Preparation And Performance Of Waterproof Adhesive Layer For Steel Bridge Deck Based On Self-stratification Effect

As the intermediate layer between the bridge deck and the asphalt pavement,the waterproof adhesive layer(WAL)not only can bond the bridge deck and the asphalt pavement as a whole,but also can prevent water and corrosive substances from seeping into the bridge deck.Therefore,the WAL with excellent performance has an important impact on the safety of the steel bridge deck pavement.Aiming at the defects of poor durability,poor flexibility,high construction cost,and long construction period of current steel bridge deck WALs,the self-stratification effect was introduced into the design and development of WALs in this paper.Three types of WALs have been prepared,and the basic performance and road performance of which have been studied in detail.The self-stratification mechanism has been discussed via surface energy theory.Finally,in order to verify the actual performance of self-stratifying WALs,the comprehensive performance of the three types of WALs was compared with the epoxy resin WAL which has been currently used for steel bridge decks.The specific research is as follows:(1)P(BA-MMA-St)block polymers were synthesized by free radical solution polymerization with the monomers which were butyl acrylate(BA),methyl methacrylate(MMA),and styrene(St),respectively.Then,the P(BA-MMA-St)block polymers were mixed with bisphenol A epoxy resin E51 in a certain proportion in the co-solvent(xylene and n-butanol)to form the self-stratifying waterproof coatings.The coatings will be automatically formed the PA/E51 WAL with the co-solvent naturally volatilizing.Finally,the self-stratifying waterproof coatings were uniformly scraped onto the surface of the steel plate.The glass transition temperature,molecular weight,thermal stability and chemical composition of P(BA-MMA-St)were characterized by differential scanning calorimetry(DSC),gel permeation chromatography(GPC),thermogravimetric analysis(TGA)and Fourier transform infrared spectroscopy(FT-IR).What`s more,5 kinds of WAL were prepared by changing the mass ratio of polyacrylic acid resin to epoxy resin.The influence of the proportions of the two kinds of resins on the performance of WAL was studied.The basic performance and road performance of PA/E51were tested according to the relevant WAL specification for steel bridge deck.The self-stratification behavior was investigated via FT-IR,static contact angle test,SEM,and surface energy theory.The results show that when the ratio of polyacrylic acid resin to epoxy resin is3:7,the comprehensive performance of WAL is the best.Its tensile strength can reach 7.12 MPa,elongation at break 108.1%,and pull-out strength 9.35 MPa.Moreover,the WALs could meet the requirements for water impermeability.In addition,by testing the pull-out strength of the waterproof adhesive layer with different spraying quantity,the optimal spraying quantity was determined to be 0.71～0.82 kg/m~2.5 kinds of self-stratifying WAL all exhibit self-stratification behavior during the curing stage,with the upper layer mainly composed of polyacrylic acid resin and the lower layer mainly composed of epoxy resin.(2)In order to overcome the defect of poor durability of existing WALs,the C-F bond with chemically stability was introduced into the above-mentioned resin.Namely,5 kinds of P(BA-MMA-St-DFHMA)with different fluorine content were synthesized via free radical solution polymerization with the monomers which were dodecafluoroheptyl methacrylate(DFHMA),BA,MMA,and St,respectively.And 5 kinds of P(BA-MMA-St-DFHMA)were mixed with epoxy resin E51 to form the waterproof coating FPA/E51.The influence of different fluorine content compositions(5%,10%,15%,20%,and 25%)on the basic performance and road performance of self-stratification WAL was systematically studied.Finally,the durability mechanism of this type of WAL was discussed in detail.The results show that when the fluorine content was 20%,the tensile strength and elongation at break of WAL could reach their maximum value,which were 7.04 MPa and 128.9%,respectively.At the same time,it exhibits the best adhesive strength(6.55MPa).In addition,aging durability test was conducted on WALs with different fluorine content.After 10 days aging test,the mechanical properties only decreased by about 10%.(3)How to improve the flexibility of WAL to meet its demand for bridge deformation following performance under driving loads has been one of the key issues that need to be urgently addressed in this field.Introducing long chain alkyl groups into the acrylic resin structure can improve the flexibility of WAL.4 kinds of P(BA-MMA-St-EHA)with different glass transition temperatures were synthesized via free radical solution polymerization with the monomers which were isooctyl acrylate(EHA),BA,MMA,and St,respectively.They were mixed with epoxy E51 to obtain a series of EPA/E51 self-stratifying WALs.Finally,the effect of glass transition temperature on self-stratification behavior was discussed.The results show that in the mechanical property test,the elongation at break of the WALs can reach 150%on average,which means that the WALs have excellent deformation resistance and deformation coordination.In addition,with the increase of the glass transition temperature,the pull-out strength shows a trend of firstly increasing and then decreasing,with the maximum of 8.35MPa.The impermeability of the WALs also meets the specific requirement.When the glass transition temperature of P(BA-MMA-St-EHA)is-15℃,WAL exhibits the best performance.Moreover,the change of glass transition temperature has no influence on the self-stratification behavior.(4)The optimal formulations of the three types of WALs mentioned above were compared with the epoxy WAL currently used for steel bridge decks to estimate the comprehensive performance of self-stratifying WALs.The results show that the high-temperature performance of self-stratifying WALs is equivalent to that of epoxy resin WAL,while the low-temperature performance of self-stratifying WAL is better than that of epoxy resin WAL.In addition,the elongation at break of self-stratifying WALs is as high as 157%,while the elongation at break of epoxy resin WAL is only 89%.And the adhesive strength and impermeability of the self-stratifying WALs and epoxy resin WAL could meet the specific requirement.To sum up,the self-stratifying WALs prepared in this paper show good performance advantage and application prospect.