PSI - Issue 44

Andrea Meoni et al. / Procedia Structural Integrity 44 (2023) 1632–1639 Andrea Meoni et al. / Structural Integrity Procedia 00 (2022) 000–000

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Keywords: Smart sensors and monitoring systems; carbon-based fillers; earth-concrete; structural health monitoring; carbon microfibers; bending tests

Introduction

The paper is aimed at investigating a novel smart and sustainable earth-based concrete for structural applications, which can couple strength capabilities with strain-sensing ones. The novel composite was investigated by performing mechanical and electrical tests on cube and beam samples. Digital Image Correlation (DIC) was also adopted to evaluate fracture opening in beam samples tested under bending. 1. State-of-art Because of its mechanical performance, durability, and adaptability, concrete is the most often used construction material in civil engineering (Collepardi (2010)). However, because of the raw resources used to make it and its large ecological footprint, it has a major environmental effect (Meyer (2009), D’Alessandro et al. (2017), Oyebisi et al. (2022)). The development of sustainable alternative concrete-based mixtures remains a potential answer for limiting energy consumption, resource waste production, and CO2 emissions during its manufacturing and usage. Possible solutions include the development of less energy-intensive manufacturing processes, the addition of specific chemicals, and the use of recycled aggregates or natural binders (Long et al. (2015), Assi et al. (2018)). In this regard, earth-based concretes, in which cement is partially replaced by earth, offer an environmental benefit over traditional concrete-based mixtures while maintaining adequate mechanical properties for structural applications (Ouellet Plamondon et al. (2016), Curto et al. (2020)). With the aim of developing a novel multi-purpose construction material characterized by a reduced environmental footprint and capable of self-monitoring changes in its strain state, therefore suitable for Structural Health Monitoring (SHM) applications (Kaewunruen et al. (2017), D’Alessandro et al. (2020)), this paper reports the findings of an experimental campaign conducted on samples of a composite produced by doping earth-based concrete matrices with carbon microfibers, an electrically conductive filler used to enhance the piezoresistive capabilities of the base material (Azhari et al. (2012), Meoni et al. (2018)). Potentially, a construction material with similar features can be used to build structures capable of detecting and locating damages developed on their load-bearing structures during their service life and, therefore, even after critical events such as earthquakes (Meoni et al. (2019)). Moreover, the use of full-field measurement techniques is undergoing a strong development in different physics and engineering fields. This growth process is due to the contact-less monitoring capability and practicability to any arbitrary geometries. The digital correlation system monitoring optical-based device which allows to measure the displacement field of a wide variety of target objects. For such a monitoring technique, the monitored surface is typically treated by reproducing a white background with a black speckled random pattern. This contrast confers to the specimen surface a clear structure that can be monitored by one or more cameras. DIC monitoring can be practiced in a single or stereo-mode (Grediac (2004)), in which a single or many cameras are used respectively. In the case of stereo-mode monitoring, the 3D displacement field of the monitored surface is determined by acquiring the deformation process of a surface starting from a reference configuration. Then, after the image acquisition and digitalization process, the matching between two different image patterns is carried out with a correlation algorithm. DIC was used to validate both analytic and finite element simulation with the experiments involving the context of both solid and fluid mechanics (Chu et al. (1985), Genovese, K., et al (2016), Falope et al. (2019)). Less widespread but equally noteworthy is also the application of the principle of virtual works to DIC (Grédiac et al. (2001), Pierron and Grédiac (2012)) for direct determination of the elastic constants of a material. 2. Materials and samples The mix design and the dimensions of the samples were tailored for the specific experimental campaigns performed to investigate the mechanical and electrical response of the novel earth-based concrete.