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.
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