INVESTIGATION ON COST EFFECTIVE SLAB SYSTEM HAVING DIFFERENT TYPES OF MICRO REINFORCEMENT

International Journal of Civil Engineering and Technology (IJCIET)
Volume 9, Issue 7, July 2018, pp. 1000–1011, Article ID: IJCIET_09_07_105
Available online at http://iaeme.com/Home/issue/IJCIET?Volume=9&Issue=7
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
© IAEME Publication Scopus Indexed
MICRO REINFORCEMENT
Umesh S.S.
Dr.A.V. Pradeepkumar
Mangalore Institute of Technology and Engineering, Moodbidre, Karnataka, India
ABSTRACT
The conventional reinforced concrete has two basic inefficiencies. i.e. a typical
125 mm thick slab weighs 2.94 kN/m2. This is to be designed for live load 1.96 kN/m2.
This becomes a design load of 4.90 kN/m2 and self-weight is 60 % therefore structural
efficiency of the RCC slab is only 40 %. The concrete in tension Zone hardly takes any
stresses as the concrete is week in tension and becomes expensive as concrete is not
resisting any tension load. Keeping in view the above two facts it is proposed to
investigate alternate roofing system. This research investigation focused on casting
cost effective slab system with combination of different types of Micro reinforcement
in concrete. The slab is thinner compared to conventional RC slab. This innovative
construction technique promises savings in cost, construction time, material and
labour compared to any traditional roofing system currently in use, achieving better
performance in strength, deflection and durability.
Keywords: Micro truss reinforcement, Flexure, Deflection
Cite this Article: Umesh S.S and Dr. A.V. Pradeepkumar, Investigation on Cost
Effective Slab System Having Different Types of Micro Reinforcement, International
Journal of Civil Engineering and Technology, 9(7), 2018, pp. 1000–1011.
http://iaeme.com/Home/issue/IJCIET?Volume=9&Issue=7
1. INTRODUCTION
Food, clothing and shelter are the basic needs for every human being. Every government
worldwide trying to fulfill affordability comfort to the every citizen is the challenging goal.
The word ‘affordability’ can be defined as the ratio of the housing rent to the income of the
house hold. The ‘affordability’ can be different for different income groups such as below
poverty line [ BPL] group, economically weaker sections [ EWS], low income group[ LIG],
and middle income group [MIG].
Investigation on Cost Effective Slab System Having Different Types of Micro
Reinforcement
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Due to significant urbanization, the whole world is facing housing shortage. Today,
worldwide about 320 million households in urban areas are at substandard levels. India, a
developing country, is also facing a huge housing demand for more than 6 crores housing
units. By 2022, this is expected to reach 11 crores. In order to meet the huge housing demand
in India, it is necessary to switch over mass housing and cost effective construction
technology and materials.
Cost effective construction technologies aim to cut down construction cost by using
alternatives to conventional construction practices and input. Construction cost can be
reduced through using locally available appropriate material along with improved skill and
technology without sacrificing the strength, performance and durability of the structure. It is
observed that increase of construction cost up to 15 percent every year due to the cost of basic
building materials such as steel, cement, bricks, sand and other materials as well cost of
labour. As a result, construction cost becoming beyond the affordable limit in particular for
low-income groups of the population as well as middle-income groups. Therefore it is
necessary to adopt cost-effective construction, either by up gradation of conventional
construction method using locally available materials or using modern construction materials
and techniques.
Structural floors/roofs account for the substantial cost of a building in a normal situation.
Therefore, any savings achieved in floor/roof considerably reduces the cost of the building.
Traditional cast– in-situ concrete roof involves the use of temporary shuttering which adds to
the cost of construction and time. Use of standardized and optimized roofing components
where shuttering is avoided prove to be economical, fast and better in quality. This
investigation focused on the casting of cost-effective slab system with a combination of
different types of micro reinforcement. The slab is thinner compared to the conventional slab.
This innovative construction technique promises savings in cost, construction time, materials
and labour compared to any traditional roofing system currently in use, achieving better
performance in strength, deflection and durability
2. LITERATURE REVIEW
Several attempts have been made by researchers to propose cost-effective alternatives to
conventional solid RC slabs. The underlying principle in these alternatives is that portion of
Concrete below the neutral axis (Tension Zone) is either eliminated, as in the case of voided,
ribbed, grid or waffle slabs are replaced by a relatively cheaper filler material. A brief survey
of literature about the alternatives to conventional concrete slab has presented below
Abdul Rahman [1] et.al., carried out research on the feasibility of precast prestressed
concrete slab incorporating structural hollow clay blocks in floors and roofs. In this study, the
precast slab strips have been tried out on a large scale of the roof of a school building at
Adyar in Madras. The total area of the roof was 420 m2. The slab strips were precast in the
pre-casting yard. All the precast slab strips had uniform width 0.57 m and 3.80 m spans and
thickness 0.83 m and a self-weight of 0.58 kN /m. The slab strips were prestressed in a long
line pre-tensioning bed by two 5mm diameter high tensile steel wires, one in each of the two
outer longitudinal ribs, and two 4 mm diameter high tensile wires in the middle longitudinal
rib. The total initial prestressing force imparted through the four wires was about 8.5 tones.
The concrete used in the precast slab strips had a mix proportion slightly richer than 1: 1.5:3
by weight. The maximum size of aggregate used was 10mm. The hourdi blocks used in the
work had an overall cross-section size of 230mm x 830mm with a length of 300mm. The
longest one precast slab strip weighs only 2.25kN. The stability of the precast slab strips for
large–scale application was further checked by field loading test. After testing, the actual
Umesh S.S and Dr.A.V. Pradeepkumar
ultimate load carried by the composite slab strip was 4.32 kN /m which were in addition to the
self-weight of 1.127 kN /m.Sharma [2] et.al., carried out a study on design and construction of
precast hollow or ribbed slab. In his study, he developed a simple design procedure based on
the ultimate strength design concepts of conventional solid slabs for precast hollow and
ribbed slabs has been developed. The variation of the flexural stiffness of the precast hollow
trough or cross ribbed structural forms due to the creation of voids has been derived and
expressed graphically in relation to conventional equivalent solid slab rigidity. By using,
developed formula, judicious balancing of the width of the ribs and thickness of the flanges in
relation to the spacing of ribs and effective depth respectively, considerable economy and
saving of time in construction can be achieved, aside from obtaining an attractive structure.
This design procedure is limited to short intermediate building spans. Desayi, [3] et.al.,
focused the research on, an experimental and semi–analytical study on the strength of
fibrocement roofing elements tested under symmetric two point loading are presented. Nine
trapezoidal – shaped fibrocement roofing elements were cast and tested. The variables
included were span / depth ratio, amount of longitudinal reinforcement and the type of mesh
wire. Methods of computing cracking load, ultimate flexural strength and deflection have
been proposed and the predicted results compared with test results. Load factors based on
limiting deflection and limiting crack width are also examined. Paramasivam [4] et.al., carried
out the research, to assess the flexural behavior of ferrocement slabs made up of cellular
mortar matrix was investigated for possible use as a partial or non-load bearing elements in
precast building construction. They studied on variables such as the thickness of the slab, the
number of layers of wire mesh and density of mortar are considered to study the cracking
behaviour of ductility and ultimate strength of slabs. The effect of inclusions of various
volume fractions of short steel fibers was also included in the test programme. Singh [5] et.al.,
carried out the research to assess the salient features of filler block roofing system, developed
at the institute which are non – autoclaved; compared to other types of cellular concrete
material available in the country. Hence, use of heavy equipment and machinery and high
capital investment for autoclaving are avoided. As the blocks need only curing under
atmospheric conditions, the considerable amount of energy is saved. Utilization of fly ash in
large quantities for the production of blocks is a major advantage. Therefore, there is a saving
in cement, steel and overall cost of construction, compared to conventional in-situ RC slabs
for floors and roofs Ambalavanan[6] et.al., carried out research on the effective analysis of
alternate one – way floor/roof systems. They did a systematic cost-effectiveness analysis of
one – way slabs with filler blocks and partial prefabrication system and the results are
compared with that of conventional R.C. slab. The study is aimed at assessing the relative
structural performance of alternate roof/floor slab systems adopting limit state design concept
with a view of evolving design tables to serve as a ready reckoner for designers. A
comparison of the relative cost and reduction in self – weight of these systems has been made
for establishing their range of applicability. Jaising [7] et.al., carried out research on A R.C
filler slab with non – autoclaved cellular concrete blocks for sustainable construction. In this
work, explained about construction technique of the floor/roof cast in situ RC filler slab with
non – autoclaved cellular concrete filler blocks. The filler blocks are 110mm thick and 260 x
560 mm at the top tapering down to 250 x 550mm at the bottom. The slab is cast with cement
concrete of grade M15. Spanning in two perpendicular directions, the slab can be designed as
a grid with compression taken by the deck concrete at top and tension taken by the
reinforcement at the bottom of the rib portion. The cellular concrete blocks act as non –
structural fillers. The technique can be adopted for floor/roof in single and multistoried
residential and other types of buildings. Sheela[8] et.al., carried out research on the ductile
behaviour of optimized Ferro cement corrugated flexural elements. In this investigation, an
attempt was made to obtain an optimum cross section of the polymer modified corrugated
Reinforcement
Ferro cement element by an efficient optimization technique like genetic Algorithm. The
study reveals that the engineering properties such as energy absorption capacity, ductility, and
cracking characteristics of corrugated element can be enhanced with the increase of polymer
content and volume fraction of reinforcement. In this experimental work, a total of 75
numbers of 3m length corrugated shaped specimens were prepared in the laboratory.
Adequate care was taken while placing the reinforcement cage over the mould to maintain a
minimum cover of 3mm on all sides of the specimen. Reinforcement cage consists of layers
of 6 x 22 gauges or 4 x 20 gauge wire mesh with 6 mm skeletal steel bars at junctions, where
the mesh changes its direction and is tied well together with the wire mesh. Hand plastering
was done for preparing the specimen with and without polymer modified cement sand mortar
of ratio 1:2. The specimens were removed from the mould after 2 days wet jute curing and
were cured for 28 days by ponding water on the specimen. During testing it was observed that
after first crack load for each increment of load, a number of smaller cracks were formed on
the flexural zone. Out of these only one crack widened to its maximum width and the
specimen failed at maximum load. Deflection is less in specimens having 6 x 22 gauge wire
meshes than 4 x 20 gauge wire mesh in lower loads and deflection is more at higher loads.
Sheela[9] et.al., carried out research on predicting the ultimate load carrying capacity of
polymer modified Ferro cement flexural elements. This paper reports the flexural behaviour
and ultimate load carrying capacity of ferro cement flexural elements having a span of 3m.
The investigation was for i) two cross-sectional shapes: channel and trapezoidal ii)mixes with
and without styrene butadiene rubber (SBR) iii) woven wire mesh of 4 x 20 gauge and 6 x 22
gauge and iv) the number of Wire mesh layers. The results indicate that the addition of
polymer in the mortar matrix and the use of 4 x 20 gauge wire mesh, instead of 6 x 22 gauge
wire mesh, significantly increased the load carrying capacity of the elements. A method for
predicting the ultimate load carrying capacity of the ferro cement flexural elements is also
proposed. YavuzYardim [10] et.al., Investigated on AAC – concrete light weight precast
composite floor slab. In this study, the use of autoclaved Aerated Concrete (AAC) as an in fill
material for semi precast panel is investigated experimentally. The effectiveness of proposed
light weight slab is reached by comparing the behavior of specimens with that of conventional
solid precast slab. The comparisons were based on structural performance and total weight
reduction. The composite AAC slabs section chosen are one way slabs with a size of 1m x 3m
x 0.13m (width x Length x Depth). The specimens vary in the AAC blocks layouts and total
weight reduction ratio. The test results showed that the AAC composite precast panel
provides reasonable weight reduction without sacrificing the structural capacity. Ganesan[11]
et.al., carried out research on the effect of steel fibre on the flexural behaviour of simply
supported one way SCC slabs. A total number of nine specimens were cast and tested with
steel fibers of aspect ratio of 50 and Volume fraction of 0 %, 0.5 % and 0.75 %. The load
deflection characteristics, first crack load, ultimate load, crack propagation and widening of
cracks were investigated. Addition of fibers enhanced the first crack load and post cracking
behaviour. A marginal improvement in the ultimate strength was observed. Ductility and
toughness characteristics improved significantly due to the fiber addition. GeethaKumari[12]
et.al., Investigated on Flexural Characteristics of SFRSCC and SFRNC one way slabs. In the
present study, a total number of 20 slabs of size (1050 x 500 x 65) mm were cast and tested
under flexure. Out of 20 slabs, 10 slabs were cast using steel fibre reinforced Normal concrete
(1.0 % Vf) and 10 steel slabs (1.0 % Vf). The grade of concrete used was M40 and M70. Five
different variations of tensile reinforcement were considered for SFRNC and SFRSCC. An
attempt has been done to produce M40 and M70 grade of SFRSCC reinforced slabs. Under
flexure, cracking load, ultimate load, mid-span deflections, the width of crack, strain in steel
reinforcement using strain gauge were measured during the testing of specimens. Literature
survey reveals that the information available on micro reinforcement in cost effective slab
system is not reported. Therefore it is proposed to study on the micro reinforcement roofing
system.
3. SCOPE AND OBJECTIVE OF THE STUDY
The conventional reinforced concrete slab has two basic inefficiencies i.e. a typical 125 mm
thick slab weighs 2.94kN/M2. This is to be designed for the live load of 1.96 kN/m2. This
becomes a design load of 4.90 kN/m2 and self-weight is 60 %, therefore, the structural
efficiency of the RCC slab is only40 %. The concrete in tension zone hardly takes ant stress
as the concrete is a week in tension and becomes expensive as concrete is not resisting any
tension load. Keeping in view the above two facts, the present study has been taken up. The
proposed roofing system with micro reinforcement consumes very less quantity of materials
and becomes cost effective. This becomes conservation of materials such as fine and coarse
aggregate which are scare. However this type of roofing system depends on several factors
that require investigations. Therefore it is proposed to study on micro reinforced roofing
system and the following objectives are set.
• To investigate the basic properties of materials used in the micro reinforced
roofing system.
• To cast the micro reinforced roofing system with different combination of
reinforcement cage
• To test the micro reinforced roofing system with suitable loading frame
• To investigate the load-deflection behaviour of micro reinforced roofing system
having different types of reinforcement cages under flexure.
• To determine the failure load and ultimate deflection of micro reinforced roofing
system subjected to flexure.
• To evaluate equivalent uniformly distributed load [EUDL] carrying capacity of
different types of a micro reinforced roofing system.
4. EXPERIMENTAL MODEL
An experimental investigation is conducted on five test specimens. All five test specimens are
of same cross-sectional dimensions of length or span 3300mm, width 600mm and varying
depth, i.e.100mm depth at rib or beam portion and 50mm depth at slab portion.
The size of micro reinforcement /micro-truss is 3300mm x 50mm x 100 mm (LxWxH).
Reinforcement of micro truss consists of two number of 3mm diameter wire at the bottom and
2 number of 3mm diameter wire at the top. Top and bottom reinforcement are connected by
using rectangular shape stirrups spaced at 300mm c/c throughout.
Each test specimen consists of two long ribs of dimension 3300mm x 50mmx 100mm
(LxWxH) and seven short ribs of dimension 600mmx 50mm x100mm. Reinforcement
arrangement in long and short ribs is common in all five test specimen as shown in Fig1 and
2. In slab portion of the test specimen, different types of meshes are used as reinforcement.
Reinforcement
Figure 2 Micro-truss reinforcement details
The experimental studies and research were carried out to determine the ultimate load,
load-deflection characteristics, and equivalent UDL.
The first type specimen is named as side braced rectangular micro-truss slab with
expanded metal mesh and designated as SREMTS. The expanded metal mesh is wrapped
around micro reinforcement and the same mesh is used as reinforcement in slab portion.
The second type test specimen is proposed with galvanized iron mesh. The same mesh is
used as reinforcement in slab portion and is wrapped around micro reinforcement. The test
specimen is named as side braced rectangular micro-truss slab with galvanized iron mesh and
it is designated as SRGMTS
The third type test specimen is named as side braced rectangular micro-truss slab with
chicken mesh and is designated as SRCMTS. The chicken mesh is wrapped around micro
reinforcement and the same mesh is used as reinforcement in slab portion
The fourth type test specimen is named as side braced rectangular micro-truss slab with
fiber mesh and it is designated as SRFMTS. Fiber mesh is used as reinforcement in slab
portion and the same mesh is wrapped around the micro reinforcement
The fifth type test specimen is designated as SRWMTS. In this test specimen, 3mm
diameter wire is placed at 150mm c/c in both directions as reinforcement in slab portion.
Figure 3 Types of Mesh
NO Slab
5 SRWMTS
3mm diameter Wire placed at 150mm c/c in both directions
MR
5. MATERIALS USED
The following materials are used in casting Micro truss reinforcement slab.
1. Cement
2. Coarse aggregate
3. Fine aggregate
4. Mixing Water
5. Types of meshes (Expanded Metal, Galvanized Iron, Chicken, Fiber mesh)
6. 3mm diameter Mild steel wire
Cement: Ordinary Portland Cement (OPC) 43 grade was used in the study. All tests were
carried out in accordance with BIS 8112-1989, BIS 269-1967 and BIS 12269. The test results
are in confirmation with BIS.
Coarse aggregate: Locally available crushed granite was used. As the thickness of slab
and size of the beams are lesser than the normal slab size, the coarse aggregate used is passing
through…

INVESTIGATION ON COST EFFECTIVE SLAB SYSTEM HAVING DIFFERENT TYPES OF MICRO REINFORCEMENT

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