Enhanced dynamic impact properties of concrete with super-fine stainless wire

The use of concrete materials in the construction of various structures has increased in the last decades. Unfortunately, technological advancement has led to the construction of more complicated structures that have posed challenges to the present concrete structures. For instance, large scale concrete structures are susceptible to various modes of failures due to static and dynamic loads. Therefore, understanding of the dynamic mechanical behaviors of concrete materials will be a great move in enhancing their properties for high-performance structural design.

Among the available methods for modification of the dynamic mechanical properties of the concrete, the use of steel fiber with different geometries and shapes have been widely practiced. On the other hand, split hopkinson pressure bar test have been preferred for strain rate characteristic of concrete analysis. Unfortunately, the current results for the strain rate sensitivity of the steel fiber are inconsistent, thus comprising on the validity of the results. To this end, researchers and scientists have been looking for alternatives for reinforcing or developing new concrete materials desired for emerging applications and have identified super-fine stainless wire reinforced reactive powder concrete as a promising solution. Super-fine stainless wire has the same excellent characteristic as common steel fiber such as high mechanical property, strong interface bonding with concrete, and similar linear expansion coefficient with concrete. Owing to the micron diameter and high aspect ratio, super-fine stainless wire can also form three-dimensional overlapping network at low volume fraction, which will be helpful to further improve the strength, toughness and deformation capacity and alter the failure criterion of concrete under compression.

Meanwhile, the micron diameter of super-fine stainless wire can also improve the microstructure of concrete and weaken the adverse effect of interface transition zone caused by common steel fiber. Even more, the addition of super-fine stainless wire endows concrete excellent functional characteristic. Therefore, super-fine stainless wire reinforced reactive powder concrete has many outstanding properties such as high strength, good toughness, multifunctional and smart characteristics. This new concrete composite is expected to be applied in military field and blast resistance engineering in the future.

In a recent research paper published in the research journal, Construction and Building Materials Dalian University of Technology Researchers: Dr. Sufen Dong (currently postdoctoral fellow), Professor Baoguo Han and Professor Jinping Ou in collaboration with Professor Xun Yu at New York Institute of Technology investigated the dynamic characteristics of the super-fine stainless wire reinforced reactive powder concrete. They used the split hopkinson pressure bar test to determine the mechanical properties of the composite at a strain range of 94/s to 826/s. Meanwhile, they revealed the modification mechanisms of super-fine stainless wire to reactive powder concrete through computed tomography and scanning electron microscope analysis. Eventually, the dynamic impact model of the composite was obtained based on the viscoelastic continuum and damage theory.

The authors observed that the established constitutive model was suitable for describing the stress-strain relationship of the newly developed composite at different strain rates. For instance, the super-fine stainless wire volume fraction and strain rates closely related to the selection of the strain threshold. Consequently, the dynamic impact toughness and dissipated energy of reactive powder concrete were significantly increased due to the incorporation of super-fine stainless wire. The destruction degree of reactive powder concrete at high strain rate was decreased significantly due to the inclusion of super-fine stainless wire. Furthermore, the uniform dispersion of super-fine stainless wire in the reactive powder concrete was good for inhibiting the cracks generation and propagation.

The study is the first to report about the dynamic characteristic of the super-fine stainless wire reinforced reactive powder concrete. It results in an increase of the dynamic impact toughness and a corresponding decrease in the damage especially under high impact loading which is ideal for severe environmental conditions. Also, it provides a framework for the investigation of the other mechanical properties such as dynamic tensile strength among others. The study is of great significance to develop new concrete materials with excellent dynamic property.