Improved durability testing for field placed concrete and emerging cement systems

向基于性能的规范的转变为新的混凝土基础设施带来了创新和挑战。生产商有能力添加新材料，因为他们不再受到规定限制的约束。在某些情况下，这些新材料可能尚未在混凝土施工中得到证实，但可能具有延长使用寿命或减少维修需求或频率的好处。这些新的规范方法的另一个复杂之处在于，不仅在资格预审阶段必须进行定量评估，而且在项目进行的过程中也必须进行定量评估。理想情况下，这些测试应该在现场放置的混凝土上进行，而不是在没有经过相同压实或养护的圆柱体上进行，当然也不是在相同的非标准暴露条件下进行。******该计划的目标是：***1)研究新兴水泥体系的水化、强度发展和耐久性，特别关注纳米颗粒。***2)检查和开发耐久性符合性的现场测试方法，特别是快速，非破坏性的方法，如吸收和表面电阻率。建立将温度/湿度影响转化为标准条件的方法。***3)现场使用嵌入式温度/湿度传感器，以更好地了解与ASR和冷冻相关的变质过程。******传统上，混凝土劣化可以通过低水灰比、使用补充胶凝材料和充分养护三管齐下的方法来减轻。不幸的是，许多补充胶结材料，特别是粉煤灰，不与水反应，而是与水泥水化的副产品。实际上，这通常表现为较低的早期强度和所需的延迟时间，直到可以获得足够的强度和耐久性。纳米颗粒由于其作为水泥水化成核位点的能力，从而克服了与其他水泥替代品相关的一些障碍，引起了研究界的兴趣。******吸水和表面电阻率是一种快速、简单的非破坏性技术。然而，这两种技术的一个缺点是，现场湿度和环境温度的影响会显著影响测试结果。该研究计划将进一步调查所需的饱和度，以获得与使用寿命预测或维修要求相关的可靠数据。******由于混凝土是一种多孔材料，进水对其劣化起着重要作用。小型无线温湿度传感器将用于实验室和室外混凝土，以了解水分在降解中的作用。

The move towards performance-based specifications brings both innovation and challenges to new concrete infrastructure. Producers have the ability to add new materials as they are no longer constrained by prescriptive limitations. In some cases, these new materials may be yet unproven in concrete construction, but may have benefits of extending service life or decreasing the need or frequency of repair. Another complication of these new methods of specification are that a quantitative assessment must be undertaken not only at the prequalification stage, but over time as the project proceeds. Ideally, these tests should be performed field placed concrete rather than cylinders that have not received the same compaction or curing and certainly not the same non-standard exposure conditions. ******The objectives of the program are:***1) Investigate the hydration, strength development and durability of emerging cement systems, with particular attention to nanoparticles.***2) Examine and develop in situ testing methods for durability compliance, specifically, rapid, non-destructive methods, such as absorption and surface resistivity. Establish methods to convert temperature/moisture influences to a standardized condition.***3) Utilize embedded temperature/moisture sensors onsite to better understand processes related to deterioration due to ASR and freezing. ******Traditionally, concrete deterioration can be lessened through a three-prong approach of low water to cement ratio, the use of supplementary cementing materials and adequate curing. Unfortunately, many of the supplementary cementing materials, particularly fly ash, do not react with water rather with by-products of cement hydration. In practice, this often translates in low early strength and a delayed period required until adequate strength and durability can be obtained. Nanoparticles have gained interest among the research community due to their ability to act as nucleation sites for cement hydration and therefore overcoming some obstacles associated with other cement replacements. ******Water absorption and surface resistivity are rapid and simple non-destructive techniques. However, one disadvantage of both these techniques are that the effects of in-situ moisture and ambient temperature can significantly affect the test results. This research program will further investigate the saturation required to obtain reliable data that can be linked to service life predication or repair requirements. ******As concrete is a porous material, water ingress plays a significant role in deterioration. Small wireless temperature and humidity sensors will be used in both lab and outdoor concrete to understand the role of moisture in degradation.