Improving shotcrete: modelling and rebound reduction

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。在过去几十年里，基础设施修复、地下空间建设和采矿事业的加速都有一个共同点，那就是大量使用喷射混凝土。喷射混凝土经常用于在垂直和架空的表面上浇筑混凝土，而不需要模板。虽然这项技术在世界各地都被使用，并被发现是高效、快速和经济的，但人们仍然对回弹(放置过程中的材料损失)和其耐用性的某些方面感到担忧。 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。主要目标是继续并扩大“喷洒标尺”方法，确定影响放置的材料和设备参数，促进最佳就地混凝土和整体应用。这将使喷射混凝土真正得到发展和优化，减少回弹，提高耐久性，提供可靠的施工和修复方法。 制定科学方法是为了实现三个具体目标： -了解和描述铺设技术对内部结构(压实空隙表面；这将导致改进现有混合料设计(减少回弹，增加早期强度)以及新的和创新的混合料设计的影响。例如，最近发现，添加再生玻璃粉作为SCM对贴装行为(高表观塑性)有显著影响；这里提出的方法将有助于理解这种影响，并利用它进一步减少回弹和提高质量。 在整个项目中，培训高素质人员本身就是一个重要目标。即将提出的研究计划将为混凝土材料领域的一批研究生、研究助理和研究工程师提供一个独特的培训机会。要处理的问题种类繁多，从材料行为表征到建模分析，都将促进广泛多样化的技能的发展。

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.