Understanding transport properties of geopolymer mortar using polarization and fluorescence microscopy
Year: 2012
Type: conference-paper
Abstract: The microstructure of concrete determines the possibility for water to penetrate the material (water transport) and therefore microstructure is a crucial parameter in concrete durability.Because of the intrinsically dense and water impermeable microstructure of geopolymer aluminosilicate reaction products, concrete made with geopolymer has the potential to be very durable.However, geopolymer concrete microstructures consist not only of the hardened, dense geopolymer paste, but also contain the aggregate paste interface, microcracks, air voids etc.These also need to be taken into consideration when trying to understand the (often variable) results of (standard) durability tests on geopolymer concrete and mortars.So far geopolymer durability studies considering the microstructure often have looked at bulk porosity measurements and high resolution techniques such as electron microscopy, thereby missing representative information and an overview of the microstructure, which should include heterogeneities and spatial variations of the hardened paste, microcracks, air voids, aggregate paste interface etc.This study proposes polarization and fluorescence microscopy, a technique often used in cement concrete studies but not yet for geopolymer concrete, to assess the microstructure.For the particular fly ash geopolymer mortar in this study, it is shown that even though a good strength performance is obtained, the microstructure consists of a lot of air voids and microcracks in between the dense geopolymer paste.This type of microstructure allows the geopolymer mortar to absorb water faster compared to Portland cement mortar, which may have implications for the durability of this particular geopolymer mortar.In general, this study shows that polarization and fluorescence microscopy is a useful and straightforward method to deal with the large variety of geopolymer concrete types for which differences in durability are not always easy to explain just by looking at bulk properties or at high resolution nanolevel.
Language: English
Subfield: Civil and Structural Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
Funder: Technische Universiteit Delft
OpenAlex ID: W2337869522