Comparative Study of the Dynamic Behavior of Conventional Concrete and Bioaggregate Concrete Containing Macauba Endocarp Through Experimental Modal Analysis

The incorporation of agro-industrial residues as alternative aggregates in cement-based composites represents a promising strategy for reducing the consumption of natural mineral resources and promoting more sustainable construction materials. This study compared the frequency-domain behavior and damping characteristics of conventional concretes with nominal strength classes of 15, 20, 25, and 30 MPa and bioaggregate concrete (containing macauba palm (Acrocomia aculeata) endocarp). In the bioaggregate concrete, 25% of the coarse aggregate volume was replaced by macauba endocarp. Experimental Single Input–Single Output (SISO) modal analysis with impact-hammer excitation was performed with the specimens tested in two geometric orientations. Frequency Response Functions (FRFs) were analyzed over the 0–2000 Hz range, and the first three dominant resonance frequencies (f1, f2, and f3) were identified. Valid damping ratios associated with the second and third resonance frequencies were estimated using the half-power bandwidth method. Linear mixed-effects models showed significant effects of concrete group, specimen position, and their interaction on all three resonance frequencies (p < 0.05). The bioaggregate concrete did not exhibit a uniform increase or decrease in resonance frequency relative to the conventional concretes; instead, its response varied according to the resonance region and specimen orientation. More pronounced differences were observed for damping. In Position 1, the bioaggregate concrete presented mean damping ratios of 0.0179 for ζ2 and 0.0337 for ζ3, compared with ranges of 0.0055–0.0085 and 0.0166–0.0194, respectively, for the conventional concretes. In Position 2, the corresponding values for the bioaggregate concrete were 0.0302 and 0.0218, compared with conventional ranges of 0.0046–0.0084 and 0.0050–0.0065. These results demonstrate that macauba endocarp produces a distinct frequency-domain response and increases vibrational energy dissipation relative to the investigated range of conventional concretes. Experimental modal analysis therefore provides a promising non-destructive approach for characterizing cement-based materials containing plant-derived aggregates.