Corrosion Characteristics And Mechanism Of Resin-Cement Interface Exposed To The Coupling Of Acid Rain And Ultraviolet

Resin light conductive cementitious materials(RLCCM)is an organic-inorganic advanced building materials made of self-compacting cement mortar and transparent resin as the light guide component.It has effects of transmittance development and lighting energy saving.The service environment of RLCCM is mainly exposed to ultraviolet light.Meanwhile,considering the serious pollution of acid rain in China,Resin light conductive cementitious materials is also often affected by acid rain in the external environment.Therefore,the typical service environment of RLCCM is ultraviolet radiation,acid rain erosion,etc.Under the typical service environment above,the aging of transparent resin,deterioration of cement matrix and weakening of organic-inorganic interface are unavoidable,which will directly affect the transmittance,mechanical properties and microstructure of resin light conductive cementitious materials.The relationship between the deterioration of interface and the evolution of microstructure is not clear under the typical service environment at presents.Therefore,transparent resin and cement matrix were used as carriers to investigate the corrosion characteristics of resin-cement interface under the condition of single and coupling of acid rain and ultraviolet radiation,the corrosion evolution model of the resin-cement interface under the coupling of acid rain and ultraviolet radiation was established in this study.The corrosion characteristics and mechanism of resin-cement interface under the single and coupling of acid rain and ultraviolet were obtained by means of Oblique shear bond strength,surface appearances,ESEM-EDS and FTIR.The results of the study are as follows.1.Oblique shear failure of specimens occurred at the interface of cement matrix and resin.2.Cement matrix started to corroded at the position close to interface,with the growth of the age,corrosion occurred from the surface to the interior gradually under influence by acid rain,oblique shear bond strength of resin-cement interface first increased and then declined,reaching the maximum value of 12.07 MPa after 9 days corrosion of acid rain.3.Yellowing of resin was deepened with the increase of UV radiation time,oblique shear bond strength of resin-cement interface first increased and then declined after exposed to the ultraviolet and reached the maximum of 11.62 MPa at 24 h.4.Yellowing occurred at resin and failure of cement matrix happened gradually from outside to inside,Oblique shear bond strength of resin-cement interface showed a tread from rising to decline and reached the maximum value of 11.38 MPa at 3d after exposed to the coupling of acid rain and ultraviolet.5.After exposed to acid rain,CH was gradually reduced and gypsum was generated to fill partial pores at the early days,making the resin-cement interface more tightly,with the increasing of time,C-S-H was gradually consumed,more and more gypsums were produced,the areas close to resin-cement interface was covered with a layer of white viscous gypsum,resulting cracks in the interface.6.Structure strength increased at the early age as a result of post-curing reaction of resin under ultraviolet radiation,making resin-cement interface more tightly,along with the extension of ultraviolet irradiation time,Photooxidation reaction happened,the O/C of resin increased from 3.57 to 5.69 after exposed to UV radiation,making obvious microcracks appeared in the bonding zone between the resin and cement matrix.7.Exposed to the coupling of acid rain and ultraviolet for 21 days,the Ca/Si of cement paste near the interface increased from 4.0 to 5.0,and the O/C of resin increased from 3.6 to 4.6,respectively.CH was gradually consumed while gypsum was produced at early age,a portion of pores at interface were filled by volume expansion.Along with the extension of corrosion time,molecular chain scission,carbonyl and ester group degradation occurred on resin.Bonding properties between resin and cement interface was weakened because of consume of C-S-H in cement paste and continuous production of gypsum.Through macro and micro analysis,three stages of organic-inorganic interface corrosion evolution model exposed to the coupling of acid rain and ultraviolet were established.Hydration products of inorganic cement matrix are mainly composed of CS-H and CH,the organic transparent resin is mainly composed of macromolecule chain,C-S-H,CH and macromolecule chain distributed among the interface between resin and cement before corrosion;at the initial stage,the organic transparent resin shows slightly yellowing,part of macromolecule chain scission and produced free radical,Ester groups and carbonyl groups et al are generated at transparent resin in the meantime,A part of CH in the inorganic cement matrix is consumed to produce gypsum,enhanced the strength of the resin cement-based material;at the later stage of coupling effect,the organic transparent resin yellowing deepen with time.More free radical are produced owing to the macromolecule chain scission,degradation of carbonyl and ester groups at organic transparent resin.C-S-H and CH are gradually consumed at the inorganic cement matrix.A large amount of plaster is generated near the interface bonding zone and enlarging the thickness of this area.Thus expansive crack happened at the interface of resin and cement and lend to sharp decline of the specimens strange in late stage exposed to the coupling of acid rain and ultraviolet.