| To solve the problem of premature failure of bridge deck pavement materials,epoxy polymer concrete is increasingly used in bridge deck pavement and building prefabricated parts due to its excellent mechanical properties and rapid prototyping characteristics.In natural environment,the mechanical properties of epoxy polymer concrete will inevitably be degraded due to violent changes in temperature,rain erosion,ultraviolet radiation,and other weather conditions.Epoxy polymer mortar,as the binder of aggregate,has the characteristics of high strength and strong anti-deformation ability,and plays the role of load transfer and deformation coordination in epoxy polymer concrete.Therefore,the change of mechanical properties of epoxy polymer mortar in natural environment has a vital impact on the strength of epoxy polymer concrete.In the current research,the mechanism by which ultraviolet radiation,humidity and temperature reduce the mechanical properties of epoxy polymer concrete is still unclear.In this paper,to investigate the influence of different aging environments on the bending performance of epoxy polymer mortar,the hygrothermal aging test and ultraviolet accelerated aging test of epoxy polymer mortar were designed according to the climate conditions in South China.In addition,the aging products and aging layer thickness of epoxy resin after hygrothermal aging and UV aging were tested by AFM-IR,and scanning electron microscope(SEM)was used to study the changes of microstructure in epoxy polymer mortar.Finally,a prediction model was established based on the change law of the flexural strength of epoxy polymer mortar in hygrothermal environment at different temperatures,and the flexural strength of epoxy polymer mortar was predicted.The main conclusions of this paper are as follows:(1)The influence of hygrothermal environment at different temperatures on the flexural properties of epoxy resin matrix and epoxy polymer mortar was studied.The epoxy resin matrix and epoxy polymer mortar were placed at 25℃,40℃,60℃ and 80℃ for different aging time.The longest aging time was 14 days.According to the change law of flexural strength and flexural modulus of materials with time in the hygrothermal environment at different temperatures,the flexural strength and flexural modulus decrease monotonously with the increase of aging temperature and aging time.After aging at 80℃ for 14 days,for 14 days,the flexural strength and flexural modulus of epoxy resin decreased by 23.1% and 18.4%respectively,and the flexural strength and flexural modulus of epoxy polymer mortar decreased by 22.8% and 21%,respectively.(2)According to the amount of ultraviolet radiation in Guangzhou,the equivalent aging time of ultraviolet accelerated aging for 1 year is determined to be 46.6 hours and the longest simulated aging time for epoxy resin matrix and epoxy polymer mortar is 7 years.The results of the three-point bending test show that the ultraviolet radiation had little effect on the bending resistance of the material.(3)The aging mechanism of epoxy resin and epoxy polymer mortar in different aging environments was studied.AFM-IR results of epoxy resin after 80℃ hygrothermal aging show that hygrothermal environment will not cause chemical aging of epoxy resin.The results of AFM-IR on the resin after ultraviolet aging showed that UV aging only occurred on the surface of the resin,and the aging products were distributed in the range of 30 ～ 50 μm,indicating that the surface aging caused by UV was not enough to weaken the bending resistance of epoxy polymer mortar.SEM results show that hygrothermal environment will weaken the bonding properties of aggregate and resin interface,resulting in the decrease of flexural properties of epoxy polymer mortar after hygrothermal aging.(4)An improved Arrhenius model is proposed to describe the change of flexural strength of epoxy mortar after hygrothermal aging test.The improved Arrhenius model shows that,shows that the epoxy polymer mortar will steadily retain 92.8%,89.1% and 79.4% of the original flexural strength after long-term hygrothermal aging at 40℃,60℃ and 80℃respectively.(5)The laminated damage beam model was established to investigate the effect of aging layer thickness on the flexural properties of epoxy polymer mortar.The results show that the thickness of aging layer is 3.63 mm,3.85 mm and 4.02 mm after hygrothermal aging at 40℃,60℃and 80℃ for 14 days. |
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