Development of three-dimensional characteristic values for the classification of aggregates - Part 2: Correlation between three-dimensional particle shape and fresh and hardened mortar properties

集料是混凝土和砂浆中体积分数最大的集料，其形状特性影响混凝土和砂浆在新拌和硬化状态下的性能。不同于标准的实验室程序，如确定片状或形状指数，计算机断层扫描能够确定聚合样品中每个颗粒的广泛的三维形状参数。在前一个项目中，开发了一个程序，将聚集的样本作为散装样本进行扫描，并自动执行必要的图像处理步骤。这包括到目前为止手动执行的接触颗粒之间边界的识别。表征具有代表性的细粒或粗粒集料样品的颗粒形状现在成为可能。在文献中，首次报道了三维颗粒形状参数对某些新拌砂浆和硬化砂浆性能影响的试验结果。然而，对骨料中形状参数的最佳分布以准确影响新拌或硬化砂浆性能的详细分析仍然缺乏。该项目未来的主要重点是分析用计算机断层扫描确定的三维颗粒形状与新拌和硬化砂浆性能之间的关系。研究了四种细粒材料的这一形状特征与新拌砂浆的用水量、堆积密度、流动性、微小坍落度、动粘度和屈服以及硬化砂浆的抗折强度、抗压强度和杨氏模数之间的关系。对于砂浆试验，使用的集料具有不同的片状、伸长率、棱角度或表面不规则性。基于协方差分析，得到了骨料分数内形状参数的最优分布。第一个目标是基于最优形状参数分布，根据期望的应用领域组成砂浆的集料分数，并通过集料形状来控制新拌和硬化砂浆的性能。第二个目标是寻找碎石生产的优化方法。

Aggregates represent the largest volume fraction of concrete and mortar and their shape properties influence the properties in fresh as well as hardened state. Unlike standard laboratory procedures like the determination of flakiness or shape index computed tomography enables the determination of a wide range of three-dimensional shape parameters for every particle within an aggregate sample. Within the previous project a procedure was developed to scan aggregate samples as loose bulks and to automatically perform the necessary image processing steps. This includes the identification of bor-ders between touching particles which was performed manually so far. Characterization of particle shape of a representative sample of fine or coarse aggregates becomes now possible. In literature, first experimental results of the influence of three-dimensional particle shape parameters on certain fresh and hardened mortar properties are reported. However, detailed analysis of optimal distribution of shape parameters within the aggregate fraction to precisely influence fresh or hardened mortar properties is still missing. Main focus of the further course of the project is the analysis of the relation between three-dimensional particle shape determined using computed tomography and fresh and hardened mortar properties. Correlation between this shape characterization of four fine materials and the fresh mortar properties water demand, packing density, flowability, mini slump, dynamic viscosity and yield as well as the hardened mortar properties bending strength, compressive strength and Young’s modulus is investigated. For mortar tests aggregates with different values of flakiness, elongation, angularity or surface irregularity are used. Optimal distribution of shape parameters within the aggregate fraction is derived based on an analysis of covariance. First aim is to compose the aggregate fraction for mortar in dependence of the aspired field of application based on the optimal shape parameter distribution and to control fresh and hardened mortar properties by means of aggregate shape. Second aim is to find optimization approaches for crushed aggregate production.