Kasthurba aia-chicago21 may2014
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Laterite Monuments of Malabar region, Western India
Dr Kasthurba A KVisiting Research Fellow, UIC, Chicago, IL
Associate Professor, Department of ArchitectureNational Institute of Technology, Calicut
APT-WGLC lecture21 May 2014, AIA Chicago
Background
The rich Architecture of India is a reflection of geological diversity of the nation. Indigenous architectural styles and construction techniques were evolved utilizing locally available building stones.
Objectives:• Laterite Monuments in W
India• Weathering issues• Conservation strategies
Outline of Presentation
• Laterite- Background• Laterite Monuments in India
– Prehistoric megaliths– Maritime Forts– Religious monuments– Traditional residences– Ancillary structures
• Laterite – Properties and weathering mechanisms
• Conservation Strategies• Summary & Conclusions
World wide distribution of laterite
– Laterite: weathered rock found in tropical and subtropical humid regions of the world.
– Major part of the Indian peninsula, which falls within Koppen’s ‘A’ climate, is subjected to formation of laterite
About laterite…
• Laterite, tropical weathered rock, defined for the first time by Buchanan(1807) as a versatile building material of Malabar region of India
• It is considered as metasomatic rock (different from other type of rocks) altered form of other rock types- igneous, sedimentary or metamorphic
• Laterite is treated as a weak rock for building applications; also as a soil group. Methods of testing-different from other rock types
• Cost effective, energy efficient and environment friendly building material in Malabar region of Kerala
• Good aesthetics, easiness to cut and hardening with age, makes it unique compared to other natural stones
Significance of Malabar laterite
National Geological Monument at Angadipuram, Kerala
Definition of Laterite in Malabar: later-ite meaning “brick-stone” by Buchanan in 1807
Laterite Quarrying
• Quarrying of laterite using rotary saw machine• Standard size specified by IS codes
Laterite Quarrying
Quarrying of laterite using mobile rotary saw machine
Obtaining laterite blocks of standard size from the same strata
Obtaining laterite specimens from quarry
Decrease in iron content with depth and increase in silica and aluminum (clay) content was seen in the profile.
Typical laterite profile: Characteristics
Prehistoric Megaliths( 2nd Cent B.C-1st Cent A.D.)
Pre-historic burial sites-lateritic zones
•Umbrella stones (kudacallu)
•Cap stones (Thoppicallu)
•Hood stones
•Caves ( muniyaras)
•Dolmens and menhirs
Protected monuments –Archaeological survey of India
Group of Umbrella Stones ( kodakkallu), Trichur (ASI Protected Monuments)
Prehistoric Megaliths ( 2nd Cent B.C-1st Cent A.D.)
Prehistoric Megaliths ( 2nd Cent B.C-1st Cent A.D.)
Maritime Forts of Malabar
• Bekkal Fort, Kasarkode (16th Century)
• Tellicherry Fort ( 18th century)
• Fort St. Angelo, Kannur ( 15th Century)
These heritage monuments and natural sites with its environmental settings has been recommended by ASI to include in the World Heritage list of UNESCO
Bekkal Fort – A Tourist Destination
BEKKAL FORT, KERALA, W.India- (16th Cent. A.D.)
Bekkal Fort, W.India
BEKKAL FORT, KERALA
Bekal Fort, Kasarkode
BEKKAL FORT, KERALA
Bastions and Fort walls facing sea
Bekkal Fort, Kasarkode, Kerala
Raised Bastion , Bekkal Fort, Kerala, India
Bekkal Fort, Kasarkode, Kerala
Main entrance from the road
Bekkal Fort, Kasarkode, Kerala
Tellicherry Fort- Entrance Structure
Tellicherry Fort ( British 18th Cent A.D.)
12m High Wall in laterite Tellicherry Fort
Tellicherry Fort, Malabar, India
Tellicherry Fort: Adjoining Areas
The Fort was built by the Portuguese in 1505
Fort St Angelo, Kannur : Main Entrance
View towards the Sea from the Fort- Cannons pointing towards sea
Fort St Angelo, Kannur 15th Century
Fort St Angelo, walls abutting the Arabian sea
Fort St Angelo, Kannur
Fort St Angelo, Kannur
Vaulted Structures in Laterite, Fort St Angelo
Fort St. Angelo- Horse stables within the fort
The Vaulted structure- Horse stables
Fort St Angelo, Kannur
Fort St. Angelo- The Prison cells within the Fort
Thick Fort Walls – Laterite Ashlar Masonry
Fort walls- Laterite Ashlar masonry
Church Within the Fort. St Angelo
Fort St Angelo- Church building within the Fort
Maintenance work by ASI- Fort St. Angelo
Fort St Angelo- Removal of vegetation
Fort St Angelo- Maintenance
Fort St Angelo, Kannur
Fort St Angelo, Kannur
Fort St Angelo, Kannur
After
Fort St Angelo, Kannur
Fort St Angelo, Kannur
Fort St Angelo, Kannur
Fort St Angelo, Kannur
Fort St Angelo, Kannur
Fort St Angelo, KannurWeathering of Laterite due to aggressive sea environment
Temples of Malabar
Trikkaikunnu Temple, Kottayam
Siva Temple at Ferooke, Calicut
Siva Temple at Calicut
Wide Projecting Eaves
Granite Door Frames
Granite Plinth Protection
Traditional Conservation Practices
Traditional residences in Malabar, Kerala
Traditional residences in Malabar, Kerala
Ancillary structures –temple entrance
Ancillary structures –temple entrance
Traditional ancillary structures
Bathing ponds attached to temples and residences Temple enclosure wall-(elephant form)
World heritage monuments: Churches and convents of Goa
Church of St. Francis of Asissi, Goa
DETERIORATION TO LATERITE: BASILICA OF BOM JESUS , GOA
Mosque , Goa
Traditional Bungalow, Goa
Bungalows in Goa
Laboratory Studies at IIT Madras-
Preparation of specimens
Engineering properties: compressive strength
Engineering Properties
Density Dry 1.80- 2.78 Saturated 2.36-3.04
Specific gravity - 2.84-3.58 Porosity % 20-40 Water absorption % 10- 18 Compressive strength ( MPa)
Parallel to bedding plane Wet 1.29-4.45 Dry 6.0-9.60
Parallel to bedding plane Wet 1.29- 4.54 Dry 4.41- 8.29
Modulus of Elasticity (Flexure) MPa
Wet 2.09-4.66 Dry 4.41-5.96
Weathering Studies
• Field studies- classification of weathering forms• Laboratory weathering studies
– Slake durability– Salt crystallisation– Wetting and drying
• Natural weathering trials• Weathering process
Field Study: Classification of weathering forms
1
4
2
5 6
3Granular
disintegration Biodegradation Vegetation growth
Human intervention
EfflorescenceSalt attack
Laboratory weathering studies
Salt crystallisation test (RILEM test No: IV)
Wetting and drying test (ASTM D 5313)
Slake durability test (ASTM D 4644)
Laboratory studies
Salt crystallisation test Slake durability test
Salt weathering Mechanism – Schematic model
Phase 1Leaching
Phase 2Salt crystallisation
Phase 3Debonding
Vesicules
Clay filled cavities Salt crystals
Fragments of debonded laterite
Honeycomb
•Field weathering forms matched with the laboratory findings
•Salt crystallisation attack was severe form of decay in laterite
•Salt and moisture were the mechanisms of salt attack
Summary
• Salt attack and biodegradation were the main cause for weathering in laterite (as determined from the field studies on monuments)
• Salt crystallisation test proved that dampness and salt were the agents for the decay mechanism
• Slake durability study established the corrosive action of acidic rains on laterite
• Strong laterite (high compressive strength) offered good resistance to weathering (salt attack and rainwater slaking)
Conclusions
• Laterite is sensitive to attack by salt crystallisation; salts migrate into the structure mainly from the ground
• Deferential weathering of laterite in the same environment suggests need for protection of weak laterite in damp environment
• Laterite with dense iron formation are found more durable and can be used in exposed conditions
• Decline in strength of laterite due to saturation suggests protection from dampness
• Protection from dampness can prevent deterioration to a large extent
THANK YOU