Towards tailoring the nanostructure of concrete

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Concrete is an artificial rock of stone and sand glued together by cement paste. Since Roman times almost all cementitious binders are based on calcium silicates which with water to form nanoporous reactions products. The nanoporosity and the nanostructure of the reaction products have a major impact on the engineering properties of the hardened concrete. Addition of micro and nanosized particles to cementitious mixtures may result in a more homogeneous and finer pore structure leading to among others improved durability. The cement paste structure and porosity can e.g. be engineered by addition of non-pozzolanic layer silicates (clay) having specific particle shapes and surface properties (e.g., charge and specific surface area). This seems mainly to be due to the growth of calcium-silicate hydrates (C-S-H) on the clay particle surfaces where the nanostructure of the C-S-H seems to depend on the size, shape and charge of the clay particles. Also, the clay particles act as nucleation sites and increase the cement’s reaction rate (Lindgreen et al., 2008). Concrete is the most widely used construction material because it is an inexpensive and low energy product, and can be made from local materials; approximately 1.6 tons of structural concrete are produced per capita each year. Due to the extensive use of concrete, even minor improvements have a large impact on the sustainability of construction. Lindgreen H, Geiker M, Krøyer H, Springer S, Skibsted J (2008), Microstructure engineering of Portland cement pastes and mortars through addition of ultrafine layer silicates. Cement & Concrete Composites, 30, 686–699, doi:10.1016/j.cemconcomp.2008.05.003
Place: DTU NanoDag
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ID: 2348805