By incorporation of fly ash or silica fume into magnesium oxychloride （MOC） cement, a high water resistance material can be formed for successful industrial applications. The influences of fly ash and silica fume on...By incorporation of fly ash or silica fume into magnesium oxychloride （MOC） cement, a high water resistance material can be formed for successful industrial applications. The influences of fly ash and silica fume on water-resistant property were investigated by SEM and EDS. It is found that the incorporation of fly ash or silica fume can improve the water-resistance of the MOC. The improvement of the water resistance of the MOC incorporated with fly ash or silica fume may be attributed to the alumino-silicate 5·1·8 gel or silicate 5·1·8 gel.展开更多
In order to study the production of porous silica compacts by the combustion of rice husk ash （RHA） for tundish lining, the experimental design technique was used to evaluate the effect of firing temperature, soakin...In order to study the production of porous silica compacts by the combustion of rice husk ash （RHA） for tundish lining, the experimental design technique was used to evaluate the effect of firing temperature, soaking time and compaction pressure on controlling both the porosity degree and compressive strength of rice husk ash compacts. The results revealed that while the porosity degree of the compacts decreased with the increase in the entire studied parameters, the compressive strength exhibited another trend especially at a lower soaking time. At a lower soaking time, the increase in firing temperature led to a slight decrease in compressive strength and then increasing thereafter. The porous silica compacts having 30% porosity and 〉 2.5 MPa compressive strength suitable for tundish lining could be obtained from the combustion of rice husk ash compacts.展开更多
The effect of fly ash and silica fume on hydration rate and strength of cement in the early stage was studied. Contrast test was applied to the complex cementitious system to investigate the hydration rate. Combined w...The effect of fly ash and silica fume on hydration rate and strength of cement in the early stage was studied. Contrast test was applied to the complex cementitious system to investigate the hydration rate. Combined with mechanical strength, the influence of fly ash and silica fume during the hydration process of complex binder was researched. The peak of the rate of hydration heat evolution and the mechanical strength decreased as the ratio of fly ash increased, however, as the ratio of silica fume increased, the peak of the rate of hydration heat evolution and the mechanical strength increased obviously. When the ratios of fly ash and silica fume are 10% and 5%, the peak of the rate of hydration heat evolution is the highest. At the same time 7 days of flexural and compressive strength are the highest as 8.89 MPa and 46.52 MPa, respectively. Fly ash and silica fume are the main factors affecting the hydration rate and the mechanical property.展开更多
The influences of nano silica (NS) on the hydration and microstructure development of steam cured cement high volume fly ash (40 wt%, CHVFA) system were investigated. The compressive strength of mortars was tested wit...The influences of nano silica (NS) on the hydration and microstructure development of steam cured cement high volume fly ash (40 wt%, CHVFA) system were investigated. The compressive strength of mortars was tested with different NS dosage from 0 to 4%. Results show that the compressive strength is dramatically improved with the increase of NS content up to 3%, and decreases with further increase of NS content (e g, at 4%). Then X?ray diffraction (XRD), differential scanning calorimetry-thermogravimetry (DSCTG), scanning electron microscope (SEM), energy disperse spectroscopy (EDS), mercury intrusion porosimeter (MIP) and nuclear magnetic resonance (NMR) were used to analyze the mechanism. The results reveal that the addition of NS accelerates the hydration of cement and fly ash, decreases the porosity and the content of calcium hydroxide (CH) and increases the polymerization degree of C-S-H thus enhancing the compressive strength of mortars. The interfacial transition zone (ITZ) of CHVFA mortars is also significantly improved by the addition ofNS, embodying in the decrease of Ca/Si ratio and CH enrichment of ITZ.展开更多
This paper investigates the experimental results on the effect of nano silica fume on compressive strength development of concretes containing high volume fly ash (HVFA). The effect of various silica fumes contents su...This paper investigates the experimental results on the effect of nano silica fume on compressive strength development of concretes containing high volume fly ash (HVFA). The effect of various silica fumes contents such as 1%, 2% & 3% (wt. %) as partial replacement of cement on the compressive strength of cements is evaluated in the first part. The nano silica fume content which exhibits the highest compressive strength above is used in high volume fly ash concretes containing 30% and 50% class F fly ash. The results show that among three different silica fumes contents, the addition of 1% increases the compressive strength of concretes. The addition of 1% silica fume also increases the early age and 28 days compressive strengths of HVFA concretes.展开更多
The strength and durability properties of concrete with or without three types of rice husk ash （RHA）, namely, amorphous, partial crystalline, and crystalline RHA, were investigates. The three types of RHA were adde...The strength and durability properties of concrete with or without three types of rice husk ash （RHA）, namely, amorphous, partial crystalline, and crystalline RHA, were investigates. The three types of RHA were added into concrete at a 20% replacement level. Consequently, the pozzolanic reactivity of amorphous RHA was higher than that of partial crystalline and crystalline RHA. Concrete added with amorphous RHA showed excellent characteristics in its mechanical and durability properties. The results showed that the higher the amount of crystalline silica in RHA, the lower the concrete resistivity value became. When compared with each other, concretes with 20% of the ce- ment replaced with these types of RHA achieved similar ultrasonic pulse velocity values, but all were lower than that of the control concrete. The incorporation of these kinds of RHA significantly reduced chloride penetration. The results not only encourage the use of amorphous materials, they also support the application of crystalline or partial crystalline RHA as mineral and pozzolanic admixtures for cement.展开更多
The effect of the composite of natural zeolite and fly ash on alkali-silica reaction (ASR) was studied with natural alkali-reactive aggregate and quartz glass aggregate respectively.The expansive experiment of mortar ...The effect of the composite of natural zeolite and fly ash on alkali-silica reaction (ASR) was studied with natural alkali-reactive aggregate and quartz glass aggregate respectively.The expansive experiment of mortar bar and concrete prism was completed.The results show that ASR can be suppressed effectively by the composite of natural zeolite and fly ash.展开更多
The compressive strength and dynamic modulus of high volume fly ash concrete with incorporation of either metakaolin or silica fume were investigated. The water to cementitious materials ratio was kept at 0.4 for all ...The compressive strength and dynamic modulus of high volume fly ash concrete with incorporation of either metakaolin or silica fume were investigated. The water to cementitious materials ratio was kept at 0.4 for all mixtures. The use of high volume fly ash in concrete greatly reduces the strength and dynamic modulus during the first 28 days. The decreased properties during the short term of high volume fly ash concrete is effectively compensated by the incorporation of metakaolin or silica fume. The DTA results confirmed that metakaolin or silica fume increase the amount of the hydration products. An empirical relationship between dynamic modulus and compressive strength of concrete has been obtained. This relation provides a nondestructive evaluation for estimating the strength of concrete by use of the dynamic modulus.展开更多
The present experimental technique is used to study the image, crystal phase, pore structure and microstructure of artificial silica fume, and the experimental results show that artificial silica fume is a non-crystal...The present experimental technique is used to study the image, crystal phase, pore structure and microstructure of artificial silica fume, and the experimental results show that artificial silica fume is a non-crystalline and porous matter with a high specific surface area and the high activity of volcanic ash. Therefore, it is a type of ideal material which can replace silica fume. (Author abstract) 5 Refs.展开更多
基金Funded by the "Hundred Talents" Project of Chinese Academy of Sciencesthe "Technology Innovation" Project of Chinese Academy of Sciences
文摘By incorporation of fly ash or silica fume into magnesium oxychloride （MOC） cement, a high water resistance material can be formed for successful industrial applications. The influences of fly ash and silica fume on water-resistant property were investigated by SEM and EDS. It is found that the incorporation of fly ash or silica fume can improve the water-resistance of the MOC. The improvement of the water resistance of the MOC incorporated with fly ash or silica fume may be attributed to the alumino-silicate 5·1·8 gel or silicate 5·1·8 gel.
文摘In order to study the production of porous silica compacts by the combustion of rice husk ash （RHA） for tundish lining, the experimental design technique was used to evaluate the effect of firing temperature, soaking time and compaction pressure on controlling both the porosity degree and compressive strength of rice husk ash compacts. The results revealed that while the porosity degree of the compacts decreased with the increase in the entire studied parameters, the compressive strength exhibited another trend especially at a lower soaking time. At a lower soaking time, the increase in firing temperature led to a slight decrease in compressive strength and then increasing thereafter. The porous silica compacts having 30% porosity and 〉 2.5 MPa compressive strength suitable for tundish lining could be obtained from the combustion of rice husk ash compacts.
基金Funded by the National Natural Science Foundation of China(No.51472168)
文摘The effect of fly ash and silica fume on hydration rate and strength of cement in the early stage was studied. Contrast test was applied to the complex cementitious system to investigate the hydration rate. Combined with mechanical strength, the influence of fly ash and silica fume during the hydration process of complex binder was researched. The peak of the rate of hydration heat evolution and the mechanical strength decreased as the ratio of fly ash increased, however, as the ratio of silica fume increased, the peak of the rate of hydration heat evolution and the mechanical strength increased obviously. When the ratios of fly ash and silica fume are 10% and 5%, the peak of the rate of hydration heat evolution is the highest. At the same time 7 days of flexural and compressive strength are the highest as 8.89 MPa and 46.52 MPa, respectively. Fly ash and silica fume are the main factors affecting the hydration rate and the mechanical property.
基金Funded by the “13th Five-Year” National Science and Technology Support Program of China(No.2016YFC0701003–05)the Science and Technology Support Program of Hubei Province(No.2015BAA084)the National Natural Science Foundation of China(No.51378408)
文摘The influences of nano silica (NS) on the hydration and microstructure development of steam cured cement high volume fly ash (40 wt%, CHVFA) system were investigated. The compressive strength of mortars was tested with different NS dosage from 0 to 4%. Results show that the compressive strength is dramatically improved with the increase of NS content up to 3%, and decreases with further increase of NS content (e g, at 4%). Then X?ray diffraction (XRD), differential scanning calorimetry-thermogravimetry (DSCTG), scanning electron microscope (SEM), energy disperse spectroscopy (EDS), mercury intrusion porosimeter (MIP) and nuclear magnetic resonance (NMR) were used to analyze the mechanism. The results reveal that the addition of NS accelerates the hydration of cement and fly ash, decreases the porosity and the content of calcium hydroxide (CH) and increases the polymerization degree of C-S-H thus enhancing the compressive strength of mortars. The interfacial transition zone (ITZ) of CHVFA mortars is also significantly improved by the addition ofNS, embodying in the decrease of Ca/Si ratio and CH enrichment of ITZ.
文摘This paper investigates the experimental results on the effect of nano silica fume on compressive strength development of concretes containing high volume fly ash (HVFA). The effect of various silica fumes contents such as 1%, 2% & 3% (wt. %) as partial replacement of cement on the compressive strength of cements is evaluated in the first part. The nano silica fume content which exhibits the highest compressive strength above is used in high volume fly ash concretes containing 30% and 50% class F fly ash. The results show that among three different silica fumes contents, the addition of 1% increases the compressive strength of concretes. The addition of 1% silica fume also increases the early age and 28 days compressive strengths of HVFA concretes.
文摘The strength and durability properties of concrete with or without three types of rice husk ash （RHA）, namely, amorphous, partial crystalline, and crystalline RHA, were investigates. The three types of RHA were added into concrete at a 20% replacement level. Consequently, the pozzolanic reactivity of amorphous RHA was higher than that of partial crystalline and crystalline RHA. Concrete added with amorphous RHA showed excellent characteristics in its mechanical and durability properties. The results showed that the higher the amount of crystalline silica in RHA, the lower the concrete resistivity value became. When compared with each other, concretes with 20% of the ce- ment replaced with these types of RHA achieved similar ultrasonic pulse velocity values, but all were lower than that of the control concrete. The incorporation of these kinds of RHA significantly reduced chloride penetration. The results not only encourage the use of amorphous materials, they also support the application of crystalline or partial crystalline RHA as mineral and pozzolanic admixtures for cement.
文摘The effect of the composite of natural zeolite and fly ash on alkali-silica reaction (ASR) was studied with natural alkali-reactive aggregate and quartz glass aggregate respectively.The expansive experiment of mortar bar and concrete prism was completed.The results show that ASR can be suppressed effectively by the composite of natural zeolite and fly ash.
基金the National Natural Science Foundation of China(No.50778078)
文摘The compressive strength and dynamic modulus of high volume fly ash concrete with incorporation of either metakaolin or silica fume were investigated. The water to cementitious materials ratio was kept at 0.4 for all mixtures. The use of high volume fly ash in concrete greatly reduces the strength and dynamic modulus during the first 28 days. The decreased properties during the short term of high volume fly ash concrete is effectively compensated by the incorporation of metakaolin or silica fume. The DTA results confirmed that metakaolin or silica fume increase the amount of the hydration products. An empirical relationship between dynamic modulus and compressive strength of concrete has been obtained. This relation provides a nondestructive evaluation for estimating the strength of concrete by use of the dynamic modulus.
文摘The present experimental technique is used to study the image, crystal phase, pore structure and microstructure of artificial silica fume, and the experimental results show that artificial silica fume is a non-crystalline and porous matter with a high specific surface area and the high activity of volcanic ash. Therefore, it is a type of ideal material which can replace silica fume. (Author abstract) 5 Refs.
