New high performance grouts with high volume stability and good fluidity were prepared with Portland cement and a multifunctional admixture (MFA). The theological characteristics and mechanical performance of the grou...New high performance grouts with high volume stability and good fluidity were prepared with Portland cement and a multifunctional admixture (MFA). The theological characteristics and mechanical performance of the grouts were investigated. The addition of MFA effectively improves the pseudo-plasticity of the grout. The Ma cone flow time decreases obviously, and the bleeding rate tends to be zero. The deformation behaviors of fresh mixture and hardened grout are systematically studied. Mercury injection method (MIP), scanning electron microscopy (SEM) and X-ray diffractory analysis experiments are used to analyze the microstructure evolution of the grouts, which manifests that the co-action of the early bubble reaction and the latter ettringite crystallization ensure the volume stability throughout the whole hydration process and result in refined pore structure of the grout.展开更多
The performance of magnesium oxychloride cement concrete(MOCC)in road engineering in the arid region in northwest China was investigated over a two-year period.Two categories of MOCC pavement,light-burnt magnesia conc...The performance of magnesium oxychloride cement concrete(MOCC)in road engineering in the arid region in northwest China was investigated over a two-year period.Two categories of MOCC pavement,light-burnt magnesia concrete road(Road-L)and dolomite concrete road(Road-D),were prepared with light-burnt magnesia and a mixture of light-burnt magnesia and caustic dolomite(1:3 by mass),respectively.Variations in the properties of the MOCC pavement,such as compressive and flexural strength,mineralogical phase,and microstructure,after being exposed to two rainy seasons in the field were monitored.The compressive strength of the cored samples were conducted after being aged for 28 d,and the compressive and flexural strength were tested at ages of 1,2,3,28,90,180,270,360 and 720 d.The mineralogical phase and microstructure of the pavement were also analyzed by X-ray diffraction(XRD)and scanning electron microscopy(SEM).The results demonstrate that MOCC pavement obtained desirable compressive and flexural strengths after curing for 3 d for Road-L and 28 d for Road-D.Both of the compressive and flexural strength of Road-L and Road-D decreased slightly after experiencing two rainy seasons,with the major hydration products being 5Mg(OH)2 MgCl28H2O(Phase 5)and 3Mg(OH)2 MgCl28H2O(Phase 3).The decomposition of Phase 5 is mainly responsible for reducing the mechanical strength of the MOCC pavement.展开更多
The degradation behaviors(mass loss,tensile strength,crystallinity index,and microstructure)of sisal fibers immersed in sodium hydroxide solution with pH of 13.6,12.9,and 11.9 were investigated via X-ray diffraction a...The degradation behaviors(mass loss,tensile strength,crystallinity index,and microstructure)of sisal fibers immersed in sodium hydroxide solution with pH of 13.6,12.9,and 11.9 were investigated via X-ray diffraction and scanning electron microscopy.A three-stage degradation process of natural fibers in an alkaline environment was proposed.The results showed that the sisal fibers exhibited a sharp mass loss over the first 7 d of degradation under all pH conditions,attributable to the rapid hydrolysis of lignin and hemicellulose at the fiber surface.The sisal fibers degraded at pH 12.9 and 13.6 over 1 month exhibited significantly lower tensile strengths(181 and 195 MPa,respectively)than the original fibers(234 MPa)because of the loosely bound structure of the component microfibrils caused by the hydrolysis of the linking lignin and hemicellulose.After 6-month degradation,stripped microfibrils occurred in the fibers,resulting in substantial degradation in tensile strength.The sisal fibers degraded at pH 11.9 largely maintained their integrity and tensile strength,even after 6 months,indicating that reducing the environment pH can effectively mitigate the degradation.展开更多
文摘New high performance grouts with high volume stability and good fluidity were prepared with Portland cement and a multifunctional admixture (MFA). The theological characteristics and mechanical performance of the grouts were investigated. The addition of MFA effectively improves the pseudo-plasticity of the grout. The Ma cone flow time decreases obviously, and the bleeding rate tends to be zero. The deformation behaviors of fresh mixture and hardened grout are systematically studied. Mercury injection method (MIP), scanning electron microscopy (SEM) and X-ray diffractory analysis experiments are used to analyze the microstructure evolution of the grouts, which manifests that the co-action of the early bubble reaction and the latter ettringite crystallization ensure the volume stability throughout the whole hydration process and result in refined pore structure of the grout.
基金Project(2014–GX-A2A)supported by Major Science and Technology Projects of Qinghai Province,ChinaProjects(2018-NN-152,2019-GX-165)supported by Science and Technology Achievements Transformation Project of Qinghai Province,ChinaProjects(2018467,2019423)supported by the Youth Innovation Promotion Association of Chinese Academy of Sciences project supported by the High-end innovative talents Thousand talents Plan of Qinghai Province,China
文摘The performance of magnesium oxychloride cement concrete(MOCC)in road engineering in the arid region in northwest China was investigated over a two-year period.Two categories of MOCC pavement,light-burnt magnesia concrete road(Road-L)and dolomite concrete road(Road-D),were prepared with light-burnt magnesia and a mixture of light-burnt magnesia and caustic dolomite(1:3 by mass),respectively.Variations in the properties of the MOCC pavement,such as compressive and flexural strength,mineralogical phase,and microstructure,after being exposed to two rainy seasons in the field were monitored.The compressive strength of the cored samples were conducted after being aged for 28 d,and the compressive and flexural strength were tested at ages of 1,2,3,28,90,180,270,360 and 720 d.The mineralogical phase and microstructure of the pavement were also analyzed by X-ray diffraction(XRD)and scanning electron microscopy(SEM).The results demonstrate that MOCC pavement obtained desirable compressive and flexural strengths after curing for 3 d for Road-L and 28 d for Road-D.Both of the compressive and flexural strength of Road-L and Road-D decreased slightly after experiencing two rainy seasons,with the major hydration products being 5Mg(OH)2 MgCl28H2O(Phase 5)and 3Mg(OH)2 MgCl28H2O(Phase 3).The decomposition of Phase 5 is mainly responsible for reducing the mechanical strength of the MOCC pavement.
基金The Natural Science Foundation of China(No.52108191)the China Postdoctoral Science Foundation(No.2021M690622)+2 种基金the Changzhou Sci&Tech Program(No.CJ20210153,CE20205050)the Qing Lan Project of Jiangsuthe Young Sci-tech Talents Promoting Project of Changzhou。
文摘The degradation behaviors(mass loss,tensile strength,crystallinity index,and microstructure)of sisal fibers immersed in sodium hydroxide solution with pH of 13.6,12.9,and 11.9 were investigated via X-ray diffraction and scanning electron microscopy.A three-stage degradation process of natural fibers in an alkaline environment was proposed.The results showed that the sisal fibers exhibited a sharp mass loss over the first 7 d of degradation under all pH conditions,attributable to the rapid hydrolysis of lignin and hemicellulose at the fiber surface.The sisal fibers degraded at pH 12.9 and 13.6 over 1 month exhibited significantly lower tensile strengths(181 and 195 MPa,respectively)than the original fibers(234 MPa)because of the loosely bound structure of the component microfibrils caused by the hydrolysis of the linking lignin and hemicellulose.After 6-month degradation,stripped microfibrils occurred in the fibers,resulting in substantial degradation in tensile strength.The sisal fibers degraded at pH 11.9 largely maintained their integrity and tensile strength,even after 6 months,indicating that reducing the environment pH can effectively mitigate the degradation.
