혼합에 대해서는 재령 28일에 비해 재령 91일에서 흡수율 증가 및 강도 감소를 나타났지만, 그 이외에는 양생 조건에 관계없이 재령에 따라 흡수율 감소 및 강도 증가를 보여주었다.

이 연구에서는 무기계 결합재 비율에 따른 섬유보강 복합재료의 압축 및 인장 특성을 조사하였다. 실험 결과, 무기계 분말 재료를 시멘트의 30 % 대체 혼입할 경우, 압축강도, 인장강도 및 인장변형성능은 각각 93.2 MPa, 6.71 MPa, 및 7.65 %로 나타났다. 이는 시멘트만 사용한 복합재료보다 인장변형성능이 약 2.2배 향상된 결과이다.

최근 화력발전소에서는 순환유동층 연소방식의 발전소가 증가하는 추세이다. 순환유동층 보일러애시는 탈황 효과를 위해 석회석을 첨가함에 따라 애시 중에 포함되는 CaO, SO3성분이 증가하여 일반적인 플라이애시 보다 free-CaO 함량이 높다. 또한 순환유동층 보일러애시는 기존의 플라이애시와 다르게 자기수경성 특성과, 높은 free-CaO함량에 의해 물과 만나면 높은 반응성을 갖는다. 본 연구는 순환유동층 보일러애시의 자기수경성 특성을 이용하여, 시멘트를 대체할 수 있는 비소성 결합재로써 활용 가능성에 대해 분석하였다. 순환유동층 보일러 애시의 함량에 따른 역학적 및 수화특성에 대해 검토하였다. 또한 석고의 종류 및 함유량에 따른 순환유동층 보일러애시 활용 비소성 결합재에 대 한 압축강도 및 미세구조에 미치는 영향을 분석하였다.

This paper presents the mechanical properties of high performance fiber-reinforced concrete composites(HFCC) according to binder replacement rate. the compressive strength and single-axial tensile strength of HFCC were evaluated according to binder replacement rete. As a result of the test, the compression strength decreased as binder replacement rates increased, and B-20 mix properties expressed the most ideal tensile strain-stress curve.

This study was performed an evaluation of compressive strength of NSB mortar according to BP contents and curing conditions. As the results of study, compressive strength increase as BP content and curing temperature was increased. When considering the strength properties of BP NSB mortar, the proper BP content and curing temperature are thought to be 20% and 60℃ respectively.

Even though cement a major foundational ingredient in modern architecture, it is known to destroy the environment due to its high energy consumption and how its production releases large amounts of carbon dioxide. To address this situation, the cement industry has proceeded to study how to reduce the amount of CO2 released and has recently started developing unused non-sintered cement. Inaddition, studies are in active development for cement that has not gone through the burning process. If it is possible to make cement using blast furnace slag and industry outgrowth without the use of clinker, it can be expected to help when running out of limestone and to mitigate the pollution problem through CO2 emissions. This study apprehended the measurement of kinematical characteristics through measuring polymer nonsintered cement flexural and compressive strength and analyzing the pH · Cl− Penetration Depth characteristic, through the SEM test also analyzes the reaction of the hydration mechanism, the result of decrementing the water/cement ratio, and entrained air contents from the mixing of polymer, and conducts that durability test for the absorption rate and carbonation experiments. The results of experimentation show excellent chemical and mechanical properties compared to ordinary Portland cement.

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.