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Graphical abstract Highlights • Innovative prefabricated construction elements designed and tested in service loads. • The structural integrity fully assessed by Acoustic Emission (AE) monitoring technique. • Cumulative AE hits distribution, Load and Calm ratios indicate progressive damage. • Damage classified into concrete cracks and reinforcing rebars deformation/slippage. • AE selected as damage sensing tool to be implemented on prefabricated constructions. Abstract The design feasibility and structural integrity of prefabricated construction elements is assessed (concrete cantilever slab carrying thermal insulation break reinforced with steel/basalt rebars and ultra-high-performance concrete) by performing incremental bending tests. The developed damage mechanisms govern failure, therefore their identification appears crucial: concrete cracking, rebars-concrete interface debonding, rebars slippage, concrete crush under compression. However, the complex fracture cannot be effectively characterized by measuring the deterioration of the mechanical properties. In this study, Acoustic Emission (AE) is applied to highlight internal damage progress. It is found based on cumulative AE hits distribution under incremental load and considering the Kaiser and Felicity effects, damage initiation is identified. The damage severity is quantified using Load/Calm ratios. AE sources localization identifies the moment at which the rebars plastically deform; debond from concrete; slip and when concrete cracks and crushes under compression. The damage mechanisms are discriminated based on acoustic signal features distribution as damage evolves (specifically, average frequency and the ratio of rise time over amplitude). It is shown that AE appears an essential and accurate monitoring method that fully characterizes the damage on complex structures. The promising results open new horizons towards the design of fully autonomous prefabricated elements carrying a smart on-line AE sensing tool. [ABSTRACT FROM AUTHOR]

A study was performed to assess the fitness of continuous monitoring methods to detect failure due to excessive strain on polymers bridging moving cracks in the context of self-healing concrete. Testing of several polymer precursors with distinct properties also allowed conclusions regarding the requirements for polymers in this application. Acoustic emission (AE) analysis was performed in parallel with digital image correlation (DIC) at the macro-scale. In addition, a micro-scale study was performed with tensile tests inside an SEM chamber. Detection of failure through AE analysis coupled with DIC was possible only in case of failure due to brittle fracture of a rigid foam after 9% strain, which generated high-energy acoustic events. Direct observation of interfaces with SEM in-situ loading allowed determination of failure of a rigid foam due to cracking of the polymer matrix and detachment at the interface with the cementitious matrix, with an onset at 5% strain and complete detachment at 16% strain. For a flexible, continuous film of polymer, detachment occurred before 50% strain. Assuming adequate adhesion, polymers with high elongation (> 100%) and modulus of elasticity much lower than 10 MPa are required if cracks subjected to a realistic amplitude of movement are targeted. [ABSTRACT FROM AUTHOR]

[Display omitted] • Concrete beams with embedded glass capsules are experimentally and numerically tested. • Virtual FE model allows for explicit identification of capsule debonding and breakage. • Concrete damage criterion model accounts for pressure-dependency. • Modified Nelder-Mead method speeds up identification of concrete model parameters. • Ratio of capsule slenderness to interface strength is key for self-healing. The fracture process in self-healing concrete with embedded brittle capsules entails challenges in terms of understanding how and when these capsules break to release the agent. This paper presents a combined experimental–numerical investigation in which a versatile three-dimensional simulation model is developed to investigate the fracture of this type of beams under three-point bending load. The model allows for correlating the overall strength with different damage events occurring in every constituent: the concrete, the capsules and the capsule-concrete interface. The constitutive concrete damage model uses a pressure-dependent failure initiation criterion followed by a bilinear softening law, whose parameters are validated by using a modified Nelder-Mead optimization algorithm enriched with user-defined constraints aimed at increasing the convergence ratio. The validated virtual model demonstrates that the ratio of capsule slenderness to concrete-capsule interface strength is the key parameter for an effective self-healing process as it gives full control to break the capsule at the right moment. The shorter the capsule is, the longer the breakage process can be. Additionally, it has been found that by increasing the length of the capsules can help to enhance the overall fracture energy of the beam even after fully broken. [ABSTRACT FROM AUTHOR]

This paper presents a combined experimental-numerical analysis to assess the strength and fracture toughness of a glass-concrete interface. This interface is present in encapsulation-based self-healing concrete. There is absence of published results of these two properties, despite their important role in the correct working of this self-healing strategy. Two setups are used: uniaxial tensile tests to assess the bonding strength and four point bending tests to get the interfacial energy. The complementary numerical models for each setup are conducted using the finite element method. Two approaches are used: cohesive zone model to study the interface strength and the virtual crack closure technique to analyze the interfacial toughness. The models are validated and used to verify the experimental interpretations. It is found that a glass-concrete interface can develop a maximum strength of approximately 1 N/mm 2 with fracture energy of 0.011 J/m 2 . [ABSTRACT FROM AUTHOR]

• Acoustic emission of hybrid composite concrete beams is examined. • Prediction of the final mode of fracture can be done before reaching 20% of the ultimate load. • Acoustic emission waveforms from cracking and debonding are very different. • Combination of Acoustic Emission and Digital Image Correlation is very effective for fracture monitoring. Lightweight hybrid concrete beams are advantageous in terms of installation, but their mechanical behaviour is not easy to predict due to their heterogeneity. In the present study composite hollow beams made of Textile Reinforced Cement (TRC) reinforced with Carbon Fibre Reinforced Polymer (CFRP) strips and a concrete layer are subjected to bending. Their fracture behaviour is complicated as they exhibit multiple failure mechanisms: cracking of the cement matrix, debonding of the CFRP and delamination between successive layers of TRC. Herein, their mechanical performance is evaluated and monitored by Acoustic Emission (AE) and Digital Image Correlation (DIC). AE indices show that beams suffering from one major failure mechanism (matrix cracking) release AE signals with high frequency content while beams suffering from delaminations exhibit longer AE waveforms of lower frequency. These tendencies are obvious even at early loading stage, enabling prediction of the mode of the subsequent failure. [ABSTRACT FROM AUTHOR]