Concrete paving blocks: Structural, thermodynamic, fluorescence, optical and mechanical properties

A chemical rationalization of the structural, thermodynamic, optical, fluorescence, and mechanical properties of concrete paving blocks was advanced. The results revealed that the values of Gibbs energy and enthalpy of the hydration reactions of the concretes prepared average -57.6 kJ mol(-1) and -67.8 kJ mol(-1), respectively. In addition, the results indicate that the processing of the concrete blocks with metakaolin as additive lead to hydrogen bond forming reactions. In this sense, both structural and thermodynamic properties of the hydrogen-bonded complexes showed that the presence of hydrogen bonding can be associated with the curing time of the concrete blocks. Further, by employing the fluorescence microscopy technique, the blue emission of the concrete materials was verified as a friendly strategy to evaluate their hydration reactions. In addition, optical microscopy experiments showed that all concrete paving blocks prepared are homogeneous. Furthermore, all concrete paving blocks with metakaolin as additive exhibit larger values of compressive strength (average 36.5 MPa) when compared to the corresponding blocks with absence of metakaolin (28.1 MPa). The addition of metakaolin also increased the cavity diameter of the concrete paving blocks in 10% when compared with the reference blocks. Finally, by considering structural, thermodynamic, optical and fluorescence properties, as well as, mechanical properties of compressive strength and abrasion resistance, the concrete paving block with the metakaolin addition of 10% present the largest potential to be applied to constructions. (C) 2019 Elsevier B.V. All rights reserved.