The durability of the cement was mainly studied. Under 1.0 MPa of hydraulic pressure for 8 hours, water could penetrate completely through the sample made by portland cement, but could not penetrate through that by al...The durability of the cement was mainly studied. Under 1.0 MPa of hydraulic pressure for 8 hours, water could penetrate completely through the sample made by portland cement, but could not penetrate through that by alite-barium sulphoaluminate cement. Under the condition of freezing and thawing cycle, the loss ratio of compressive strength of the cement was only about 17.3% at curing 28 d ages, but the loss of portland cement was as high as 29.5%. Alite-calcium barium sulphoaluminate cement also has an excellent resistance to sulfate attack. The coefficients of resistance to sulfate attack of the cement exceeded 1.0. Meanwhile, the composition and microstructure of the hardened paste of alite-calcium barium sulphoaluminate cement were analyzed by XRD and SEM.展开更多
As a 3D micro-nano material, layered double hydroxides have been widely used in many fields, especially for reinforced composite materials. In this paper, Li Al-LDHs was obtained by a hydrothermal method. In order to ...As a 3D micro-nano material, layered double hydroxides have been widely used in many fields, especially for reinforced composite materials. In this paper, Li Al-LDHs was obtained by a hydrothermal method. In order to investigate the effects of Li Al-LDHs on the early hydration of calcium sulphoaluminate（CSA） cement paste, compressive strength, setting time and hydration heat were tested while X-ray diffraction（XRD）, Fourier transform infrared spectroscopy（FT-IR）, scaning electron microscopy（SEM） and differential scanning calorimetry（DSC） analysis were employed. The results indicated that Li Al-LDHs could significantly improve the early compressive strength and shorten the setting time of calcium sulphoaluminate cement paste with 3 wt% concentration. Besides, the hydration exothermic rate within 5h was accelerated with increasing Li Al-LDHs content. Moreover, the addition of Li Al-LDHs did not result in the formation of a new phase, but increased the quantity of hydration products providing higher compressive strength, shorter setting time and denser microstructure.展开更多
The mining industry often uses shotcrete for ground stabilization. However, cracking within shotcrete is commonly observed, which delays production schedules and increases maintenance costs. A possible crack reduction...The mining industry often uses shotcrete for ground stabilization. However, cracking within shotcrete is commonly observed, which delays production schedules and increases maintenance costs. A possible crack reduction method is using expansive shotcrete mixture consisting of calcium sulfoaluminate cement(CSA), ordinary Portland cement(OPC), and calcium sulfate(CS) to reduce shrinkage. Furthermore, fibers can be added to the mixture to restrain expansion and impede cracking. The objective of this paper is to study the effects of nylon fiber, glass fiber, and steel fiber on an expansive shotcrete mixture that can better resist cracking. In this study, parameters such as density, water absorption, volume of permeable voids, unconfined compressive strength(UCS), splitting tensile strength(STS), and volume change of fiber-added expansive mixtures were determined at different time periods(i.e. the strengths on the 28 th day, and the volume changes on the 1 st, 7 th, 14 th, 21 st, and 28 th days). The results show that addition of fibers can improve mixture durability, in the form of decreased water absorption and reduced permeable pore space content. Moreover, the expansion of the CSA-OPC-CS mixture was restrained up to50% by glass fiber, up to 43% by nylon fiber, and up to 28% by steel fiber. The results show that the STS was improved by 57% with glass fiber addition, 43% with steel fiber addition, and 38% with nylon fiber addition. The UCS was also increased by 31% after steel fiber addition, 26% after nylon fiber addition, and16% after glass fiber addition. These results suggest that fiber additions to the expansive shotcrete mixtures can improve durability and strengths while controlling expansion.展开更多
The present study assesses the hydration behavior of polymer modified and non-polymer containing calcium sulfoaluminate(CSA)cement pastes containing minor phase tri-calcium aluminate(C3A)when cured at ambient laborato...The present study assesses the hydration behavior of polymer modified and non-polymer containing calcium sulfoaluminate(CSA)cement pastes containing minor phase tri-calcium aluminate(C3A)when cured at ambient laboratory temperature with 50%relative humidity.The particular CSA cement is unique as it offers two potential paths for ettringite formation.In the presence of sufficient calcium sulfate,these two potential paths stem from either hydration of yeelimite or hydration of tri-calcium aluminate.The study assesses the microstructural behavior of cement pastes utilizing powdered x-ray diffraction(XRD)and thermogravimetric analysis(TGA/SDT).Additionally,the study utilizes direct tensile strength testing according to ASTM C307,Standard Test Method for Tensile Strength of Chemical Resistant Mortar,Grouts and Monolithic Surfacings to quantify relationships between microstructural characteristics and mechanical property performance for representative mortars.The present study is significant as it illustrates differences in microstructural behavior for CSA cement materials with and without polymer cured at constant 50%relative humidity.The present study suggests ettringite decomposition occurs within non-polymer containing CSA cement paste samples cured at constant low humidity.The present study presents polymer modification as an effective means for mitigating ettringite decomposition and subsequent strength loss in materials containing CSA cement cured at constant 50%relative humidity and 23℃.展开更多
采用工业原料配料,对以硅酸三钙(C_3S, C =CaO,S =SiO_2)、硫铝酸钙(C_4A_3, C =CaO,A=Al_2O_3,=SO_4^(2-))为主导矿物的含C_4A_3S矿物硅酸盐水泥熟料的矿物形成及其强度进行了研究。借助X射线衍射和热重差热分析研究了矿物形成过程...采用工业原料配料,对以硅酸三钙(C_3S, C =CaO,S =SiO_2)、硫铝酸钙(C_4A_3, C =CaO,A=Al_2O_3,=SO_4^(2-))为主导矿物的含C_4A_3S矿物硅酸盐水泥熟料的矿物形成及其强度进行了研究。借助X射线衍射和热重差热分析研究了矿物形成过程;探讨了微量元素ZnO对熟料性能的影响及在熟料体系中的固溶情况。研究结果表明:生料中掺入ZnO可使C_4A_3和C_3s等矿物通过低温反应形成,共存于同一熟料体系中,并可提高熟料的强度;过高的ZnO含量亦会降低C_4A_3矿物的分解温度。展开更多
基金Funded by the National Natural Science Foundation of China (No.50672033)the "973"National Key Fundamental Research Plan ofChina (No.2009CB623101-1)
文摘The durability of the cement was mainly studied. Under 1.0 MPa of hydraulic pressure for 8 hours, water could penetrate completely through the sample made by portland cement, but could not penetrate through that by alite-barium sulphoaluminate cement. Under the condition of freezing and thawing cycle, the loss ratio of compressive strength of the cement was only about 17.3% at curing 28 d ages, but the loss of portland cement was as high as 29.5%. Alite-calcium barium sulphoaluminate cement also has an excellent resistance to sulfate attack. The coefficients of resistance to sulfate attack of the cement exceeded 1.0. Meanwhile, the composition and microstructure of the hardened paste of alite-calcium barium sulphoaluminate cement were analyzed by XRD and SEM.
基金Funded by the National Natural Sciense Foundation of China(No.51272068)
文摘As a 3D micro-nano material, layered double hydroxides have been widely used in many fields, especially for reinforced composite materials. In this paper, Li Al-LDHs was obtained by a hydrothermal method. In order to investigate the effects of Li Al-LDHs on the early hydration of calcium sulphoaluminate（CSA） cement paste, compressive strength, setting time and hydration heat were tested while X-ray diffraction（XRD）, Fourier transform infrared spectroscopy（FT-IR）, scaning electron microscopy（SEM） and differential scanning calorimetry（DSC） analysis were employed. The results indicated that Li Al-LDHs could significantly improve the early compressive strength and shorten the setting time of calcium sulphoaluminate cement paste with 3 wt% concentration. Besides, the hydration exothermic rate within 5h was accelerated with increasing Li Al-LDHs content. Moreover, the addition of Li Al-LDHs did not result in the formation of a new phase, but increased the quantity of hydration products providing higher compressive strength, shorter setting time and denser microstructure.
基金financial support from Natural Sciences and Engineering ResearchCouncil(NSERC)(NSERC EGP 501335-16) along with the donated CSA cement
文摘The mining industry often uses shotcrete for ground stabilization. However, cracking within shotcrete is commonly observed, which delays production schedules and increases maintenance costs. A possible crack reduction method is using expansive shotcrete mixture consisting of calcium sulfoaluminate cement(CSA), ordinary Portland cement(OPC), and calcium sulfate(CS) to reduce shrinkage. Furthermore, fibers can be added to the mixture to restrain expansion and impede cracking. The objective of this paper is to study the effects of nylon fiber, glass fiber, and steel fiber on an expansive shotcrete mixture that can better resist cracking. In this study, parameters such as density, water absorption, volume of permeable voids, unconfined compressive strength(UCS), splitting tensile strength(STS), and volume change of fiber-added expansive mixtures were determined at different time periods(i.e. the strengths on the 28 th day, and the volume changes on the 1 st, 7 th, 14 th, 21 st, and 28 th days). The results show that addition of fibers can improve mixture durability, in the form of decreased water absorption and reduced permeable pore space content. Moreover, the expansion of the CSA-OPC-CS mixture was restrained up to50% by glass fiber, up to 43% by nylon fiber, and up to 28% by steel fiber. The results show that the STS was improved by 57% with glass fiber addition, 43% with steel fiber addition, and 38% with nylon fiber addition. The UCS was also increased by 31% after steel fiber addition, 26% after nylon fiber addition, and16% after glass fiber addition. These results suggest that fiber additions to the expansive shotcrete mixtures can improve durability and strengths while controlling expansion.
文摘The present study assesses the hydration behavior of polymer modified and non-polymer containing calcium sulfoaluminate(CSA)cement pastes containing minor phase tri-calcium aluminate(C3A)when cured at ambient laboratory temperature with 50%relative humidity.The particular CSA cement is unique as it offers two potential paths for ettringite formation.In the presence of sufficient calcium sulfate,these two potential paths stem from either hydration of yeelimite or hydration of tri-calcium aluminate.The study assesses the microstructural behavior of cement pastes utilizing powdered x-ray diffraction(XRD)and thermogravimetric analysis(TGA/SDT).Additionally,the study utilizes direct tensile strength testing according to ASTM C307,Standard Test Method for Tensile Strength of Chemical Resistant Mortar,Grouts and Monolithic Surfacings to quantify relationships between microstructural characteristics and mechanical property performance for representative mortars.The present study is significant as it illustrates differences in microstructural behavior for CSA cement materials with and without polymer cured at constant 50%relative humidity.The present study suggests ettringite decomposition occurs within non-polymer containing CSA cement paste samples cured at constant low humidity.The present study presents polymer modification as an effective means for mitigating ettringite decomposition and subsequent strength loss in materials containing CSA cement cured at constant 50%relative humidity and 23℃.
文摘采用工业原料配料,对以硅酸三钙(C_3S, C =CaO,S =SiO_2)、硫铝酸钙(C_4A_3, C =CaO,A=Al_2O_3,=SO_4^(2-))为主导矿物的含C_4A_3S矿物硅酸盐水泥熟料的矿物形成及其强度进行了研究。借助X射线衍射和热重差热分析研究了矿物形成过程;探讨了微量元素ZnO对熟料性能的影响及在熟料体系中的固溶情况。研究结果表明:生料中掺入ZnO可使C_4A_3和C_3s等矿物通过低温反应形成,共存于同一熟料体系中,并可提高熟料的强度;过高的ZnO含量亦会降低C_4A_3矿物的分解温度。
