Bio-inorganic composites as repair mortar for Heritage structures

1.  The bio-inorganic lime mortar is used for the
preparation of repair mortar for restoration works
of heritage structures.
Eg:Vadakunnathan temple in Kerala
 This involves the usage of herbs such as Oonjalvalli,
Pananchikkai, Kulamavu, Kadukai and Jaggery.
 These mortar leads to the formation of Gismodine
and Calcium Aluminum Hydrate, which increases
the strength and durability.
1

2.  The temple was constructed during the 7th century,
has proven its durability over 1300 years.
 Traditional lime mortar used in the temple
composed of hydrated lime, sand and water.
 Different herbs are used for the construction of the
temple, they are
Oonjalvalli (Cissus glauca Roxb)
Pananchikaai (Cochlospermum religiosum)
Kulamavu (Persea macrantha)
Kadukai (Terminalia chebula)
Palm jaggery
2

3.  No proper water to lime ratio and the grinding
period is maintained.
 The following fig. shows the herbal mortar
prepared at Vadakunnathan temple.
3

4. 4

5. Lime
 Lime is the eco-friendly, green and versatile
building material.
 It is cheaper to produce, biodegradable and
recyclable.
 It allows the building to “breathe”.
 It is soft and flexible & it allows the building to
move without cracking.
 Lime stone and shell lime in equal proportion
are used as binder, called as lime powder.
5

6.  The chemical composition of lime powder is
Sample CaO MgO SiO2 Al2O3 Fe2O3
Lime
stone
62.10 1.21 14.3 2.14 2.29
Shell
lime
66.00 0.543 19.5 0.63 0.27
The quick lime in plaster reacts with CO2 to form
CaCO3 which is the binder in lime plasters.
Ca(OH)2 + CO2-------CaCO3 +H2O
6

7. Aggregates
 Well graded washed river sand is used, which
is free from organic matters.
 The specific gravity of well graded sand is
2.61.
7

8. Herbs
 Different herbs are used for the preparation of
herbal extract.
 All herbs are polysaccharides in nature and
produce carbon-dioxide on fermentation.
 This leads to early carbonation and accelerated
initial setting of the lime mortar through the
formation of calcite crystals.
 Oonjavalli, Kulamavu and Kadukai alter the
workability of the lime mortar.
8

9.  Pananchikaai, the cotton fibres imparts gleaming
whiteness and texture to the base.
 Jaggery accelerates the initial hardening of the
mortar and significantly improves the weather
resistance.
 Jaggery and kadukai are widely used across the
country for weather proof construction.
 Kadukai prevents the attack of insects.
9

10. a. Herbal extract
Herbs are crushed and mixed with 10l of water in
separate containers and fermented for a minimum
period of 7 days.
Particulars of herbal extract are
Particulars Amount (Kg)
Pananchikaai fruit 7.5
Oonjalvalli stem 2
Kulamavu leaves 0.5
Kadukai 1
Jaggery 3
10

11. b. Mortar preparation
 Lime powder & sand are mixed in the ratio of
1:3 & then mixed with herbal extract and kept
for 15 days.
 The consistency of the mortar is decided by
the sthapathis in such a way that the mortar on
the back of trowel should not fall from height.
 No proper water to lime ratio and the grinding
period is maintained.
11

12. In laboratory, 3 types of mixes are prepared
 LM-R (Reference mix)
 HEX-F(without control in water to lime ratio)
 HEX-L (with controlled water to lime ratio)
 lime powder passing through 850μm sieve Is
mixed with herbal extract in equal proportion.
 It is stirred for 5 minutes and left aside for one
day. It is then mixed with 3 parts of sand.
 The mortar is kept in a container for 24 hours for
fermentation to control the drying shrinkage of
the mix.
12

13.  The water to lime ratio of the mix is fixed to
0.65 based on workability test.
 Results of workability (no. of bumps for a spread
of 190 mm):
Samples
Water to lime ratio
0.6 0.65 0.7
LM-R 7 6 5
HEX-F - - -
HEX-L 5 2 2
13

14.  Ingredients of herbal extract
14

15. c. Compressive strength
 Mortar cubes of size 50 x 50 x 50 mm are cast for
LM-R, HEX-F and HEX-L mixes.
 It is demolded after three days and left in
atmospheric condition for 28 and 90 days for
curing.
 The results are given below;
Description
28th day
(N/mm2)
90th day
(N/mm2)
LM-R 1.28 1.78
HEX-F 1.56 2.76
HEX-L 2.46 4.52
15

16. d. Bulk density and porosity
 The bulk density is calculated as ratio of 28th day
weight of the sample to its volume.
 Porosity is indirect measure of water absorption and
easy measure of carbonation.
 The results are given below,
Description Unit weight
(KN/mm2)
Porosity %
LM-R 16.50 15.00
HEX-F 17.50 21.10
HEX-L 20.00 13.40
16

17. e. Carbonation
 Carbonation is responsible for hardening of the
mortar.
 During carbonation, the change in pore volume takes
place due to the attachment of calcite crystals to the
surface of aggregates particles.
 It can be assessed by pouring dye on the broken
surfaces of the mortar samples.
 The colorless region indicates carbonation, while dark
region indicates the uncarbonation.
17

18. HEX-L
HEX-F (Interior)
HEX-F (Exterior)
18

19. f. Mineralogical Analysis
 XRD is carried out by using Bruker’s D2-PHASER
Desktop.
 The detector used is 1D LynxEye, with operating
voltage of 30 KV, 10 mA and Nickel based filters are
used to filter the monochromatic radiation.
 The XRD spectra of the raw materials of lime
powders and the hydration of lime mortars at 90th
day are carried out.
19

20. g. Microstructure Analysis
 Microstructure analysis of LM-R, HEX-F and HEX-L
mortar is performed by using SEM.
 Gismondine is the strength gain phase.
Gismondine
20

21. 1. Compressive strength
 HEX–L mix has the higher strength.
 It is due the interaction of the mixes with organic
admixtures.
 The strength gain is by the formation of Gismondine
and Calcium Alumino hydrate.
 The effects of herbal extract on HEX-L mix towards
the precipitation of Gismodine and CAH during the
hydration are assessed through XRD and SEM analysis.
21

22. 2. XRD Analysis
 The strength gain of HEX-L mix is due to the
formation of Gismondine, which are rich in the mixed
hydrates of calcium, silica and alumina and is
influenced by polysaccharides.
 The CO2/H2O ratio is controlled in the HEX-L mix,
leads to the controlled formation of calcite and CSH.
 The low compressive strength of HEX-F mix is due to
the formation of calcite, because of the uncontrolled
CO2/H2O ratio and it affects the CSH formation due
to the disturbance caused to the structurally
bounded water.
22

23.  For LM-R mix, the formation of Gismondine is
not activated during hydration due to the
absence of polysaccharides.
 The CSH and CAH modify the microstructure
of lime mortar mix such as size, shape and
structure of carbonate crystals and hence
increased hydraulic properties, which
ultimately results in enhanced mechanical
strength.
23

24. 3. Porosity Analysis
 The order of the porosity of the mixes are
HEX-F > LM-R > HEX- L.
 Self-healing will occur in partially carbonated lime
mortar, where the uncarbonated part will provide
Ca(OH)2 to fill thin cracks & enhance durability.
 The polymorphs of CaCO3 are Vaterite, Aragonite and
Calcite .
 These combinations influence the dissolution and the
subsequent recrystalization process and thereby
contribute to the self-healing nature of mortars.
24

25. 4. SEM Analysis
 LM-R shows the denser microstructure with evenly
distributed phases.
 The morphology of HEX- L refers the presence of
compacted and well refined microstructure. The
controlled addition of herbal extracts reduces the
porosity & the carbonation or the breathability of the
lime mortar is not significantly affected.
 In the case of HEX -F mix, the anhydrate phases are
detected, which indicate the anhydrate of Larniteas.
The deposition of precipitate is noticed, which
indicate the highest porosity of the mix.
25

26. LM-R HEX-L
HEX-F
Texture analysis of lime mortar using SEM
26

27.  Among all the 3 mixes HEX-L performed better and
proved by XRD, SEM and strength analysis.
 The strength of HEX–L mix is high compared to HEX-F
and LM-R mixes due to the addition of optimum
water to lime ratio.
 The improved bio-inorganic lime mortar can be used
for plastering, construction of wall, etc. and has
compatibility with old mortar and hence, suitable
for restoration work of Heritage structures.
27

28.  S. Thirumalini, S. K. Sekar, B. Bhuvaneshwari, and Nagesh R.
Iyer (2015), A study on “Bio-inorganic composites as repair
mortar for heritage structures”, Journal of Structural
Engineering Vol. 42.
 Cristiana Nunes, ZuzanaSlížková, and Dana Křivánková, (2013)
A study on “Lime-based mortars with linseed oil: sodium chloride
resistance assessment and characterization of the degraded
material”, An International Journal of Mineralogy,
Crystallography, Geochemistry, Ore Deposits, Petrology,
Volcanology And Applied Topics On Environment, Archeometry
And Cultural Heritage.
 P Thirumalini, Dr S K Sekar (2013), A study on “Review on Herbs
used as Admixture in Lime Mortar used in Ancient Structures”,
Indian Journal Of Applied Research.
 Athuman M. K. Ngoma (2009), A study on “Characterization and
Consolidation of Historical Lime Mortars in Cultural Heritage
Buildings and Associated Structures in East Africa”.
28

29. 29