Spall Behaviors of Metaconcrete: 3D Meso-Scale Modelling

Abstract

Spalling is a typical tensile fracture phenomenon due to insufficient tensile strength of concrete. Concrete structure might experience severe spall damage at the rear surface of the structure owing to reflected tensile stress wave induced by impulsive load. In recent years, metaconcrete consisting of engineered aggregates has attracted attentions as metaconcrete exhibits extraordinary wave-filtering characteristics. Metaconcrete can be used to attenuate stress wave generated by impulsive load and hence possibly mitigate the spall damage. In this study, engineered aggregate is designed via the software COMSOL to have the frequency bandgap coincide with the dominant frequency band of stress wave propagating in the normal concrete (NC) specimen to reduce the stress wave propagation and hence spall damage. The wave propagation behaviors in metaconcrete specimen with periodically distributed engineered aggregates have been investigated in a previous study. This study establishes 3D meso-scale model of metaconcrete including mortar, randomly distributed natural aggregates and engineered aggregates to simulate spall behaviors of metaconcrete via the software LS-DYNA. The responses of metaconcrete composed of engineered aggregates with single bandgap and multiple bandgaps are studied. The results show that stress wave can be more effectively attenuated by using engineered aggregates with multiple bandgaps. It is found that although engineered aggregates mitigate stress wave propagation, the soft coating of the engineered aggregates reduces the concrete material strength, therefore spall damage of metaconcrete specimen is not necessarily less severe than the normal concrete, but has different damage mode. In addition, the influences of loading intensity and duration on stress wave, as well as the spall behaviors of metaconcrete specimen are also studied.

Effect of enhanced coating layer on the bandgap characteristics and response of metaconcrete

“…This study extends the previous work reported by the authors [24]. The latter study found that although the stress wave amplitudes were reduced owing to the wave propagation mitigation effect by NEA in metaconcrete material, the spalling damage was not necessarily less severe compared to NC without NEA because mixing NEA reduced the concrete strength.…”

“…All components in the specimen are simulated by the constant stress solid element. Mesh convergence test and model calibration have been conducted and reported in Jin et al [23,24], which is not repeated here. The mesh size of 0.5 mm after conducting mesh convergence test is determined and used in this study [23,24].…”

“…It was reported that the energy absorption ability of NMC was affected by the volume fraction of NEA, the elastic modulus and thickness of soft coating. Jin et al [24] proposed a procedure to properly design the engineered aggregates to have their bandgaps coinciding with the targeted predominant wave frequencies of stress wave in NC specimen, and demonstrated using the properly designed NEA can lead to more effective stress wave attenuation in metaconcrete via 3D meso-scale modelling.…”

“…Empirical equations were proposed to predict the attenuation of stress wave propagation in concrete. Jin et al [24] also built a 3D meso-scale model of metaconcrete composed of NEA aggregates to study the spall behaviors of the metaconcrete material.…”

Design and evaluation of dual-resonant aggregates metaconcrete

“…Gao et al (2018) numerically studied wave attenuation performance of metaconcrete slab under two-dimensional plane wave and found that the metaconcrete slab could effectively weaken the mechanical wave and better protect the concrete mortar. Jin et al (2020Jin et al ( ,2021) conducted analytical derivation and numerical simulation to study the dynamic respones of metaconcrete structure under explosion loading and the impact of elastic modulus and thickness of coating, aggregates kinds on the anti-explosion behavior of metaconcrete was investigated. It was found that the engineered aggregates can mitigate the damaged of metaconcrete structural against blast loading.…”