Shotcrete placement automation for improved quality and zero rebound losses

对快速、高效、经济，尤其是耐用的施工方法的需求比以往任何时候都更加重要，因为这是耐用设计和使用寿命优化的关键。过去几十年来，各种基础设施的修复和恢复、地下空间的建设以及在具有挑战性的土地上进行的采矿活动急剧增加；它们都有一个共同点，就是广泛使用喷射混凝土。喷射混凝土通常用于在垂直和架空的表面上浇筑混凝土，具有明显的优点：良好的密实度和粘结性，不需要复杂的模板，可以包裹钢筋。在混合物设计和应用类型方面的可能性几乎是无限的。例如在多伦多地区最近的建筑中广泛使用大量的结构喷射混凝土墙和支撑元件，就是喷射混凝土不断进步的性质的见证。然而，尽管它在100多年前就被发明了，它在世界各地的使用也越来越多，但最终的放置质量--回弹损失量、正确的固结和适当的钢筋封装--仍然掌握在喷嘴工人的手中。因此，本研究方案的长期目标是提高我们对喷射混凝土浇筑控制机理的认识，以提高浇筑质量和工艺流程，设计新的设备，并优化配合比设计方法。通过探索自动化浇筑技术，使用实验室最近获得的完全可编程的6轴工业机器人，进一步实现了这一目标，以生产高质量的结构喷浆混凝土。我们确实发现自己在喷射混凝土研究和开发方面处于一个有趣的、以前从未达到的时刻：一方面，我们比以往任何时候都更好地了解喷射混凝土浇注动力学的基本机制，包括基质流变学和材料速度(从而减少回弹、充分固结和完全加固封装)；另一方面，我们正在发现浇注自动化如何能够精确控制喷嘴移动和轨迹，这为通过利用、调整和控制喷嘴流变性以及在浇注过程中精确地控制喷嘴移动来进一步减少回弹损失和提高浇筑质量开辟了道路。该方法的新颖性和独到之处在于在受控环境中实现了喷射混凝土的全面生产，并通过研究喷雾和颗粒对表面的影响带来了优化。拟议的研究计划旨在利用拉瓦尔大学多年来开发的独特设施和技术诀窍，其设备齐全，可在受控环境下进行室内全年喷射混凝土，并为干拌和湿拌喷射混凝土提供真人大小的设备。

The need for construction methods that are rapid, efficient, economical and, above all, durable is more important than ever as it is the key to durable design and service life optimization. Infrastructures repair and rehabilitation of all kinds, the construction of underground spaces and the mining undertaking in challenging grounds have increased sharply over the last decades; they all have in common the extensive use of shotcrete. Shotcrete is regularly used to place concrete on vertical and overhead surfaces with obvious advantages: excellent compaction and adhesion, the absence of complex formwork and the possibility to encapsulate reinforcement. The possibilities in both mixture designs and types of applications are almost limitless. Examples such as the extensive use of massive structural shotcrete walls and shoring elements in recent constructions in the Toronto area are witnesses of the ever-advancing nature of shotcrete. However, despite having been invented more than a 100 years ago and its increasing usage around the world, the final quality of placement -amount of rebound losses, correct consolidation and proper reinforcing bars encapsulation- is yet still in the hands of the nozzleman. The long-term objective of this research proposal therefore is to improve our understanding of the mechanisms that control the placement of shotcrete in order to improve the placement quality and the technological process, to design new equipment, and to optimize the mixture design methods. This objective is further built upon through the exploration of automated placement techniques for producing high quality structural shotcrete, using a fully programmable 6-axis industrial robot recently acquired in the laboratory. We indeed find ourselves at an interesting and never attained before moment in shotcrete research and development: on the one hand, we have a better understanding than ever of the fundamental mechanisms of shotcrete placement dynamics involving substrate rheology and material velocity (and hence rebound reduction, adequate consolidation and complete reinforcement encapsulation) while, on the other hand, we are discovering how the automation of placement allows for precise control of the nozzle movements and trajectories, which opens the way to further reduce rebound losses and improve placement quality by exploiting, adapting, and controlling shotcrete rheology as well as precise nozzle movement during placement. The novelty and uniqueness of the approach is the coupling of full-scale production of shotcrete in a controlled environment and the optimization brought by study of the spray and particle impact on the surface. The proposed research program is designed to leverage the unique facilities and the know-how developed at Université Laval over the years with its fully equipped for indoor, year-round shotcreting in a controlled environment and offering life-size equipment for both dry-mix and wet-mix shotcrete.