Development and performance of self-consolidating concrete with adapted thixotropy

自固结混凝土（SCC）是一种新兴的技术，它使混凝土的浇筑没有任何机械固结时，将需要使用传统的混凝土。这可以显著减少浇注时间和劳动力成本，并生产优质混凝土产品。尽管SCC在预制行业得到了广泛的认可（北美市场份额高达30%），但在预拌行业使用SCC仍存在一些技术问题，预拌行业是加拿大混凝土建筑的最大部分。在稳定和坚固的SCC的日常设计中仍然存在技术变化，可以在垂直结构部分（柱，元件，桥墩等）中浇注。而不会在模板上施加过大的侧向压力。这一点很重要，因为SCC表现得像液体，与更硬的传统混凝土相比，SCC可以对模板施加更大的侧向压力，对施工成本产生相当大的影响。SCC可以设计成具有可逆的结构形成（触变性），以降低成型压力并确保硬化材料的更大原位均匀性。生产高触变性混凝土可能会导致一些表面缺陷（施工提升线的外观和形成的表面上的大气泡），并且需要调整混凝土的流变性能以匹配浇筑条件。拟议的研究计划的目标是（i）开发测试协议，以评估可逆的结构建立在休息和特殊的测试方法，以评估触变性在现场;（ii）阐明控制触变性的机制;（iii）开发新一代的SCC适应触变性和上级工程性能和耐久性。该研究的最终目标是开发新一代高流动性混凝土，从而彻底改变加拿大及其他地区的建筑业。这种混凝土可以导致施工过程的优化和自动化，增加复杂结构的创新设计的使用，并确保高性能的建筑和维修材料，以应对在加拿大建造耐用混凝土基础设施的巨大挑战。

Self-consolidating concrete (SCC) is an emerging technology that enables the casting of concrete without any mechanical consolidation which would be required when using conventional concrete. This can lead to remarkable reduction of casting time and labour cost and the production of premium concrete products. Although SCC has gained wide acceptance in the precast industry (up to 30% of the market share in North America) some technical issues remain at hand for the use of SCC in the ready-mix industry, which holds the largest segment of concrete construction in Canada. Technical changes remain in daily designs of stable and robust SCC that can be cast in vertical structural sections (columns, elements, bridge piers, etc.) without exerting excessive lateral pressure on the formwork. This is important given the fact that SCC behaves like a liquid and could exert greater lateral pressure on formwork compared to stiffer conventional concrete, with considerable impact on construction cost. SCC can be designed to exhibit a reversible structural build-up (thixotropy) to reduce form pressure and secure greater in-situ homogeneity of the hardened material. Producing highly thixotropic concrete could lead to some surface defects (appearance of construction lift lines and large entrapped air bubbles at formed surfaces) and would necessitate adapting the rheological properties of the concrete to match placement conditions. The objectives of the proposed research program are to (i) develop test protocols to evaluate the reversible structural build-up at rest and special test methods to assess thixotropy in the field; (ii) elucidate mechanisms governing thixotropy; (iii) develop new generation of SCC with adapted thixotopy and superior engineering properties and durability. The ultimate goal of the research is to develop new generation of highly flowable concrete that could revolutionize the construction industry in Canada and beyond. Such concrete can lead to optimization and automation of the construction process, increase the use of innovative designs for complex structures, and secure high-performance construction and repair materials to meet the great challenge of building durable concrete infrastructure in Canada.