Abstract
The performance of impregnation treatments used for protection and remediation of porous building materials relies on sufficient penetration depth. The penetration of sol–gel impregnation products into partially saturated porous material is driven by capillary suction and depends on material properties, such as pore size distribution on one hand, and on the other hand on sol physical properties, viscosity, density, surface tension and contact angle, along with the time in which the sol gels. In this work we analyse, by the way of modelling and experiments, the penetration depth of a sol–gel impregnation product as the function of pore size distribution and sol properties. The main goal is to determine the importance of sol’s physical properties for the penetration depth for a specific pore size, which will serve as a basis of the optimization of impregnation products to maximize their penetration depth. The model is first calibrated in terms of penetration depth and sol uptake by the experimental data obtained from mortar samples each with a specific pore-size distribution. The correlation between penetration depth and physical parameters is then established by the use of Monte-Carlo method. The results show that the most important parameters for the optimization are surface tension, whose influence increases for larger pores, and gelation time, which with decreasing importance for larger pores.
Highlights
One of the pertinent concerns in the fields of civil engineering and cultural heritage preservation refers to the durability of building materials, which are exposed to increasingly aggressive environments due to factors such as pollution and climate change [1]
The results indicate that the importance and the sensitivity of each parameter to the penetration depth varies for different pore sizes and, the sol physical properties required to achieve an optimal penetration depth may vary depending on the material properties
The analysis reveals that the influence of each property varies with the pore size following a different trend
Summary
One of the pertinent concerns in the fields of civil engineering and cultural heritage preservation refers to the durability of building materials, which are exposed to increasingly aggressive environments due to factors such as pollution and climate change [1]. The effectiveness and durability of impregnation products is closely related with their penetration depth, which depends on the substrate characteristics such as pore size distribution [10], and on the physical properties of the products such as surface tension, density, viscosity and contact angle. More elaborate sensitivity analysis is time-consuming and experimentally difficult to perform For this reason the methodology presented here combines experimental work with numerical analysis to determine the most important optimization parameters and their ranges. On the basis of this model we evaluated the importance of different sol parameters towards the penetration depth at a set of given material properties (i.e. pore size distribution). The results indicate that the importance and the sensitivity of each parameter to the penetration depth varies for different pore sizes and, the sol physical properties required to achieve an optimal penetration depth may vary depending on the material properties. We showed that the penetration depth doubled when the sol was applied at À10 °C compared to the application at room temperature (20 °C)
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