Methodology of numerically aided optimisation of consolidants for surface treat- ments of mortars

Author(s): Methodology of numerically aided optimisation of consolidants for surface treatments of mortars
Paper category: Proceedings
Book title: Proceedings of the International Conference on Sustainable Materials Systems and Structures (SMSS2019) Durability, Monitoring and Repair of Structures
Editor(s): Ana Baričević, Marija Jelčić Rukavina, Domagoj Damjanović, Maurizio Guadagnini
ISBN: 978-2-35158-217-6
e-ISBN: 978-2-35158-218-3
Publisher: RILEM Publications SARL
Publication year: 2019
Pages: 812-813
Total Pages: 848
Language: English

Abstract: Tetraethoxysilanes (TEOS), an alkoxysilane, are widely used consolidants which form the basis of most existing commercial strengthening agents for protecting porous building materials against deterioration. These products can provide consolidation and water repellent behaviour simultaneously. TEOS are polymerized inside the pores of porous materials in the presence of water. It is necessary to achieve a sufficient penetration depth of TEOS into the porous building material before polymerization to achieve a good performance Alkoxysilanes are immiscible with water and alcohol is often used as the mutual solvent. Alcohol assures not only miscibility but also influences the reaction kinetics and rheology of the consolidants. Moreover, properties of the water-alcohol-TEOS mixture are time dependent. For example, initial viscosity, which is one of the factors influencing the penetration depth, is lower when more alcohol is added. On the other hand, higher concentration of alcohol in a mixture causes faster gelation and evaporation which would decrease the penetration depth. Reaction kinetics also depends on a pore size which is the function of (aged) material. Since cementitious structures are not fully saturated when consolidants are applied, the main mechanism of consolidants penetration in a porous material, such as concrete, is by capillary forces. Studies on cementitious materials indicate that the capillary sorption of fluid in concrete exhibits a complex time dependence, and depends on several parameters, such as surface tension and contact angle between consolidants and the material. The process is additionally complicated because sol-gel behaves initially as a Newtonian fluid, but later as a thixotropic fluid where viscosity is time dependent and increases during gelation. Obviously, defining an optimised mixture of water and alcohol which defines the penetration depth and consequently assures good performance of consolidants is a complex process. As a part of EC project InnovaConcrete, an ambitious plan is developed to combine experimental observations with numerical capabilities in order to facilitate the development of optimized consolidants. This methodology includes numerical developed degraded matrix, experimental rheological properties of consolidants and pore-scale model to determine the penetration depth. In this presentation we describe the methodology and first steps taken forward to combine experimental and numerical means of the optimisation of consolidants for surface treatments of mortars.

Online publication :2019
Publication type : full_text
Public price (Euros) : 00