Effect Of Nano-materials And Glass Powder On Properties Of Cement Mortar

China produces a large amount of waste glass every year.Using waste glass to prepare cement mortar is one of the methods for the reuse of waste glass resources.Refined glass powder has pozzolanic activity,when used as cementitious materials in cement,there is no risk of alkali aggregate expansion and cracking.At the same time,compared with fly ash,slag and other common auxiliary cementitious materials,glass powder has stable chemical properties and is a potential cementitious material to replace cement.However,the activity of glass powder is low.After partially replacing cement,the early strength is significantly reduced and the frost resistance is poor,which limits its application.Nanoparticles with high specific surface areas and high reactivity,which can greatly improve the compactness and early strength of cement-based materials,therefore the advantage can exactly make up for the negative influence of glass powder.Therefore,from the perspective of improving the utilization rate of glass powder,nano-SiO₂ and nano-CaCO₃ were selected to modify the cement mortar containing glass powder in this paper.The effects of nano-SiO₂ and nano-CaCO₃ mixed with glass powder on the compressive strength,flexural strength,drying shrinkage and frost resistance of cement mortar were studied.Combined with SEM,thermogravimetric analysis and mercury intrusion method,the changes in microstructure of mortar mixed with nano-materials and glass powder were comprehensively analyzed to explain the reasons for the changes in macroscopic properties.As follows,here are the major research contents and results:（1）The influence of glass powder and nano-materials on the fluidity of cement mortar was studied.The results show that 10%-30%glass powder leads to the decrease of fluidity of cement mortar,and the addition of nano-SiO₂ or nano-CaCO₃continuously reduces the fluidity of mortar,and the influence of nano-CaCO₃ on the fluidity of cement mortar is smaller than that of nano-SiO₂.（2）The effects of glass powder and nano materials on compressive strength and flexural strength of cement mortar were studied.The results show that 10%-30%glass powder can significantly reduce the compressive/flexural strength of cement mortar,especially the 3d strength,and the early strength develops slowly.Nano-SiO₂ and nano-CaCO₃ can significantly improve the mechanical properties of cement mortar containing glass powder at 3d,7d and 28d.The addition of 3%nano-SiO₂ can completely compensate the strength loss caused by 20%glass powder replacing cement,and the addition of 3%nano-CaCO₃ can completely compensate the strength loss caused by 10%glass powder replacing cement.（3）The effects of glass powder and nano-materials on the drying shrinkage performance of cement mortar were studied.The results show that 10%and 20%glass powder can reduce the drying shrinkage of cement mortar,and adding nano-SiO₂ andNano-CaCO₃ can greatly increase the drying shrinkage.The addition of less than20%glass powder and nano-SiO₂ or nano-CaCO₃ can partially offset the drying shrinkage increment of mortar caused by nano-materials,so that the drying shrinkage value of mortar is within the acceptable range of the specification.（4）The effect of glass powder and nano materials on frost resistance of cement mortar was studied.Result display:The frost resistance of mortar is improved by adding 10%glass powder,but the frost resistance becomes worse when the glass powder content exceeds 20%.The frost resistance of mortar is enhanced by adding nano-SiO₂ or nano-CaCO₃,the frost resistance of mortar mixed with 10%glass powder and 3%nano-SiO₂ is the best.The frost resistance of mortar mixed with 20%glass powder and 3%nano-SiO₂ is better than that of the control group,and the frost resistance of mortar mixed with 20%glass powder and 3%nano-CaCO₃ is almost the same as that of the control group.（5）The effects of glass powder and nano-materials on the microstructure of mortar were discussed.Glass powder will increase the porosity of mortar,and nano-SiO₂ and nano-CaCO₃ can optimize the pore size distribution of mortar,promote the hydration of cement mortar containing glass powder,reduce the proportion of pores and improve the compactness of mortar.The improvement effect of nano-SiO₂ on microstructure is better than that of nano-CaCO₃.（6）Considering comprehensively,without affecting the early mechanical properties and durability of cement mortar,3%nano-SiO₂ increases the utilization rate of glass powder in cement to 20%.Therefore,it is recommended to replace cement with 3%nano-SiO₂+20%glass powder,to maximize the use of glass powder,and it has great environmental effectiveness.