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Blanka Kolinkeová
University of Pardubice – Faculty of Restoration
Diagnosing and restoring Roman cement façades: cases of
investigations, trial tests and restoration concepts in the Czech Republic
Natural cements in European cultural heritage Les ciments naturels dans le patrimoine européen
PARIS – 26/27-04-2012
Basic information about object 1
• Category: apartment house
• Location: Brno, South-Moravia
• Built: around 1885, unknown architect
• Current owner: Association of the flats' owners
• Style: historicism, Renaissance Revival
• Masonry: brickwork with lime plasters
• Decoration: run-profiles and cast elements from Roman cement mortars
Details of the façade decoration
Restoration investigations
• documentation of the damaged areas on the façade
• sampling and analysis
• identification of mortar types and their capillary water uptake
• investigation of stone elements
• colour paints
• investigation of water-soluble salt content and gypsum crusts
• tests on cleaning and removing of finish layers
• tests on RC mortar application
Present state - ground floor
Portland cement fillings bare masonry
open surface of cast elements due to the rainwater acrylic paint layer closing the surface
Present state – the 1st floor
dust layer
gypsum crust
bare masonry network of cracks
missing parts of renderings and casts
rainwater leaking
Cleaning tests • low-pressure steam with the final mechanical cleaning
• rotary abrasive method (JOS) using different abrasives (fine graded dolomite, glass powder, corundum)
• steam in combination with sharp mechanical tools
• combination of high-pressure water with abrasive and final mechanical cleaning
steam JOS - dolomite JOS - glass powder combination of methods
Evaluation of the mortar composition
1
2 4 3 5
• coarse lime mortar as the underlying layer (0) • renderings and the final surface layer are made of reddish
Roman cement mortar with fine aggregate (1) • workshop casts are made of ochre coarse Roman cement
mortar (2) • thin ochre lime layer, most probably the final layer (3) • the façade has a layer of thin reddish-brown mortar based
on white air lime with added ochre pigments (4) • ochre painting from the last repair (5)
Cross-section – cast element
Roman cement mortar
lime paint
sulphated lime paint
lime paint with ochre pigment
original ochre lime paints
Mortar tests
• Folwark (light ochre) and W&P (reddish), carbonatic sand • Sample 1 – combination of both cements 1:1; cement : aggregate ratio 1:2 by volume Sample 1a with retarder, 1b DARC (RC deactivated with water) • Samples 2, 2a – combination of both cements 1:1; 1:2 weight ratio with aggregate
• Mortar recipe 1 was selected after evaluating the setting time, workable life and the characteristics of the samples (colour etc.)
Application of the selected mortar
Basic information about object 2
• Category: originally – public building (State Technical College)
• Location: Pardubice, East Bohemia
• Built: 1887, architect JindYich Fialka
• Current owner: University Pardubice
• Neorennaisance style
• Masonry: brickwork with lime plasters
• Decoration: run-profiles and cast elements from Roman cement mortars
Historic coloured photography
Sampling
sample from lime mortar part
sample from RC mortar part
Cast elements
cross-section from cast
SEM photography
Steel reinforcements in cast elements
uncovered steel reinforcement X-ray photography of steel reinforcement
state before cleaning basic cleaning by commercial paint removal P05 and high pressure steam
Cleaning of Roman cement relief
after final cleaning by steam and mechanical cleaning
Cleaning of Roman cement relief
Restoration of the statues
steam laser
micro-blasting
micro-blasting laser laser
micro-blasting
laser laser
steam
Statue of the allegory of Architecture
Statue of the allegory of Industry
net of cracks under paint layer
orange painting from the last repair in 1990
surface of RC cast
layer of dirt on the gray cement painting
gray cement painting
Original surface and secondary layers
Evaluation of the research • originally was the façade made up in ochre colour in two hues
– passive areas and renderings - very light ochre hue, cast elements - slightly darker
• the whole façade was originally with no paint – presented in colours of used mortars
• plasters and renderings were made in mortar of hydraulic lime
• decorative elements were casted from mortar on a base of RC • socle is made of light beige sandstone • two later repairs • damages are mostly on parts exposed to the rainwater • corrosion of reinforcements in casts
• inappropriate fillings from previous renovations
• cleaning of the façade is possible with very low risk of harming the original surface
• repairing the lime mortars with similar material
Restoration concept elaborated
• removing the rust from bare reinforcements in cast elements
• repairs based on RC mortars
• filling the large cracks by grout based on RC
• final layer of silicon ochre paint, corresponding to the original appearance, for unification of the façade and prevention of the corrosion of steel reinforcements
If you have any questions contact me at [email protected]
For additional information see www.rocare.eu