Effect of nano-SiO2 hydrosol on size distribution, coalescence and collapse of entrained air bubbles in fresh cement mortar

Graphene’s outstanding properties make it a potential material for reinforced cementitious composites. However, its shortcomings, such as easy agglomeration and poor dispersion, severely restrict its application in cementitious materials. In this paper, a highly dispersible graphene (TiO2-RGO) with better dispersibility compared with graphene oxide (GO) is obtained through improvement of the graphene preparation method. In this study, both GO and TiO2-RGO can improve the pore size distribution of cement mortars. According to the results of the mercury intrusion porosity (MIP) test, the porosity of cement mortar mixed with GO and TiO2-RGO was reduced by 26% and 40%, respectively, relative to ordinary cement mortar specimens. However, the TiO2-RGO cement mortars showed better pore size distribution and porosity than GO cement mortars. Comparative tests on the strength and durability of ordinary cement mortars, GO cement mortars, and TiO2-RGO cement mortars were conducted, and it was found that with the same amount of TiO2-RGO and GO, the TiO2-RGO cement mortars have nearly twice the strength of GO cement mortars. In addition, it has far higher durability, such as impermeability and chloride ion penetration resistance, than GO cement mortars. These results indicate that TiO2-RGO prepared by titanium dioxide (TiO2) intercalation can better improve the strength and durability performance of cement mortars compared to GO.

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Influence of nano SiO2 in cement mortar using taguchi analysis

IOP Conference Series Materials Science and Engineering ◽

10.1088/1757-899x/992/1/012013 ◽

2020 ◽

Vol 992 ◽

pp. 012013

Author(s):

P Vasanthi ◽

S Senthil Selvan

Keyword(s):

Cement Mortar ◽

Taguchi Analysis ◽

Nano Sio2

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Numerical Simulation Study on Distribution of Bubble in Flow near Aerator Based on CFD-PBM Coupled Model in Tunnel

Mathematical Problems in Engineering ◽

10.1155/2021/6635856 ◽

2021 ◽

Vol 2021 ◽

pp. 1-24

Author(s):

Jiaming Lei ◽

Jianmin Zhang ◽

Lifang Zhang

Keyword(s):

Size Distribution ◽

Bubble Size ◽

Numerical Models ◽

Coupled Model ◽

Bubble Size Distribution ◽

Balance Model ◽

Main Process ◽

Air Bubbles ◽

Air Concentration ◽

Aerated Flow

The aerator can reduce erosion by mixing a large amount of air into the water in the solid wall area. The effectiveness of erosion reduction is mainly based on air concentration and its bubble size distribution. However, simultaneous simulation of the air concentration and its bubble size distribution in numerical simulations is still a hot and difficult area of research. Aiming at the downstream aerated flow of hydraulic aeration facilities, several numerical models, such as VOF, mixture, Euler, and Population Balance Model (PBM), are compared and verified by experiments. The results show that the CFD-PBM coupled model performs well compared to other conventional multiphase models. It can not only obtain the evolution law of the bubble distribution downstream of the aerator but also accurately simulate the recombination and evolution process of bubble aggregation and breakage. The Sauter mean diameter of the air bubbles in the aerated flow decreases along the way and eventually reaches a stable value. The bubble breakage is the main process in the development of the bubbles. It reveals the aeration law that the small air bubbles are closer to the bottom plate, while the large bubbles float up along the aerated flow, which provides a powerful support for the basic research on the mechanism of aeration and erosion reduction.

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Effects of fly ash, mixing procedure and type of air-entraining agent on coalescence of entrained air bubbles in mortar of self-compacting concrete at fresh state

Construction and Building Materials ◽

10.1016/j.conbuildmat.2018.04.138 ◽

2018 ◽

Vol 180 ◽

pp. 437-444 ◽

Cited By ~ 7

Author(s):

Nipat Puthipad ◽

Masahiro Ouchi ◽

Anuwat Attachaiyawuth

Keyword(s):

Fly Ash ◽

Air Bubbles ◽

Self Compacting Concrete ◽

Fresh State ◽

Entrained Air

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Performance of Nano-SiO2 and Nano-ZnO2 on Compressive Strength and Microstructure Characteristics of Cement Mortar

Lecture Notes in Civil Engineering - Sustainable Construction and Building Materials ◽

10.1007/978-981-13-3317-0_2 ◽

2018 ◽

pp. 13-22

Author(s):

Raje Gowda ◽

H. Narendra ◽

R. Mourougane ◽

B. M. Nagabhushana

Keyword(s):

Compressive Strength ◽

Cement Mortar ◽

Microstructure Characteristics ◽

Nano Sio2

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Pore size distribution of cement mortar prepared with crushed limestone sand

KSCE Journal of Civil Engineering ◽

10.1007/s12205-015-0300-9 ◽

2015 ◽

Vol 20 (2) ◽

pp. 762-767 ◽

Cited By ~ 4

Author(s):

Xudong Chen ◽

Shengxing Wu ◽

Jikai Zhou

Keyword(s):

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Cement Mortar ◽

Limestone Sand ◽

Crushed Limestone

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Air Entrainment and Bubble Generation by a Hydrofoil in a Turbulent Channel Flow

Volume 5: Multiphase Flow ◽

10.1115/ajkfluids2019-5457 ◽

2019 ◽

Author(s):

Ichiro Kumagai ◽

Kakeru Taguchi ◽

Chiharu Kawakita ◽

Tatsuya Hamada ◽

Yuichi Murai

Keyword(s):

Channel Flow ◽

Flow Rate ◽

High Speed ◽

Air Flow ◽

Air Entrainment ◽

Air Bubbles ◽

Air Flow Rate ◽

Bubble Generation ◽

Gas Liquid Flow ◽

Entrained Air

Abstract Air entrainment and bubble generation by a hydrofoil bubble generator for ship drag reduction have been investigated using a small high-speed channel tunnel with the gap of 20 mm in National Maritime Research Institute (NMRI). A hydrofoil (NACA4412, chord length = 40 mm) was installed in the channel and an air induction pipe was placed above the hydrofoil. The flow rate of the entrained air was quantitatively measured by thermal air flow sensors at the inlet of the air induction pipe. The gas-liquid flow around the hydrofoil was visualized by a backlight method and recorded by a high-speed video camera. As the flow velocity in the channel increased, the negative pressure generated above the suction side of the hydrofoil lowered the hydrostatic pressure in the channel, then the atmospheric air was entrained into the channel flow. The entrained air was broken into small air bubbles by the turbulent flow in the channel. The threshold of air entrainment, the air flow rate, and gas-liquid flow pattern depends on Reynolds number, angle of attack (AOA), and hydrofoil type. We identified at least three modes of air entrainment behavior: intermittent air entrainment, stable air entrainment, and air entrainment with a ventilated cavity. At high flow speed in our experimental condition (9 m/s), a large volume of air bubbles was generated by this hydrofoil system (e.g. air flow rate was 50 l/min for NACA4412 at AOA 16 degrees), which has a high potential to reduce ship drag.

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