CEMENT

[:ru]Кристман А.[:en]Christmann A.[:] [:ru]Hexion Specialty Chemicals[:en]Hexion Specialty Chemicals[:]

[:ru]Гризолет М. К.[:en]Grisolet M. C.[:] [:ru]Hexion Specialty Chemicals[:en]Hexion Specialty Chemicals[:]

[:ru]Петер У.[:en]Peter U.[:] [:ru]Hexion Specialty Chemicals[:en]Hexion Specialty Chemicals[:]

[:ru]Сари М.[:en]Sari M.[:] [:ru]Hexion Specialty Chemicals[:en]Hexion Specialty Chemicals[:]

[:ru]Риб Р.[:en]Reeb R.[:] [:ru]Hexion Specialty Chemicals[:en]Hexion Specialty Chemicals[:]

Alitinform №3-4 (04-05) 2008 г. 44-55 p.

Abstract

Water ingress is a key issue for durable performance in cement based materials: It is well known that moisture leads to a degradation of the mechanical properties of construction compounds such as mortars, grouts, etc. It also adversely affects their aesthetics and original appearance (due to dirt pick-up, discoloration, efflorescence, fungal and algal proliferation, especially in coloured grouts and decorative renders…), with even a negative impact on their durability.

Various water repellents are thus available to minimize water absorption [1]: Fatty acid salts (like calcium, potassium, magnesium or zinc stearates, oleates and other fatty compounds), silanes, polysiloxanes and siliconates are often used as hydrophobic agents in construction materials. New water repellents such as organosilanes supported by mineral carriers have also appeared recently. Most conventional water repellents present quite serious concerns linked to their intrinsic hydrophobicity: in addition to the mixing problem (with the fresh cementitious materials), they often tend to migrate towards the air-dried surface, leading to a heterogeneous compound with an irregular performance and a limited durability [2].

A new kind of water repellent is presented in this paper, based on an innovative concept making hydrophobic species easily dispersible in aqueous media. More precisely, hydrophobic active species are dispersed in water, producing stable emulsions that can be spray-dried. The resulting dry emulsion can then be easily redispersed in cementitious materials, giving an efficient and homogenous damp proofing of their bulk.

We present and discuss the enhanced properties of grouts after addition of a hydrophobic agent prepared according to this concept. We show uniform waterproofing properties, leading to a significant reduction in water up-take at very low levels of incorporation. This also leads to improved colour preservation after moisture contact. This concept is thus also very interesting for other finishing materials (like renders), in order to preserve their initial aspect and physical properties.