Water-Resistance of Mortars with Lightweight Aggregates

Abstract

The incorporation of lightweight aggregates in cement-based coating mortars contributes to a better performance of some of their physical properties, influencing their hygrothermal behaviour. This paper analyses the effect of some lightweight aggregates (expanded clay, granulated cork and silica aerogel) on the following mortars’ characteristics: porosity, bulk density, capillary water absorption coefficient, drying index and water vapour permeability. The experimental results showed that low percentages of incorporation of lightweight aggregates led to more porous mortars with lower bulk density, higher capillary water absorption coefficient and greater drying facility, relative to the reference cement-based mortar. The incorporation of silica aerogel in cement-based mortars resulted in major differences in terms of water resistance, with significant benefits in terms of the drying process due to their porous structure.

Concrete-Based and Mixed Waste Aggregates in Rendering Mortars

“…The water/cement ratio was determined after the aggregates were dried, and was based on the amount of required water to achieve a proper workability to the mortar. Taking into account that renders require good plasticity for application over a vertical substrate and proper spread, the water/cement ratio obtained in this paper follows a similar trend to previous research [5,27,53].…”

“…Several studies noticed that increasing the RA content leads to a linear increase of the water needs as occurred in this research [2,5,6,24,53]. Table 6 presents the results of the bulk density.…”

Drying parameters of rendering mortars

“…The drying curve allows calculating the drying index, which can be used to evaluate the speed and quantity of water that evaporated from the mortar samples over time FARIA, 2011;GRILO et al, 2014). The drying index (Di) is related to the resistance of the mortar to the drying process and is obtained by Equation 1 (SOARES et al, 2014). The higher the drying index, the more difficult it becomes for the material to lose water to the environment.…”

“…The assay was conducted at 20 °C room temperature and 50% relative humidity. The mortar samples were prepared by immersion saturation, without the waterproofing of the faces, similar to the procedures adopted by Páscoa (2012) and Soares et al (2014).…”

“…Among the test methodologies available to assess the drying process on building materials, it is possible to use non-destructive methods that provide an approach for moisture distribution and drying depth estimation, such as nuclear magnetic resonance (GONÇALVES; PEL; RODRIGUES, 2009) and impedance spectra (SUN et al, 2017). Nevertheless, a simple (gravimetric) evaporation test can provide information on the transport of liquid water and vapor, which can then be correlated with other physical parameters of mortars such as vapor permeability and water absorption (SCHEFFLER;PLAGGE, 2010;SOARES et al, 2014;FLORES-COLEN et al, 2016).…”