Improved durability testing for field placed concrete and emerging cement systems

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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.