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A
seminar report on
by: Jinesh K. Mehta
(semester- V) Faculty Advisors: Prof. S. S.
Trivedi
Mr. R. P. Vasani
NIRMA
INSTITUTE OF TECHNOLOGY AHMEDABAD Date of presentation: 05/08/2000
Index Topics
page no. ·
Ferrocement:
Introduction
2 ·
Materials
used for Ferrocement
3 ·
Construction
procedure: with an example of “chabutara” Ř
Objects
of making “chabutara”
4 Ř
Concrete
column specification
4 Ř
Mix
design for column
5 Ř
Batching,
mixing, placing, finishing & curing
6 Ř
Ferrocement
bases –specifications
7 Ř
Sizing
and cutting of mesh
7 Ř
Placing
and tiding of mesh
8 Ř
Mortar
preparation, application and finishing
8 Ř
Painting
9 ·
Costing
of “chabutara”
9 ·
Different
constructions with special features
10 Ferrocement boat construction
11 Ferrocement coracle & water tank
12 Ferrocement roofs
13 Ferrocement houses
14 ·
Conclusion
14 ·
References
Books
14 Web-sites
14 International
Network to Promote Ferrocement Technology
15 Ferrocement:
Introduction (Ferrous products + cement) Definition: Ferrocement is a highly versatile form of
reinforced concrete, constructed of hydraulic cement mortar
reinforced with closely spaced layers of continuous and relatively small
diameter mesh. The mesh may be made of a metallic or other suitable material. Understanding
ferrocement Ferrocement is a type of concrete,
primarily differs from conventional reinforced or prestressed concrete by the
manner in which the reinforcing elements are dispersed and arranged. It is the kind of material where the
filler material, usually brittle in nature, called matrix is reinforced with
fibers dispersed throughout the composite resulting in better structural
performances than that of individual one. Thus it is a versatile form of a
composite material made of cement mortar and layers of wire mesh or similar
small diameter mesh closely bound together to create a stiff structural form.
This material which is special from reinforced concrete, exhibits a behavior so
different from conventional reinforced concrete in performance, strength and
potential application that it must be classed as a separate material. Advantages of ferrocement construction
over R.C.C. construction ·
It is highly versatile and
can be formed into almost any shape for a wide range of uses ·
Advantageous in spatial
structures, has relatively better mechanical properties and durability than
R.C.C. within certain loading limits ·
Thin elements and light structures, reduction in self weight ·
Its simple techniques require a minimum of skilled labor ·
Reduction in expensive form work so economy & speed can be
achieved ·
Only a few simple hand tools are needed to build any structures ·
Structures are strong and have good impact resistance. ·
Structures are highly waterproof ·
Higher strength to weight ratio than R.C.C ·
20% savings on materials and cost ·
Suitability for pre-casting ·
Flexibility in cutting, drilling and jointing ·
Very appropriate for developing countries; labor intensive Disadvantages: ·
ferrocement for smaller structures is its high density (2600
kg/m3), however for larger structures it is not a big problem. ·
The large amount of labor required for ferrocement constructions Materials
used for Ferrocement 1.
Reinforcing
mesh : 1 to 8% of the total structural volume.
Placed throughout the structure. No. of layers, thickness and spacing are
decided according to strength requirement. Table
-1 COMMON
TYPES OF METALLIC MESH FOR REINFORCEMENT
MESH TYPE
THICKNESS
SPACING
SP. SURFACE
MM
MM
MM2/MM3
Hexagonal
wire mesh
0.5-1.5
10-25
0.275
(chicken mesh) Squre
welded mesh
1.0-2.5
10-50
0.248
Expanded
metal mesh
2.0-3.0
20-50
0.245
(diamond mesh)
Woven mesh
1.0-1.5
10-25
0.255 Watson mesh
1.0-2.0
10-20
0.260 2.
Skeleton
steel: ·
Thickness varies from 6-20mm according to loading condition ·
Generally mild steel or Fe 415 or Fe 500 bars are used ·
Spacing 7.5cm to 12m 3.
Cement: ·
Ordinary portland cement ·
Cement: Sand should be 1:1.5 to 1:2.5 ·
W/C ratio should be 0.4 to 0.6 4.
Sand: ·
confirming to zone-I or Zone-II ·
free from impurities 5.
Water: ·
Free from salts and organic impurities ·
Minimum to achieve desired workability Standards for ferrocement: Min cover-
2.0 mm Max cover-
5.0 mm Min thickness of member-
12.5 mm for impermeable Steel content-
125-250 kg/m3
Construction procedure: with an example of “chabutara” Objects
of making “chabutara” : To
get feel of ferrocement & R.C.C.: The total understanding of any material
you can achieve only when you work with it. So I have decided to prepare a “chabutara”
in which I have constructed a R.C.C. pillar and on that 4 ferrocement bases
are supported. Total work in
ferrocement is @ 4.0 m2 and in R.C.C. is 9000 cm3. To satisfy need
This was essential because due to
constant harassment of cats the birds can not come to eat. So
to give the birds a better place to eat. To use waste materials I was having old wire meshes from my old
shop. They were woven meshes of 2mm diameter and 10mm spacing and chicken mesh.
So I found that it was quite suitable to use for ferrocement structure. Step
by step Construction procedure of “chbutara” : CONCRETE COLUMN Specifications: Dimensions: Height (above G.L.): 2000 mm
height (below G.L.) : 360 mm Diameter: 75 mm For footing a circular pit of 360 * 75 mm
excavated and by applying rich concrete layer of 40 mm a solid base was made.
Then reinforcement bars were placed aligned and then hole pit is filled up by
rich cement mortar and a cement seal of 20 mm was provided on the top most
portion of the footing. Reinforcement
steel: Re-bars: 3- 8 mm dia. Fe 415 bars Lateral ties: 3mm dia steel wire @ 100 mm c/c. Concrete
: M30 (mix design according to I.S.
method) Sand : zone II Aggregates: crushed angular and washed(free from dust) Approx. load carrying
capacity: 25KN (250 Kg) Self wt. Of column: 9.8KN (98 Kg) Net load bearing capacity: 152 Kg Mix
design (According to IS method) Reference: hand book on concrete mixes ( SP 23: 1982) a)
Design
stipulations Ř
characteristic
concrete strength required in field at 28- days
30 N/mm2 Ř
maximum
size of aggregate
20 mm( angular) Ř
degree
of workability
0.8 compacting factor Ř
degree
of quality control
good Ř
type
of exposure
mild b)
Test data for materials Ř
cement:
O.P.C. ; Sidhee 53 Grade; satisfying the requirements of IS : 269 – 1976 Ř
specific
gravity of cement:
3.15 Ř
specific
gravity of coarse aggregate
2.60 Ř
specific
gravity of fine aggregate
2.60 Ř
saturated
surface dry condition of aggregates Ř
sieve
analysis : sand conforming to zone-II c)
Target mean strength of concrete for a tolerance factor of 1.65 and using
table 39, fck = 30 + 6*1.65= 39.9 Mpa d)
Selection of water cement ratio from fig –47, W/C ration required for
39.9 Mpa is 0.43. (E- curve for 53 Mpa) this is lower than the max. value of 0.65
prescribed for mild exposure (see table 23) e)
Selection of water and sand content from table –42, for 20 mm M.S.A. and
sand conforming to zone –II water content / m3 of
concrete = 186 Kg sand content as percentage of total
aggregate by absolute volume = 35% change
in condition
adjustment required (see
table 44)
water content %
sand in total aggregate for
decrease in W/C ratio by
0
0.17/0.05= 3.4% (0.6-0.43)
= 0.17
no change in C.F.
0
0
final water content w= 186 Kg/m3
final sand content p = 35
- 3.4 = 31.6% f)
Determination of cement content water-cement
ratio =0.43 water
= 186 Kg cement
= 186/0.5 = 372 Kg this
cement content is adequate for mild exposure condition (see table 23) g)
Determination of coarse and fine aggregate content from
table 41, for M.S.A. –20 mm , the amount of entrapped air = 2%. Taking
this in to account and applying eq. 2 and 3 Eq.
2 -- 0.98 = [ 186 + 372/3.15 + 1/ 0.316* fa/2.6]* 1/1000=> fa= 555.32 Kg Eq.
3 -- 0.98 = [ 186 + 372/3.15 + 1/ 0.684* Ca/2.6]* 1/1000=> Ca= 1202.03 Kg The
mix proportion then becomes: Water
cement
fine aggregate
coarse aggregate 186
lit. 372
Kg
555 Kg
1202 Kg 0.43
1
1.5
3.23 the mix is 0.43 : 1.0 : 1.5 : 3.23 Formwork Ř
PVC
pipes of 75mm diameter were used as
formwork. The pipe of different lengths(0.2m-0.6m) was used and concreting was
done in five stages, after each stage two lateral bars are placed horizontally
for support of ferrocement base. Thus whole 2m height was achieved.(see
Photo) Ř
The
reinforcement bars were tied up with stirrups at 100 mm c/c. Burnt oil was
applied on the inner side of the pipe thoroughly such that no concrete stick
with the pipe. Weigh
batching Ř
Weigh batching was done for the whole concreting process. There
might be little bit error due to use of simple weighing balance as a weigh
batcher. Ř
A proper attempt was made to achieve SSD condition before weigh
batching was done. Mixing Ř
Hand mixing was done for at least 3.0 min for each batching. Ř
Proper mixing was achieved in the case of hand mixing also because
total quantity for each batching was not more than 2500 cm3 i.e. 5.5 Kg in any
stage. Placing
Ř
Concrete placing was done with the hands by wearing the gloves. Ř
To achieve better compaction 20 blows of tamping rod were applied 3
times in each stage. Finishing
and curing Ř
The formwork pipes are removed after 24 hours of placing. Then the
potholes, occurred due to very much confined structure or improper hand
compaction and also at the joints of 4 stages at lateral bars, were filled with
rich mortar. Ř
Curing was done for 14 days by simple application of water. Photo
graph on the left page shows removal of formwork pipe after last stage of
concreting FERROCEMENT BASES Specifications: Skeleton
steel: Ř
8 mm diameter Fe 415 bars (for topmost base) and 6 mm diameter Fe
250 bars( for 2nd , 3rd and 4th base), were
provided as skeleton steel. These were the lateral bars inserted in the column
during concreting. Ř
At each base two bars were provided length of
which are corresponding to diameter of that base. Reinforcing
mesh (wire mesh): Ř
Two types of meshes were available and each stage single layer of
wire mesh was provided because here impermeability was not a desired criterion.
Then also from four bases in two base complete permeability is achieved at 9 mm
thickness. Ř
One was woven mesh of 2 mm thick and 10 mm spacing total
available size of which was 1.2 m * 2.5 m. Ř
The other was chicken mesh of 1mm thick and 5 mm spacing and size
available was 1 m * 2 m. Mortar Cement : sand = 1 : 1.5 Cement : Sidhee 53 Grade Sand : ZoneII Thus there are total four bases made up
of ferrocement for birds to alight and eat food. The all four bases are
basically circular and of different diameter and with different shapes as
explained below. NO.
DIAMETER
SHAPE
WIRE MESH The topmost base
1200 mm
Chinese roof shape
Woven mesh The second base 600 mm
Circular plate type
Woven mesh The third base
500 mm
Circular plate type
Woven mesh The fourth base 800 mm
Circular bowl type
Chicken mesh The top three bases are provided with
exposed, sharp, and upward projected wire mesh to stop the cats to climb on it. Sizing
and Cutting of mesh Ř
The sizes of the base were decided considering convince of birds,
aesthetics and availability of material. Markings were done in such a way that
optimum utilization of available roll would be achieved. Ř Cutting was the most tedious t | ||||||||||||||||||||||||||
