durability assessment of consolidation effect on … · 2016-10-13 · durability assessment of...

DURABILITY ASSESSMENT OF CONSOLIDATION EFFECT ON SANDSTONE MONUMENTS

Marco Ludovico-Marques (IPS/ESTB)Carlos Chastre (FCT/UNL)

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DEGRADATION PATTERNS ON THE SANDSTONE

WALLS OF ST. LEONARD’S CHURCH

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Five types of stone deterioration patterns(ICOMOS-ICS glossary):

Crack & deformation

Detachment

Features induced by material loss

Discoloration & deposit

Biological colonization.

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INTRODUCTION

St. Leonard's Medieval Church40th

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EXPERIMENTAL PROGRAMME

• Four varieties of sandstones (A, B, C, M).

• Lithic arkose with carbonate cement according to Folk (1974).

• The varieties C and M have around 20-25% carbonates and 40-51% quartz.

MINERALOGICAL CHARACTERIZATION

PREPARATION OF SPECIMENS• Samples were extracted from stone masonry walls close to

the built heritage.• Similarity to the stones in the monuments: appearance,

mineralogical composition, texture and structure.• Specimen sizes: 5x5x5 [cm] and 5x5x10 [cm]

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CONSOLIDATING PRODUCTS

. Treatment of stones were carried out in a laboratory environment and in the monument

. Evaluation of the viability of two ethyl silicate consolidating products on stones:

Tegovakon V (TG) and Redur 420 (R)

. Selection criteria: commercial availability and reasonable costs.

. TG is produced by Goldschmidt in a single component(Before application: unit weight of 0.95±0.02 g/cm3 at 25ºCAfter application: dry residue of 34% after evaporationof solvents at 20ºC and 60% of RH).

. R is manufactured by Promasil in a single component(Before application: unit weight of 0.83±0.02 g/cm3After application: dry residue of 17% after evaporationof solvents at 20ºC and 60% of RH).

EXPERIMENTAL PROGRAMME41

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CONSOLIDATION PROCEDURES

. 5 cm-long cubic samples.

. Applications step by step by immersion and capillarity over all stone mass (Ludovico-Marques, 2008).

.The amounts of absorbed products were around 5% of mass content in variety M.

. Drying at at room temperature and RH of Laboratory (Civil Engineering Department of FCT-UNL).

. A dry residue of about 40% of TG and 25% of R after evaporationof solvents during 8 weeks.

. Capillarity procedure was followed on samples used to carryout drying tests. Capillarity height reached 2.5 cm and theamounts of absorbed products were around 3% of mass content.


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PROCEDURES FOR PHYSICAL TESTS

• Porosity and density on sandstone samples following the Recommendations of RILEM (1980) and EN1936 (1999).

• Four varieties samples exhibit similar values of porosity to the historical building stones, ranging from 3.6% (variety A) to 12.7% (variety C) and 18.5% (variety M).

• Pore size distribution of sandstone varieties M was obtained by mercury intrusion porosimetry. Microporosity settled as the percentage of pores radii lower than 7,5 μm (Pellerin, 1980), is 75-81% in variety M.

• Drying tests were carried out on top face of sandstonecubic samples of variety M before and after treatments,following the Recommendations of NORMAL 29/88 (1991)and RILEM (1980) at laboratory environment of 20 ± 2 º Cand 55 ± 10% of RH.

• RILEM (1980) water absorption under low pressure testprocedure was carried out on prismatic and cubicsandstone samples. After consolidation treatments wasonly applied on cubic samples.


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The uniaxial compression tests on the sandstones used aSeidner servo-controlled press, model 3000D:

• Load capacity up to 3000kN and a piston stroke of 50 mm.

• Tests carried out under axial displacement control at a rateof 10 mm/s on cubic specimens of variety M.

EXPERIMENTAL PROGRAMME

PROCEDURES FOR MECHANICAL TESTS

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• Crystallization tests by total immersion were carried outfollowing RILEM V.1a, b, V.2 (1980) [6] and EN 12370 [10],replacing sodium sulphate solutions by sodium chloridesolutions.

• Salt crystallization-dissolution ageing tests were carriedout in an automatic ageing chamber prototype.

EXPERIMENTAL PROGRAMMEPROCEDURES FOR DURABILITY TESTS

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ANALYSIS OF RESULTS OF EXPERIMENTAL PROGRAMME

PHYSICAL BEHAVIOUR (DI)

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0

5

10

0 500 1000 1500

Moi

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t (%

)

M27TG, M42TG, M23TG, M26TG, M29TG, M6TG

t (h)

M103,106,104,105,107,108

0

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8

9

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0 500 1000 1500t (h)

Moi

stur

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t (%

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M103,106,104,105,107,108

M47R, M57R, M53R, M61R, M51R, M64R

VarietyDrying Index

Average ± SD (CV %)

M 0.10 ± 0.01 (9.80)


Consolidatingproduct

Drying Index

Average ± SD (CV %)

TG 0.12 ± 0.01 (8.33)

R 0.11 ± 0.01 (9.09)

Minor increase

20% on TG

10% on R

PHYSICAL BEHAVIOUR (DI)

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PHYSICAL BEHAVIOUR (k)

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0

1

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5

6

7

8

9

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0 10

1

2

3

4

5

6

7

8

9

100 10 20 30 40 50 60

)s(t)mkg( SmΔ 2

M26

TG

M6T

GM

27T

GM

26T

G

M47

R

M51

RM

61R

M57

R

)h(t

M10

6,10

8M

104

MP2

,3,4

M10

5, M

P5

M10

3,10

7

MP1


PHYSICAL BEHAVIOUR (k)

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Con

solid

ants

Water absorption coefficient, k (kg/m2/√h)Average ± SD (CV %)

NT 24.0 ± 1.6 (6.8)

TG 12.6 ± 1.0 (8.2)

R 20.9 ± 1.9 (8.8)

Significant decrease

48% on TG

13% on R

ANALYSIS OF RESULTS OF EXPERIMENTAL PROGRAMMEDURABILITY ASSESSMENT BY SALT

CRYSTALLIZATION DISSOLUTION ARTIFICIAL AGEING TESTS

After 60 salt cycles the average mass loss of sandstone samples is about 8%

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0

2

4

6

8

10

12

14

16

18

20

0 5 10 15 20 25 30 35 40 45 50 55 60Nc

Dm/m

(%)

M80

M69M78

M95, M76

M99, M96, M93, M102, M100

M75, M90

M79, M101 M72, M81, M77

M91, M94

M97, M73M98, M74, M70

ANALYSIS OF RESULTS OF EXPERIMENTAL PROGRAMMEDURABILITY ASSESSMENT BY SALT


After 30 salt cycles reduction of 50% After 60 salt cycles reduction higher on TG than NT

After 70 salt cycles reduction on R less than NT

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Clear increment of about 26% on TG and 10% on R treatments before salt artificial ageing tests

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DURABILITY ASSESSMENT BY SALT CRYSTALLIZATION DISSOLUTION ARTIFICIAL

AGEING TESTS


• NT decreased about 56% during 60 cycles • TG treated specimens have an average reduction of

circa 75% • R treated have a minor reduction of about 18% to the

initial values of non treated specimens at 70th cycle • Compressive strength data of NT specimens

extrapolated for more than 100 cycles decreased to about 30% of the initial values.

• At 115th cycle the compressive strength should be less than 30% of its value before salt ageing, being higher than its value on R treated specimens that is null.41

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nDURABILITY ASSESSMENT BY SALT


CONCLUSIONS

• On sandstone specimens were applied two ethylsilicates (TG and R).

• Minor harmful characteristics of the R applications on Mvariety of sandstones and a better consolidation effectof TG.

• Salt crystallization artificial ageing tests highlightedgood durability of R applications and a worst behavior ofTG treatments.

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THANK YOU

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