• International Journal of Concrete Structures and Materials
• /
• 제10권4호
• /
• pp.539-553
• /
• 2016

Polymer concrete (PC) has been favoured over Portland cement concrete when low permeability, high adhesion, and/or high durability against aggressive environments are required. In this research, a new class of PC incorporating Multi-Walled Carbon Nanotubes (MWCNTs) is introduced. Four PC mixes with different MWCNTs contents were examined. MWCNTs were carefully dispersed in epoxy resin and then mixed with the hardener and aggregate to produce PC. The impact strength of the new PC was investigated by performing low-velocity impact tests. Other mechanical properties of the new PC including compressive, flexural, and shear strengths were also characterized. Moreover, microstructural characterization using scanning electron microscope and Fourier transform infrared spectroscopy of PC incorporating MWCNTs was performed. Impact test results showed that energy absorption of PC with 1.0 wt% MWCNTs by weight of epoxy resin was significantly improved by 36 % compared with conventional PC. Microstructural analysis demonstrated evidence that MWCNTs significantly altered the chemical structure of epoxy matrix. The changes in the microstructure lead to improvements in the impact resistance of PC, which would benefit the design of various PC structural elements.

• Composites Research
• /
• 제36권2호
• /
• pp.86-91
• /
• 2023

Thermoplastic polyurethane (TPU) is a material whose mechanical properties change according to the phase separation of its unique internal microstructure and is therefore used in various industries. Use of TPU as composites helps in improving the desirable characteristics and properties in accordance with usage. Eco-friendly fillers one of the fillers are on the rise and those are mostly used for reinforcing role. Suberin, which can be extracted from cork, is the main component of cork. It is known to serve high damping property of elastomer composite. The original chemical structure of Suberin is an aliphatic polyester aggregate. In this research, Suberin is obtained after depolymerization into an oligomer having 2 or 3 ester bonds through alkaline hydrolysis. The extracted suberin was added to the matrix which is thermoplastic polyurethane as an eco-friendly filler for improving vibration damping property. As a result, when 10 wt% of suberin was added into thermoplastic polyurethane the existing trade-off relationship was overcome. And it is attained the elastic modulus and damping factor at room temperature improving 92 and 59%, respectively, compared to the original matrix. Those results are from the interaction between the microstructure of TPU and suberin.

• 한국농공학회논문집
• /
• 제49권4호
• /
• pp.51-59
• /
• 2007

Recently, concrete has been made porous and used for sound absorption, water permeation, vegetation and water purification according to void characteristics. Many studies are carried out on the utilization of sewage sludge, fly ash and waste concrete to reduce the environmental load. This study was performed to evaluate the void, strength, relationship between void and strength, permeability and chemical resistance properties of porous polymer concrete for pavement with different fillers. An unsaturated polyester resin was used as a binder, crushed stone and natural sand were used as an aggregate and bottom ash, fly ash and blast furnace slag were used as fillers. The mix proportions were determined to satisfy the requirement for the permeability coefficient, $1{\times}10^{-2}$ cm/s for general permeable cement concrete pavement in Korea. The void ratios of porous polymer concrete with fillers were in the range of $18{\sim}23%$. The compressive strength and flexural load of porous polymer concrete with fillers were in the range of $19{\sim}22$ MPa and $18{\sim}24$ KN, respectively. The permeability coefficients of porous polymer concrete with fillers were in the range of $5.5{\times}10^{-1}{\sim}9.7{\times}10^{-2}$ cm/s. At the sulfuric acid resistance, the weight reduction ratios of porous polymer concrete immersed during 8-week in 5% $H_{2}SO_{4}$ were in the range of $1.08{\sim}3.56%$.

• 한국건축시공학회지
• /
• 제22권6호
• /
• pp.543-551
• /
• 2022

폴리머 혼입 모르타르를 대상으로 폴리머 혼입률에 따른 실험체의 역학적 성능 및 진동감쇠비 성능 평가를 실시하였다. 폴리머로서는 Styrene Butadiene Rubber(SBR) 고형분이 약 49~51%인 액상형 폴리머를 사용하였으며, 5%씩 액상 폴리머 함량을 증가시켰으며, 고형분 기준으로 약 2.5%씩 증가하였다. 실험체는 40×40×160(mm)로써 경화 후에 압축강도, 휨강도, 초음파펄스법을 통해 진동감쇠비를 측정하였다. 그 결과, 폴리머 혼입률이 증가함에 따라 압축강도는 감소하나 휨강도는 증가하였으며, 진동감쇠비는 폴리머 고형분 2.5% 첨가에서 11% 증가, 폴리머 고형분 5%에서 28% 증가, 폴리머 고형분 7.5%에서 33% 증가, 폴리머 고형분 10%에서 72%로 급격히 증가하여 모르타르의 진동 저감을 위하여 폴리머의 혼입이 매우 유효함을 알 수 있었다. 또한, SEM 및 SEM-EDS 분석을 통하여, 폴리머 혼입에 의한 진동 저감의 원인은 골재의 천이대 및 내부 공극에 형성된 폴리머 막이 모르타르의 진동을 내부에서 완충시킨 것으로 판단된다. 이를 종합하면, 본 연구의 범위에서 모르타르의 진동 저감을 위한 적정 폴리머 혼입 비율은 고형분 기준 약 7.5% 정도로 판단된다.

• 한국전산구조공학회논문집
• /
• 제24권1호
• /
• pp.43-53
• /
• 2011

철근 콘크리트 부재에서 부착강도는 콘크리트와 보강근 사이에 중요한 요소 중 하나이다. 본 실험에서는 인공경량골재를 사용한 경량콘크리트와 이형철근의 부착강도의 특성을 확인하기 위하여 인발실험을 수행하였다. 콘크리트의 압축강도, 이형철근의 직경과 묻힘길이를 변수로 하는 144개의 인발실험 시험체가 사용되었다. 보통콘크리트와의 비교를 위하여 물/시멘트 비 50%의 보통콘크리트의 인발실험을 수행하였으며, 실험을 통해서 부착응력-미끌림 관계와 파괴형상을 평가하였다. 물/시멘트 비에 따른 콘크리트의 압축강도가 증가할수록 부착강도는 증가하였다. 또한 인발실험을 토대로 회귀분석을 실시하여 경량 콘크리트의 부착응력에 대한 산정식을 제안하였다.

• 한국도로학회논문집
• /
• 제17권6호
• /
• pp.47-54
• /
• 2015

PURPOSES : The objective of this study is to evaluate the early adhesive characteristic of asphalt emulsions, including polymer-modified emulsions, for chip seals using the surface energy concept, the bitumen bond strength (BBS) test, and the Vialit test. METHODS : Two general methods, the BBS test and Vialit test, were applied to investigate the bond strength and the aggregate loss, respectively. A new theory, the surface free energy (SFE) theory, was used to evaluate the adhesive characteristic between the emulsion and the aggregate. Based on the theory, the contact angles were measured, and then the surface energy components were calculated. Using those components, the work of adhesion (Wa) was calculated for each emulsion. To ensure reliable results, all the tests were performed under the same conditions, i.e., at $25^{\circ}C$ for 240 minutes of curing time. For the materials, three emulsions (CRS-2, CRS-2L, and CRS-2P) and one aggregate type (granite) were employed. RESULTS AND CONCLUSIONS : Under the same conditions, the modified emulsions showed better adhesive characteristics and curing behaviors than the unmodified emulsions. In addition, there was no significant difference between the various modified emulsions. One of the important findings is that the analysis by Wa presents more sensitive results than other methods. The results of the Wa showed that the CRS-2P emulsion has the best adhesive characteristics. Consequently, the use of modified emulsions for chip seals could prevent aggregate loss and allow open traffic earlier.

• 한국생물공학회:학술대회논문집
• /
• 한국생물공학회 2000년도 춘계학술발표대회
• /
• pp.541-545
• /
• 2000

For the sustained release formulation of recombinant human growth hormone (rhGH), dissociable rhGH aggregates were microencapsulated within poly(D,L-lactic-co-glycolic acid) [PLGA] microparticles. rhGH aggregates with 2 - 3 m Particle diameter were first produced by adding a small volume of aqueous rhGH solution into a partially water miscible organic solvent phase(ethyl acetate) containing PLGA. These rhGH aggregates were then microencapsulated within PLGA polymer phase by extracting ethyl acetate into an aqueous phase pre-saturated with ethyl acetate. The resultant microparticles were 2 - 3 m in diameter similar to the size of rhGH aggregates, suggesting that PLGA polymer was coated around the protein aggregates. Release profiles of rhGH from these microparticles were greatly affected by changing the volume of the incubation medium. The release rhGH species consisted of mostly monomeric form with having a correct conformation. This study reveals that sustained rhGH release could be achieved by microencapsulating reversibly dissociable protein aggregates within biodegradable polymers.

• 한국농공학회지
• /
• 제39권4호
• /
• pp.75-81
• /
• 1997

This study was performed to evaluate the engineering properties of surlightweight polymer concrete using synthetic lightweight aggregate. The following conclusions were drawn; 1. The unit weight was in the range of 0.849~0.969t/$m^3$, the unit weights of those concrete were decreased by 58 ~ 63% than that of the normal cement concrete. 2. The highest strength was achieved by $P_1$, and compressive strength was increased by 93% and bending strength by 364% than that of the normal cement concrete, respectively. 3. The ultrasonic pulse velocity was in the range of 2, 346~2, 702m/s, which was low compared to that of the normal cement concrete. 4. The dynamic modulus of elasticity was in the range of $1.561{\times} 10{^5}~1.916{\times} 10{^5}kgf/cm^2$, which was approximately 52~98% of that of the normal cement concrete. 5. The compressive and bending strength were increased with the increase of unit weight. But, the dynamic modulus of elasticity and ultrasonic pulse velocity were decreased with the increase of unit weight.

• 한국고분자학회:학술대회논문집
• /
• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
• /
• pp.297-297
• /
• 2006

Recently columnar liquid crystals have been studied due to their possible application to organic conducting materials. Supramolecular columnar liquid crystals consist of mesogenic unit which can aggregate into discs that will make up the columns which associate to form a two-dimensional network. In this study, we prepared supramolecular columnar liquid crystals containing hydrogen bonding between carboxylic acid and, pyridine moieties. Thermal and structural properties of prepared complexe were investigated, and it exhibited hexagonal columnar structure ($Col_{h}$) at room temperature.

• 한국도로학회논문집
• /
• 제16권5호
• /
• pp.1-8
• /
• 2014

PURPOSES : The objective of this study is to evaluate the bond strength of asphalt emulsions including polymer-modified emulsions for chip seals and fog seals using the bitumen bond strength (BBS) test. METHODS : For the laboratory testing, the Pneumatic Adhesion tensile Testing Instrument(PATTI) device is used to measure the bond strength between the asphalt emulsion and aggregate substrate based on the AASHTO TP-91. In order to conduct all the tests in controled condition, all test procedures are performed in the environmental chamber. The CRS-2L and the SBS CRS-2P emulsions are used as a polymer-modified emulsion, and then unmodified emulsion, the CRS-2, is compared for the evaluation of chip seal performance. For the fog seal performance evaluation, two types of polymer-modified emulsions and one of unmodified emulsion, the CSS-1H, are employed. For chip seal study, the BBS tests are performed at 30, 60, 120, and 240 minutes of curing times with curing and testing temperatures of $15^{\circ}C$, $25^{\circ}C$, and $35^{\circ}C$. The fog seal tests are conducted at 30, 60, 90, 120, 180 minutes, and 24 hours with curing and testing temperatures of $25^{\circ}C$, $30^{\circ}C$, and $35^{\circ}C$. RESULTS AND CONCLUSIONS : Overall, chip seal emulsions and fog seal emulsions show the similar bond strength trend. At the same testing condition, polymer-modified emulsions show better bond strength than unmodified emulsions. Also, there is no significant difference between polymer-modified emulsions. One of important findings is that the most bond strength reaches their final bond strength within one hour of curing time. Therefore, the early curing time plays a vital role in the performance of chip seals and fog seals.