Diagnosing and restoring Roman cement façades: cases of ... · University of Pardubice – Faculty...

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 blanka.kolinkeova@upce.cz

For additional information see www.rocare.eu