Shotcrete placement automation for improved quality and zero rebound losses

对快速，高效，经济，最重要的是持久的施工方法的需求比以往任何时候都更加重要，因为它是持久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、地下空间的建设和在困难地区的采矿活动急剧增加；它们都有一个共同点，就是大量使用喷射混凝土。喷射混凝土通常用于将混凝土放置在垂直和架空表面上，具有明显的优点：良好的压实性和附着力，没有复杂的模板和封装钢筋的可能性。混合设计和应用类型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了大型结构喷射混凝土墙和支撑元件，这些都是喷射混凝土不断发展的见证。然而，尽管早在100多年前就已经发明出来，并且在世界各地的使用越来越多，但最终的放置质量-反弹损失的数量，正确的巩固和适当的钢筋封装-仍然掌握在喷嘴工人的手中。因此，本研究计划的长期目标是提高我们对喷射混凝土浇筑控制机制的理解，以提高浇筑质量和工艺流程，设计新设备，优化混合料设计方法。通过使用最近在实验室获得的完全可编程的6轴工业机器人，探索生产高质量结构喷射混凝土的自动化放置技术，进一步建立了这一目标。在喷射混凝土的研究和发展中，我们确实发现自己正处于一个有趣的、前所未有的时刻：一方面，我们比以往任何时候都更好地了解喷射混凝土浇筑动态的基本机制，包括基材流变学和材料速度（从而减少回弹，充分固结和完全加固封装），而另一方面，我们正在发现自动化浇筑如何允许精确控制喷嘴运动和轨迹。通过利用、调整和控制喷射混凝土的流变性，以及在充填过程中精确的喷嘴运动，进一步减少回弹损失，提高充填质量。该方法的新颖和独特之处在于将喷射混凝土在受控环境下的全尺寸生产与喷浆和颗粒对表面的冲击研究带来的优化耦合在一起。拟议的研究项目旨在利用拉瓦尔大学多年来开发的独特设施和专有技术，在受控环境中为室内全年喷射提供全套设备，并为干拌和湿拌喷射提供实物大小的设备。

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.