Study On The Effect And Mechanism Of Silane Emulsion On The Waterproof And Anti-icing Performance Of Foamed Concrete

Under the background of promoting building energy conservation,foamed concrete is gradually being promoted due to its good heat preservation and heat insulation properties,and it can be well compatible with many building materials,and its strength can be adjusted according to actual engineering needs.Therefore,the application fields of foamed concrete are gradually expanding.However,due to the special preparation technology of foamed concrete,it is necessary to introduce bubbles by physical or chemical methods,which makes the foamed concrete have many pores.This is the structural defect of foamed concrete and the reason why foamed concrete can easily absorb water.It affects the durability of foamed concrete and shortens the working time of foamed concrete.Therefore,improving the waterproof performance of foamed concrete is a key issue for improving its durability.At present,surface waterproofing treatment is an effective method to improve the waterproof performance of foamed concrete.Usually,the waterproof material is coated on the surface of foamed concrete to form a certain thickness of waterproof layer,thereby preventing water from entering the inside of the foamed concrete.To develop new and effective waterproof materials is of great significance to improve the waterproof performance of foamed concrete.In this article,four silane emulsions were synthesized by isobutyltriethoxysilane（IBTS）,graphene oxide（GO）,and tetraethylorthosilicate（TEOS）:Silane emulsion（IBTS emulsion）,graphene oxide/silane composite emulsion（GO/IBTS composite emulsion）,tetraethylorthosilicate/silane composite emulsion（TEOS/IBTS composite emulsion）,graphene oxide/tetraethylorthosilicate/Silane composite emulsion（GO/TEOS/IBTS composite emulsion）.Applied them to the surface of self-developed foamed concrete to study the waterproof and anti-icing performance and mechanism of foamed concrete.（1）During the test preparation stage,four kind of waterproof emulsions and foamed concrete were prepared.Using IBTS,GO,TEOS as the main raw materials,PPG O as the water-based emulsifier,Span 80 as the oily emulsifier,and polyethylene glycol 2000 as the dispersant,four silane emulsions were prepared by the sol-gel method;Using high Belite sulphoaluminate cement and grade I FA as raw materials,three foamed concretes with different density and one foamed concrete with fly ash were prepared by physical foaming,and the basic property of foamed concrete,such as apparent density,specific strength,pore structure,thermal conductivity,and water absorption were tested.（2）The four waterproof emulsions were used to coat the surface of foamed concrete.Through capillary water absorption test,it was found that GO/TEOS/IBTS composite emulsion has the best waterproof effect on foamed concrete,in a single coating,the capillary water absorption coefficient of foamed concrete was only513.51 g·m^-2·h^-1/2;Through the penetration depth test,it was found that the IBTS emulsion penetrated into the foamed concrete through capillary action and generated the thickest waterproof layer,the thickness of the waterproof layer reached 16.05 mm;Through the contact angle test and the rolling angle test,it was found that the combination of the emulsion and the foamed concrete created super-hydrophobic waterproof layer;When faced with flowing water,it only soaked the surface of the foamed concrete and not immersed the inside of the foamed concrete.At the same time,it also took away the dust on the surface of the foamed concrete and had a certain self-cleaning function.（3）In the laboratory environment,the influence of four kind of silane emulsions on the waterproof performance of foamed concrete was studied at three temperatures of-20℃,0℃and 40℃.It was found that the waterproof effect of the four emulsions was generally better than 40°C at-20°C and 0°C.At the same time,the thickness of the waterproof layer generated by the silane emulsion acting on the foamed concrete at different temperatures was different.At-20℃,the thickness of the waterproof layer produced by foamed concrete was the thickest,and the smallest at 40℃;Through the rolling angle test,it was found that the foamed concrete coated with the four emulsions had good waterproof effect at-20℃,and the rolling angle of the waterproof layer was basically within 10°,reached a super-hydrophobic state,In addition,the foamed concrete coated with GO/IBTS composite emulsion and GO/TEOS/IBTS composite emulsion had smaller rolling angle,and its waterproof effect was better;The contact angle test results were consistent with the rolling angle test results.The contact angles of foamed concrete coated with GO/IBTS composite emulsion and GO/TEOS/IBTS composite emulsion with water reached 120°and 130°,respectively.（4）In the natural environment,the waterproof effect of emulsion on foam concrete was studied,the exposure test was conducted from mid-November to mid-February of the following year.The test proved that after three months of exposure in the natural environment,GO/IBTS composite emulsion had the best waterproof effect,and its ability to withstand the test of atmosphere,temperature and light was strong;IBTS emulsion was second only;GO/TEOS/IBTS composite emulsion had good waterproof effect in the early stage,but its ability to withstand the test of the natural environment was poor,resulting in a decline in the waterproof effect in the later stage;TEOS/IBTS composite emulsion had the worst waterproof effect.（5）The effect of four emulsions on the anti-icing performance of foamed concrete was studied.Through the freezing time test,it was found that the four emulsions delayed the freezing time of water droplets on the foamed concrete surface and reduced the interface free energy of the foamed concrete;Through the icing volume test,it was found that the larger the inclination angle of the foamed concrete test block,the weaker the ability to capture water droplets and the smaller the icing volume.The surface of the test block coated with GO/IBTS composite emulsion had the least amount of icing,and its ability to capture water droplets was the weakest;Through the ice repellency test,it was found that the surface of the foamed concrete coated with emulsion exhibited super-hydrophobic performance,the water failed to penetrate into the test block,only froze on the surface of the test block.（6）Though surface contact angle,rolling angle,SEM,EDS,XRD,FT-IR,TG microscopic test,it was found that the super-hydrophobic mechanism of foamed concrete was that needle-like ettringite grows in the pores of foamed concrete,which made the foamed concrete change rough.After the emulsion was coated on the surface,the emulsion penetrated into the pores through capillary action and acted on the surface of the foamed concrete.A large amount of hydrated calcium silicate and organic waterproof material were attached to the surface of needle-shaped ettringite.It greatly reduced the surface energy of the foamed concrete and made the foamed concrete became super-hydrophobic,which satisfied the Cassie theoretical model.