About the preparation of the supports

The scrupulous preparation of the supports is the essential prerequisite for the correct realization of cementitious coatings in general and osmotic ones in particular. It is therefore essential to prepare an accurate evaluation and preparation plan. The essential checks can be summarized as follows:

  • Checks concerning the strength and compatibility factors of the substrate and application mortars
  • Controls relating to the roughness of the support
  • Verification of the absorption capacity of the support
  • Assessment of the flatness conditions of the support with the relative dimensional implications relating to the coating

Among the essential conditions that must exist at the time of installation, it is absolutely necessary to consider the condition “saturated with a dry surface”, which can be defined as the “condition” of a support which, having wet a few hours before, has completely absorbed the water that was applied to it, until it dried on the surface. In this way the support does not remove water from the material applied and the surface does not have veils of water that can interpose between the two materials, jeopardizing adhesion.

What is indispensable to eliminate from the supports:

SoilingPre-existing paintingsLimestone filmsEfflorescence of lime
Saline eventsOxidative relevanceInhomogeneity of thicknessAlgae, molds, lichens
Seasoning residuesCement lactose, lime, etc.Parts incoherent and / or degradedInhomogeneity of absorption
Cracks and microcracksPowderDisarming oil residuesVegetation

What is important to check:

Superficial planar continuityPresence of microporosityPossible non-homogeneous thicknessCrack state
Cohesion and compactnessDegree of cleanlinessNo dustWettability
Absorption homogeneitySurface temperatureSaturated condition with dry surfaceWater repellency

Corrective actions:
Wash, remove, fill, eliminate, compensate, seal, fill, inject, check, make sure that the supports are perfectly ready to receive the osmotic coatings. Pending the cancellation of the promised characteristics and the early detachment.

Warnings before and after application:
– Thermal application range (check the external or internal temperature for the application, between 5 and 30 ° C).
– Events that may compromise the result (make sure of the risk of atmospheric events that can compromise both the installation: sun, rain, wind, cold).
– Importance of protection and moist curing of exposed surfaces (Curing).

About the aggressive chemical agents

Osmotic cementitious waterproofing products in general, including the products of the OSMOCEM Line, as the definition states, are cementitious systems characterized by high values ​​of intrinsic impermeability and sealing capacity. As such, they are able to provide improved performance even in terms of protection against chemical agents. However, with regard to aggressive industrial chemicals, the superior intrinsic impermeability of osmotic cement-based waterproofing products is not, however, to be considered sufficient to guarantee adequate chemical resistance to the various operating situations that may, from time to time, arise and therefore the adoption of measures may be necessary specific protection (resinous coatings, etc.).

Degree of aggressiveness of some substances most frequently found:

AGGRESSIVE AGENTEFFECTS ON CONCRETE
WEAK BASESNo degradation
STRONG BASESNo degradation
WEAK ACIDSDilution and removal of cement paste
STRONG ACIDSStrong leaching and disintegration of the binding matrix
SWEET WATERDilution, superficial removal of the cement paste
OILS AND GREASEDisruption of the cement matrix
SULPHATESExpansion, cracking, misalignment, disintegration

Concerning mixing systems

The wheelbarrow cannot be used in any way to “mix” cementitious compounds and osmotic products in particular. The correct mixing must in fact take place either in special “mixers” or with low-speed drills and must be continued until a lump-free mixture is obtained, of the desired consistency.

Regarding the reinforcement of the osmotic coating thickness

To improve the performance of cementitious coatings, even in the case of osmotic systems, it is always advisable to insert a reinforcing fiberglass mesh type ARMAGLASS 160 (160 g / m² weight with 4 x 4 mm mesh) between one layer of osmotic compound and the next. The mentioned method, in the presence of thick coatings (> 6 mm), of structures expected to be subject to movement, is to be considered essential.
In case of foreseeable risk of strong counter-thrust, use a 2 mm galvanized steel mesh and 5 x 5 cm mesh suitably fixed to the support.

Regarding the correct distribution of stress

In order to obtain a correct distribution of the stress, in correspondence with the connections between horizontal and vertical structures, it is essential to make a  preliminary construction of connection joints suitable for the shape and dimensions to the geometry of the structures.