Study On The Effect Of Li Compounds On The Performance Of Glass Powder-cement System

Chloride penetration is one of the main reasons of deterioration of concrete structures,while the improvement of chloride ion binding ability of cement paste has a positive effect on the resistance of concrete to chloride permeability.As fly ash and glass powder below certain fineness has pozzolanic activity and can be used to raise chloride binding performance and improve density of concrete,they are supposed to improve the resistance of concrete to chloride permeability.In this thesis,in order to improve the resistance of concrete to chloride permeability,the influence of Li compounds added with other compounds such as triethanolamine?TEA?on performance of cement paste and mortar,eg,chloride binding ability,compressive strength,porosity were systematically investigated in the glass powder-fly ash-cement system.The related mechanism was also analyzed with XRD and SEM+EDS.Firstly,the effect of Li compounds on the dissolution of glass powder in glass powder-Ca?OH?₂ slurry system in stirring condition was investigated.It is shown that the incorporation of LiOH,LiNO₃ and Li₂CO₃ in the glass powder-Ca?OH?₂ slurry system can increase the dissolution of glass powder in Ca?OH?₂.Glass powder was determined to dissolute to most extent in the LiOH added glass powder-Ca?OH?₂ system of those with the Li compounds.Therefore,LiOH was selected to promote the dissolution of glass powder and fly ash in order that the chloride binding capacity can be improved in the cement paste.Secondly,the effects of LiOH on the chloride binding ability and compressive strength of glass powder-fly ash-cement paste were studied.It is determined that chloride ion binding amount and the density of the glass powder-cement paste was increased with the addition of LiOH,although the compressive strength of the paste was detected not to increase.Contractorily,the chloride binding amount of the was decided not to improve with LiOH addition,as a result of Friedel's salt reduction.The compressive strength of the paste of the glass powder-fly ash-cement paste with LiOH addition,however,was discovered to increase with small addition of LiOH with its maximum at 0.5%.The co-addition of LiOH and TEA in the glass powder-fly ash-cement paste was found to have its optimum dosage at 0.075%of LiOH and 0.5%of TEA,resulting in the maximum chloride binding amount of 7.20mg/g.Finally,the effects of LiOH and TEA on the strength,porosity and alkali-aggregate reaction expansion of glass powder-fly ash-cement mortar were studied.It is verified that LiOH can improve the strength of the mortar of glass powder-fly ash-cement system,with the maximum compressive strength of mortar at addition of 0.5%of LiOH.LiOH was meanwhile tested to reduce ASR expansion of mortar,although the density was not found to increase.TEA was discovered to improve the early strength of the glass powder-fly ash-cement mortar,although with little effect on the strength of mortar at later age.The incorporation of TEA was also tested to increases the porosity of glass powder-fly ash-cement mortar,accordingly,not conducive to improve the density.