A new multi-scale approach to characterize concrete creep - Phase 2: drying effects, application to emerging concretes and micro-to-macro validation

表征混凝土徐变的新多尺度方法 - 第 2 阶段：干燥效果、新兴混凝土的应用和微观到宏观验证

• 批准号: RGPIN-2022-05406
• 负责人: Sorelli, Luca
• 金额: $ 2.26万
• 依托单位: Université Laval
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=753871
• 关键词: new; multi; scale; approach; characterize

A recent survey on 71 concrete bridges monitored over a period of about 20 years showed that the creep deflection increases incessantly and it overestimates by far the predictions of several national codes. A wake-up call was then launched stating that the current national design recommendations and codes "are not only theoretically obsolete, but also indefensible". The proposed research program aims at better understanding and characterizing the long-term creep of concrete, and finally, to enhance the current design methods for predicting the long-term behavior. The reason is that concrete creep depends on many factors so that published results are often controversial. Predicting the creep deflection of structure after decades from experimental compression creep tests lasting few months is a tremendous and error-prone challenge. Current methods to characterize concrete creep are time consuming and rarely applied in practice (3). Furthermore, there is a limited availability of creep data on emerging modern concretes, such as ultra-high performance concretes (UHPCs), which have enormous potentials for fostering the design lifetime and reduce the maintenance cost towards a more sustainable infrastructure system (4). By pioneering an innovative new research direction, this research program aims setting-up a groundbreaking multi-scale approach for enhancing current knowledge on concrete creep in terms of characterization methods, design accuracy and advanced material development. The specific objective of this research program is six-fold: (1) Foster the knowledge on the mechanisms of concrete creep under environmental changes by innovative micro-mechanical testis; (2) Develop a multiscale method to upscale the measured properties from the cement paste level to the concrete level; (3) Validate the proposed two-scale method (2SM) for characterizing cement paste, mortars and concrete at different water-to-cement ratios with emphasis on modern concretes and emerging UHPC; (4) Contribute to the Canadian design for predicting long-term deflection of concrete structures and improve the current practise; (5) Develop an international network of excellence on concrete micromechanics; (6) Train students in highly specialized competences requested for innovating industry.

最近对71座混凝土桥梁近20年的监测表明，徐变挠度不断增大，远远高估了几个国家规范的预测值。然后敲响了警钟，声明目前的国家设计建议和规范“不仅在理论上过时，而且站不住脚”。提出的研究方案旨在更好地了解和表征混凝土的长期徐变，并最终改进现有的预测长期行为的设计方法。原因是混凝土徐变取决于许多因素，因此发表的结果往往是有争议的。从持续几个月的压缩蠕变实验中预测结构在几十年后的蠕变挠度是一个巨大且容易出错的挑战。目前表征混凝土徐变的方法非常耗时，而且很少在实践中应用。此外，新出现的现代混凝土，如超高性能混凝土(超高性能混凝土)的蠕变数据有限，这在延长设计寿命和降低维护成本以实现更可持续的基础设施系统方面具有巨大潜力(4)。通过开创一个创新的新研究方向，该研究计划旨在建立一种突破性的多尺度方法，以在表征方法、设计精度和先进材料开发方面增强对混凝土徐变的现有知识。这项研究的具体目标有六个方面：(1)通过创新的微观力学测试，培养对环境变化下混凝土徐变机理的认识；(2)开发一种多尺度方法，将测量的性能从水泥浆体水平提升到混凝土水平；(3)验证所提出的双尺度方法(2SM)，以表征不同水灰比下的水泥净浆、砂浆和混凝土，重点关注现代混凝土和新兴的超高性能混凝土；(4)为加拿大预测混凝土结构长期挠度的设计做出贡献，并改进当前的实践；(5)发展混凝土细观力学的国际卓越网络；(6)培养创新行业所需的高度专业化能力的学生。