Study On The Effect Of Admixture And Nano-SiO₂ On The Properties Of Alkali-activated Mortar Containing Glass Powder

The preparation of alkali activated mortar from waste glass is one of the methods to reuse waste glass resources.However,the alkali-activated mortar prepared from waste glass has the problems of high drying shrinkage and easy freeze-thaw damage.Therefore,the mechanical properties（compressive strength,flexural strength）,drying shrinkage and frost resistance of alkali activated slag/glass powder mortar were analyzed.The influence of fly ash（FA）,silica fume（MS）and nano-SiO₂（NS）on the micro-structure of alkali-activated slag/glass powder mortar was analyzed by means of SEM and XRD.The main research contents and results are as follows:（1）The effects of the FA on the compressive strength,flexural strength,dry shrinkage and frost resistance of alkali-activated mortar were thoroughly investigated.The results showed that the compressive and flexural strength of the produced mortar maximized when the FA content was 5%,However,the mortar strength decreased when FA content was in the range of 5%to 25%.Meanwhile,FA could contribute to reduce the drying shrinkage.When the FA content increased from 0%to 25%,indicated by an obvious drying shrinkage reduction.In addition,with the FA content increased from 0%to 25%,the frost resistance of could be negatively affected.（2）The effects of the MS on the compressive strength,flexural strength,dry shrinkage and frost resistance of the alkali-activated mortar were systematically evaluated.The results showed that when the MS content was 5%,the resulting mortar had the highest mechanical strength.At the same time,the lowest drying shrinkage could be observed.However the frost resistance was adversely affected when the MS content ranging from 0%to 25%.（3）The effects of the NS on the compressive strength,flexural strength,dry shrinkage and frost resistance of alkali-activated mortar were analyzed.The results showed that NS had a significant positive effect on the deve lopment of the early strength of the alkali activated slag/glass powder mortar.The mechanical strength of the mortar peaked when the NS content was 2%.And a favorable frost resistance was observed.However,an increased drying shrinkage could be observed when the NS content increased from 0.5%to 3%.When the NS content was lower than 1.5%,the drying shrinkage of the mortar was lower than that of the control group.（4）The effects of fly ash,silica fume and nano-SiO₂ on the micro-morphology of alkali-activated slag/glass powder mortar were observed by scanning electron microscope.The results showed that when the FA content increased from 5%to 25%,the micro-cracks and voids in the matrix increased,which would affect the density of the matrix and led to the poor strength and frost resistance.However,when the MS content was greater than 5%,it was easy to agglomerate under the alkaline environment with low concentration,which makes the matrix not dense enough,and the strength and frost resistance dec rease.When the content of nano-SiO₂ increased from 0%to 2%,the micro-cracks and pores decreased,the matrix became denser,and the strength increased,but when the content of nano-SiO₂was more than 2%,the aggregation occurred easily.（5）The effects of fly ash,silica fume and nano-SiO₂ on the phase and products of alkali-activated slag/glass powder mortar were observed by X-ray diffraction.The results showed that the peak value of C-S-H phase decreased with the increase of the FA content,the generated products decrease,the matrix compactness decreases,which was not conducive to the strength development,and at the same time reduces the frost resistance of mortar.When the MS content was more than 5%,the peak value of C-S-H decreases and the generated products decrease,which makes the strength and frost resistance deteriorate.Then,the peak value of C-S-H gel and zeolite mineral diffraction was the highest when 2%nano-SiO₂ was blended,indicating that the mortar had favorable mechanical strength an d frost resistance.