To solve the problems such as high denstiy,foam instability,low compressive strength,high porosity and poor durability associated with conventional foam cements,a novel colloidal gas aphron(CGA)based foam cement syste...To solve the problems such as high denstiy,foam instability,low compressive strength,high porosity and poor durability associated with conventional foam cements,a novel colloidal gas aphron(CGA)based foam cement system was investigated and tested for properties.CGA is used in a base slurry as the foam component and the recipe was optimized with hollow sphere and micro-silica in terms of particle size distribution(PSD).Porosity,permeability,strength,brittleness,elasticity,free water content,foam stability and density tests on the CGA based foam cement system were carried out to evaluate the performance of the system.According to the experiment results,at the foam proportion of 10%,the cement density was reduced to 1040 kg/m3,and stable microfoam net structure not significantly affected by high temperature and high pressure was formed in the cement system.The optimal CGA based foam cement has a free water content of 0%,porosity of 24%,permeability of 0.7×10-3μm2,low elasticity modulus,high Poisson’s ratio,and reasonable compressive strength,and is more elastic and flexible with capability to tolerate regional stresses.展开更多
A new form of foam cement was produced by mixing alkali-activated slag,clay,a small amount of polypropylene fibers with prepared foam during stirring.The preparation of the material is quite different from the normal ...A new form of foam cement was produced by mixing alkali-activated slag,clay,a small amount of polypropylene fibers with prepared foam during stirring.The preparation of the material is quite different from the normal one,which is produced just at room temperature and without baking.The fabrication of this energy-saving and low-price material can be favorable for lowering carbon emission by using recycled industrial wastes.Thermal conductivity of 0.116 W/（m·k）,compressive strength of 3.30 MPa,flexural strength of 0.8 MPa and density of 453 kg/m3 can be achieved after 28 days aging.The hydration product is C-S-H with less Ca（OH）2,calcium aluminum and zeolite,which was characterized by X-ray diffraction（XRD） measurement.This prospective foam cement may be expected to be an excellent economical energy-saving building material.展开更多
Microstructural features including pore size distribution, cell walls and phase compositions of magnesium oxychloride cement foams（MOCF） with various MgO powders and water mixture ratios were studied. Their infl uen...Microstructural features including pore size distribution, cell walls and phase compositions of magnesium oxychloride cement foams（MOCF） with various MgO powders and water mixture ratios were studied. Their infl uences on compressive strength, water absorption and resistance of MOCF were also discussed in detail. The experimental results indicated that moderate and slight excess MgO powders（MgO/MgCl2 molar ratios from 5.1 to 7） were beneficial to the formation of excellent microstructure of MOCF, but increasing water contents（H2O/MgO mass ratios from 0.9 to 1.29） might result in opposite conclusions. The microstructure of MOCF produced with moderate and slight excess MgO powders could enhance the compressive strength, while serious excess MgO powders addition（MgO/MgCl2 molar ratios = 9） would destroy the cell wall structures, and therefore decrease the strength of the system. Although MOCF produced with excess MgO powders could decrease the water absorption, its softening coefficient was lower than that of the material produced with moderate MgO powders. This might be due to the instability of phase 5, the volume expansion and cracking of cell walls as immersed the sample into water.展开更多
The study focused on investigating the effectiveness of functional acrylic polymer (AP) in improving the ability of airfoamed sodium silicate-activated calcium aluminate/Class F fly ash cement (slurry density of ￡1.3...The study focused on investigating the effectiveness of functional acrylic polymer (AP) in improving the ability of airfoamed sodium silicate-activated calcium aluminate/Class F fly ash cement (slurry density of ￡1.3 g/cm3) to mitigate the corrosion of carbon steel (CS) after exposure to hydrothermal environment at 200?C or 300?C. Hydrothermally-initiated interactions between the AP and cement generated the formation of Ca-, Al-, or Na-complexed carboxylate derivatives that improved the AP’s hydrothermal stability. A porous microstructure comprising numerous defect-free, evenly distributed, discrete voids formed in the presence of this hydrothermally stable AP, resulting in the increase in compresive strength of cement. The foamed cement with advanced properties conferred by AP greatly protected the CS against brine-caused corrosion. Four major factors governed this protection by AP-incorporated foamed cements: 1) Reducing the extents of infiltration and transportation of corrosive electrolytes through the cement layer deposited on the underlying CS surface;2) Inhibiting the cathodic reactions at the corrosion site of CS;3) Extending the coverage of CS by the cement;and 4) Improving the adherence of the cement to CS surface.展开更多
In this study, Y-and Ce-modified Cr coatings applied by pack cementation method were prepared on the surface of open-cell nickel-based alloy foam. The morphologies and microstructures of Y- and Ce-modified Cr coatings...In this study, Y-and Ce-modified Cr coatings applied by pack cementation method were prepared on the surface of open-cell nickel-based alloy foam. The morphologies and microstructures of Y- and Ce-modified Cr coatings with various Y and Ce contents were investigated in detail. Then, the effects of Y and Ce addition on the mechanical properties of open-cell nickel-based alloy foams were analyzed and compared. Simultaneously, the energy absorption capacity and energy absorption efficiency of the Y- and Ce-modified Cr coated alloy foams were discussed and compared at the room and high temperatures. The results show that Cr coatings containing minor amounts of rare earth element （Y and Ce） are well adhered to the nickel-based foam struts. Especially, the microstructure of the 2 wt% Ce-modified Cr coating is denser and uniform. In addition, the compressive strength and plateau stress of Y- and Ce-modified Cr coated alloy foams firstly increase and then decrease by increasing the Y and Ce contents at room and high temperatures. The energy absorption capacity of Y/Cr and Ce/Cr coated alloy foams increases linearly with the strains increasing. The Ce/Cr coated alloy foams can absorb more energy than Y/Cr coated alloy foams in the plateau and densification regions at room temperature. Compared to those at room temperature, the Y- and Ce-modified Cr coated alloy foams show higher energy absorption efficiency when deforma- tion within 10%-30% at high temperature.展开更多
文摘To solve the problems such as high denstiy,foam instability,low compressive strength,high porosity and poor durability associated with conventional foam cements,a novel colloidal gas aphron(CGA)based foam cement system was investigated and tested for properties.CGA is used in a base slurry as the foam component and the recipe was optimized with hollow sphere and micro-silica in terms of particle size distribution(PSD).Porosity,permeability,strength,brittleness,elasticity,free water content,foam stability and density tests on the CGA based foam cement system were carried out to evaluate the performance of the system.According to the experiment results,at the foam proportion of 10%,the cement density was reduced to 1040 kg/m3,and stable microfoam net structure not significantly affected by high temperature and high pressure was formed in the cement system.The optimal CGA based foam cement has a free water content of 0%,porosity of 24%,permeability of 0.7×10-3μm2,low elasticity modulus,high Poisson’s ratio,and reasonable compressive strength,and is more elastic and flexible with capability to tolerate regional stresses.
基金Funded by the Ministry of Science & Technology of China(No.2006BAJ04A04)
文摘A new form of foam cement was produced by mixing alkali-activated slag,clay,a small amount of polypropylene fibers with prepared foam during stirring.The preparation of the material is quite different from the normal one,which is produced just at room temperature and without baking.The fabrication of this energy-saving and low-price material can be favorable for lowering carbon emission by using recycled industrial wastes.Thermal conductivity of 0.116 W/（m·k）,compressive strength of 3.30 MPa,flexural strength of 0.8 MPa and density of 453 kg/m3 can be achieved after 28 days aging.The hydration product is C-S-H with less Ca（OH）2,calcium aluminum and zeolite,which was characterized by X-ray diffraction（XRD） measurement.This prospective foam cement may be expected to be an excellent economical energy-saving building material.
基金Funded by the National Natural Science Foundation of China(No.51478370)the EPSRC-NSFC Joint Research Projec(No.51461135005)
文摘Microstructural features including pore size distribution, cell walls and phase compositions of magnesium oxychloride cement foams（MOCF） with various MgO powders and water mixture ratios were studied. Their infl uences on compressive strength, water absorption and resistance of MOCF were also discussed in detail. The experimental results indicated that moderate and slight excess MgO powders（MgO/MgCl2 molar ratios from 5.1 to 7） were beneficial to the formation of excellent microstructure of MOCF, but increasing water contents（H2O/MgO mass ratios from 0.9 to 1.29） might result in opposite conclusions. The microstructure of MOCF produced with moderate and slight excess MgO powders could enhance the compressive strength, while serious excess MgO powders addition（MgO/MgCl2 molar ratios = 9） would destroy the cell wall structures, and therefore decrease the strength of the system. Although MOCF produced with excess MgO powders could decrease the water absorption, its softening coefficient was lower than that of the material produced with moderate MgO powders. This might be due to the instability of phase 5, the volume expansion and cracking of cell walls as immersed the sample into water.
文摘The study focused on investigating the effectiveness of functional acrylic polymer (AP) in improving the ability of airfoamed sodium silicate-activated calcium aluminate/Class F fly ash cement (slurry density of ￡1.3 g/cm3) to mitigate the corrosion of carbon steel (CS) after exposure to hydrothermal environment at 200?C or 300?C. Hydrothermally-initiated interactions between the AP and cement generated the formation of Ca-, Al-, or Na-complexed carboxylate derivatives that improved the AP’s hydrothermal stability. A porous microstructure comprising numerous defect-free, evenly distributed, discrete voids formed in the presence of this hydrothermally stable AP, resulting in the increase in compresive strength of cement. The foamed cement with advanced properties conferred by AP greatly protected the CS against brine-caused corrosion. Four major factors governed this protection by AP-incorporated foamed cements: 1) Reducing the extents of infiltration and transportation of corrosive electrolytes through the cement layer deposited on the underlying CS surface;2) Inhibiting the cathodic reactions at the corrosion site of CS;3) Extending the coverage of CS by the cement;and 4) Improving the adherence of the cement to CS surface.
基金financially supported by the National Natural Science Foundation of China (Nos.51501133 and 51405358)the China Automobile Industry Innovation and Development Joint Fund (No.U1564202)+1 种基金the Natural Science Foundation of Hubei Province (No.2016CFC773)the State Key Laboratory of Advanced Welding and Joining,Harbin Institute of Technology (No.AWJ-M16-11)
文摘In this study, Y-and Ce-modified Cr coatings applied by pack cementation method were prepared on the surface of open-cell nickel-based alloy foam. The morphologies and microstructures of Y- and Ce-modified Cr coatings with various Y and Ce contents were investigated in detail. Then, the effects of Y and Ce addition on the mechanical properties of open-cell nickel-based alloy foams were analyzed and compared. Simultaneously, the energy absorption capacity and energy absorption efficiency of the Y- and Ce-modified Cr coated alloy foams were discussed and compared at the room and high temperatures. The results show that Cr coatings containing minor amounts of rare earth element （Y and Ce） are well adhered to the nickel-based foam struts. Especially, the microstructure of the 2 wt% Ce-modified Cr coating is denser and uniform. In addition, the compressive strength and plateau stress of Y- and Ce-modified Cr coated alloy foams firstly increase and then decrease by increasing the Y and Ce contents at room and high temperatures. The energy absorption capacity of Y/Cr and Ce/Cr coated alloy foams increases linearly with the strains increasing. The Ce/Cr coated alloy foams can absorb more energy than Y/Cr coated alloy foams in the plateau and densification regions at room temperature. Compared to those at room temperature, the Y- and Ce-modified Cr coated alloy foams show higher energy absorption efficiency when deforma- tion within 10%-30% at high temperature.
