Evaluation of the Durability of Hydrophobic Treatments on Concrete Architectural Heritage
Abstract The protection of historical concrete structures is a challenge for the coming years. Hydrophobic treatment may reduce the deterioration process while providing protection against water penetration. Existing commercial products - mainly silane or siloxane in either water or solvent based formulations - were submitted to different ageing processes including UV radiation, dry-wet cycles, thermal shocks, freeze-thaw cycles, carbonation and their effectiveness has been evaluated on the basis of contact angle, vapour and chloride permeability and, capillarity water absorption. The results obtained clearly show that hydrophobic treatments display a good behaviour under the main ageing conditions.
The evaluation of the surface free energy of liquids and solids in concrete technology
Abstract This paper presents initial results from an extensive study on the calculation of the surface free energy of mineral materials. The usefulness of such evaluation is demonstrated through the technological operation of casting and moulding concrete. Surface interactions will firstly act on the dispersion of particles inside the concrete mix and the viscosity of the fresh material; the specific effect of superplasticizers and Modifying Viscosity Agent is presented through the determination of surface free energy properties. The second analysis is dealing with the interactions between mineral and vegetal oils applied on the wooden or steel formwork and fresh concrete. The evaluation of contact angle and interfacial forces help to efficiently select the most appropriate material.
Contact angles and adhesive bonding
Abstract The starting point of this paper is the measurement of the surface tension of a liquid. It then considers how the surface tension, or surface free energy, of a liquid can be split into polar and dispersive components, and how these same components can be obtained for a solid surface by the measurement of contact angles. The final step in the argument is the derivation of equations for the thermodynamic work of adhesion in dry conditions and in the presence of a liquid. Examples from the literature show that this approach can predict the durability of adhesive bonds in the presence of water.