We adopted a notch method to study the influence of crack width （macro level） on chloride transport and binding of cracked concrete under a non-steady state migration test. The results show that migration coefficien...We adopted a notch method to study the influence of crack width （macro level） on chloride transport and binding of cracked concrete under a non-steady state migration test. The results show that migration coefficient of cracked concrete increases with increasing crack width up to a critical value （0.43 mm）, for the whole concrete or the area close to crack; the increase of migration coefficient could be independent from crack parameter when a critical crack width is reached. For chloride binding, Langmuir isotherms of cracked concrete samples exhibit the similar decreasing trend as crack width increases from 0.27 to 1.96 mm. The increased current value could be responsible for the trend based on the hypothesis of electric force.展开更多
Chloride binding is often described by chloride binding isotherm, which is closely related to the service life of concrete structures in chloride environments. Many methods have been proposed to determine chloride bin...Chloride binding is often described by chloride binding isotherm, which is closely related to the service life of concrete structures in chloride environments. Many methods have been proposed to determine chloride binding isotherm. Compared to other methods, chloride binding isotherms obtained directly from non- steady-state diffusion tests seem closer to the reality. We studied the chloride binding isotherm from both non- steady-state electrical-accelerated migration and diffusion tests at different temperatures. Twelve concrete mixes with different supplementary cementing materials and water-to-binder ratios of 0.35, 0.48 and 0.6 were cast for study. The specimens after diffusion （or migration） tests were sliced layer by layer, and acid-soluble and free chloride contents of each layer were measured. A chloride binding isotherm was obtained from one specimen. Experimental results indicated that electrical voltage had a slight effect on the chloride binding isotherm of concrete. Temperature had a positive effect on chloride binding. The higher the water-to-binder ratio was, the higher the chloride binding was.展开更多
The aim of the present study was to investigate the influence of heavy metals on the polymorph transformation of tricalcium silicate.Heavy metal（0.1wt% to 3.0wt%） of Cr,Zn,Cu,Ni and Pb（in oxides form） was added in...The aim of the present study was to investigate the influence of heavy metals on the polymorph transformation of tricalcium silicate.Heavy metal（0.1wt% to 3.0wt%） of Cr,Zn,Cu,Ni and Pb（in oxides form） was added into the raw mixtures and then sintered together three times at 1450 ℃ for 2 h.The f-CaO content of doped C3S was determined by the glycerol-ethanol method,and their polymorph transformation was investigated by means of XRD and FTIR.Thermal analysis（DTA/DTG） was conducted to determine the reaction temperatures and mass losses during the sintering process of raw mixtures.The concentration of heavy metal in C3S after sintering was determined by ICP-AES.The experimental results indicate that heavy metal doping contributes to a higher symmetry of C3S except for Pb.Addition of up to 3.0wt%,Cr will lead to a decomposition of C3S into C2S and CaO;Zn will cause a transformation from T1 to M2 polymorph,and then to R polymorph;Cu and Ni cause a gradual transformation from T1 to T2 and then to M1 and/or M2 polymorph.During the sintering process,all the Pb releases into atmosphere because of evaporation.展开更多
基金Funded by China Scholarship Council,the Special Research Fund(BOF)of Ghent UniversityNational Natural Science Foundation of China(No.51178363)
文摘We adopted a notch method to study the influence of crack width （macro level） on chloride transport and binding of cracked concrete under a non-steady state migration test. The results show that migration coefficient of cracked concrete increases with increasing crack width up to a critical value （0.43 mm）, for the whole concrete or the area close to crack; the increase of migration coefficient could be independent from crack parameter when a critical crack width is reached. For chloride binding, Langmuir isotherms of cracked concrete samples exhibit the similar decreasing trend as crack width increases from 0.27 to 1.96 mm. The increased current value could be responsible for the trend based on the hypothesis of electric force.
基金Funded by Ghent University,Belgium and Central South University(No.2010QZZD018)
文摘Chloride binding is often described by chloride binding isotherm, which is closely related to the service life of concrete structures in chloride environments. Many methods have been proposed to determine chloride binding isotherm. Compared to other methods, chloride binding isotherms obtained directly from non- steady-state diffusion tests seem closer to the reality. We studied the chloride binding isotherm from both non- steady-state electrical-accelerated migration and diffusion tests at different temperatures. Twelve concrete mixes with different supplementary cementing materials and water-to-binder ratios of 0.35, 0.48 and 0.6 were cast for study. The specimens after diffusion （or migration） tests were sliced layer by layer, and acid-soluble and free chloride contents of each layer were measured. A chloride binding isotherm was obtained from one specimen. Experimental results indicated that electrical voltage had a slight effect on the chloride binding isotherm of concrete. Temperature had a positive effect on chloride binding. The higher the water-to-binder ratio was, the higher the chloride binding was.
基金Funded by the National Natural Science Foundation of China(51002110)the Fundamental Research Funds for the Central Universities(2012-IV-025)the State Scholarship Program of China Scholarship Council
文摘The aim of the present study was to investigate the influence of heavy metals on the polymorph transformation of tricalcium silicate.Heavy metal（0.1wt% to 3.0wt%） of Cr,Zn,Cu,Ni and Pb（in oxides form） was added into the raw mixtures and then sintered together three times at 1450 ℃ for 2 h.The f-CaO content of doped C3S was determined by the glycerol-ethanol method,and their polymorph transformation was investigated by means of XRD and FTIR.Thermal analysis（DTA/DTG） was conducted to determine the reaction temperatures and mass losses during the sintering process of raw mixtures.The concentration of heavy metal in C3S after sintering was determined by ICP-AES.The experimental results indicate that heavy metal doping contributes to a higher symmetry of C3S except for Pb.Addition of up to 3.0wt%,Cr will lead to a decomposition of C3S into C2S and CaO;Zn will cause a transformation from T1 to M2 polymorph,and then to R polymorph;Cu and Ni cause a gradual transformation from T1 to T2 and then to M1 and/or M2 polymorph.During the sintering process,all the Pb releases into atmosphere because of evaporation.
