非晶合金纤维和钢纤维单/混掺增强混凝土开裂及断裂性能研究

Cracking Behavior and Fracture Toughness of Concrete Strengthened by Single/Mixed Amorphous Alloy Fiber and Steel Fiber

为探索纤维混凝土抗裂性能,本文研究了不同类型纤维(平直型钢纤维、平直型非晶合金纤维、钢纤维+非晶合金纤维)和不同纤维体积掺量(1.0%,1.5%和2.0%)混凝土的早期开裂性能和硬化后的断裂性能。首先通过平板法试验并借助数字图像对混凝土的早期裂缝特征进行量化分析,评估了纤维混凝土的早期开裂性能;再通过带切口棱柱体试件的三点弯曲试验,基于双K断裂参数,分析并评估了混凝土硬化后的断裂性能。结果表明,钢纤维单掺和混掺纤维混凝土的早期抗裂性能最好;纤维掺量由1.0%增加至2.0%时,钢纤维、合金纤维和混掺纤维混凝土失稳韧度分别增加了58.9%、44.3%和55.5%,且掺量为2.0%的混掺混凝土断裂能是普通混凝土的11.8倍。钢纤维和非晶合金纤维可在混凝土硬化过程的不同时期发挥协同作用,两种纤维混掺不仅能阻止混凝土早期的塑性开裂,还可有效控制硬化后受拉裂缝的形成和发展,达到分阶段抗裂的目的。综合考虑混凝土的早期开裂性能、硬化后受拉性能以及断裂性能,体积掺量相同情况下混掺纤维混凝土整体性能更优。

To reveal cracking resistance of fiber reinforced concrete(FRC),an experimental investigation was conducted on concrete with various types of fibers(straight steel fiber,amorphous alloy straight fiber,and steel fiber+amorphous alloy fiber)and various volume fractions(1.0%,1.5%and 2.0%)to evaluate early cracking behavior and post-hardened fracture toughness.First,the concrete early cracking feature was quantitatively analyzed by using plate method and image quantitative technique,aiming to evaluate early cracking behavior of FRC.Then,the three-point bending tests were conducted on notched prism specimens,the hardened fracture toughness of FRC was analyzed and assessed based on the double K fracture parameters.The results show that the single steel fiber reinforced concrete and hybrid fiber concrete exhibit the best cracking resistance at early age.As the fiber fraction increases from 1.0%to 2.0%,the unstable fracture toughness of steel fiber,amorphous alloy fiber,and hybrid fiber reinforced concrete increases by 58.9%,44.3%and 55.5%,respectively.Meanwhile,the fracture energy of hybrid fiber concrete with 2.0%fiber reaches 11.8 times that of normal concrete.It shows that steel and amorphous alloy fibers have a synergistic effect at different periods of concrete hardening process.As a result,steel fiber and amorphous alloy fiber have a synergistic effect at the different periods of the hardening process,the hybrid steel and amorphous alloy fibers can not only prevent the early-age concrete plastic cracking but also effectively control the formulation and propagation of post-hardened tensile cracks,thus,achieving a staged anti-crack purpose.Considering the early cracking properties,post-hardening tensile properties,and fracture properties of concrete,the overall performance of hybrid fiber concrete with the same fiber content shows better performance.