Bendable Concrete: A Study on PVA Fibres and Superplasticizer in Engineered Cementitious Composites

This paper discusses bendable concrete, its features, and how PVA fibres and superplasticizer are used in Engineered Cementitious Composites. It also covers the mixture design, casting procedure, and curing of ECC concrete specimens. The study aims to check the ECC nature under split tensile test, compression, and flexural test, and to obtain the deflection of ECC beams.

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BENDABLE CONCRETE
Student’s Name
Institution
City
Date

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Project summary
Bendable concrete is a mortar-like that is
easily moulded composite that is
reinforced particularly with short random
fibres. The traditional concrete experiences
a great failure as a result of being strained
in an earthquake or by a routine overuse,
compared to the bendable concrete which
keeps its tensile strength of up to 5%
remaining intact and safe. Traditional
concrete cannot sustain a weight of 0.01%
tensile strain. To address the future
demand for concrete and to develop fibre
materials in this paper, PVA is used in
order to lower the amount of cement and
improve the flexibility of the concrete. It
contains high aspect ratio, better water
affinity, and ultimate high tensile strength,
no risks to health, relatively high elasticity
modulus.
Keywords: PVA fibres, superplasticizer,
ECC
Introduction
Background
Conventional concrete nearly does not
have bendability features having a strain
capacity of 0.01% that results in their high
brittleness and rigidity. Its lack of
bendability characteristics is the major
leading result to failure when exposed to
strain. This has pushed for the need to
design an elegant component called
Engineered Cementitious Composites.
This material is able to exhibit
considerably a suitable flexibility. The
polymer fibres reinforced in bendable
concrete are micro-chemically designed
whereas ECC is achieved from basic
ingredients that are the same as of the ones
for the conventional concrete. Although it
contains High Range Reducing agents that
are added to it so as attain a good
workability. There is no usage of coarse
concrete in ECC hence, it is instead a
mortar, not concrete.
[1].
Objectives of the research
 To check the ECC nature under
split tensile test, compression and
flexural test.
 To obtain the deflection of ECC
beams.
Significance
This ECC is more flexible than the
traditional concrete it is therefore seen as a
metal as compared to glass. Traditional
concrete is deemed to ceramic brittle and
rigid. It can experience a catastrophic
failure if under strain and by routine
overuse. It is studded with reinforcements
of especially fibre coatings that keep it
together. This ensures that the ECC even at
5% tensile strength it is still intact and
safe. Traditional concrete fractures will not
be able to sustain a tensile strain load of
0.01%.
Nowadays constructors of buildings
reinforce concrete structures with steel
bars just in any case cracks will show up,
they would exist as micro-cracks. It is
unfortunate as the cracks would not be that
small to adequately heal. Water and
deicing salts that penetrate through the
concrete and to the steels leads to
corrosion of the steel which in return
weakens structures. This concrete with
self-curing feature may not corrode
because it does not need steel
reinforcements in order for the concrete to
retain the width of the cracks intact [6].
Definitions
PVA fibre – Polyvinyl Alcohol fibre

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Permeability – Rate of flow of fluid
through porous media. In this case, flow
through concrete.
Self-healing – Process of filling the micro-
cracks in concrete by the occurring internal
reactions.
Durability – The ability of concrete to
sustain strain imposed on it.
Workability – The ease of compaction,
transportation and mixing of concrete.
ECC – Engineered Cementitious
Composite.
Literature review
[2]Carried out a research on steel and
synthetic fibres both commercially
available. The relationships between
flexural and deflection stress are used to
obtain flexural strength and the ratio of
equal flexural strength. The flexural
toughness of the concrete revealed in
having increased averagely upon the use of
steel and synthetic fibres. However, the
same dosage of various fibres did not lead
to similar flexural toughness in the
specimens.
[3] Performed an investigation that
experimented on the flexural feature of
self-compact concrete that is reinforced
with hooked-end and straight end steel
fibres levelling 1.5%, 0.5% and 1.0% in
comparison with Normally Vibrated
Concrete. Tests from the laboratory were
to be acquired in accordance with the
recommendations of RILEM TC 162-TDF.
Normally Vibrated Concrete had similar
SCC flexural features. This because an
increase in the fibres volume ratio resulted
in an increase in the pre-peak and post-
peak parameters of SCC. The kind of steel
fibres to large extent influenced the
dependency. Therefore, the SCC attains
the greatest displacement in the crack
mouth for least deflections than the
Normally Vibrated Concrete.
[4]Conducted an experiment on the likely
applications of ECC that is reinforced with
fibres with features of less drying
shrinkage in the concrete’s pavements to
achieve elimination of the joint that
usually accommodates deformation of
temperature and shrinkage. It was
discovered that composite slab containing
both LSECC and conventional concrete
with steel bars at the interface of LESS or
concrete as well as procedures that have
been designed for construction, would lead
to localization of the tensile cracks into the
LSECC strips. This would prevent
cracking in the adjacent slabs.
[5]Researched on the self-healing
characteristic of the LESS to study the
impact of pre-cracking time and curing
conditions. The ECC beams were pre-
cracked using four-point bending at a
varied age, then by different curing
conditions. For all curing conditions, self-
curing and capacity to deflect would even
recover or exceed those of virgin samples
at each pre-cracking stage.
Methodology
Ingredients of bendable concrete
Sand
Sand s used in making of mortar and
concrete as well as polishing and
sandblasting. The sands with fewer
contents of clay are used in making of
moulds in foundries. The sands weight
changes from 1,538 - 1842kg/m3 basing
on the grains size and composition. The
passing through of the fine aggregate in
4.75mm sieve having 2.68 special gravity
is usually used [7].
Cement
The cement which is normally used is the
Ordinary Portland Cement. The definition
of cement is as, the several organic
compounds used for adhering and
fastening of materials. The furnace blast is

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very necessary as they are used in
particular cement and it is known as
Portland slag cement. The colour of the
cement is greatly influenced by the
presence of iron oxide and in the event,
they were no impurities the cement would
retain its white colour. The cement in most
cases applied is the ordinary Portland
cement grade 53 [8].
Fly Ash
The kind of fly ash that is normally used is
called pozzocrete dirk 60 and the
specifications by a certain supplier are
tabled below. In the building of RCC the
use of fly ash has been a success in the
lowering of heat produced without loss of
strength, production of other fines to be
compacted and increasing strength that
average exceeding 180 days. Stages of
replacement of a primary class fly ash in
cementitious material vary from 30% to
75% solid volume of the cementitious
materials. In the proportioning of mixes,
one important fly ash role is to fill empty
spaces that could have been occupied by
the cement or water. The occupancy of the
void spaces by water would result in a
reduction in strength of the concrete [9].
Table 1
[10].
Superplasticizer
The kind of superplasticizer applied is
called Melamine Formaldehyde
Sulphonate. It is applied to have an
influence on the rheological nature of fresh
concrete. Generally, this is an additive to
the concrete and is applied for uniform
cement dispersion in the mix. Cement
agglomerates deflocculation is achieved in
this manner, thereby, releasing the
collected water from the grains of cement
for workability.
Typically, superplasticizer results to
increase of the slump without the adding
water. However, when the superplasticizer
is used to reduce the water content which
is used for mixing, it can reduce water to
almost 15 or 20%. Therefore, the cement
to water ratio would reduce averagely by a
similar amount. As a result, there is an
increase in strength also increase in other
characteristics such as density and water
tightness [11].
Polyvinyl Alcohol Fibres
PVA fibres have such an important
property whereby they are, reinforcement
composites for cementitious materials. It
has various suitable characteristics such as;
high bonding strength with the concrete
matrix, durability, high elasticity modulus
and high elasticity strength. PVA fibres
possess high strength and high elasticity
modulus of up to 25pa to 40pa as
compared to normal organic fibres that are
usually applied for reinforcement of
cement. Fibre can be enlarged to about
6%-10%. The tensile strength of fibre
varies from 880Mpa to1600Mpa. High
bonding strength with cement matrix is
one of the important characteristics of
PVA fibres [12].
Water
The making of concrete can be
accomplished with the use of drinking
water. Water should not have impurities

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which include; alkalis, vegetables and oil.
Soft water produces concrete that is
weaker. There are 2 major functions of
water when mixing concrete. One, cement
and water chemical reaction makes cement
paste, in that it holds inactive aggregates to
the point of cement paste hardening.
Lastly, water lubricates cement and fine
aggregate mixes [13].
Mixture design
Concrete proportioning
The initial mix proportioning was
1:8004:1.996; water to cementitious ratio
was 0.274, superplasticizer dose was
1040.47ml/bag and PVA fibre was 1%.
The proportion of the mix for the second
trial was 1:0.9:1.1 where water to
cementitious materials ratio was increased
to 0.3048, the superplasticizer dosage was
retained whereas PVA contents were
increased to 1.2%. The mixture
proportions for the third trial was 1:1:1
whereby superplasticizer dose was reduced
to 600ml/bag, the percentage of PVA was
retained at 1.2% and cementitious
materials to water ratio was 0.33. The mix
proportions for the fourth trial was
1:0.9:1.1, PVA percentage was 1.2%,
superplasticizer dosage was 600ml/bag and
the water to cementitious ratio was 0.3118.
In order to achieve workability, several
trials were done but for the proportioned
mixture of the fourth trial, the
superplasticizer dose was reduced so as to
attain workability. For each trial mix, 3
cubes were developed and cured using the
raised curing tank and later tested to attain
the desired strength requirement. After
cubes for each trial were tested, the trial
mix number three was considered the most
suitable hence the final proportion mix
[14].
ECC concrete casting procedure
Mixing affects the ECC performance.
Therefore, it means that better and proper
practice of mixing leads to the improved
and quality performance of the ECC
concrete. Homogeneity of the mix
composites also affects the quality of the
concrete. It is advisable to mix the
concrete properly in order to attain the
strength desired and for better bonding of
the cement of the cement and PVA fibres.
Mixing is done using a hand mixer. The
procedure of hand mixing is as follows:
put cement, 50% fly ash, sand, water
amounting to 50% and superplasticizer.
Then slowly add the remaining fly ash
amount, water and plasticizer. After the
homogenous fed of the mixture, add
slowly the PVA fibres and mix all the
components till fibres are uniformly mixed
in the matrix [15].
Placing, compaction and casting of
concrete specimens
Before placement of the concrete, oiling is
done first to allow concrete specimens to
strip easily. Keenness must be observed
when oiling to prevent concrete staining
the mould. After performing the ECC test
on workability, fresh concrete would be
put in concrete moulds for the hardened
properties test. Tamping is done after the
placement of the fresh concrete into
concrete moulds using a tamping rod to
lower honeycombing [16]. Vibrations
using a table vibrator are done after the
fresh concrete has been placed into
moulds. This helps in full compaction of
the fresh concrete where the entrained void
spaces present are removed. Levelling of
the concrete is therefore done on the
surface of the concrete, this is the initial
operation done by compaction and
placement of the concrete. Concrete in the
moulds is left overnight so as for the fresh
concrete to set [17].
Curing
After setting, the specimens of the
concrete were removed. The specimens of
concrete were identified and then placed
into curing tank after twenty-four hours at
250 0 C. Curing is helped in protecting of
the concrete specimens from losing
moisture while it gains the desired. After

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28 days of curing, the concrete specimen
the taken out of the curing tank for
hardened property test of the ECC to be
done [18].
Comparison to other composite materials
property ECC Normal concrete
Earthquake resistance The concrete is flexible thus
resistant to failure or
fracture during earthquakes.
The buildings are
vulnerable to earthquakes
and can fracture or collapse
easily during earthquakes.
durability The structures are more
flexible and durable.
The structures have less
flexibility and durability.
Self-healing property Contains a greater property
of self-curing because the
small cracks are self-healed
through water and carbon
dioxide reactions.
Has less self-curing feature
because the free cement
concrete is reduced.
Maintenance and repair Has a reduced maintenance
and repair costs because of
the reduced crack
formations.
Has high maintenance and
repair costs because of the
fractures and defect
formations
TimeLine
Conclusion
Even though the ordinary Portland cement
is expensive, it is the crucial ingredient in
concrete mix development. It is sad that
production of cement involves emission of
carbon dioxide into the atmosphere in
large amounts which greatly results in
greenhouse effects and global warming.
However, cement cannot be replaced by
another material or be avoided. Numerous
research about ECC and its uses has
proved to be the appropriate and a material
to replace concrete in future. Curing is

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essential as it protects the concrete from
moisture loss and helps it to achieve the
desired strength. The process of vibration
allows complete compaction of fresh
concrete thus removing empty spaces
present in the concrete.

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