About silicates and OBTEGO silicate portfolio History 2000 years ago the Romans used Opus Caementicium, also known as “Roman concrete”. This mixture consisted essentially of sand, water, lime and rocks. To make this mixture harder, volcanic ash was added. This volcanic ash came from the Pozzuoli area, hence the current name pozzolana come from. Pozzolans consist of clay, iron oxide, alkaline components and silicates. The silicates contained served then as now to solidify the concrete. Nowadays the individual silicates are used in pure form or with additives to improve the hardness of the concrete surface and to reduce the capillarywater absorption. Different types of silicate are available for this. Mode of action Water glass is alkali silicate powder dissolved in water, e.g. Sodium, potassium or lithium silicate. These dissolved silicates react in concretewith hydrated lime to formcalciumsilicate hydrate. The gel formation that can be observed when applying silicates on concrete is a process that can be attributed to this reaction. A stable structure similar to glass is created in the pore structure, which has a positive effect on the concrete properties in terms of scratch resistance and the reduction of capillarywater absorption. The application of silicates also reduces any sanding of the concrete, which significantly simplifies the subsequent maintenance of the floor. Silicates react with hydrated lime to formcalciumsilicate hydrate, which hardens the concrete structure. Volcanic ash with silicate Sand, stones, lime, water „Roman concrete“ Concrete pore with hydrated lime Addition of silicate Concrete pore filled with calcium silicate hydrate 44
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