强紫外线辐射环境对水泥石干缩变形的影响及其机理

Influence of intense ultraviolet radiation on drying shrinkage of cement paste and its mechanism

为了掌握强紫外线辐射环境下水泥基材料体积稳定性的演变规律,确保服役于强辐射地区的水泥基材料性能的稳定性,通过硬化水泥浆体干燥收缩试验,研究标准干燥环境和强紫外线辐射环境下硬化水泥浆体的干缩变形和质量损失的演化规律。结合热重分析(TG)和汞孔隙率(MIP)测试方法,探讨强紫外线辐射环境对硬化水泥浆体的干燥收缩的影响机理。同时,基于减缩剂的减缩机理,探讨其在强紫外线辐射环境下的作用效果。研究结果表明:相较于标准干燥环境,强紫外线辐射环境显著增加水泥石的干燥收缩和质量损失,降低水泥水化程度,从而使水泥石的孔隙结构粗化。掺入减缩剂可以降低水泥石的介孔率(<50 nm),有效降低强紫外线辐射环境下水泥石的干燥收缩。此外,在强紫外线辐射环境下,减缩剂的掺入会进一步降低孔隙溶液的表面张力,增强减缩剂的减缩效果。值得注意的是,当减缩剂掺量为1%时,强紫外线辐射对减缩剂效果的增强作用最为显著。当掺量进一步增加时,这种增强作用将受到限制。研究结果厘清了强紫外线辐射环境下的水泥基材料变形规律,为服役于类似环境的水泥基材料体积稳定调控提供技术依据。

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.