Effect of Expanded Perlite and Exfoliated Vermiculite Aggregate Additives on Water Vapor Permeability Performance of Cement-Based Lightweight Mortars
Vapor diffusion is the movement of water vapor molecules through porous materials such as wood, insulation products, and lightweight wall elements due to differences in vapor pressure. Vapor retarders are used to control vapor diffusion through wall sections and surfaces. All building materials...
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| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Yildiz Technical University
2025-06-01
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| Series: | Journal of Sustainable Construction Materials and Technologies |
| Subjects: | |
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| Summary: | Vapor diffusion is the movement of water vapor molecules through porous materials such as wood, insulation products,
and lightweight wall elements due to differences in vapor pressure. Vapor retarders are used to control vapor diffusion
through wall sections and surfaces. All building materials provide some resistance to vapor diffusion, and the amount of
resistance varies depending on the material’s properties. These properties can vary with relative humidity and moisture
content, age, temperature, and other factors. Vapor resistance is usually expressed using the inverse term of “vapor
permeability,” which is the relative ease of vapor diffusion through a material. Water vapor permeability in building
materials is an essential factor that allows moisture formed indoors in a building section to pass to the outside and
prevents damage from moisture inside. Condensation that may occur inside and/or on the surface of a building section
due to inadequate water vapor diffusion negatively affects heat transfer in building materials and reduces insulation
performance. The type of aggregate used in cement-based mortars is an essential factor influencing the water vapor
permeability of the mortar. The water vapor permeability of normal-density aggregate mortars is lower than that
of lightweight aggregate mortars. In this study, a series of cement-based composite mortar designs using expanded
perlite and expanded vermiculite aggregates were created, and in addition to physical and mechanical analyses, water
vapor permeability properties were also comparatively investigated according to the control mortar sample. In the mix
designs, 32% expanded perlite and exfoliated vermiculite aggregates were used as lightweight aggregates. As expanded
perlite aggregate, two different characteristic aggregates expanded under the effect of 765 °C and 985 °C were used.
As vermiculite aggregate, two characteristic aggregates with 55% and 85% opening phenomenon under expansion
temperature were used. According to the study results, water vapor resistance coefficients varied between 3.40 and 6.70
for lightweight aggregate test samples. It has been observed that the high expansion/opening rates in the production
of materials used as lightweight aggregates cause lower water vapor resistance coefficients of cement-based mortars
obtained with these materials. |
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| ISSN: | 2458-973X |