Golewski Grzegorz Ludwik
Department of Structural Engineering, Faculty of Civil Engineering and Architecture, Lublin University of Technology, Nadbystrzycka 40 str., 20-618 Lublin, Poland.
Materials (Basel). 2020 Nov 19;13(22):5241. doi: 10.3390/ma13225241.
This study investigated the influence of the curing time on the fracture toughness of concrete produced with different content of low calcium fly ash (LCFA). During the study, the amounts of 20% and 30% of pozzolanic additive were used. In order to observe the effect of the applied pozzolanic additive on the analyzed concrete properties, the obtained results were compared with the values obtained for the reference concrete. Compressive strength- and fracture toughness, by using mode II loading- (shearing), were determined between the 3rd and 365th days of curing. In the course of experiments, changes in the development of cracks in individual series of concrete were also analyzed. In addition, the microstructures of all composites and the nature of macroscopic crack propagation in mature concretes were assessed. It was observed that the greatest increase in fracture toughness at shear was in the case of reference concrete during the first 28 days, whereas, in the case of concretes containing LCFA, in the period of time above 4 weeks. Furthermore, concrete without the LCFA additives were characterized by a brittle fracture. In contrast to it, concretes with LCFA additives are mainly characterized by a quasi-plastic process of failure. Moreover, most of the samples showed a typical pattern of the destruction that occurs as a result of shearing. The presented test results may be helpful in selecting the composition of concrete mixtures containing LCFA to be used in concrete and reinforced concrete structures subjected to shear loads.
本研究调查了养护时间对不同低钙粉煤灰（LCFA）含量混凝土断裂韧性的影响。研究过程中，使用了20%和30%的火山灰添加剂用量。为了观察所施加的火山灰添加剂对分析的混凝土性能的影响，将所得结果与参考混凝土所得值进行了比较。在养护的第3天至第365天之间，采用II型加载（剪切）测定了抗压强度和断裂韧性。在实验过程中，还分析了各系列混凝土中裂缝发展的变化。此外，评估了所有复合材料的微观结构以及成熟混凝土中宏观裂缝扩展的性质。观察到，参考混凝土在最初28天内剪切时断裂韧性增加最大，而对于含LCFA的混凝土，在4周以上的时间段内增加最大。此外，不含LCFA添加剂的混凝土表现出脆性断裂。与之相反，含LCFA添加剂的混凝土主要表现为准塑性破坏过程。此外，大多数样品显示出典型的因剪切而发生破坏的模式。所呈现的试验结果可能有助于选择含LCFA的混凝土混合料组成，用于承受剪切荷载的混凝土和钢筋混凝土结构。
