Resources / Publications
Isabel M.R. Bernal (1), Shiva Shirani (1), Ana Cuesta (1), Isabel Santacruz (1), Miguel A.G. Aranda (1)
Construction and Building Materials, 300, June 2021. DOI: 10.1016/j.conbuildmat.2021.124054
CO2 footprint; LC3 cements; Rietveld analysis; synchrotron X-ray microtomography; Microstructure; Porosity; Pore connectivity
Limestone Calcined Clay Cements, LC3, are attracting a lot of attention as it is possible to reduce the clinker factor by 50%, which means a cement CO2 footprint reduction of 40%. This is compatible with maintaining the mechanical strength performances after one week, if the kaolinite contents of the raw clays are above ~40 wt%. Durability properties are also maintained or even enhanced. Here, it is used a multi-technique approach to understand the phase and microstructure developments. From the thermal analysis, partial limestone reactivity is proven. Chiefly, high-resolution synchrotron microtomography has been employed, for the first time in these systems, to characterize their microstructures. The measured total porosities, within our 1 μm spatial resolution (voxel size 0.32 μm), were 16.6, 10.0 and 2.4 vol% at 7, 8 and 60 days of hydration, respectively. Pore connectivity strongly decreases with hydration time due to the chemical reactions producing new phases filling the pores. The 6-connected porosity fractions were 92, 78, and 9% at 7, 8 and 60 days. The reactions filling the pores were investigated by Rietveld quantitative phase analysis and 27Al MAS-NMR.
Dragonfly was used to perform image segmentation, analysis and interpretation. It was also used to carry out pore analysis to differentiate pores that are connected to the surface of the evaluated sample volume from pores that are isolated.
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