SILRES® BS 1801 is a mixture of octyltriethoxysilanes isomers, with iso-octyltriethoxysilane as the main component. SILRES® BS 1801 is used in undiluted form as an admixture for the integral waterproofing of fresh concrete.


In the fresh concrete SILRES® BS 1801 reacts with the water in the building material’s pores, eliminating alcohol. The active thus substance formed greatly reduces the concrete’s absorbency, but without blocking any pores or capillaries. The impregnated building material retains very high water-vapor permeability.

SILRES® BS 1801 is approved as a water resisting admixture under EN 934-2:2009 Tab. 9. The recommended admixture range is 0.1 % to 1.0 % of the cement content. A significant reduction in water uptake can already be achieved at a concentration of 0.2 % of the cement. SILRES® BS 1801 is added either simultaneously with or immediately after the mixing water – it should never be added along with other additives. We recommend testing compatibility with other concrete admixtures separately. A longer mixing time will thoroughly distribute the product within the overall system, which in turn will make it highly effective. An initial test according to DIN Technical Report 100, section 9.5, (alternative: EN 206-1 and EN 1045-2) must be conducted for each new concrete composition. Finer adjustment of the fresh and set concrete properties by, for instance, varying the binder content pursuant to EN 206-1 and EN 1045-2 is recommended on a case-by-case basis. The concrete may harden more slowly during the first days in isolated cases. When used in concrete goods or similar concrete products according to EN 1338, 1339 or EN 1340, an initial-type test (cf. section 6.2 of the respective standard) is recommended.

SILRES® BS 1801 is recommended as a waterproofing concrete admixture.


The containers must be protected against sunlight. The 'Best use before end' date of each batch is shown on the product label. Storage beyond the date specified on the label does not necessarily mean that the product is no longer usable. In this case however, the properties required for the intended use must be checked for quality assurance reasons.


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