PSI - Issue 73

Kateřina Matýsková et al. / Procedia Structural Integrity 73 (2025) 100 – 105 Kateřina Matýsková, Marie Horňáková / Structural Integrity Procedia 00 (2025) 000 – 000

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products and construction waste into concrete mixtures, which not only reduces environmental burden but can also enhance the performance characteristics of concrete in certain applications ( Šimonová et al., 2020 ; Tokbolat et al., 2020). However, the fracture behavior of such modified mixtures sometimes remains insufficiently understood, especially when it comes to their microstructural features and crack propagation mechanisms. Fracture characteristics, including fracture energy, crack initiation, and propagation behavior, are critical for assessing the structural performance and durability of concrete under service loads (Khalilpour et al., 2019; Ojha et al., 2022; Ramachandra Murthy et al., 2013). In this context, numerical simulations and inverse analysis using stochastic calculations offer powerful means of investigating the fracture processes and determination of material's fracture properties for further numerical simulations (Červenka and Papanikolaou, 2008; Sucharda et al., 2017) . This study focuses on the identification and characterization of the fracture properties (static modulus of elasticity, tensile strength and fracture energy) of concrete mix containing waste material from CETRIS board production as a replacement for 100% of fine aggregate and a reference concrete without this waste material. A numerical model is developed in ATENA 2D software and an inverse analysis is performed using SARA stochastic software in order to find the best parameters that fit the numerical simulation to the experimentally obtained data from three-point bending tests. 2. Materials and methods 2.1. Waste material from CETRIS production (WCM) The overall research programme is aimed at investigating the effect of replacing fine aggregate in concrete with waste material obtained from the production of CETRIS boards on the mechanical parameters of concrete. This waste material (WCM) is produced during the grinding of the surface of the boards before the application of the final surface finishing. It is a fine powder consisting of wood chips and cement matrix residues (Fig. 1). The volume density of WCM is 770 kg/m 3 and the absorbency of water is about 45% (Matyskova et al., 2024). Due to the high water absorption, WCM was pre-wetted to study the effect on the internal curing of high strength concrete.

Fig. 1: Fine waste material from the CETRIS board production (Matýsková et al., “in a review process” )

2.2. Concrete design and measured characteristics The concrete mixes were designed as high-performance concrete with low water-cement ratio of 0.25 and with a maximum aggregate grain size of 8 mm. Other used materials included white cement CEM I 52.5R, white silica fume, ground limestone and superplasticizers. The used natural aggregates were standard sand in two fractions (0.08/0.5 mm and 0.5/1 mm) and crushed granite in the 4/8 fraction. The CET0 mix was designed as a reference concrete and the CET100 mix used 100% replacement of the finest natural aggregate fraction with WCM (Matýsková et al., “in a review process” ). Tests were performed to determine the volume density, compressive strength, bending strength, static and dynamic moduli of elasticity and fracture parameters of samples at the age of 28 days. The volume density was measured according to (EN 12390-7:2019, 2019) and the bending strength and subsequently the compressive