A Preliminary Investigation of Fiber Reinforced Concrete under Quasi-Static and Dynamic Loads

Abstract

The world has been reminded in recent years that there is no boundary that terrorists won’t cross and there are no limits to what they will do to achieve their political objectives. With the United States at the center of their focus, the list of potential targets has expanded to include any critical and/or vulnerable structure that symbolically plays a part in the American way of life, such as government, communications and financial networks, and nuclear power.

With the increased threat to structural infrastructure, research studies have been conducted on various ways to augment defensive capabilities and protect against blast and impact affects in addition to general wear and tear. Nuclear containment structures are of particularly high threat due to the level of potential collateral damage their failure could inflict. Current nuclear facilities construction involves over three feet of concrete and conventional steel reinforcement. This containment structure serves multiple functions including a physical barrier against blast and impact loading. Having the additional benefit of reducing construction time and cost by lowering the required amount of conventional steel, it has been suggested that external fiber reinforced concrete panels be used for the function of blast and impact protection. The addition of unconventional reinforcement to concrete, specifically fiber reinforcement, has been shown to have the desired characteristics for blast and impact resistance including increased durability, toughness and high energy absorption.

This is a preliminary study of the fundamental behavior of fiber reinforced concrete. The ultimate goal for this research project is to develop an analytical model to simulate fiber reinforced concrete structures under dynamic loading as well as assist in designing fiber reinforced concrete structures. The aim of this study was to obtain a usable fiber reinforced concrete and conduct quasi-static and dynamic experiments.

This study succeeded in determining an appropriate mixing technique and batch proportions for creating a workable fiber reinforced concrete using Forta Ferro fibers. Furthermore, this project examined fiber reinforced concrete through several experiments. To better understand fiber reinforced concrete properties, test specimens were statically tested for compressive strength, splitting tensile strength, and most importantly average residual strength using ASTM Standards when applicable. Fiber reinforced concrete has the ability to carry load past initial cracking, this characteristic is demonstrated by average residual strength. The mean value of average residual strength of 5 specimens was found to be around 350psi.

An experimental procedure had to be developed for dynamic impact testing. A drop weight test setup was created by dropping a cylindrical mass through a PVC pipe. A load cell was connected to the falling mass while an accelerometer was attached to the beam. Although, no definite numerical results were obtained, impact resistance of fiber reinforced concrete was demonstrated by test specimens that resisted multiple impacts. Even though a crack developed, some concrete specimens continued to carry load. Most importantly, the development and calibration of the test procedure will benefit future experimentation.

While this study is only a preliminary investigation into fiber reinforced concrete, it has shown that fiber reinforcement has great potential for mitigating blast and impact effects and it has laid the ground work for future work.