incorporating coir-pith for efficient thermal insulation and water...
TRANSCRIPT
Hazards related to coir pith:
Normally, coir pith is dumped as agricultural waste and become
accumulated as a waste product in the form of heaps of coarse and
fine dusts.
It is estimated that at present there is an accumulated stock of 10 X
106 metric tons of coir pith in the southern states of India viz. Kerala,
Tamil Nadu, Andhra Pradesh, Karnataka, and Orissa.
Coir pith has been traditionally been disposed off by burning. This
burning has resulted in various environmental problems, including
carbon deposits and the warming of the atmosphere.
During the rainy season, the tannins and phenols of the coir pith are
leached out into the soil and into the irrigation canals, thereby making
agricultural lands unproductive. Also, the water pollution caused by
such leaching is harmful to the aquatic and soil biological life.
Coir pith is a biomass residue generated during the extraction of
coir fibre from coconut husk and is a by-product of the coir
manufacturing industry.
The Coconut husk contains 20% to 30% fibre of 60 to 300mm
length. After grinding the husk, the long fibres are removed and used for
various industrial purposes, such as rope and mat making. The
remaining 70% material is composed of short and medium-length fibres
as well as pith tissue, this is commonly referred to as waste-grade coir.
The waste grade coir may be screened to remove part or all of the fibre,
and the remaining product is referred to as coir pith.
Introduction:
Thermal insulation on roofs Heat exchange between a building and its surroundings occurs
primarily through the ‘skin’ of the building e.g. roof, walls, fenestrations
etc.
Roofs and ceiling may amount to about 15 to 50% of the total
heat gain depending upon the roof area and height of the building.
Hence insulation in roofing play an important role in contributing to the
energy loads of a building for achieving thermal comfort through air
conditioning or other strategies.
Improper thermal insulation on roofs may lead to excessive
expenditure on air conditioning and also add to the global energy
consumption when observed on a global scale.
Many agencies have prescribed standards for the thermal
conductance/resistance of roofing assemblies. ECBC prescribes such
values depending upon the region, climate and usage of buildings.
There are many technologies that provide such insulation. But
the production of constituent materials of many such assemblies is
from non-renewable sources and they generally also have a larger
carbon foot print
Most commonly constructed insulation and
water proofing system in India, Brick Bat Coba
(BBC): Roof slabs constructed by RCC need insulation for thermal
comfort and waterproofing treatment to prevent leakage of water. Both
these requirements are supposed to be fulfilled by BBC assembly.
Drawbacks of brick bat Coba:
The drawbacks of brick-bat coba are as follows:
• Provides insufficient thermal insulation
• It imposes unnecessary load on the parent slab
• Damages the parent slab during repairs as bricks adhere to the
parent slab
• If rain water reaches the bricks through cracks, the bricks absorb
the water. But they dry slowly, hence a reservoir of water is created
inside, specially in regions of heavy rainfall
• Needs excellent workmanship
Aims and objectives: Aim: Incorporating coir pith for efficient thermal insulation and
water proofing on terrace RCC slabs.
Objectives:
• To study the applicability of coir pith in a thermal insulation and
water proofing assembly.
• To compare the thermal performance of commonly used system
i.e. brick-bat coba with thermal insulation and water proofing
assembly using coir pith.
• To study the water proofing performance of a thermal insulation
and water proofing assembly of coir pith.
Design of the study Brick-bat coba is the most commonly used system for thermal
insulation and water proofing in India. There are many disadvantages
in using brick-bat coba as a thermal insulation and water proofing
system on terrace RCC slabs as mentioned. Coir pith shows
potentially better thermal insulating and water absorbing properties
than burnt clay bricks and can be a potential replacement for bricks in
conventional brick-bat coba technology.
A comparative study of thermal and water-proofing performance of
Brick-bat coba (BBC) and a system cast by replacing bricks by coir
pith blocks in brick bat coba (Coir Pith Block Assembly, CPBA) is
carried out..
Limitations: • The research needed a detailed study about the thermal properties
of coir pith. No such studies are available, and the laboratory testing
of coir pith for its thermal properties was not possible due to the local
unavailability of apparatus or a laboratory that could perform such
tests.
• There could be many different ways to use coir pith in thermal
insulation and water proofing systems. But due to the limitations of
the time for this study, the assembly casted by replacing bricks by
coir pith blocks in brick bat coba was adopted.
• It was not possible to calculate the exact thermal
conductance/resistance of the two assemblies, that are compared,
due to the time and availability constrains of apparatus and local
laboratories.
• The experiment is conducted on specimen size of 300x300mm, due
to which the implications of the use of coir pit on larger scale cannot
be conclusively found out.
• Due to limitations of time, the specimens could not be tested in very
harsh weather of summer or intense rains.
• This use of this technology is restricted to south Indian coastal
regions due cost implications
• Coir pith blocks loosen up in the presence of excessive water. This
problem was not explored to detail and remains a limitation of the
product.
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Comparative study of thermal performance of CPBA as compared
to Brick-bat coba
Analysis and discussion of resultant data
Conclusion
• Durability
• Load bearing capacity
• Water absorption capacity
• Chemical reactivity
• Fungal and bacterial infections
• Theoretical comparison of thermal performance
• Experimental comparison of thermal performance
• Thermal insulation
Experimental study of water proofing performance
• Designing controlled space
for experiment
• Selecting instruments
and sampling method
• Performing experiment
• Data collection
Applicability of coir pith in thermal insulation and water proofing
system
• Casting of specimen
assemblies
•
• Performing the
experiment
• Observations
Durability
Coir Pith contains three major constituents .
• Cellulose: A polymeric chain of anhydrous glucose units, which
exists mostly in crystalline form
• Hemi Cellulose: Which is made up of mixed polymers of various
pentose and hexose sugars and is amorphous in nature.
• Lignin: A complex amorphous ploymer of phenyl propane which
surrounds the cellulose in cell walls. Lignin is relatively inert to
hydrolysis.
Chemical composition of raw coir pith is listed below: Contents
%(w/w)
Cellulose……………………….35
Lignin…….……………………25.20
Ash…………….………………8.70
Moisture………….…………..11.90
Pentosans………….………….7.45
Fats and Resins…...…………..1.80
Other Materials….…………...10.06
Fixed Carbon………………….37.10
Coir Pith contains Lignin and cellulose in almost equal quantities
around 25 to 35% .
Highly lignified materials are extremely durable and do not
degrade under normal atmospheric conditions. Coir Pith contains lignin
in the same percentage as teak i.e. 30% lignin, Hence it is extremely
durable like teak wood and does not degrade even in the presence of
moisture or water.
Applicability of coir pith in thermal insulation and water
proofing system:
Thermal Insulation
Both Coir and Coir pith have similar chemical composition with slightly
different physical appearance and properties. Coir Pith is more porous and has
more water absorption capacity than coir. Following is the comparison of
porosity and density of coir and coir pith:
Coir Coir pith
Porosity(%) 40 76.77
Density (g/cc) 1.44 0.1525
Coir has Thermal conductivity 0.075 W/mK . Considering the above factors
where the porosity of coir pith is more porous and density of coir pith is less
than coir, it can be concluded that the thermal conductivity of coir pith would be
more and never less than coir. As there is data available on thermal
conductivity of coir pith, for the purpose of this study we consider that the
Thermal conductivity of coir pith as equal to that of coir i.e. 0.075W/mK
Load bearing capacity
For the purpose of our study we would be using coir pith blocks which
are manufactured by compressing coir pith. As there are no available
studies related to the compressive strength of the coir blocks, a
laboratory testing was conducted to evaluate the compressive strength of the coir blocks.
0.000
5.000
10.000
15.000
20.000
25.000
30.000
35.000
0.0 10.0 20.0 30.0 40.0 50.0
Results: Load of failure (kN): 29.1 Stress (Mpa): 0.84
29.1kn=2967.37kg force ~ 3000kg force
Considering the applicability of coir pith blocks on the terrace,
there will be an absence of walls and other dead load and dynamic point
loads, 3000kg force is satisfactory and applicable for terrace thermal
insulation and water proofing system.
Water absorption capacity
In the absence of any study related to absorption capacity of coir pith
blocks, water absorption capacity of coir pith block was experimentally
compared to the water absorbing capacity of burnt cay brick
Design of study
Specimens of burnt clay brick bat and coir pith block having equal
volume were selected. Coir block as wrapped in porous membrane to
avoid loosening These specimens were placed in plastic troughs of equal
size each. The weight of the two specimens and the plastic troughs was
recorded. The experiment was carried out in a controlled atmosphere of
humidity controlled room.
Observations: It is clearly observed that coir pith block had absorbed
962gm and brick had absorbed 234gm of water for the same volume of
specimen size.
Hence, coir pith is a better absorbent of water than Brick. This property of
Coir pith block will be helpful in absorbing any water that percolates into
the system and shall obstruct the water from reaching the parent slab
INCORPORATING COIR-PITH FOR EFFICIENT THERMAL INSULATION AND WATER PROOFING IN ROOF RCC SLAB 2013-2014
Chemical reactivity of coir pith with water
When lignin comes in contact with water for long durations of
more than 6months some of the lignin and phenols are washed away
into the water to the extent of 5 to15%. But studies have shown that
there is no further loss of constituents or mass of coir pith even after
coir pith is in contact with water for further prolonged periods. Studies
conducted on 15 year old hillocks of coir pith have shown that there
has been 5 to 10% loss of lignin and same amount of loss of phenols
with negligible change in other constituents. Lignin forms the outer
lining of cellulosic material and protects it from disintegration. The
physical properties of coir pith unaltered.
The inert behaviour of coir pith towards water proves it as an
applicable material in the water proofing system.
Fungal and bacterial infections
Coir pith is not infected by commonly present bacteria or fungi.
Due to this it requires a highly complicated procedure where controlled
atmospheric conditions and rare bacteria are required to disintegrate
coir pith into compost which can be used for agriculture.
Due to the absence of potential infections due to fungi and
bacteria, coir pith is extensively exported to gulf and European
countries as a growing medium for horticulture without the risk of
exporting indigenous specious of fungi and bacteria to foreign
countries.
As coir pith does not bare a risk of getting infected by fungi
and bacteria unless under controlled circumstance in the presence of
rare bacteria and fungi, it can be effectively used as part of thermal
insulation and water proofing assembly in the construction industry.
Theoretical comparison of thermal performance: Thermal insulation and water proofing system with
Brick Bat Coba (BBC): .
The achieved resistance of the assembly is 0.351m2k/w which is very
low as compared to the minimum required 2.1 m2k/w by ECBC
Standard for all climates for day use buildings in India.
Dead load on parent slab calculation:
The total dead load exerted by brick-bat coba on parent slab is 4.2kN/
m3
Thermal Insulation and water proofing cast by replacing bricks
by coir pith blocks in the brick bat coba (CPBA):.
The achieved resistance of the assembly is 2.321m2k/w which
complies with the minimum required 2.1 m2k/w by ECBC Standard for all
climates for day time use buildings in India.
Dead load on parent slab calculation:
The total dead load exerted by coir pith system on parent slab is
1.365kN/m3
Table of comparison:
Sr.No
. Design Details
Resistance
– m2k/w
Dead load
kN/m3
A Brick Bat Coba 0.351 4.2
B CPBA 2.321 1.365
Experimental comparison of thermal performance
Casting of specimen
assemblies
Designing controlled space for experiment
Selecting instruments and sampling method
Performing the experiment
Data collection
INCORPORATING COIR-PITH FOR EFFICIENT THERMAL INSULATION AND WATER PROOFING IN ROOF RCC SLAB
Designing controlled space for experiment The study of thermal performance of the two specimens involves
recording the temperatures of the top and bottom of the assemblies. The
top surface has to be exposed to the sky and the respective solar radiation.
The bottom of the slab needs to be insulated from the direct solar radiation.
In order to protect the bottom of the slab from direct exposure to the solar
radiation and to achieve identical environments at the bottom of the slab a
small enclosure of size 300x300mm is created using polystyrene sheets as
insulation.
Experiment enclosure for BBC Experiment enclosure for CPBA
Performing experiment
• The two assemblies on the stands with the enclosed room at the bottom
of each are placed on the terrace such that no shadows of the over-head
water tank fall on them.
• 4 temperature sensing probes are attached to the surface of the top and
bottom of the two assemblies respectively.
• The probes are connected by wires to the microtronics temperature data
logger.
• The data logger is set to record temperatures at intervals of 20mins
• The experimental setup is let undisturbed for 5 consecutive days.
• After 5 days, the data logger is disconnected from the temperature
probes and connected to a computer having Microtronics Soft software.
• The data is downloaded from the data logger to the computer.
Data Collection:
The top and bottom temperatures of the 2 assemblies are plot on a
graph for each day and data of three days is selected for analysis.
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BBC slab top
BBC slab bottom
CPB slab top
CPB slab bottom
Day 1: 07-08-2014
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BBBC slab top
BBC slabbottom
CPB slab top
CPB slabbottom
Day 2: 08-08-2014
Day 2: 09-08-2014
Observations and analysis:
After conducting the experiment and observing the graphs of the thermal
performance of BBC and CPBA the following points are found:
• By the use of coir pith better thermal insulation was achieved.
• The parent RCC slab bottom of CPBA got heated only up to the ambient
air temperature. Heat did not get transferred through the CPBA to the
bottom of the parent RCC slab. Whereas the RCC slab bottom for BBC
showed temperatures higher than the ambient temperature, proving that
some amount of heat got transferred through the BBC to the parent RCC
slab.
• The slab top of CPBA got heated quickly and also cooled down quickly.
CPBA top got heated more than BBC as there was no heat dissipation
through coir pith blocks. It also cooled down quicker than BBC as only
the 25mm thick screed retained heat and hence the thermal mass was
low. CPBC acted as a thermal barrier or insulator.
• In BBC heat dissipated through the screed to the bricks and to the
parent slab. This whole assembly acted as a thermal mass. Hence BBC
took more time to cool down or heat up.
Experimental study of water proofing
performance In order to actually test the water proofing performance of an
assembly in natural weather conditions it would take years. So in
order to expedite the process and limited time span of the study a
simpler and quicker method was devised.
In actual scenario, wear and tear of the water proofing
assembly as well as the parent RCC slab takes place due to
expansion and contraction and varying loads. Water leakage starts
when water enters the water proofing assembly from cracks on its
surface and reaches the parent slab and seeps to the bottom of the
slab. When the water reaches the RCC slab, it means that the water
proofing assembly has failed. So it means that a water proofing
assembly is successful if the water is stopped from reaching the
parent slab.
Performing the experiment
The screed on the surface of the CPBA was cracked with the
help of a hammer.
The assembly was left exposed to the monsoon rains from 12th June
to 20th June.
Observations were made after separating the CPBA assembly from
the Parent RCC slab
Observations • The surface of the RCC parent slab was dry.
• All the water that seeped through the cracks on the surface was
absorbed by the coir pith block.
• While separating the CPBA from the parent slab, no damage was
done to the slab, which is persistent to BBC as bricks adhere to
the slab.
• The water proofing compound layer was not damaged.
Summery and Conclusion The introduction and use of RCC technology for constructing
buildings in India has increased the pace and reliability of Indian
construction Industries. But due to the inefficient thermal insulation
and water proofing capabilities of concrete, technologies like brick
bat coba have to be used for terrace level slabs. Brick bat coba is
used abundantly because other technologies are unavailable in
most parts of India and casting brick bat coba is much cheaper.
But brickbat coba in itself is inefficient in thermal insulation
and water proofing due to the extreme climatic conditions in most
parts of India. This leads to the cooling energy loads in the
buildings. Hence there is a lack of energy efficiency leading to
national and global energy crises. Also there are frequent water
leakage problems in roof slabs due to inefficiency of brick bat coba.
From the study done in this research it was found that coir
pith is applicable as a material in thermal insulation and water
proofing assembly. CPBA is a much more efficient thermal
insulation and water proofing system than brick bat coba.
Incorporation of coir pith in the thermal insulation and water
proofing assembly would help in insulating the parent slab from the
heat of the sun, hence reducing the heat transfer to the interior
spaces. There will be lower consumption of energy required for air
conditioning the interior spaces, achieving energy efficiency. Also,
CPBA acted as an efficient water proofing system.
Coir pith absorbed almost all the water that percolated into
the assembly and did not allow it to reach the parent slab, which
proved that coir pith can be efficiently used for water proofing.
Coir pith is a by-product of coir industry and is proving to
be a soil pollutant due to excessive dumping and air pollutant due to
burning of coir pith for its disposal. Through further research, if a
consolidated technology is developed and more uses for coir pith
are explored in construction industry, it would prove to be a boon for
the nature and also a money spinner.
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BBC slab top
BBC slabbottom
CPB slab top
Tem
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2013-2014