Size-independent fracture energy of concrete at very early ages by inverse analysis

Abstract

This paper deals with the analysis of fracture characteristics of concrete at very early ages. Experimentally, three-point bending tests are performed on concrete notched beams at very early age (before 24 h) to obtain the Load-Crack Mouth Opening Displacement (CMOD) curves. In order to find a trend of the fracture energy evolution, inverse analysis procedure is performed using finite element analysis. A damage softening model is used to describe the softening behaviour and a nonlinear inverse analysis algorithm (Levenberg-Marquardt) is adopted. As the softening damage model used does not take into account boundary effects, only a part of the Load-CMOD curves is fitted. Therefore, a good estimation of the size-independent fracture energy is obtained. The results obtained from the experimental test and the inverse analysis indicate an upward trend of the evolution of the fracture energy and other fracture concrete characteristics.

How to consider the Interfacial Transition Zones in the finite element modelling of concrete?

“…So, without the possibility to take into account the petrology and the morphology of aggregate [4] and their reactivity with the cement paste, the modelling of the microstructure behaviour of various concretes can be performed by taking into account the ITZs with different densities. The local properties into the ITZs have to be compared to experimental measurements as possible and fracture properties could be calibrated on specific experimental tests [36]. • The interest to consider the ITZs in the modelling of concrete has been shown by the results on the crack opening.…”

Mesoscale analysis of failure in quasi-brittle materials: comparison between lattice model and acoustic emission data

“…Bažant and Pijaudier‐Cabot determined the FPZ size experimentally as the ratio of the fracture energy to the energy dissipated per unit volume during the failure process. With the advent of displacement field measurement techniques, such as digital image correlation, access to local field quantities in the vicinity of the crack became possible in order to characterize the FPZ, opening the way for comparisons with results obtained from nonlinear models and calibration of constitutive models that describe the FPZ .…”

“…Bažant and Pijaudier-Cabot [3] determined the FPZ size experimentally as the ratio of the fracture energy to the energy dissipated per unit volume during the failure process. With the advent of displacement field measurement techniques, such as digital image correlation, access to local field quantities in the vicinity of the crack became possible in order to characterize the FPZ, opening the way for comparisons with results obtained from nonlinear models and calibration of constitutive models that describe the FPZ [4].The localization of acoustic events that can be detected during crack propagation is another wellestablished technique from which the FPZ can be visualized and characterized, in concrete [5][6][7][8][9] or rocks [10]. The acoustic events generated during micro-cracking are recorded and post-processed in order to localize them with the help of time-of-flight algorithms.…”

Fracture mechanics based design of reinforced concrete beams-An analytical study

“…for the conversion of size dependent to the size independent fracture energy assuming a distribution which is bilinear stating that the fracture energy (local) varies at the end due to back face stress variation effect. Matallah et.al [5] found the size independent fracture energy of the specimens at early ages (i.e. specimens which are less than 24hours old) using inverse analysis.…”