Diagnosing and restoring Roman cement façades: cases of investigations, trial tests and restoration concepts in the Czech Republic

Transcription

1 Natural cements in European cultural heritage Les ciments naturels dans le patrimoine européen PARIS 26/ Diagnosing and restoring Roman cement façades: cases of investigations, trial tests and restoration concepts in the Czech Republic Blanka Kolinkeová University of Pardubice Faculty of Restoration

2 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

3 Details of the façade decoration

4 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

5 Present state - ground floor bare masonry Portland cement fillings open surface of cast elements due to the rainwater acrylic paint layer closing the surface

6 Present state the 1 st floor dust layer gypsum crust missing parts of renderings and casts bare masonry network of cracks rainwater leaking

7 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

8 Evaluation of the mortar composition 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)

9 Cross-section cast element lime paint with ochre pigment sulphated lime paint original ochre lime paints lime paint Roman cement mortar

10 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.)

11 Application of the selected mortar

12 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

13 Historic coloured photography

14 Sampling sample from RC mortar part sample from lime mortar part

15 Cast elements cross-section from cast SEM photography

16 Steel reinforcements in cast elements uncovered steel reinforcement X-ray photography of steel reinforcement

17 Cleaning of Roman cement relief state before cleaning basic cleaning by commercial paint removal P05 and high pressure steam

18 Cleaning of Roman cement relief after final cleaning by steam and mechanical cleaning

19 Restoration of the statues

20 steam laser micro-blasting microblasting laser laser micro-blasting steam laser laser

21 Statue of the allegory of Architecture

22 Statue of the allegory of Industry net of cracks under paint layer

23 Original surface and secondary layers surface of RC cast orange painting from the last repair in 1990 gray cement painting layer of dirt on the gray cement painting

24 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

25 Restoration concept elaborated repairing the lime mortars with similar material 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

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