Research On The Influence Of Ultraviolet Radiation On Carbonation Performance For Fly Ash Concrete

In practical engineering,a large number of concrete structures are in service under the condition of sunlight.Scholars have noticed that the ultraviolet radiation in the sunlight will affect the carbonation performance of concrete,but its influence law and mechanism have not been deeply studied.In order to study the effect of ultraviolet radiation on concrete carbonation,the rapid carbonation tests of concrete with different fly ash content and different cement varieties under three different ultraviolet radiation conditions were carried out.The research results of this paper can provide new ideas for the design of concrete fly ash content,the design of protective layer thickness and the prediction of concrete durability under UV irradiation.The main contents of this paper are as follows:(1)Concrete specimens with different fly ash content and cement varieties were poured,and their compressive strength was tested at 3d,7d and 28 d.The analysis data show that adding fly ash into concrete will reduce the compressive performance of concrete,and the weakening of compressive stress of concrete with high content of fly ash is particularly obvious.When other conditions are the same,the compressive strength of concrete specimens poured with P.O42.5 cement is significantly higher than that of concrete specimens poured with P.C32.5 cement,and the difference between the two increases with the increase of curing time.(2)Rapid carbonization tests of concrete with different fly ash content and different cement varieties under three UV irradiation conditions were carried out.The test results show that ultraviolet radiation accelerates the carbonation process of concrete.The addition of fly ash will reduce the carbonization resistance of concrete.Under the condition of ultraviolet radiation,the carbonization depth of fly ash decreases first and then increases with the increase of fly ash content.From the analysis of test results,it can be seen that the optimum carbonization depth of fly ash content should be 15%;The addition of fly ash will weaken the promotion effect of ultraviolet radiation on concrete carbonization.It is inferred that the influence of ultraviolet radiation on concrete carbonization is closely related to the compactness of concrete.The results of variance analysis show that fly ash content,ultraviolet intensity and their interaction have significant effects on concrete carbonization,but the effect is more significant than others.(3)The analysis of carbonization depth data under ultraviolet radiation shows that the thickness of carbonization layer will weaken the promotion of ultraviolet radiation on carbonization,but the influence of ultraviolet radiation on concrete carbonization can not be ignored even under certain basic carbonization layer thickness.The relationship between the increase of carbonation depth of concrete caused by ultraviolet radiation and ultraviolet radiation is fitted,and a prediction model of carbonation depth of concrete considering ultraviolet radiation is given.