by

P.Thirumalini

R.Ravi

CHARACTERISATION OF ANCIENT MORTAR

Our country India, has extraordinarily rich, vast and

diverse cultural heritage

In order to conserve our heritage, we should repair, restore

and protect our monuments.

Retain the original mortar

The use of materials and techniques employed in the

original construction should be thoroughly understood.

A necessary & appropriate methodology for the

production of compatible restoration mortars based on

criteria that originate from experience with historic

mortars

Lack of fundamental knowledge

Understanding construction of monuments

Interest in our past, lack of public awareness

Industrial revolution

Rapidly transforming life style

Finite, non renewable and irreversible resources of our

country is fast disappearing with out any record for the

posterity.

Step 1: Characterization of historic mortars

Step 2: Selection of raw materials

Step 3: Preparation of mortars

Step 4: Experimental investigation

Step 5: Optimization – Standardization

Step 6: Pilot application of restoration mortars

The temple is located in cuddalore coast of Tamil Nadu in

southern India surrounded by east bay of Bengal

Temple lies at 2 kM away from sea.

Step 1 : Sampling

Step 2 : Chemical analysis

Step 3 : Acid loss analysis

Step 4 : Granulometry of sand

Step 5 : Mineralogical analysis

Step 6 : FT-IR

Step 7 : TGA with DTA

Step 8 : Texture analysis

Step 9 : Organic test

Step 10 : Interpretation of results

Select location for sampling

Samples were taken from the upper parts of the temple to

avoid such phenomena caused by capillary rise.( P.

Maravelaki ,2005)

Altered and non altered material samples were taken from

both internal and external portion of the temple.

The analyses were carried out in a significant quantity of

samples in order to avoid errors caused by heterogeneity.

Avoid sampling near decay portion and cracks

Non-altered original mortars (P. Maravelaki 2005)

To classify lime

CaO + MgO = Binder

Al2 O3 +Fe2 O3 + SiO2 = Clay minerals or impurities

Presence of K, Na , Cl, S

HI , CI and LOI

Sample CaO MgO Al2O3 Fe2O3 SiO2 Na + Cl-

P1 15.26 0.25 0.19 0.10 20.53 0.58 1.51

P216.71 1.21 0.28 0.49 29.52 0.62 1.28

P315.52 0.86 0.20 0.30 24.05 0.64 1.48

Sample LOI HI CI

P1 11.25 1.34 3.74

P212.15 1.69 4.64

P313.70 1.5 4.13

HI range

CI Range

Presence of Sodium and chloride ions

Insoluble fraction formed by aggregates

Soluble fraction from calcium content and clay minerals

Volatile fraction

To find

Binder / Aggregates ratio and Aggregates’ Grain Size Distribution

Sample Initial

weight

Acid loss Weight after

acid loss

Weight of sand

retained

Weight of

binder

B/A Ratio

P1 29.7 1.5 28.2 19 9.2 1:2

P228 1.32 26.68 18.08 8.6 1: 2.1

P325.2 1.23 23.97 15.47 8.5 1:1.82

Description Protocol Unit Result

Starch

( on dry basis)

By Lane and Eynon’s

Method

% by mass Absent

Protein(N6.25) By Kjeldhal Method % by mass 0.12

Carbohydrates By Calculation Method % by mass 9.29

Possible minerals and hydrated phases

Weight loss over temperature ( dehydration , dehydroxylation , oxidation

and decomposition )

TGA should be in agreement with XRD.

Hydroscopic water - 0 to 120 ° C

Structurally bound water of hydraulic compounds - 120 to 400 ° C

Decarbonation of Calcite – 600 to 900 ° C

New minerals above – 800 to 1000

Sample

Weight loss per temperature Range (%)

< 120 ° C 120 -400°C 400 -550°C 600 - 800° C

P1 0.7 2.68 3.08 90.87

P25.18 4.07 4.07 84.92

P33.1 7.8 6.08 83.77

Table 4.8 Results of Thermal analysis

Differential thermogram – temperature corresponding to

maximum rate of decompostion

CSH – CAH - Endothermic Peaks - 30 -200° C

Organics - Exothermic peaks – 300-500 ° C

Alumino silicates -Endothermic peaks- 200-650 ° C

Dehydration peak of Portlandite – 400-520 ° C

Clay minerals – endothermic peaks -500-650 ° C

Quartz – 500-580 ° C

Syngenite -Endo thermic peak – 290- 400 ° C

Characteristic peak of gypsum dehydration - 120 -200°C

Hydraulic character of mortar

Ratio of CO2 / H2O which inversely expresses the level of hydraulicity

Generally less than 3 for hydraulic mortars

The wave band corresponding to 712, 874,

1440,1790,2515 and 2854 cm-1 – Calcium carbonate forms

3430 cm-1 is due to portlandite

Organic carbon at 2922, 2932, 2990 and 2986 cm-1

The stretching corresponding to 1083 cm-1 is due to quartz

Sample C O Si Al Fe Ca Mg Na Cl

P1 31.33 57.27 0.86 0.67 0.13 9.21 0.82 0.29 0.25

P2 31.48 38.68 14.16 4.62 7.93 6.41 1.21 1.45 1.27

P3 43.79 33.08 15.97 1.83 0.77 4.13 1.32 - -

Charcaterisationof ancient mortars

Type of Lime

Amount of clay minerals

Binder to aggregate ratio

Presence of organics

Formation of hydrated phases( CSH and CAH )

Degree of carbonation

Microstructure Simulation of new

mortars

SIMULATION OF NEW OLD MORTARS

Physical and chemical characterizationof the lime

Establishing an optimum water/lime(W/L) ratio

Determining the optimum grindingduration

To arrive at a better method ofpreparing lime mortar

Changes in chemistry

Fresh state properties

Mechanical resistance

Physical parameters

Durablity

Textural and microstructure analysis

Lime

Chemical characteristics

Physical characteristics

Field tests for building lime

Visual Examination

Ball Test

Hydrochloric acid Test

Consistency and setting time of lime

S. no Chemical parameters Limits as per IS 712-

1984 for Class A lime

(% )

1. Calcium and Magnesium Oxides

(on ignited basis)60 min

2. Magnesium Oxides

(on ignited basis)6 max

3. Silica, Alumina and Ferric

Oxides.(on ignited basis)10 min

4. Ferric Oxides -

5. Insoluble Residue in dilute acid

and alkali (on ignited basis)15max

Physical characteristics

Consistency and setting time of lime

Vicat Apparatus

Raw lime found to be stiff

Need to be improved

Visual examination

Lime examined for color, state of

aggregation - lumpy, powdery, soft, hard

Class C and D limes have white color.

Lumpy form indicate unburnt limestone.

Lime free from coarse and gritty pieces

larger than about 2.50 mm may be

categorized as Class ‘A ‘ lime.

Lime made to a ball of 50 mm diameter

Left undisturbed for six hours.

Sample is gently immersed in a jar ofwater.

No signs of disintegration-Class A

Very little expansion and numerous cracks- Class B

Signs of disintegration within few minutes- Class C or Class D

Presence of inert material present

Lime added up to 5 ml markin a 50 mlcylinder

25 ml hydrochloric acid added

The contents were stirred with the glassrod. left with the contents for 24 hours

A thick gel formation indicates Class Alime

Properties of sand in a mix have amajor effect on its workability, finalstrength and durability.

The quality of sand is of primaryimportance in achieving a high qualitylime mortar.

Sand provides structural strength,with the lime putty coating andcementing the particles together.

Grain size distribution

40% finer and 60% sharper for mortar and render mixes.

66.87

27.82

4.88

0.80.09

0

10

20

30

40

50

60

70

80

0 0.2 0.4 0.6 0.8 1 1.2 1.4

particle size (mm)

% f

iner

Clean potable drinking water is

preferable.

Chlorine, fluorine or high iron content in

the water will produce unacceptable

blemishes in the mortar.

brought down to acceptable levels by aweek of storage in sunlight in widetubs.

Mix proportion of 1: 3

Lime thoroughly mixed with water for 5minutes – Lime putty

The putty so prepared was grind mixedalong with sand

left aside for 24 hours to preshrink

Prepared mortar filled in noncorrosive

moulds in three layers

Pressed in thumb

The filled up mould was stored for 3 days

undisturbed in an atmosphere 90 percent

RH and at a temperature of 27° ± 2°C.

Demoulded after 3 days and kept in the

same atmospheric condition for a 4

days, cured in water for 21 days

Determination of consistency of mortar

Workability of mortar

Consistence is a measure of the fluidityand/or wetness of the fresh mortar.

Mould of defined diameter has beenplaced in a centre of a flow table andfilled with fresh mortar.

After removing the mould, mortar hasbeen spread out on the disc by joltingthe flow table 15 times.

Consistence is the mean value ofmortar diameter in cm measured inthree directions.

Comp. strength of a mortar providesinformation on its structural resistance

In hydraulic lime mortars initialstrength gain achieved fromdrying, combined with a gain achievedthrough an hydraulic set, up to 28days, depending on the hydraulicity oflime.

Subsequent to this, the strength gains are due to carbonation.

Water/binder ratio has a marked effecton the structural performance ofcement-based mortars.

This relationship is known as Abrams'rule, which states that “ when a cementmortar is fully compacted, its strengthis inversely proportional to thewater/cement ratio”.

Applied successfully on hydraulic limemortars

both cement and hydraulic limesrequire a minimum quantity of water toproduce the chemical set resultingfrom the hydration of calcium silicatesand calcium aluminates.

Surplus water eventually driesout, leaving micro pores in the matrixwhich would weaken the resulting setmortar.

In china lime mortar mixture has beenstirred using stirring machine until theconsistency of the mortar did notchange(Fuwei Yang)

Stirring has an accelerating effect onthe slaking process of the quicklime byproviding a rapid diffusion of waterinto quicklime (Boynton 1980).

The traditional method of preparing limemortar in India especially in Southernparts involve grind mixing the lime puttyand sand

To have an intimate contact of the binderand aggregate to allow a homogeneous andintimate mix and kneading of lime withsand. However there is no specific recordsof the duration of grinding.

Lime-Sand Mortar ( 1: 3 ) is prepared ( 50mm mould )

Lime passing through 850 microns isused for the preparation of lime putty.

Load shall be steadily and uniformlyapplied, starting from zero increasing atthe rate of 1.5 N/min

Specimen size (4 x 4 x 16 cm) were used

Flexural strength was calculated from following formula:

F= 1.5 Ff L /bd2

Age of 1, 3 and 12 months,

Bulk density

Porosity

Water absorption

Capillary suction

(RILEM1980)Samples were saturated with water in avacuum oven and then weighed (Msat).

The samples were dried 103 ºC at leastfor 24 hours dry weights (Mdry)measured

Hydrodstatic mass measured (Mhyd)

Water absorption is the ratio of themass of water a mortar can retain to thedry mass of the mortar.

97% water absorption takes placewithin few minutes

To find how much water and howquickly gets absorbed into material.

Besides water, the test has beenperformed using salt solution (10% byweight NaCl) to see whether the ions inwater can significantly affect theprocess of capillary action.

Coefficient of water (salt solution)absorption by capillary action has beenmeasured using half-prism specimens ofsize of approximately 4 x 4 x 8 cm.

After drying the specimen for 2 days at(65±5) °C, specimens have been immersedin 1 cm of distilled water (salt solution) bytheir rough surface face

Container with the specimen sealed toavoid evaporation. Specimens weighedafter 10 and 90 minutes and theincrease in mass determined.

C= 0.1.(m90-m10)

C is the coefficient of water (saltsolution) absorption [kg/(m2.min0.5)],

m10 is the mass after 10 minutes [kg],

m90 is the mass after 90 minutes [kg].

Suction

Salt crystallization is one of the majorcauses of decay of ancient structures.Presence of soluble salts in the mortarcan contribute to the decay process.

Mortar quarter-prism specimens of weight (100±20) g were used for testing.

Tested in two different types of cycles

Initially specimens have been allowedto absorb 10wt% NaCl solution bycapillary rise for 24 hours and thendried in a ventilated oven for 2 days at(65±5)°C.

Similar procedure adopted with 10 wt%Sodium sulphate solution

No appreceable change in weight evenafter 15 cycles

Another, more efficient cycle has beenset up, using both 10wt% NaCl and10wt% Na2SO4 solution, withparameters as follows:

6 hours full immersion in salt solution

18 hours drying in ventilated oven at 85°C

In the first cycle NaCl has beenused, since it is one of the mostcommon salt,

In the second type of cycle Na2SO4 hasbeen used concurrently toNaCl, because Na2SO4 is moredamaging salt than NaCl.

Specimens were weighed after eachcycle and the weight change as apercentage of the original weight wasplotted. Damage has been monitoredvisually, photographically

Cycles have been repeated until thedestruction of specimens gotdestroyed, but maximum 30 times.

XRD

FT-IR

TGA with DTA

SEM with EDX

Calcium Oxide

Portlandite

Vaterite

Aragonite

Calcite

Magnesite

Hydromagnesite

Calcium Silicate Hydrate (CSH)

Calcium Aluminium Hydrate ( CAH)

Calcium Aluminium Silicate Hydrate ( CASH)

Di-Calcium Silicate (Ca2SiO4)

Gehlenite (Ca2Al2SiO7)

Merwinite (Ca3Mg(SiO4)2)

Hydromagnesite[4MgCO3 Mg(OH)2

4H2O)

Polysaccharides, Proteins and fats inthe presence of Ca(OH)2 could sufferstructural modification, resulting inthe ability of the polymer to form a gelnetwork, hence promoting a betterbinding of solid microstructure.

Mechanical properties would reflectthese phenomena

Environmental concerns worldwide areincreasing and are likely to influencethe choice of an admixture. Admixtureshas been addressed toward the goal ofusing cheap, effective molecules at lowor ‘‘zero’’ environmental impactenvironmentally benign naturalproducts.

These natural organic compounds areeither synthesized or extracted fromthe plants. Plant extracts are viewed asan incredibly rich source of naturallysynthesized chemical compounds thatcan be extracted by simple procedureswith low cost and are biodegradable innature

S Chandra et al. tested the influence ofoils, and black grams on OPC mortarsand found a substantial improvementin the durability.

Mortar made hydrophobic andconsequently more durable againstdeterioration. Such mortars were usedespecially in areas suffering highercontact with water and humidity

Chandra et al. 1994 studied effect oflinseed, corn, and mustard oils onproperties of Portland cement mortar.

Linseed, sunflower, olive, soyabeans, corn and rapeseeds oils weretested in 0.5% and 1.5% concentrationby the weight of cement.

Flexural,compressivestrength, capillary water absorptionand water vapour diffusion was tested.The 3-year compressive strength wasreduced by 30%, but had still increasedfrom the 28 days strength.

Chloride intrusion reduced by 35-66%of the reference sample

Boiled linseed oil was tested in 1%, 5%and 10% concentration by the weight ofmortar mixture

Increased workability of fresh mortar“due to the hydrophobicity of oil”.

Hardened mortar showed lowerporosity and water absorptioncomparing to reference.

Compressive strength wassignificantly increased with additionof oil, however flexural strength waslower, probably because of the physicalaction of oil.

Addition of natural organiccompounds like sticky rice soup, thejuice of vegetable leaves, eggwhite, tung oil, fish oil, or animalblood, (Song 1958) performance of lime mortars can be

greatly improved, and these mortarsare believed to play an important rolein the longevity of ancient Chinesebuildings.( Li, Xu. 2005)

Influence of organic admixtures(polysaccharides fatty acids proteins) hasbeen investigated

Use of proteins doubles the compressivestrength

Polysaccharides increased thecarbonation by a factor of 2.

Fats reduce the pore system by half. Italso improves the impermeability of themortar acting as a water proof material.