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:
| Soiling | Pre-existing paintings | Limestone films | Efflorescence of lime |
| Saline events | Oxidative relevance | Inhomogeneity of thickness | Algae, molds, lichens |
| Seasoning residues | Cement lactose, lime, etc. | Parts incoherent and / or degraded | Inhomogeneity of absorption |
| Cracks and microcracks | Powder | Disarming oil residues | Vegetation |
What is important to check:
| Superficial planar continuity | Presence of microporosity | Possible non-homogeneous thickness | Crack state |
| Cohesion and compactness | Degree of cleanliness | No dust | Wettability |
| Absorption homogeneity | Surface temperature | Saturated condition with dry surface | Water 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 AGENT | EFFECTS ON CONCRETE |
|---|---|
| WEAK BASES | No degradation |
| STRONG BASES | No degradation |
| WEAK ACIDS | Dilution and removal of cement paste |
| STRONG ACIDS | Strong leaching and disintegration of the binding matrix |
| SWEET WATER | Dilution, superficial removal of the cement paste |
| OILS AND GREASE | Disruption of the cement matrix |
| SULPHATES | Expansion, 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.