Improving shotcrete: modelling and rebound reduction

对快速、高效、经济、最重要的是耐用的施工方法的需求比以往任何时候都更加重要，因为它是耐用设计和使用寿命优化的关键。在过去的几十年里，建筑物的修复，地下空间的建设和采矿事业的加速都急剧增加;它们都有广泛使用喷射混凝土的共同点。喷射混凝土通常用于将混凝土放置在垂直和高架表面上，而无需模板。虽然该技术在世界各地使用，并已被发现是高效，快速和经济的，但仍然存在关于回弹（在放置过程中的材料损失）和其耐久性的某些方面的问题。 使用比以往任何时候都更基本的方法，拟议的项目将受益于最近完成的项目的独特结果。主要目标是继续和扩大“喷射-规模”办法，确定影响浇筑的材料和设备参数，促进最佳的现浇混凝土和全面应用。这将允许真正的发展和优化，以减少回弹和提高喷射混凝土的耐久性，提供可靠的施工和维修方法。 制定科学方法是为了实现三个具体目标： - 理解并描述铺筑技术对内部结构（压实空隙表面）的影响;这将导致现有混合料设计的改进（减少回弹，增加早期强度）以及新的和创新的混合料设计。例如，最近发现，添加粉末状回收玻璃作为SCM对放置行为（高表观塑性）有显着影响;这里提出的方法将有助于理解这种影响，并利用它来进一步减少回弹和提高质量。 在整个项目中，培训高素质的人员本身就是一个重要目标。该研究计划将为混凝土材料领域的研究生，研究助理和研究工程师提供独特的培训机会。从材料行为表征到建模分析，要处理的各种各样的问题将促进广泛多样化技能的发展。

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, the construction of underground spaces and the accelerating of mining undertakings 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 without the need for formwork. Although the technique is used all around the world and has been found to be highly efficient, rapid and economical, concerns are still present with regards to rebound (material losses during placement) and some aspect of its durability. Using a more fundamental approach than ever before, the projects proposed will benefit from the unique results of a recently completed project. The main objective is to continue and expand the “spray-scale” approach and identify the material and equipment parameters that affect placement and promote the best in-place concrete and overall application. This will allow true development and optimization for reduced rebound and improved durability of shotcrete, providing a reliable construction and repair method. The scientific approach is elaborated to meet three specific objectives: - Understand and describe the effect of the placement techniques on the internal structure (compaction voids urface; this will lead to both improvements of existing mixture design (reduction of rebound, increased early strength) as well as new and innovative mixture design. It was recently found, for example, that the addition of powdered recycled glass as a SCM has a significant effect on the placement behaviour (high apparent plasticity); the approach proposed here will help understand this effect and exploit it to further reduce rebound and improve quality. The training of highly qualified personnel is, throughout the project, an important goal by itself. The research program to be proposed will provide a unique training opportunity for a number of graduate students, research assistants and research engineers in the field of concrete materials. The wide variety of issues to be treated, from material behavior characterization to modeling analysis, will promote the development of widely diversified skills.