Leandro Marochio Fernandes

Objective: This study evaluates the variation of pH and electrical conductivity of distilled water containing hardened mortar samples with FIBRO, artificially aged, in order to investigate the influence of ornamental rock beneficiation fines (FIBRO) in cementitious mortars. Theoretical Framework: Based on studies on waste reuse in construction, the viability of FIBRO as an alternative material is highlighted. The chemical composition of these fines may influence the physical-chemical behavior of cementitious mixtures, impacting the durability of structures. Method: Mortar specimens with and without FIBRO were molded and subjected to saturation and drying cycles in distilled water and saline solution at 28 days of age. Over six weeks, pH and electrical conductivity of the solutions were monitored to evaluate the influence of FIBRO. Results and Discussion: The mortars with FIBRO had an initial pH between 6.7 and 9.9, stabilizing at 8, without altering the distilled water. Electrical conductivity increased due to mineral leaching, especially in saline solutions. Although FIBRO does not change the pH, leaching may affect mortar durability under different conditions, as well as water quality. Research Implications: The study contributes to the characterization of FIBRO as a sustainable material and emphasizes the need to assess its chemical compatibility with cementitious materials. Originality/Value: This research expands the knowledge on mortars with FIBRO, analyzing electrical conductivity and pH stabilization, providing support for more sustainable mixtures.

Boundary layers over concave surfaces may become unstable due to centrifugal instability that manifests itself as stationary streamwise counter rotating vortices. The centrifugal instability mechanism in boundary layers has been extensively studied and there is a large number of publications addressing different aspects of this problem. The results on the effect of pressure gradient show that favorable pressure gradients are stabilizing and adverse pressure gradient enhances the instability. The objective of the present investigation is to complement those works, looking particularly at the effect of pressure gradient on the stability diagram and on the determination of the spanwise wave number corresponding to the fastest growth. This study is based on the classic linear stability theory, where the parallel boundary layer approximation is assumed. Therefore, results are valid for Görtler numbers above 7, the lower limit where local mode linear stability analysis was identified in the literature as valid. For the base flow given by the Falkner-Skan solution, the linear stability equations are solved by a shooting method where the eigenvalues are the Görtler number, the spanwise wavenumber and the growth rate. The results show stabilization due to favorable pressure gradient as the constant amplification rate curves are displaced to higher Görtler numbers, with the opposite effect for adverse pressure gradient. Results previously unavailable in the literature identifying the fastest growing mode spanwise wavelength for a range of Falkner-Skan acceleration parameters are presented.