A importância da aplicação do ensaio de reconstituição do traço de concreto em perícias da engenharia

Abstract

Concrete is one of the most widely used construction materials worldwide due to its highly demanded strength properties for structural applications. To achieve the required properties, concrete must undergo technological control during its production, ensuring that each step is properly planned and executed. One critical stage is the mix proportioning or batching of concrete, which determines the ratio of its constituent materials. Structures are typically evaluated for compliance throughout their service life to anticipate or address potential issues. Mix proportion reconstitution enables technical professionals conducting inspections to collect data from concrete samples and analyze whether they align with the designed mix proportions, aiming to implement corrections or identify potential causes of deterioration. This research aims to emphasize the importance of applying the concrete mix proportion reconstitution test in forensic engineering. To achieve this goal, 18 specimens were prepared using transparent plastic molds, with concrete made of coarse aggregates and varying water-cement (w/c) ratios of 0.6, 0.5, and 0.4. These specimens were subjected to a calcination process, where the samples were heated to 900°C for 30 minutes to accelerate material degradation, thus facilitating subsequent steps. Following calcination, chemical analysis was performed by treating the samples with hydrochloric acid (HCl) to dissolve the binder, leaving only the aggregates. This allowed for a comparison between the final and initial mass to reconstruct the binder-to-aggregate ratio. Results showed differences in the obtained mix proportions ranging from approximately 2.5% to 16.3% compared to the actual mix proportions. The findings highlighted the impossibility of reliably reconstituting the water-to-cement ratio since there is no guarantee that the entire volume of water used in the mix reacted fully with the cement particles. Therefore, it was concluded that technological control during concrete production, especially in the batching stage, is essential. Additionally, the methodology employed in this study can be applied in forensic engineering, as it enables the collection of data regarding the mix proportions used in concrete production.