Surface Protection through Hydrophobic Impregnation for the Pilaster Strips of the Egbert-Gymnasium

The Egbert-Gymnasium Münsterschwarzach (EGM), founded in 1901, is a state-recognised secondary school governed by the Benedictine Abbey of Münsterschwarzach in the Lower Franconian district of Kitzingen (Bavaria, Germany). School operations will continue during the comprehensive general renovation in several construction phases. The refurbishment is scheduled to be completed by the 125th anniversary celebrations in 2025.

In the fourth construction phase, the building owner decided to retain the visual structure of the day care centre’s architecture. The approximately 700 square metres of pilaster strips of the modern concrete facade were given a thorough cleaning using high-pressure jets. The in-house craftsmen reprofiled any damage or breakouts that occurred using the quick-repair mortars StoCrete SM or StoCrete SM P. The latter was used when the damaged area required corrosion protection for the reinforcing steel. The rapid hardening of both mortars meant that a timely overcoating was possible.

The façade then received a hydrophobic impregnation with the silane gel StoCryl HG 200. The gel is was applied undiluted to the concrete substrate using airless spraying method in the desired layer thickness.

Hydrophobic gel protects the concrete
StoCryl HG 200 forms a protective layer several millimetres thick under the concrete surface.
Unlike a conventional hydrophobic impregnation, StoCryl HG 200 completely blocks the capillary absorbency of the porous concrete edge zone. This is made possible by the high penetration depth of the active agent of around six millimetres. The concrete edge zone remains permeable to water vapour.

Long-chain silanes and bentonite carrier material
The StoCryl HG 200 hydrophobic gel is based on long-chain silanes and the bentonite carrier material. This non-Newtonian fluid allows large amounts of material to be applied in one step.

Thus, a large active agent layer is available on the component surface. The interfacial tension between the silane and the pore wall filled with water, actively transports the agent into the concrete edge zone. The surface tension of the long-chain silanes changes very slowly. This enables a long penetration time and a high penetration depth.

Positively influence the service life of concrete structures
Deep hydrophobic impregnation can increase the service life of new buildings, but also of existing structures. This significantly reduces the costs of a concrete structure in relation to its life cycle. This is sustainable.

Long-term studies confirm effectiveness and durability
StoCryl HG 200 protects reinforced concrete permanently and effectively against the penetration of water and water-soluble pollutants. It thus prevents damage caused by frost, chloride ingress and chloride-induced steel corrosion. The service life of the structure is significantly extended. Both research results and successful practical experience from the last 15 years prove that the deep hydrophobic impregnation of cement-bound components is an effective and sustainable protective measure against the ingress of substances that are aggressive to concrete.

It is precisely these properties that fulfil the building owner's refurbishment plan to secure and protect the high school and its buildings for the future.

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