Influence of intense ultraviolet radiation on drying shrinkage of cement paste and its mechanism
To evaluate the influence of intense ultraviolet radiation conditions on the volume stability of cement-based materials,and ensure the performance stability of cement-based materials serving in the intense radiation area,the drying shrinkage test was carried out to study the drying shrinkage and mass loss of cement paste under standard drying conditions and intense ultraviolet radiation conditions.The influences of intense ultraviolet radiation on the mechanism of drying shrinkage were analyzed by thermogravimetric(TG)analysis and mercury intrusion porosimetry(MIP)tests.The effectiveness of shrinkage reduction agents(SRA)under intense ultraviolet radiation conditions was discussed by considering the mechanism of shrinkage reduction agents.The results indicate that compared with the standard drying conditions,the intense ultraviolet radiation conditions significantly increase the drying shrinkage and mass loss rate of the cement paste,reduce the hydration degree,and coarsen the pore structure.The addition of SRA can reduce the mesoporosity(＜50 nm)of the cement paste,leading to the drying shrinkage of the cement paste under intense ultraviolet radiation conditions can be effectively reduced.Additionally,the surface tension of the pore solution can be further reduced by the SRA under intense ultraviolet radiation,thereby improving its capacity to reduce drying shrinkage.It is worth noting that the enhancement effect of intense ultraviolet radiation on the effects of the SRA is most pronounced when the concentration of the SRA is 1%,while this enhancement effect becomes limited as the dosage is further increased.This research can clarify the deformation law of cement-based materials under intense ultraviolet radiation conditions.The results can provide a technical basis for the volume stability control of cement-based materials serving in similar environments.
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