STONE STRENGTHENING DR. HARTMUT ACKERMANN Wacker SILICONES, 04.05.2010
CREATING TOMORROW'S SOLUTIONS
TYPES OF DETERIORATION OF STONE
mechanical damages: • damage due to volumetric changes of water upon freezing and thawing, • salt damage due to crystallization, hydration, hygroscopic and de-icing salt • salvation and transportation of salts forms additional pores and weakens the construction chemical damages: • chemical reactions with participation of water or products using water as a vehicle: => water soluble reaction products (e.g.: salts, gases like SOx) are moved / removed by water => reaction products with bigger volume cause mechanical stress biological damages: • colonization and attack by microorganisms (such as algae, lichen, mosses and bacteria) => microorganisms store additional water, secrete aggressive metabolism products, etc. other damages: loss of thermal insulation properties, optically unpleasing appearance
STONE STRENGTHENING CONSTRUCTION CHEMICALS Slide 1 Dr. Hartmut Ackermann
TYPES OF DETERIORATION OF STONE
gypsum crust
slate like cleavage shell formation chemical corrosion
salt and frost damage
mould attack
moss colonization STONE STRENGTHENING CONSTRUCTION CHEMICALS Slide 2 Dr. Hartmut Ackermann
TYPES OF DETERIORATION OF STONE PORTAL FIGURE AT HERTEN CASTLE BUILT END OF 18TH CENTURY
Foto from 1900 STONE STRENGTHENING CONSTRUCTION CHEMICALS Slide 3 Dr. Hartmut Ackermann
Foto from 1969, Rapid degradation
DAMAGE MECHANISMS DAMAGES DUE TO VOLUMETRIC CHANGES Alkali Silica Reaction x SiO2 + 2 NaOH
CO2 / H2O
Na2CO3 + x SiO2 * aqua bulky Silica Gel
Sulfate Reactions 3CaCO3 + H2SO4 (air pollution + water)
CaSO4 + H2O + CO2 volume increased x2
3CaO * Al2O3 + 3CaSO4 * 2H2O Tricalcium aluminate
+ 26 H2O
e
STONE STRENGTHENING CONSTRUCTION CHEMICALS Slide 4 Dr. Hartmut Ackermann
3CaO * Al2O3 * 3CaSO4 * 32H2O
Ettringite: volume increased x8
CHRONOLOGICAL OVERVIEW ABOUT CONSOLIDATION METHODS
• Middle age: Glues and gelatine
• Waterglas: salt- and crust formation K2SiO3 . xH2O + CO2
SiO2
.
aq + K2CO3
• Hydrofluoric acid and fluorosilicates: no binding effect, caustic to stone Ca(OH)2 + 2HF
CaF2 + 2 H2O
STONE STRENGTHENING CONSTRUCTION CHEMICALS Slide 5 Dr. Hartmut Ackermann
CHRONOLOGICAL OVERVIEW ABOUT CONSOLIDATION METHODS
• Linseed oil, poppy seed oil, waxes and paraffines tacky surface, resin building products, glossy surface, sealing of pores
• Baryta water: no binding effect Ba(OH)2 + CO2
acid
BaCO3 + H2O
• Organic resins: low penetration depth, sealing of pores (Epoxid resins, polyurethan resins)
STONE STRENGTHENING CONSTRUCTION CHEMICALS Slide 6 Dr. Hartmut Ackermann
STONE STRENGTHENING WITH SILICID ACID ESTERS • Silicic acid esters: very good penetration depth, very good binding effect. No harmful by-products. Si(OR)4 + 4H2O
SiO2
.
x H2O + 4 ROH + 2 H2O
Quartz 1861 August W. Hoffmann
Si(OC2H5)4
STONE STRENGTHENING CONSTRUCTION CHEMICALS Slide 7 Dr. Hartmut Ackermann
SiO2*aq
CHEMICAL PHYSICAL PROPERTIES OF SILRES® BS OH 100 •Chemical character:
Tetraethylsilikathydrolysat
•Active content:
> 98 wt%
•Organic Solvent:
-
•Gel deposition after 28d/RT:
30 wt%
•Physical state:
liquid, clear, colourless
•Density:
0,997 g/cm3
•Viscosity, dynamic:
1,6 mPa*s
at 25°C
•Flash point:
40°C
DIN 51758
•Ignition Temperature:
230°C
DIN 51794
•R-Phrase:
R 10, 20, 36/37, 52/53
•S-Phrase:
-
•VbF:
A II
•WGK:
2 STONE STRENGTHENING CONSTRUCTION CHEMICALS Slide 8 Dr. Hartmut Ackermann
STONE STRENGTHENING SILRES® BS OH 100 – THE LIQUID STONE
SILRES® BS OH 100 before cure: low viscous liquid after cure: brittle hard solid
SiO2
Cl2
quartz crystalline
EtOH SiCl4
[SiOx(OH2CH3)4-x] y SILRES® BS OH 100 low viscous liquid STONE STRENGTHENING CONSTRUCTION CHEMICALS Slide 9 Dr. Hartmut Ackermann
H2O
SiO2 silica gel amorphous
STONE STRENGTHENING WORKING PRINCIPLE FOR STONE STRENGTHENING
crust
weathered zone intermediate zone
undeteriorated zone hardness profile of deteriorated stone
• deposition of fresh, weather-resistant, mineral binder • penetration into the stone down to the undamaged core • build-up of a uniform strength profile through the cross-section of the stone • no formation of harmful salt-like byproducts • no discoloration of the stone surface
hardness profile of successfully consolidated stone
• no impairment of water-vapour permeability, thermal and hygric behaviour • reduced water and pollutant absorption
STONE STRENGTHENING CONSTRUCTION CHEMICALS Slide 10 Dr. Hartmut Ackermann
deposition rate [%]
STONE STRENGTHENING CURING OF SILRES® BS OH 100
days STONE STRENGTHENING CONSTRUCTION CHEMICALS Slide 11 Dr. Hartmut Ackermann
STONE STRENGTHENING CURING OF SILRES® BS OH 100 deposition rate [%]
100 90 80 70 60 50 40 30 20 10 0
BS-OH 100 / Ethanol 100:0 BS-OH 100 / Ethanol 80:20 BS-OH 100 / Ethanol 60:40
0
10
20
30
The required gel disposition rate can be adjusted. STONE STRENGTHENING CONSTRUCTION CHEMICALS Slide 12 Dr. Hartmut Ackermann
40 days
STONE STRENGTHENING CLASSIFICATION OF STONE Geological classification of stone Sedimentary rock => sandstone, limestone, tuff, Igneous rock => Granite, lava Metamorphic rock => Gneiss Chemical classification Silicate-quartzite Silicate-clay Silicate-calcareous Calcareous
=> limestone, shell limestone, travertine
Physical classification Dense stone Absorbent stone Highly absorbent stone
=> water absorption < 3 %, pore volume < 6 % => water absorption 3 - 7 %, pore volume 6 - 15 % => water absorption 7 - 20 %, pore volume 15 - 30 %
=> various types of sandstone
various types of stone vary in wheather ability and durability, depending on their porosity and composition
STONE STRENGTHENING CONSTRUCTION CHEMICALS Slide 13 Dr. Hartmut Ackermann
STONE STRENGTHENING CONSERVATION WITH SILRES® BS OH 100 1. 2. 3. 4.
sandstone before treatment
sandstone after treatment
Define test area (approx. 1 m²) Cleaning, apply if necessary a biocide treatment Drying time: 2-3 days / at high humidity longer Conservation with SILRES® BS OH 100: Keep safety instructions: wear gloves, glasses … protect plants and windows relative humidity 40 – 70% temperature on the construction material 10 – 25°C applying by low pressure spraying or flooding 2 - 3 applications wet-on-wet; approx. 5 l / m² 20 - 30 minutes between cycles freshly treated surfaces must be covered for 2-3 day against rain 5. Let cure for 2 - 4 weeks 6. 2nd conservation + water repellent impregnating agents 7. Assess samples (drilled cores) after 18 months
STONE STRENGTHENING CONSTRUCTION CHEMICALS Slide 14 Dr. Hartmut Ackermann
STONE STRENGTHENING FURTHER APPLICATION TIPS
- Before-treatment Start with test areas on the object: approx.0.25 - 0.50 m² determination of strength, coloring, brilliance in comparison to untreated areas - After-treatment if only small sections are treated or if there is too much material on the surface, it is advisable to follow up the last treatment with solvent (Aceton) to avoid shining
STONE STRENGTHENING CONSTRUCTION CHEMICALS Slide 15 Dr. Hartmut Ackermann
STONE STRENGTHENING FURTHER APPLICATION TIPS
- Limitation of application: * high rate of hygroscopic salts
maybe demineralization
* stones with high density, without enough absorbency cannot be treated * Cracks cannot be sticked together with stone strengthener * High moisture penetration
STONE STRENGTHENING CONSTRUCTION CHEMICALS Slide 16 Dr. Hartmut Ackermann
bad penetration depth, too quick reaction
STONE STRENGTHENING CLEANING PROCEDURES
- Water cold or warm, with or without pressure, applicable by water soluble contaminations. - Chemicals: acid or alkaline cleaning agents often often lead to stone damages through salification, discoloration, change of surface - Sand blasting - Rotation cleaning method with specific blasting agents - Laser cleaning removes the dirt layers effective and gently, very expensive, only for specific cases
STONE STRENGTHENING CONSTRUCTION CHEMICALS Slide 17 Dr. Hartmut Ackermann
THANK YOU FOR YOUR ATTENTION
Burghausen Castle
Wacker-Chemie AG, Production Plant Burghausen STONE STRENGTHENING CONSTRUCTION CHEMICALS Slide 18 Dr. Hartmut Ackermann
