Research On The Preparation And Performance Of Glass Powder And Glass Flake Anti-efflorescence Morta

Efflorescence often occurs on the surfaces of cement-based cement mortar,tile joints,bricks and walls,etc.,which seriously affects the aesthetics of buildings and greatly limits the application range of cement-based materials.Generally,metakaolin and fly ash are adopted to inhibit the efflorescence of cement mortar,however,the inhibitory effect of fly ash on efflorescence is not remarkable,and metakaolin lead to poor fluidity,which affects the workability of cement mortar.Therefore,seeking a material which is able to inhibit the efflorescence significantly,without affecting the workability of cement mortar is of enormous economic benefit.Typically,the efflorescence could be prevented by materials which are capable of consuming Ca（OH）₂inside cement mortar and simultaneously improving the pore structure of cement mortar.Theoretically,both glass powder and glass flakes can impede efflorescence,but research on this aspect has not been reported yet.In this study,recycled glass powder and glass flakes were employed to replace a portion of cement,and the effects of the content and particle size of glass powder and glass flakes on the efflorescence resistance,rheological properties（directly reflecting the workability）,and strength of cement mortar were studied.The essence of the influence of glass powder and glass flakes on the strength and rheological properties,and the efflorescence inhibition mechanism were revealed.Based on the above results,a new cement-based mortar sealant with anti-efflorescence performance was prepared by optimizing the mix ratio through orthogonal test.The main research results are as follows:（1）The higher the activity index of glass powder,the better the anti-efflorescence of glass powder added mortar.The activity index of the glass powder with a particle size of 6.63μm is up to 93.1%at the age of 28 days,and prime inhibitory effect on efflorescence was achieved by using glass powder with a particle size of 6.63μm and addition of 9%,and the degree of efflorescence of glass powder added mortar was reduced by 58.7%compared with the base group.（2）The efflorescence degree of glass powder added mortar firstly decreased and then increased,with the increase in glass powder content.When the addition of glass powder reached 24%,the efflorescence degree was almost the same as that of the reference group.Moreover,the inhibitory effect of glass powder on efflorescence decreased with the increase in particle size of glass powder,and the efflorescence degree of glass powder added mortar with glass particle size of 6.63μm decreased by 45.6%,compared with that of glass powder added mortar with glass particle size of 49.38μm.（3）The activity index of glass flakes was extremely low.The degree of efflorescence was high,whether the proportion of glass flakes was excessive or insufficient.As the glass flakes content was between 6%～10%,the water blocking effect of the unique palace shaped structures formed by glass flakes endowed them a certain inhibitory effect on efflorescence.（4）For glass powder added mortar,the yield stress and rheological property index decreased,the plastic viscosity increased,and the hysteretic loop area firstly decreased and then increased,with the increase in glass particle size.Moreover,the yield stress decreased,the plastic viscosity increased,the rheological property index firstly decreased and then increased,and the hysteresis loop area increased,with the increase in glass powder content.The phenomena indicate that appropriate content of glass powder with proper particle size has little influence on the workability of cement mortar.（5）The fluidity of cement mortar decreased significantly with the increase in glass flakes content,when the sand or cement was equivalently replaced by glass flakes.Nonetheless,the yield stress,plastic viscosity,hysteresis loop area and rheological property index of cement mortar and cement paste all increased with increasing glass flakes content.As the content of glass flakes exceeded 6%,the cement paste underwent a transition from a pseudoplastic fluid to dilatant plastic fluid.The linear correlation coefficient of plastic viscosity between glass flakes added cement paste and cement mortar is up to 0.99.（6）Smaller glass particle size resulted in higher compressive strength and flexural strength of mortar.However,the flexural and compressive strength of mortar firstly increased and then decreased with increasing glass powder content,and the strength reached maximum when the content of glass powder was 9%.With the increase of age,the compressive strength of glass powder added mortar containing 12%and 9%glass powder was almost the same at the age of 360 days.Nevertheless,the addition of glass flakes was unfavorable to the strength of cement mortar,consequently,the flexural and compressive strength of mortar decreased with the increase in glass flakes content.（7）Considering the influence of glass powder and glass flakes on the performance of mortar,glass powder was finally selected to prepare a cement-based sealant with excellent anti-efflorescence performance.The optimal mix ratio of mortar consists of 10%glass powder,1.5%silicone hydrophobic agent,0.25%water reducing agent,1.25%mixing agent,and the cement/sand ratio is 2:3.Furthermore,the proportion of efflorescence area of glass powder added mortar at this mix ratio was only 5.74%.