The cement-fly ash composite expansive stable grout was prepared to deal with the problems of poor stability and volume shrinkage of ordinary cement grout,and the effects of fly ash ratio and water-binder ratio on the...The cement-fly ash composite expansive stable grout was prepared to deal with the problems of poor stability and volume shrinkage of ordinary cement grout,and the effects of fly ash ratio and water-binder ratio on the properties of the grout and its consolidation were analyzed.In addition,the mineral composition and microstructural characteristics of grout consolidation with different mixing ratios were investigated.The experimental results indicate that fly ash and the increase of water-binder ratio reduce the strength of the grout consolidation,and increase the fluidity,bleeding rate,and setting time of the composite grout.However,the magnitude of the fly ash-induced strength reduction decreases with time.And the effect of fly ash on the setting time and compressive strength becomes more significant with the water-binder ratio.The later expansion performance of grout consolidation(after 7-42 d)is improved by fly ash.But the expansibility of consolidation with fly ash decreases at the early curing stage,and the reduction amplitude of expansion rate is smaller and the reduction age is shorter with the water-binder ratio increase.Fly ash improves the corrosion resistance performance of grout consolidation,and the corrosion resistance coefficient rises first and then falls with the fly ash ratio.And for 0.6:1 water-binder ratio,the corrosion resistance coefficient of the samples mixed with fly ash are greater than 100%.XRD and SEM show that fly ash inhibited the formation of ettringite in the early stage,which is unfavorable to the expansion of the slurry,and with the increase of age,this effect gradually weakened.展开更多
A huge amount of shield muck is generated during shield tunneling,and the reutilization of shield muck to produce tail grout has attracted growing attention,aiming to mitigate the environmental issues related to the t...A huge amount of shield muck is generated during shield tunneling,and the reutilization of shield muck to produce tail grout has attracted growing attention,aiming to mitigate the environmental issues related to the transport and disposal of shield muck.However,conventional binders,such as cement,used in this technique are associated with high carbon emission.Therefore,this study investigates the use of low-carbon binder,i.e.,carbide sludge(CS)-activated ground granulated blast furnace slag(GGBS),in shield muck treatment,aiming to achieve sustainable reutilization.Various commercial additives and phosphogypsum(PG),an industry waste,were added to further enhance the properties of treated shield muck.Results show that incorporating sulfate-containing additives to GGBS-CS-stabilized shield muck significantly reduced the setting time from 26.75 to 8.00–12.00 h,with Na_(2)SO_(4) and PG showing a relatively higher reducing rate.In addition,adding Na_(2)SO_(4) and PG to GGBS-CS-stabilized shield muck could enhance the 3-day strength by 67.0%and 37.0%,respectively,while their effects on improving the 28-day strength were marginal,yielding increases of just 16.0%and 0.4%.Results also indicated that additives led to a higher stone shrinkage rate of grout.Nonetheless,all additives posed negligible effects on the consistency and flowability.Microstructure analysis indicated that additives promoted the generation of ettringite(AFt)and aluminate ferrite monosulfate(AFm)phases.These phases consume free water and refine pores,leading to the higher stone shrinkage rate.Isothermal titration calorimetry highlighted that the additives affect the heat rate in the time interval of 4–50 h after mixing,and this should be the reason for the significant influence of additives on setting time and 3-day strength as well as limited impact on consistency and flowability.The findings confirmed the feasibility of using stabilized shield muck to produce tail grout,and PG is efficient in further enhancing its properties.展开更多
基金Funded by the National Natural Science Foundation of China(No.51979153)the Yunnan Key Research and Development Program(No.202103AA080016)。
文摘The cement-fly ash composite expansive stable grout was prepared to deal with the problems of poor stability and volume shrinkage of ordinary cement grout,and the effects of fly ash ratio and water-binder ratio on the properties of the grout and its consolidation were analyzed.In addition,the mineral composition and microstructural characteristics of grout consolidation with different mixing ratios were investigated.The experimental results indicate that fly ash and the increase of water-binder ratio reduce the strength of the grout consolidation,and increase the fluidity,bleeding rate,and setting time of the composite grout.However,the magnitude of the fly ash-induced strength reduction decreases with time.And the effect of fly ash on the setting time and compressive strength becomes more significant with the water-binder ratio.The later expansion performance of grout consolidation(after 7-42 d)is improved by fly ash.But the expansibility of consolidation with fly ash decreases at the early curing stage,and the reduction amplitude of expansion rate is smaller and the reduction age is shorter with the water-binder ratio increase.Fly ash improves the corrosion resistance performance of grout consolidation,and the corrosion resistance coefficient rises first and then falls with the fly ash ratio.And for 0.6:1 water-binder ratio,the corrosion resistance coefficient of the samples mixed with fly ash are greater than 100%.XRD and SEM show that fly ash inhibited the formation of ettringite in the early stage,which is unfavorable to the expansion of the slurry,and with the increase of age,this effect gradually weakened.
基金supported by the National Natural Science Foundation of China(No.52308366)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(No.23KJB560023).
文摘A huge amount of shield muck is generated during shield tunneling,and the reutilization of shield muck to produce tail grout has attracted growing attention,aiming to mitigate the environmental issues related to the transport and disposal of shield muck.However,conventional binders,such as cement,used in this technique are associated with high carbon emission.Therefore,this study investigates the use of low-carbon binder,i.e.,carbide sludge(CS)-activated ground granulated blast furnace slag(GGBS),in shield muck treatment,aiming to achieve sustainable reutilization.Various commercial additives and phosphogypsum(PG),an industry waste,were added to further enhance the properties of treated shield muck.Results show that incorporating sulfate-containing additives to GGBS-CS-stabilized shield muck significantly reduced the setting time from 26.75 to 8.00–12.00 h,with Na_(2)SO_(4) and PG showing a relatively higher reducing rate.In addition,adding Na_(2)SO_(4) and PG to GGBS-CS-stabilized shield muck could enhance the 3-day strength by 67.0%and 37.0%,respectively,while their effects on improving the 28-day strength were marginal,yielding increases of just 16.0%and 0.4%.Results also indicated that additives led to a higher stone shrinkage rate of grout.Nonetheless,all additives posed negligible effects on the consistency and flowability.Microstructure analysis indicated that additives promoted the generation of ettringite(AFt)and aluminate ferrite monosulfate(AFm)phases.These phases consume free water and refine pores,leading to the higher stone shrinkage rate.Isothermal titration calorimetry highlighted that the additives affect the heat rate in the time interval of 4–50 h after mixing,and this should be the reason for the significant influence of additives on setting time and 3-day strength as well as limited impact on consistency and flowability.The findings confirmed the feasibility of using stabilized shield muck to produce tail grout,and PG is efficient in further enhancing its properties.
