Consolidation of stone materials Flashcards
What has do be done before the consolidation methods?
First we have to do some preliminary investigation, menaing that we have to characterize the stone material from petropraohic and mineralogical viewpoint, to assess and to evaluate the conditions.
Then when we know the stone, we have to investigate on the chemical, phycial and mechanical weathering to set a diagnos on the weathering stone.
Which are the conservation actions?
- Cleaning
- Consolidation
- Protection
Explain what is done through cleaning
Aim is to recover the original material before doing the next steps.
Can be done through
* Methods based on the use of water
* Methods based on the mechanical cleaning
* Laser cleaning
* Cleaning by chemical agents
* Use of biocidal agents
Explain the water based methods
- Soft water flow
- High pressure water
- Low pressure water spraying
- Compresses of water
- Water vapour
Explain the methods based on mechanical cleaning
- Dry sandblasting
- Hydro-sandblasting (sand+water)
- Micro-sandblasting
Explain laser cleaning
It is a special non ohysical tool to remove crusts
Advantages:
* Minimal invasiveness
* High precision
* Selectivity of the treatment
Limiteations: high cost
What is consolidating?
Förstärkning. Using inorganic or organic agnets to consolidate the material.
The aim is to preserve the material from further degradation and environmental agents. Also recover the load-bearing and structural characteristics
What are the ideal features of the consolidating agents?
- No release of by-products
- Easy penetration inside the material
- Compability with the substaret
- High stability of the consolidating affect over time
- Easy removal and/or re-application
With what types of methods can we apply consolidating agents?
- Brush or painbrush
- Spraying
- Capillary rising
- Immersion
- Under vacuum
Describe inorganic consolidating agents
Chemical treatments to strengthen and stabilize the material
Good:
* Deposition of new stone like material inside pores and cracks
* May be water soluble, since we may want to use a consolidating agent that we want to remove later
* High durability over time
Bad:
* Irreversible process
* The consolidating material is typically fragile
* Poor capability of penetrating inside the substrate
* Not good for large fractures
Give som examples of the inorganic consolidating agents
Lime: good for carbonatic stones
Calcium bicarbonate
Barium hydroxide: insoluble in water
Tetraethyl otrhosilicate (TEOS): soluble in water
Describe organic consolidating agents
These are polymers
Good:
* improvement of menchanical properties - such as tensile strength
* good for adhesive properties adn also barrier effect (water proof)
* Good penetration capacility
* No soluble salts
Bad:
* Degradation over time
* Non-optimal compability with substrate
Which are the main types of the organic consolidating agents?
There are three organic consoldating agents for restoration:
1. Adhesives
2. Filling materials
3. Replacement
Thera re one organic consolidating agent for prevention:
1. Protective agents
What is the glass transition temperature in polymers?
This is the tmperature when the secondary bonds dont exist anymore and the polymer becomes soft.
The glass transition temperature can be changed by changing the degree of branchingor crosslinking in the polymers, or by the addition of plasticizers
The mechanical properties are strongly dependent on the temperature. Many polymers are brittle in RT, but move to ductile when moving towards Tg
What are the differences between thermoplastics and thermosetting?
Thermoplastic are linear of branched polymers. They can be plastic deformed, meaning they can go above Tg and break the secondary bonds, but when cooling down the secondary bonds will built up again.
Thermosetting polymers are networks or cross-linked, and have no secondary bonds, and are therefore not plastic deformable.
