Experimental analysis on rheological properties for control of concrete extrudability

Lee, Hojae,Kim, Jang-Ho Jay,Moon, Jae-Heum,Kim, Won-Woo,Seo, Eun-A Techno-Press 2020 Advances in concrete construction Vol.9 No.1

In this study, we examined the relationship among the rheological properties, workability, and extrudability in the construction of concrete structures using additive manufacturing. We altered the component materials (binder type, water-binder (W/B) ratio, sand ratio) to assess their effect on the rheological properties experimentally. The results indicated that the W/B and sand ratios had the largest effect on the rheological properties. In particular, when the sand ratio increased, it indicated that adjusting the sand ratio would facilitate control over the rheological properties. Additionally, we compared the rheological properties with the results of a traditional workability evaluation, namely the table flow test. This indicated the possibility of inferring the rheological properties by using traditional methods. Finally, we evaluated extrusion quantity according to table flow. The extrusion rate was 350 g/s for a flow of 210 mm and 170 g/s for a flow of 130 mm, indicating that extrusion rate increased as flow increased; however, we concluded that a flow standard of approximately 140-160 mm is suitable for controlling the actual extrusion quantity and rate.

Assessment of Rheological and Piezoresistive Properties of Graphene based Cement Composites

Sardar Kashif Ur Rehman,Zainah Ibrahim,Mohammad Jameel,Shazim Ali Memon,Muhammad Faisal Javed,Muhammad Aslam,Kashif Mehmood,Sohaib Nazar 한국콘크리트학회 2018 International Journal of Concrete Structures and M Vol.12 No.6

The concrete production processes including materials mixing, pumping, transportation, injection, pouring, moulding and compaction, are dependent on the rheological properties. Hence, in this research, the rheological properties of fresh cement paste with different content of graphene (0.03, 0.05 and 0.10% by weight of cement) were investigated. The parameters considered were test geometries (concentric cylinders and parallel plates), shear rate range (300–0.6, 200–0.6 and 100–0.6 s<SUP>−1</SUP>), resting time (0, 30 and 60 min) and superplasticizer dosage (0 and 0.1% by weight of cement). Four rheological prediction models such as Modified Bingham, Herschel–Bulkley, Bingham model and Casson model were chosen for the estimation of the yield stress, plastic viscosity and trend of the flow curves. The effectiveness of these rheological models in predicting the flow properties of cement paste was verified by considering the standard error method. Test results showed that the yield stress and the plastic viscosity increased with the increase in graphene content and resting time while the yield stress and the plastic viscosity decreased with the increase in the dosage of superplasticizer. At higher shear rate range, the yield stress increased while the plastic viscosities decreased. The Herschel–Bulkley model with the lowest average standard error and standard deviation value was found to best fit the experimental data, whereas, Casson model was found to be the most unfitted model. Graphene reduces the flow diameter and electrical resistivity up to 9.3 and 67.8% and enhances load carrying capacity and strain up to 16.7 and 70.1% of the composite specimen as compared with plain cement specimen. Moreover, it opened a new dimension for graphene-cement composite as smart sensing building construction material.

Rheological properties of hydrogen fermented food waste

Kim, Min-Gyun,Sivagurunathan, Periyasamy,Lee, Mo-Kwon,Im, Seongwon,Shin, Sang-Ryong,Choi, Chang-Su,Kim, Dong-Hoon Elsevier 2019 International journal of hydrogen energy Vol.44 No.4

<P><B>Abstract</B></P> <P>Although rheological properties are essential in scaling up fermenters, there has been no report on hydrogen fermentation of organic solid wastes. In the present work, hydrogen fermentation of food waste (FW) was conducted at various substrate concentrations (10–50 g Carbo. COD/L) and operational pHs (4.5–6.5), and rheological properties were attained. High hydrogen production performance showing over 1.7 mol H<SUB>2</SUB>/mol hexose<SUB>added</SUB> was achieved at 10–40 g Carbo. COD/L and pH 5.5 and 6.0. The viscosity tended to increase with substrate concentration increase, and fermentation led to a significant reduction of viscosity. Before fermentation, zero viscosity and infinite viscosity of FW ranged 6.8–1274.1 mPa s and 2.2–58.1 mPa s, which were reduced to 10.4–346.2 mPa s and 1.1–5.3 mPa s after fermentation, respectively. Compared to substrate concentration, operational pH showed a less effect on rheological properties. At the similar volatile solids concentration range, hydrogen-fermented FW showed lower values of rheological properties than that of anaerobic digester sludge. Based on the agitation speed values assuring turbulent condition (complete mixing), the energy required for agitation can be reduced by 30–67% by lowering the applied agitation speed with fermentation time.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Shear thinning behaviour was found in all H<SUB>2</SUB>-fermented FW. </LI> <LI> Hydrogen fermentation led to a significant reduction of viscosity. </LI> <LI> Compared to substrate concentration, operational pH showed a little effect on rheological properties. </LI> <LI> H<SUB>2</SUB>-fermented FW showed lower rheological property values than those of digester sludge. </LI> <LI> Energy saving by 30–67% by slowing down the agitation speed with time. </LI> </UL> </P>

Rheological and electrical properties of polystyrene nanocomposites via incorporation of polymer-wrapped carbon nanotubes

박재상,안지훈,장건수,이성재 한국유변학회 2019 Korea-Australia rheology journal Vol.31 No.2

Carbon nanotubes (CNTs) are used as nanofillers in polymer nanocomposites to improve the properties of a matrix polymer because of their excellent properties. However, CNTs tend to aggregate due to the strong van der Waals force between CNTs. To solve the problem, surface-modified CNTs with hydrophilic polymers, such as polyvinyl pyrrolidone (PVP) and polystyrene sulfonate (PSS), were employed. Polystyrene (PS)/CNT nanocomposites were fabricated by latex technology, which is a suitable method for dispersing nanofillers in aqueous particle suspension. The effect of the incorporation of the modified CNT was significant, thereby resulting in increased modulus at lower frequencies when compared to that of neat PS. Electrical percolation thresholds of PS/PSS-wrapped CNT and PS/PVP-wrapped CNT nanocomposites corresponded to 0.39 and 0.52 wt.%, respectively. The PS/PSS-CNT nanocomposites exhibited higher rheological and electrical properties than the PS/PVP-CNT counterparts due to the hydrophilic nature of PSS with strong negative charge groups.

Trehalose가 빵용 반죽의 Rheology 특성에 미치는 영향

김영자(Young-Ja Kim),이정훈(Jeong-Hoon Lee),정구춘(Koo-Chun Chung),이시경(Si-Kyung Lee) 한국식품과학회 2014 한국식품과학회지 Vol.46 No.3

Trehalose가 밀가루 반죽의 rheology에 미치는 영향을 평가하기 위하여 밀가루 대비 설탕을 6% 첨가한 것을 대조구로 하여 trehalose를 각각 2, 4, 6% 첨가하여 farinograph, viscograph, 반죽의 pH 및 총산도, 반죽의 발효팽창력 등을 분석하였다. Farinograph 분석에서 trehalose 첨가량이 증가함에 따라 반죽의 견도와 반죽형성시간은 증가하였으나, 흡수율, 안정도, 약화도, FQN 등은 감소하였다. Viscograph 분석에서 trehalose 첨가가 호화개시온도, 최고점도온도에는 영향을 주지 못하였으나, 최고점도는 trehalose 6% 첨가구에서 가장 낮았다. Trehalose 첨가량이 증가할수록 최종점도, breakdown, setback 등은 감소하였다. 120분 발효 동안 반죽의 pH 변화는 trehalose 4% 첨가구가 가장 낮았고, 반죽의 총산도는 trehalose 4% 첨가구가 가장 높았다. 반죽의 발효팽창력도 trehalose 4% 첨가구가 다른 시험구에 비해 큰 부피를 나타냈다. 이상과 같이 trehalose 첨가량을 달리한 실험에서 trehalose의 첨가는 빵용 밀가루 반죽의 rheology 특성에 영향을 주어 빵 제조에 첨가 시 빵의 부피가 크고, 부드럽고, 노화가 지연될 것으로 생각된다. This study was conducted to evaluate the effect of trehalose on the rheological properties of bread flour dough. Farinographic and viscographic properties, pH, total titratable acidity (TTA), and fermentation power were analyzed for flour dough rheology. Flour dough containing trehalose showed greater water absorption capacity and longer development time. However the stability, degree of softening, and farinograph quality number (FQN) were lower for the trehalosecontaining flour dough, however, these factors decreased with increasing amounts of trehalose. Trehalose did not affect the beginning of gelatinization temperature and maximum viscosity temperature of flour. The maximum viscosity was the lowest with 6% trehalose, the end of final holding period, breakdown and setback values decreased with increasing amounts of trehalose. Flour dough with 4% trehalose had the lowest pH value for 120 min fermentation at 30℃, and the highest TTA value. Addition of 4% and 6% trehalose showed larger fermentation volume of dough than the control. The results suggested that trehalose positively affected the rheological properties of flour dough such as bread volume, softness, and staling delay.

볶은 쌀겨를 첨가한 밀가루 반죽의 rheology 특성

신현광,이정훈,정구춘,이시경 한국식품과학회 2018 한국식품과학회지 Vol.50 No.6

This study was carried out to investigate the effect of roasted rice bran (RRB) on the rheological properties of bread dough. According to farinograph analysis, the consistency of the control sample was greatest. There were no significant differences in water absorption (p<0.05). Lower values of development time, stability, and time to breakdown, which were affected, by the addition of RRB, were observed for RRB-containing dough samples, compared to the control dough sample. Addition of RRB significantly increased the mixing tolerance index (MTI). According to rheofermentometer analysis, the values of H'm, T'1, and retention volume decreased with increase in the amount of RRB added. According to the rapid visco analyzer (RVA) analysis, peak viscosity, holding strength, and setback values were greater in the control than in the RRB-containing samples. The addition of RRB to the flour influenced rheological properties like fermentation volume and acidity. The total acidity increased with the increase in the amount of RRB added. The present study has indicated that there was no significant difference between the rheological properties of the control and 5% RRB-containing dough samples. Therefore, the addition of 5% RRB could be an effective way to produce functional flour bread without affecting its desirable physical properties.

Compatibility of biodegradable poly (lactic acid) (PLA) and poly (butylene succinate) (PBS) blends for packaging application

Bhatia, Amita,Gupta, Rahul K.,Bhattacharya, Sati. N.,Choi, H.J. The Korean Society of Rheology 2007 Korea-Australia rheology journal Vol.19 No.3

Biodegradable polymeric blends are expected to be widely used by industry due to their environmental friendliness and comparable mechanical and thermal properties. Poly (lactic acid) (PLA) and poly (butylene succinate) (PBS) are such biodegradable polymers which aim to replace commodity polymers in future applications. Since cost and brittleness of PLA is quite high, it is not economically feasible to use it alone for day to day use as a packaging material without blending. In this study, blends of PLA and PBS with various compositions were prepared by using a laboratory-scale twin-screw extruder at $180^{\circ}C$. Morphological, thermal, rheological and mechanical properties were investigated on the samples obtained by compression molding to explore suitability of these compositions for packaging applications. Morphology of the blends was investigated by scanning electron microscopy (SEM). Morphology showed a clear phase difference trend depending on blend composition. Modulated differential scanning calorimetry (MDSC) thermograms of the blends indicated that the glass transition temperature ($T_g$) of PLA did not change much with the addition of PBS, but analysis showed that for PLA/PBS blend of up to 80/20 composition there is partial miscibility between the two polymers. The tensile strength and modulus were measured by the Instron Universal Testing Machine. Tensile strength, modulus and percentage (%) elongation at break of the blends decreased with PBS content. However, tensile strength and modulus values of PLA/PBS blend for up to 80/20 composition nearly follow the mixing rule. Rheological results also show miscibility between the two polymers for PBS composition less than 20% by weight. PBS reduced the brittleness of PLA, thus making it a contender to replace plastics for packaging applications. This work found a partial miscibility between PBS and PLA by investigating thermal, mechanical and morphological properties.

Emulsion rheology and properties of polymerized high internal phase emulsions

Lee, Seong-Jae The Korean Society of Rheology 2006 Korea-Australia rheology journal Vol.18 No.4

High internal phase emulsions are highly concentrated emulsion systems consisting of a large volume of dispersed phase above 0.74. The rheological properties of high internal phase water-in-oil emulsions were measured conducting steady shear, oscillatory shear and creep/recovery experiments. It was found that the yield stress is inversely proportional to the drop size with the exponent of values between 1 and 2. Since the oil phase contains monomeric species, microcellular foams can easily be prepared from high internal phase emulsions. In this study, the microcellular foams combining a couple of thickeners into the conventional formulation of styrene and water system were investigated to understand the effect of viscosity ratio on cell size. Cell size variation on thickener concentration could be explained by a dimensional analysis between the capillary number and the viscosity ratio. Compression properties of foam are important end use properties in many practical applications. Crush strength and Young's modulus of microcellular foams polymerized from high internal phase emulsions were measured and compared from compression tests. Of the foams tested in this study, the foam prepared from the organoclay having reactive group as an oil phase thickener showed outstanding compression properties.

보습제의 종류와 pH에 따른 피부 각질층의 팽윤 및 레올로지 특성에 관한 연구

박승환 ( Seung Hwan Park ),하병조 ( Byung Jo Ha ) 대한미용학회 2010 대한미용학회지 Vol.6 No.4

Skin is the largest organ of the body as determined by its wet weight or by its surface area. The swelling and rheological properties are very important factor in human dermatology. It is known that a relationship exists between the swelling and rheological property. Female pig skin 45~50 g were kept under conventional laboratory conditions. Dorsal hairs, over an area of approximately 8 cm2, were shaved with electric clipper 1 day prior to the experiment. Crude sample of pig Stratum Corneum (SC) was prepared with 0.1 M tris buffer pH 7.2 (2 M urea, 0.5% trypsin) solution (78 hr) at 37℃. The sample was further purified from n-hexane during 5 hr. The sample pieces (1.5 mm×15 mm) of pig SC were weighted and immersed in the appropriate test solution and reweighed after the immersion to estimate the extent of swelling of the sample in each pH controlled solutions. Moisture contents for pig SC were measured under various humidity conditions. The mechanical properties of pig SC were also estimated by rheometer. The results showed the acidic pH solution gives the pig SC its toughness, an important mechanical property primarily attributable to the intra- and intermolecular interactions of keratin molecules. At pH 3~5, keratin molecules were considered to be oppositely charged and electrostatically bound to each other. Above pH 7, the swelling of pig SC was ascribed to the deionization of the amino groups, which would break the electrostatic linkage between the two functional groups and make the protein chains negatively charged. However, to clarify the swelling and rheological mechanism of the human SC, further study is needed with quantitative investigation on the charge density of the keratin molecule and the distribution of ionic species between keratin molecule and the ambient solution.

Emulsion rheology and properties of polymerized high internal phase emulsions

이성재 한국유변학회 2006 Korea-Australia rheology journal Vol.18 No.4

High internal phase emulsions are highly concentrated emulsion systems consisting of a large volume of dispersed phase above 0.74. The rheological properties of high internal phase water-in-oil emulsions were measured conducting steady shear, oscillatory shear and creep/recovery experiments. It was found that the yield stress is inversely proportional to the drop size with the exponent of values between 1 and 2. Since the oil phase contains monomeric species, microcellular foams can easily be prepared from high internal phase emulsions. In this study, the microcellular foams combining a couple of thickeners into the conventional formulation of styrene and water system were investigated to understand the effect of viscosity ratio on cell size. Cell size variation on thickener concentration could be explained by a dimensional analysis between the capillary number and the viscosity ratio. Compression properties of foam are important end use properties in many practical applications. Crush strength and Young's modulus of microcellular foams polymerized from high internal phase emulsions were measured and compared from compression tests. Of the foams tested in this study, the foam prepared from the organoclay having reactive group as an oil phase thickener showed outstanding compression properties.