Influences of Micropowder Gradation on Rheological Properties of Cement-Based Composite Pastes

2007 ◽  
Vol 353-358 ◽  
pp. 1398-1401
Author(s):  
Jian Qing Gong ◽  
Han Ning Xiao ◽  
Zheng Yu Huang ◽  
Jiu Su Li ◽  
Jing Nie ◽  
...  
Keyword(s):  
Shear Stress ◽  
Rheological Properties ◽  
Packing Density ◽  
High Performance ◽  
High Performance Concrete ◽  
Plastic Viscosity ◽  
Rheological Parameters ◽  
Ultra High Performance Concrete ◽  
Cement Pastes ◽  
Compressible Packing Model

The rheological parameters of cement pastes were investigated by varying the type and content of micropowders and the ratio of water to binder. Compressible packing model was used to calculate the packing density and to evaluate the influence of micropowders gradation on the rheological properties of fresh cement pastes. Results indicate that the higher the packing density is, the lower the yielding shear stress and plastic viscosity will be. When the ratio of water to binder is less than 0.20, the cement paste with 15% UFA and 15% SF has highest packing density and lowest yielding shear stress and plastic viscosity, which is beneficial to the workability of ultra-high performance concrete.

scholarly journals Rheological Properties of Cement Pastes with Multiwalled Carbon Nanotubes

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Gintautas Skripkiunas ◽  
Ekaterina Karpova ◽  
Irmantas Barauskas ◽  
Joana Bendoraitiene ◽  
Grigory Yakovlev
Keyword(s):  
Carbon Nanotubes ◽  
Rheological Properties ◽  
Yield Stress ◽  
Multiwalled Carbon Nanotubes ◽  
High Performance ◽  
High Performance Concrete ◽  
Plastic Viscosity ◽  
Multiwalled Carbon ◽  
Cement Pastes ◽  
Rheological Test

The evaluation of rheological properties of cement systems is getting more relevant with growing interest to self-consolidating concrete (SCC), high-performance concrete (HPC) and ultrahigh-performance concrete (UHPC). The rheology models are a perspective tool to predict and manage the properties of cement systems in the fresh and hardened state. The current research is focused on the rheological test of cement systems modified by multiwalled carbon nanotubes (MWCNT) dispersion with and without polycarboxylate ether (PCE). The content of dispersion with 1% concentration of MWCNT in cement pastes varied from 0.125 to 0.5% by weight of cement. The dosage of PCE was taken as 0.6% by weight of cement. The cement pastes were prepared based on Portland cement without mineral additives. The rheological test was carried out at 5, 30, 60, and 120 min after mixing of cement paste. The rheological test established that modification of cement pastes by MWCNT dispersion in dosage 0.25% leads to the decrease of yield stress by 30.7% and increase of plastic viscosity by 29.6%. The combined modification by PCE and MWCNT dispersion shows the decrease in plastic viscosity of cement pastes by 9.90% in dosage of MWCNT equal to 0.5% by weight of cement, reduction of water demand by 20% for the same workability, and decrease of yield stress till 0 Pa. It gives the ability to obtain the self-compacting mixtures. The cement pastes with and without MWCNT dispersion revealed the shear-thinning behavior during 120 min after mixing. The modification of cement pastes by PCE with and without MWCNT dispersion showed the shear-thickening behavior which remains during 120 min after mixing.

Influence of Glass Powder on Rheological Properties of Ultra-High Performance Concrete Paste

2021 ◽  
Vol 1036 ◽  
pp. 419-431
Author(s):  
Xue Li Nan ◽  
Jian Rui Ji ◽  
Rong Yang Li ◽  
Yi Wang ◽  
Hao Chen ◽  
...  
Keyword(s):  
Rheological Properties ◽  
Yield Stress ◽  
Silica Fume ◽  
High Performance ◽  
Glass Powder ◽  
High Performance Concrete ◽  
Shear Thickening ◽  
Plastic Viscosity ◽  
Ecological Problem ◽  
Ultra High Performance Concrete

Replacing cement and silica fume with glass powder to prepare ultra-high performance concrete (UHPC) is beneficial to solve the ecological problem in the field of civil engineering, but the technologies of preparation, transportation, pumping, and hardening of UHPC mainly relate to its rheological property. Therefore, this paper studied the influence of glass powder on the rheological properties of UHPC paste by performing the flow and the rheological test. Experimental results showed that when the cement and silica fume partially replaced by glass powder, the UHPC paste appears shear thickening, yield stress, plastic viscosity, and area of hysteresis loop decrease. This means that mixing glass powder can somehow inhibit the problems of segregation and bleeding of UHPC during pumping. In this manner, the dosage of the superplasticizer in UHPC is appropriately reduced, the filling capacity of UHPC during pouring is improved, and the energy required for UHPC in the pumping process is weakened. Compared with replacing cement, replacing silica fume with glass powder significantly increases the shear thickening and fluidity of UHPC paste, and at the same, reduces its yield stress and plastic viscosity. This indicates that the construction performance of UHPC is greatly improved with the replacement of silica fume. The fluidity and yield stress of UHPC paste satisfy the quadratic polynomial function relationship, and the replacement of cement and silica fume with glass powder should be less than 33% and 50%, respectively. Under this condition, the rheological properties of the UHPC paste are greatly improved and result in little negative impact on the mechanical properties of UHPC.

Optimized design of ultra-high performance concrete (UHPC) with a high wet packing density

2019 ◽  
Vol 126 ◽  
pp. 105921 ◽  
Author(s):  
Xinpeng Wang ◽  
Rui Yu ◽  
Qiulei Song ◽  
Zhonghe Shui ◽  
Zhen Liu ◽  
...  
Keyword(s):  
Packing Density ◽  
High Performance ◽  
High Performance Concrete ◽  
Optimized Design ◽  
Ultra High Performance Concrete

scholarly journals CRITERIONAL FEATURES OF STRUCTURAL CHARACTERISTICS OF FINE TEXTILE MEAT

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
М. П. Сичевський ◽  
Л Войцехівська ◽  
К В Копилова ◽  
C Б Вербицький ◽  
Ю І Охріменко
Keyword(s):  
Shear Stress ◽  
Rheological Properties ◽  
Maximum Shear Stress ◽  
Fat Content ◽  
Plastic Viscosity ◽  
Poultry Meat ◽  
Rheological Parameters ◽  
Limit Values ◽  
Mechanically Separated Meat ◽  
Minced Meat

Poultry meat mechanically separated from broiler carcasses and compared with minced meat from manual deboning was studied. It has been found that an increase in the free moisture content of mechanically separated meat by 10-15% causes a reduction in shear characteristics by almost 2 times. The shear stress values ​​in hand-rolled meat samples were, on average, 1.3 times higher than in physico-chemically similar samples of mechanically separated meat. The samples of hand-rolled meat differed by 1.4 times the values ​​of plastic viscosity, as well as larger, on average 1.5 times, the values ​​of the coefficient of consistency. A set of rheological parameters and their limit values, close to the characteristics of minced meat from manual deboning, namely: the maximum shear stress (penetration) - from 1.9 kPa to 2.2 kPa; plastic viscosity - from 33 Pa • s to 45 Pa • s; coefficient of consistency - from 1.4 to 1.7. It has been established that the most important factors influencing the difference between the rheological parameters of mechanically separated meat and hand-rolled meat are the fat content and the degree of grinding. The reduction of fat content, processing pressure, as well as the speed of grinding of raw materials allows to bring the rheological characteristics of mechanically separated meat to the characteristics of manual deboning meat. The nature of the change in the rheological properties of meat mechanically separated over time is revealed: during the first stage (lasts about 2-3 hours) the structure remains unchanged, the second stage is the period of growth of all indicators to the maximum value, this is the period of critical aging. Further aging (third period) is characterized by a decrease in the numerical values ​​of all indicators, due to a decrease in the strength of the structure under the action of a complex of microbiological and biochemical processes. The study of the rheological properties of mechanically separated meat of broiler chickens and the comparison of the obtained indicators with the corresponding characteristics of minced meat formed by mincing hand-rolled meat, gave grounds for concluding on the possibility and expediency of mechanically separated meat in meat products.

scholarly journals Influence of high volumes of silica fume on the rheological behavior of oil well cement pastes

2021 ◽  
Author(s):  
Jedadiah Burroughs ◽  
Jason Weiss ◽  
John Haddock
Keyword(s):  
Silica Fume ◽  
Rheological Behavior ◽  
High Performance ◽  
High Performance Concrete ◽  
Oil Well ◽  
Ultra High Performance Concrete ◽  
Conventional Concrete ◽  
Cement Pastes ◽  
Specific Source ◽  
Well Cement

Specialized classes of concrete, such as ultra-high-performance concrete, use volumes of silica fume in concrete that are higher than those in conventional concrete, resulting in increased water demand and mixing difficulty. This study considered the effects of eight different silica fumes in three dosages (10%, 20%, 30%) with three w/b (0.20, 0.30, 0.45) on rheological behavior as characterized by the Herschel-Bulkley model. Results indicated that the specific source of silica fume used, in addition to dosage and w/b, had a significant effect on the rheological behavior. As such, all silica fumes cannot be treated as equivalent or be directly substituted one for another without modification of the mixture proportion. The rheology of cement pastes is significantly affected by the physical properties of silica fume more so than any chemical effects.

scholarly journals Experimental Study on Bond Stress between Ultra High Performance Concrete and Steel Reinforcement

2018 ◽  
Vol 3 (12) ◽  
pp. 1235 ◽  
Author(s):  
Ahad Amini Pishro ◽  
Xiong Feng
Keyword(s):  
Mechanical Properties ◽  
Shear Stress ◽  
High Performance ◽  
High Performance Concrete ◽  
Longitudinal Shear ◽  
Steel Reinforcement ◽  
Bond Stress ◽  
Axial Deformation ◽  
Ultra High Performance Concrete ◽  
Cement Based Materials

Due to axial deformations generally caused by flexure, shear stress will be generated across the interface between reinforcement and surrounding concrete. This longitudinal shear stress is called bond stress and coordinates deformation between concrete and reinforcement. With increasing a member's axial deformation, bond stress finally reaches its ultimate value, bond strength, after which deformation of reinforcement and surrounding concrete will be not coordinated any more. Studies have shown that addition of nanosilica into cement-based materials improves their mechanical properties. Considering the unique characteristics of nanosilica, it seems that this material can be used in ultra-high performance concrete. Therefore, further research is needed on how to use it in concrete mixes. Due to the importance of examining bond stress and the lack of exact equations for bond stress of ultra-high performance concrete and steel reinforcement, the present study aimed to assess the bond stress between concrete and steel reinforcement.

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