Degradation and restoration of the tuff

Tuff building material between beauty and decay

The tuff, represents one of the very widespread building materials, its use can be found in the construction of all kinds of construction:
With it are made bearing structures such as walls, pillars, supporting walls, arches, vaults, etc.

The tuff it’s a rock sedimentary pyroclastic of volcanic origin, whose porous nature makes it a stone easily workable.

Thanks to his elevate technical characteristics such as workability, lightness, toughness and compressive strength, tuff is one of the most used products in construction.

The natural beauty of this material is in fact highly sought after by artisans, designers and architects for the creation of interiors with a simple and welcoming taste.

In Italy its use has been widespread since the dawn of architecture and therefore it is found in buildings scattered throughout the territory, characterized by different shades of the material, in relation to the geographical location in which the work was created.

Degradation of the tuff works main causes

The presence of a plot particularly porous which characterizes it for being a light and easily workable material, lo exposes to the attacks of humidity and all those volatile substances that contribute to its degradation.

I phenomena of degradation more commonly found in the works made in tuff, they can be traced back to decohesion of the constituent elements and manifest themselves with the posting and consequent fall of pyroclastic granules and fragments of variable shape and size.

To these disruptive phenomena, they often join efflorescenze whitish, spots e encrustations dark due to biological activity and / or surface deposits.

To address the issue of the recovery of such degraded walls, a distinction must be made immediately between walls face to sight e plastered walls.

This differentiation is fundamental in order to prepare an adequate recovery intervention for these structures.

Plastered tuff walls: how to treat them

The tuff walls intonacate, when they are affected by degradation phenomena, they manifest this event with plaster detachment, swelling and the presence of superficial lesions.

The latter, when not associated with phenomena of static instability, follow the trend of the underlying convexes of the segments, when the latter lose their cohesion function.

Effects of rising damp on tuff masonry
In the presence of such phenomena, it is necessary to carry out a series of on-site surveys to try to identify any phenomena infiltrations of water resulting from phenomena of rising damp or lateral infiltrations.

The search for such infiltrations is important as it is the water itself that generates the dangerous hygroscopic salts, capable of crumble, with their volumetric increase, the tender tuffaceous structure.

The main operational phases to intervene in the case of a plastered wall consist in check the tightness of old plaster, striking the affected surface with a mallet.

Evaluate the degradation with ancient methods

From the noise with no such percussion, it is possible to detect the phenomenon of decohesion plaster, which must be removed.
If the percussion action, it produces a sound sordo it means that the plaster is enough cohesive at least in most of the surface.

In presence of humidity, it is necessary remove the plaster existing on the masonry for a height of at least 50 cm beyond the evident humidity line, removing even the first few centimeters of existing bedding mortar if it is inconsistent or degraded.

Percussion of the plastered masonry to check the seal of the plaster
Once the masonry has been exposed, an operation must be carried out cleaning of the support with suitable means, in order to make the wall surface free of dust, bacterial proliferation, saline efflorescence, oils, greases, waxes, residues of previous workings, etc.

The importance of surface cleaning

If necessary, this cleaning phase can also be carried out using thehydro wash pressure and in the most resistant cases the sandblasting.

At this stage it is also possible to proceed with reconstruction gods wall ashlars or to their replacement, by undoing and stitching, in order to create a wall perfectly renovated and complete with well-styled convexes.

Clean tuff wall with state of the art styling
Thereafter, one must apply impregnating solution ecological, water-based, specific to eliminate the superficial efflorescence present, in order to limit the crystalline deposits of hygroscopic salts present, a consequence of capillary rise humidity.

The aqueous vehicle allows for good penetration of the active substances in the capillarity of the masonry subject to rising damp, thus producing an action of contrast the formation of salts inside the pores present.

The application can be done with two brush or spray passes on homogeneous masonry subject to capillary rising damp in tuff, both internal and external.

Rebuild the structural continuity

To get good continuity structural, it is useful to use a specific product such as liquid tuff.

Malta’s pozzolanic hydraulic lime for the consolidating and transpiring injection of historic masonry.

This is obtained from the cold mixing of pure aerial lime with a high content of calcium hydrate and selected natural pozzolans, mixed with micronized carbonate aggregates and expansive elements for the control of plastic shrinkage.

consolidation operation using Calchera San Giorgio liquid tuff
It does not contain sulphates, free lime, or any form of clinker, it is highly breathable and does not alter the vapor permeability of the masonry, free from materials harmful to health and the environment.

Recyclable as inert at the end of its life. The mentioned product is suitable for Consolidation of tuff walls and al filling of cracks and injuries by injections even at very low pressure, to be performed preferably after masonry plating or for the conservation and consolidation of valuable plasters.

Redo the plaster with compatible materials

A now rebuilt and consolidated wall structure is possible to apply an adequate state of plaster consisting mainly of hydraulic mortars with bindersexclusively derived from cooking of pure limestone at temperatures below 900/1000 ° C.

This is to ensure complete compatibility between the plaster and the underlying tuff wall structure.

Visible tuff walls: how to protect them from decay

As a preventive operation for to protect walls, vaults and more in tuff exposed, it is advisable to use specific products with consolidating and protective action.

This method is valid for all the different varieties of tuff existing in the area, whose main feature is the presence of pore on the whole surface of the wall ashlars.

Vaults in tuff facing suitably treated and protected
Even if this presence of porosity helps to ensure excellent transpiration to the support, unfortunately it is at the same time cause of absorption of water and pollutants harmful to the integrity of the tuff stone.

The factors described are consequently the cause of the phenomenon of chalking of the stone, which if neglected can over time produce the complete crumbling of the material.

The phase of Start of this degradation on the exposed tuff walls, it can be easily detected by the presence on the underlying floor of dust precipitated as a result of this degradation phenomenon.

Ecological products for safe and durable protection

Among the products useful for the consolidation of tuffaceous materials, we find Compact®Eco of Camp S.r.l. a stone consolidator expressly formulated for the treatment of crumbling and non-cohesive building materials, such as tuff.

The small dimensions of the micelles that make up the product allow both a good penetration into porous and absorbent supports and the preservation of the sought-after characteristics of transpiration of the material.

Thanks to its non-toxicity, the product can also be used in closed and poorly ventilated environments. Its surface consolidation action strengthens the structure of the treated support and prevents chalking, its use does not involve particular operations being ready for use and easy to use.

Easy to perform applications to protect the masonry

It lends itself effectively to application by roller or brush, but it is optimal, especially in the case of treating very crumbling substrates, to be applied by nebulization.

Armoston consolidating protective treatment by Dracoe
Another product useful for the surface consolidation of porous materials is Armostone of Italian Draco breathable cortical consolidator with high penetration capacity, based on silicic acid esters in an alcoholic vehicle.

Armostone is a specific product for the cortical consolidation of masonry elements, plasters, porous stones, tuff and weak or incoherent supports.

It does not alter the surfaces, resists chemical agents, is not reactive to alkalis and is ideal for interventions on buildings of historical and artistic interest.

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