self curing and self compacted concrete
description
Transcript of self curing and self compacted concrete
DEVELOPMENT OF SELF CURING SELF COMPACTED CONCRETE
By
VEKARIYA SANKETKUMAR M(120070720006)
PROF. NANAK J. PAMNANIPrinciapal,
H.b.patelpolytehnic,Limbodara,
Lunawada, (dist. Mahisagar)
DR. DARSHANA R. BHATTAssociate professor,
Department of structural engineeringBvm engineering college, vvn
A Dissertation Phase-I (730003) Submitted toGujarat Technological University
In Partial Fulfillment of the Requirements forThe Degree of Master of Engineering
In Structural Engineering
December 2013
BIRLA VISHVAKARMA MAHAVIDYALAYA ENGINEERING COLLEGEVALLABH VIDYANAGAR
I
CERTIFICATE
This is to certify that research work embodied in this dissertation entitled “DEVELOPMENT OF SELF CURING SELF COMPACTED CONCRETE” was carried out by Mr. VEKARIYA SANKETKUMAR M (120070720006) at Birla Vishvakarma Mahavidyalaya (BVM) Engineering College for Dissertation Phase-I (730003) of M.E Structural Engineering. This research work has been carried out under our supervision and is to our satisfaction.
Date:
Place:
Signature of Guide Signature of Co-Guide
(PROF. NANAK J PAMNANI) (DR. DARSHANA R. BHATT)
II
ACKNOWLEDGEMENT
With great pleasure & deep sense gratitude I would like to extent out sincere thanks to
almighty GODfor his peace and blessings for granting me the chance and the ability to
successfully complete this study.
I would like to take this opportunity to thank my guidesPROF. NANAK J
PAMNANI,princiapal, h.b.patelpolytehnic, limbodara, lunawada, (dist. mahisagar). DR.
DARSHANA R. BHATT,associate professor,department of structural engineering, Birla
VishvakarmaMahavidyalayaEngineering College, VallabhVidyanagar, Whose timely and
persistent guidance has played a key role in making my dissertation a success.
I express sincere thanks to DR.F.S.UMRIGAR, Principal, Birla
VishvakarmaMahavidyalayaEngineering College, VallabhVidyanagar andPROF. A.K.VERMA,
Associate Professor and Head, Structural Engineering, Birla
VishvakarmaMahavidyalayaEngineering College, VallabhVidyanagar for giving us an
opportunity to undertake this research study.
Special thanks to MY FAMILY members for their everlasting love and financial support
throughout my numerous academic years. Without their support, I would not have been
able to accomplish my dreams.
I would also like to thank all MY FRIENDS who have directly or indirectly provided their
unerring support throughout the course of this dissertation work, without whom none of
this would have been possible.
VEKARIYA SANKETKUMAR MANSUKHBHAI
M.E. STRUCTURAL ENGINEERING
ENROLLMENT NO: 120070720006
III
TABLE OF CONTENTS
TITLE PAGE …I
CERTIFICATE …
II
ACKNOWLEDGEMENT …
III
TABLE OF CONTENTS …
IV
LIST OF FIGURES …
VI
LIST OF TABLES …
VII
Chapter 1: INTRODUCTION …1
1.1 General …2
1.2 Need for study …3
1.3 Objective …3
1.4 Scope of work …3
1.5 Study pattern and resources …4
Chapter 2: LITERATURE REVIEW …5
2.1
2.2
2.2.1 V-funnel Test
2.2.2 Slump Test
IV
TABLE OF FIGURE
Figure 2.1 …7
Figure 2.2 …8
Figure 2.3 …9
Figure 2.4 …
10
Figure 2.5 …
12
Figure 2.6 …
12
Figure 2.7 …
17
VI
CHAPTER 1
INTRODUCTION1.1 GENERAL
Self-compacting concrete (SCC), which flows under its own weight and does not
require any external vibration for compaction, has revolutionized concrete placement.
Adequate curing is essential for concrete to obtain structural and durability properties
and therefore is one of the most important requirements for optimum concrete
performance in any environment or application. Curing of concrete is the process of
maintaining the proper moisture conditions to promote optimum cement hydration
immediately after placement
Enough water needs to be present in a concrete mix for the hydration of cement to
take place. However, even mix contains enough water, any loss of moisture from the
concrete will reduce the initial water cement ratio and result in incomplete hydration
of cement especially with the mixes having low water cement ratio. This results in
very poor quality of concrete. When the concrete is exposed, water evaporates from
its surface. Evaporation from the freshly placed concrete results in plastic shrinkage
cracking. The poor surface characteristics lead to high permeability on the surface of
concrete which increases the risk of carbonation and heightens the susceptibility of
corrosion to the steel.
Curing techniques and curing duration significantly affect curing efficiency.
According to Gowripalan (JUNE- 2012) , the mechanism of self curing can be
explained as follows:
“Continuous evaporation of moisture takes place from an exposed surface due
to the difference in chemical potentials (free energy) between the vapour and liquid
phases. The polymer added in the mix mainly form hydrogen bonds with water
molecules and reduce the chemical potential of the molecules which in turn reduces
the vapour pressure. Physical moisture retention also occurs. This reduces the rate of
evaporation from the surface”
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 1
1.2 CHARACTERISTICS OF SELF-CURING CONCRETE
Today concrete is most widely used construction material due to its good
compressive strength and durability. Plain concrete needs an atmosphere by providing
moisture for a minimum period of 28 days for good hydration and to attain desired
strength.
The present study involves the use of shrinkage reducing admixture
polyethylene glycol (PEG 400) in concrete which helps in self curing and helps in
better hydration and hence strength.
It was also found that 1% of PEG 400 by weight of cement was optimum for
M20, while 0.5 % was optimum for M40 grade concretes for achieving maximum
strength without compromising workability.
Defination :
Self-curing or internal curing is a technique that can be used to provide
additional moisture in concrete for more effective hydration of cement and
reduced self-desiccation.
Methods of self curing :
Currently, there are two major methods available for internal curing of concrete.
1. Saturated porous lightweight aggregate (LWA) in order to supply an
internal source of water, which can replace the water consumed by chemical
shrinkage during cement hydration.
2. Poly-ethylene glycol (PEG) which reduces the evaporation of water from
the surface of concrete and also helps in water retention.
Mechanism of Internal Curing:
Continuous evaporation of moisture takes place from an exposed
surface due to the difference in chemical potentials (free energy) between the
vapour and liquid phases. The polymers added in the mix mainly form
hydrogen bonds with water molecules and reduce the chemical potential of the
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 2
molecules which in turn reduces the vapour pressure, thus reducing the rate of
evaporation from the surface.
Potential Materials for Internal Curing (IC) :
a) Lightweight Aggregate (natural and synthetic, expanded shale)
b) Super-absorbent Polymers (SAP) (60-300 nm size)
c) SRA (Shrinkage Reducing Admixture) (propylene glycol type i.e.
polyethylene-glycol)
Advantages of Internal Curing :
a) Internal curing (IC) is a method to provide the water to hydrate all the cement,
accomplishing what the mixing water alone cannot do.
b) Provides water to keep the relative humidity (RH) high.
c) Eliminates largely autogenous shrinkage.
Maintains the strengths of mortar/concrete at the early age (12 to 72 hrs.) above the
level where internally & externally induced strains can cause cracking.
Can make up for some of the deficiencies of external curing, both human related
(critical period when curing is required in the first 12 to 72 hours) and hydration.
1.3 NEED FOR STUDY
Proper Curing for freshly placed concrete is required and in general practice
many times concrete does not get proper water for the process of hydration.
Hence, internal curing with different method if achieved than it is very
effective.
As same way proper vibration during placing of concrete in beam and in other
formwork can not done properly
And it leads to the improper casting of concrete in beam and in other
formwork
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 3
Hence, if both self curing, self compacting properties if achieved than this
problem can be solved easily and its comes out very effective.
In general, a newly placed concrete is compacted by vibrating
equipment to remove the entrapped air, thus making it dense and homogeneous;
Compaction is the key to producing good concrete with optimum strength and
durability but while we use Admixtures compaction is eliminated, the internal
segregation between solid particles and the surrounding liquid is avoided which
results in less poroustransition zones between paste and aggregate &a more even
colour of the concrete also it's Improved strength, durability and finish of SCC can
therefore be anticipated.
1.4 OBJECTIVE
Finding out appropriate chemical compound for self curing
Development of mix design for medium strength SCC
Development of self curing, self compacted concrete
Mix design for medium strength NVC
Development of mix design for self compacted NVC
Finalization of optimum dosage for self curing properties in SCC & NVC
Find out optimum dosage of chemical compound for self curing
1.5 SCOPE OF WORK
Identify appropriate admixtures and its proportion to achieve pumpability and
self compatibility of concrete.
Mix-design for M30 & M50 grade Self Compacted Concrete (SCC).
To study effect of extreme weather condition curing on various properties of
fresh and hardened Self Compacted Concrete (SCC).
To identify best curing condition for Self-curing of SCC.
1.6 STUDY PATTERN & RESOURCE
Literature review
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 4
Literature pertaining to self curing, self-compacting concrete will be
reviewed from published papers of journals and codes practice.
Data collection
Data will be collected by for identifying appropriate admixtures for
self curing and self compacting concrete. And than by using different
proportion of different self curing compound and after that compressive
strength of different proportion will be calculated.
Data analysis
Based on the data collected during literature review and practical, we
will be able to find out optimum ratio of different chemical admixture used for
self curing in self compacting concrete.
Conclusions
Based on the analysis relevant conclusions will be made and scope for
the future work will be suggested.
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 5
CHAPTER 2
LITERATURE REVIEW
Y.B. Raghavendra, M.U. Aswath (JUNE- 2012)[1] : give research on experimental
investigation on concrete cured with various curing methods and From the results of
the investigation, it can be concluded that the concrete cured with self curing
compound and membrane curing compound have an efficiency of 92.5% and 90%
respectively when compared to conventionally cured standard water curing method
whereas Non standard water curing and air curing method have an efficiency of 75%
and 70% respectively when compared to Standard water curing method. Therefore
non standard water curing and air curing methods has to be avoided at the
construction sites otherwise which may leads to loss in strength of concrete. Hence
curing of concrete with self curing compound and membrane curing can be adopted
efficiently where ‘performance specifications’ are important than ‘prescriptive
specifications’ for concrete. Self curing method of curing is most suitable for concrete
at inaccessible areas of the structure like high rise buildings especially columns.
AGGARWAL Paratibha, SIDDIQUE Rafat, AGGARWAL Yogesh (June 2008)[2] :
give
Procedure for Mix Design of Self-Compacting Concrete and conclude that
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1. At the water/powder ratio of 1.180 to 1.215, slump flow test, V-funnel test and L-
box test results were found to be satisfactory, i.e. passing ability, filling ability and
segregation resistance are well within the limits.
2. SCC could be developed without using VMA as was done in this study.
3. The SCC1 to SCC5 mixes can be easily used as medium strength SCC mixes,
which are useful for most of the constructions; the proportions for SCC3 mix
satisfying all the properties of Self-Compacting Concrete can be easily used for the
development of medium strength self compacting and for further study.
4. By using the OPC 43 grade, normal strength of 25 MPa to 33 MPa at 28-days was
obtained, keeping the cement content around 350 kg/m3 to 414 kg/m3. As SCC
technology is now being adopted in many countries throughout the world, in absence
of suitable standardized test methods it is necessary to examine the existing test
methods and identify or, when necessary to develop test methods suitable for
acceptance as International Standards. Such test methods have to be capable of a
rapid and reliable assessment of key properties of fresh SCC on a construction site. At
the same time, testing equipment should be reliable, easily portable and inexpensive.
A single operator should carry out the test procedure and the test results have to be
interpreted with a minimum of training. In addition, the results have to be defined and
specify different SCC mixes. One primary application of these test methods would be
in verification of compliance on sites and in concrete production plants, if self-
compacting concrete is to be manufactured in large quantities.
M.V.Jagannadha Kumar, M.Srikanth, Dr.K.Jagannadha Rao(SEP 2012)[3] :
give
strength characteristics of self-curing concrete and from the experiments and test
results i found that The optimum dosage of PEG400 for maximum strengths
(compressive, tensile and modulus of rupture) was found to be 1% for M20 and 0.5%
for M40 grades of concrete. As percentage of PEG400 increased slump increased for
both M20 and M40 grades of concrete. Strength of self curing concrete is on par with
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 7
conventional concrete. Self curing concrete is the answer to many problems faced
due to lack of proper curing.
A.Aielstein Rozario, Dr.C.Freeda Christy (April – 2013)[4] : gives Experimental
Studies on Effects of Sulphate Resistance on Self-Curing Concrete and from this it
came to know that The permeability of concrete decreases with increase in the
replacement of fly ash with cement and in addition of P.E.G dosages. So the
penetration of chemicals is decreased with the addition of PEG and the concrete is
safe against sulphates. The percentage of weight loss of the concrete specimens are
also decreased for every grades of concrete. From the results, we know that the
selfcuring concrete has the ability to resist the sulphates present in the soils and in the
sea waters. It is very economical also, So it can be adoptable for the constructions.
C. Selvamony, M. S. Ravikumar (March 2010) [5] : investigations on self-
compacted self-curing concrete using limestone powder and clinkers and From the
experimental investigation, it was observed that both admixtures affected the
workability of SCC adversely. A maximum of 8% of lime stone powder with silica
fume, 30% of quarry dust and 14 % of clinkers was able to be used as a mineral
admixture without affecting the self compactability. Silica fume was observed to
improve the mechanical properties of SCC, while lime stone powder along with
quarry dust affected mechanical properties of SCC adversely.
C. Chella Gifta, S. Prabavathy and G. Yuvaraj Kumar[6] : study on internal curing of
high performance concrete using super absorbent polymers and light weight
aggregates and Based on the results of these investigations the following conclusions
can be drawn.
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 8
(i) The internal cured specimens are proved to better than conventional cured
specimens
in all means.
(ii) The addition of internal curing agent increases the degree of hydration, producing
a
denser microstructure leading to better results.
(iii) Compressive strength results reveals that compressive strength of internal cured
specimens at 7days and 28 days are greater but at the age of 3 days the strength is
lower than
conventionally cured specimens. SAP specimens shows a significant improvement of
about
6.88 % increase in compressive strength and LWA specimens are found to be 12.35%
on 28
days compressive strength than the control concrete mix. Hence ,the incorporation of
Internal Curing components in high performance concrete by means of LWA has
proven to
be effective than internal cured HPC using SAP with respect to strength.
(vi) The durability studies have showed that internal curing by means of SAP has less
chloride penetration than internal cured specimens using LWA.
(vii) The RCPT value for the control mix was 783 coulombs which was greater than
both
the internal cured specimens, while the mix using SAP had lower RCPT value of 483
coulombs which proved to be the best.
(viii) The coefficient of permeability of mix M2 was 13.68 x10-12 m/sec which was
lesser than all the other mixes. Lesser the coefficient of permeability betters the
results.
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 9
Fareed Ahmed Memon, Muhd Fadhil Nuruddin (2011) [7] : studied Effect of
Curing Conditions on Strength of Fly ash-based Self-Compacting Geopolymer
Concrete
In this experimental work, the effect of curing conditions on the compressive strength
of fly ash-based self compacting geopolymer concrete was investigated. Test results
indicate that curing time and curing temperature significantly affect the compressive
strength of hardened concrete. Based on the test results reported here, the following
conclusions can be drawn.
1. Longer curing time improves the geopolymerisation process resulting in higher
compressive strength. Increase in compressive strength was observed with increase in
curing time. The compressive strength was highest when the specimens were cured
for a period of 96 hours; however, the increase in strength after 48 hours was not
significant.
2. Compressive strength of concrete increased with the increase in curing temperature
from 60°C to 70°C; however an increase in the curing temperature beyond 70°C
decreased the compressive strength of selfcompacting geopolymer concrete.
A.M.M. Sheinn, C.T. Tam (August 2004)[8] : done comparative study on hardened
properties of selfcompacting concrete (scc) with normal slump concrete (nsc)
Through the investigations and comparisons between Self-compacting Concrete
(SCC) and
Normal Slump Concrete (NSC) in this study, the following observations and
concluding remarks can
be made.
a) With similar water/cement ratios and coarse aggregate content, SCC and NSC can
be
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 10
expected to have similar mechanical properties.
b) Incorporation of fine filler could reduce the porosity in the concrete through the
filling
effect and subsequently improve the interfacial zone properties. Thus the concrete of
similar compressive strength, the splitting tensile strength of SCC is possible to be
higher than that of normal concrete.
c) Drying shrinkage and creep deformations of SCC are similar to that of normal
slump
concrete if both types of concrete are of similar compressive strength level.
d) With similar mix proportions and strength level, there is no Significant difference
in
mechanical properties and long-term deformation between SCC and NC. Thus,
existing structural design code for normal slump concrete can be used to design the
structural applications of SCC.
M. M. Rahman, M. H. Rashid, M. A. Hossain, F. S. Adrita (AUGUST 2011)[9] :
have done research on mixing time effects on properties of self compacting concrete
and This work gives attention to an effect, which affects the performance of SCC mix
adversely and hence, its hardened properties also. This effect is the time delay or the
time elapsed during the mixing process.
As soon as water applied to the cement, chemical reaction starts simultaneously
between them. During long mixing time of SCC, some portion of water are used in
the hydration of cement and some portion of water evaporate to the atmosphere and
that’s why, amount of added water is increased with long mixing time for maintaining
constant workability.
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 11
After adding water for maintaining constant flowability, the amount of water/cement
ratio increases in SCC for prolonged mixing time, which affects the cohesion among
the constituents of concrete. So, compressive and tensile strength of SCC decreases
with this water quantity.
With long mixing time of concrete, the pores in concrete are increased. That is why
the water absorption and the chloride ion permeability increase with increase in
mixing time.
Martin Hunger; H.J.H. Brouwers [10] : give research on Development of Self-
Compacting Eco-Concrete.
In this study a new design tool for SCC based on the controlled grading of the entire
solid mix was introduced. It has been shown that grading has a fundamental effect on
both fresh and hardened concrete properties. Here an improvement of various
parameters was found for mixes with low cement contents and decreasing values of
the distribution modulus q. Only viscosity was affected by too low q values. An
optimum in regard to the workability was found for 0.30 < q < 0.35. Furthermore the
mechanical and porosity parameters were strongly enhanced by optimized packing.
Dense packed granular blends showed good workability since less void fraction had to
be filled with water and on the other hand also high strength values due to a dense
packed granular skeleton. In this connection a raise of the compressive strength of
more than 60 % in average based on the introduced cement efficiency was registered.
Furthermore it was shown that broad grain size distributions with as many
overlapping fractions as possible (within the bounds of practical possibility) and
intermediate fractions (e.g. gravel 2-8) result in good packed mixes. The application
of a broadly graded unwashed sand 0-4 (so including the fines) of broken granite also
proved promising. On the basis of sound indirect parameters of durability as well as
on the compressive strength the minimum cement contents required by the standards
seem to be a little outdated. The same applies for the water cement ratio for which it is
recommended to replace it by a water/powder ratio. All these observations strongly
suggest a change from the present prescriptive.
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 12
CONCLUSIONS FROM LITERATURE REVIEW
a) The proportions for SCC mix satisfying all the properties of Self-Compacting
Concrete can be easily used for the development of medium strength self-
compacting.
b) There are many methods for self curing among that use of chemical
compound is very effective
c) For self curing widely used methods include use of Light Weight Aggregate
(LWA), and Poly-ethylene glycol
d) Silica fume was observed to improve the mechanical properties of SCC
e) The selfcuring concrete has the ability to resist the sulphates present in the
soils and in the sea waters.
f) SCC has a significant contribution in shrinkage reduction, enhancing
durability and hence improving overall concrete performance.
CHAPTER 3
MATERIALS USED IN EXPERIMENT
3.1 INTRODUCTION:
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 13
In this chapter include information about materials used for development of
self curing, self compacting concrete
3.2 MATERIALS USED IN CONCRETE:
Concrete is a homogeneous mixture of cement, coarse aggregate, fine aggregate and
water and admixtures
3.3 CEMENT(IS: 8112 – 1989)
In the most general sense of the word, cement is a binder, a substance
that sets and hardens independently, and can bind other materials together. The most
important use of cement is the production of mortar and Concrete the bonding of
natural or artificial aggregates to form a strong building material that is durable in the
face of normal environmental effects. Concrete should not be confused with cement,
cement
aggregate
admixture & construction
chemicalwater
fly ash
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 14
because the term cement refers to the material used to bind the aggregate materials of
concrete. Concrete is a combination of cement, aggregate and water.
Cement is a powder manufactured from limestone that is mixed with
other aggregates, notably sands, gravels and stone, to produce mortars and concretes.
The vast majority of cement used in the India is Portland Cement, sometimes referred
to as Ordinary Portland cement or OPC, although there are also specialist cements,
such as Sulphate-Resistant Cement (SRC) which is often used for sub-surface works,
and High-Alumina Cement (HAC).
3.3.1 ORDINARY PORTLAND CEMENT (OPC) (IS 269: 1976)
Portland cement is the most common type of cement in general usage. It is a basic
ingredient of concrete, mortar and plaster. English masonry worker Joseph Aspdin
patented Portland cement in 1824; it was named because of its similarity in colour to
Portland limestone, quarried from the English Isle of Portland and used extensively in
London architecture. It consists of a mixture of oxides of calcium, silicon and
aluminium. Portland cement and similar materials are made by heating limestone (a
source of calcium) with clay and grinding this product (called clinker) with a source
of sulfate (most commonly gypsum).The Ordinary Portland Cement of 53 grade
conforming to IS: 8112 is be use.
FIG 4.1, Sanghi Cement (OPC 53 GRADE)
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 15
Table-4.1 Physical Properties of Portland cement
PROPERTY VALUE IS CODE IS : 8112 - 1989
Specific Gravity 3.15 3.10-3.15
Consistency 28% 30-35
Initial setting time 35min 30min minimum
Final setting time 178min 600min maximum
Compressive strength at 7 days N/mm2 38.49 N/mm2 43 N/mm2
Compressive strength at 28 days N/mm2 52.31 N/mm2 53 N/mm2
Table-4.2 Chemical Properties of Portland cement
OXIDE CONTENT By %
Lime CaO 60-67
Silica SiO2 17-25
Alumina Al2O3 3-8
Iron Oxide Fe2O3 0.5-0.6
Magnesia MgO 0.5-4
Alkaline K2O, Na2O 0.3-1.2
Sulphates SO3 1.0-3.0
Source: SICART lab, V.V.N
3.4 AGGREGATE
The aggregates normally used for concrete are natural deposits of sand
and gravel, where available. In some localities, the deposits are hard to obtain and
larger rocks must be crushed to form the aggregate. Crushed aggregate usually costs
more to produce and will require more cement paste because of its shape. More care
must be used in handling crushed aggregate to prevent poor mixtures and improper
dispersion of the sizes through the finished concrete. At times, artificial aggregates,
such as blast-furnace slag or specially burned clay are used.
TYPES OFAGGREGATE — Aggregates are divided into two types as
follows:
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 16
3.4.1 FINE AGGREGATE (SAND) (IS: 383-1970)
Sand is a naturally occurring granular material composed of finely
divided rock and mineral particles. The composition of sand is highly variable,
depending on the local rock sources and conditions, but the most common constituent
of sand is silica (silicon dioxide, or SiO2), usually in the form of quartz.
TABLE 4.3 Properties of Sand or fine Aggregate
Sr.no Particulars Value of Sand
1 Source Bodeli, Gujarat
2 Zone Zone II
3 Specific Gravity 2.55
4 Fineness Modulus 2.87
5 Bulk Density 1776.29 kg/m3
6 Colour Yellowish White
3.4.1.1 USES
Concrete: Sand is often a principal component of this critical construction
material.
Brick: Manufacturing plants add sand to a mixture of clay and other materials
for manufacturing brick.
Mortar: Sand is mixed with cement and sometimes lime to be used in masonry
construction.
Glass: Sand is the principal component in common glass.
Aggregate
FineSand
below 4.75mm
CourseGrit
4.75mm to 12.5mm
Gravel12.5mm to 20mm
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 17
Landscaping: Sand makes small hills and slopes (for example, in golf
courses).
Paint: Mixing sand with paint produces a textured finish for walls and ceilings
or non-slip floor surfaces.
Railroads: Train operators use sand to improve the traction of wheels on the
rails.
Roads: Sand improves traction (and thus traffic safety) in icy or snowy
conditions.
3.4.2 COURSE AGGREGATE
As a basic raw material aggregates can be put to many uses, although
certain tasks may require a specific type of aggregate.
The largest proportion of the primary aggregate was used to manufacture concrete
(36%), with a further 10% used to manufacture the cement that is also used in the
concrete. Used in roads was the second largest category (26%), while 20% of
aggregates were used in other construction uses & fills and another 2% were used for
railway ballast.
Aggregates are the most mined material in the world. Aggregates are a component of
composite materials such as concrete and asphalt concrete; the aggregate serves as
reinforcement to add strength to the overall composite material. Due to the relatively
high hydraulic conductivity value as compared to most soils, aggregates are widely
used in drainage applications such as foundation and French drains, septic drain
fields, retaining wall drains, and road side edge drains.
Aggregates are also used as base material under foundations, roads, and
railroads. In other words, aggregates are used as a stable foundation or road/rail base
with predictable, uniform properties (e.g. to help prevent differential settling under the
road or building), or as a low-cost extender that binds with more expensive cement or
asphalt to form concrete.
3.4.2.1 COURSEAGGREGATE (GRIT) (IS: 383)
Another granular material that can be thought of as a transition stage between a coarse
sand and small pebbles. Generally 4.75mm-12.5mm in size, grit has limited uses in
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 18
the construction industry on its own, other than as a surface dressing. However, over
recent years with the development in block paving specifications, it has become a
viable alternative bedding material for permeable paving and other forms of elemental
paving used in areas of high water ingress.
TABLE 4.4 Properties of Grit or Course Aggregate
Sr.no Particulars Value of Sand
1 Source Sevalia, Gujarat
2 Specific Gravity 2.75
3 Fineness Modulus 5.76
4 Bulk Density 1764.14 kg/m3
5 Colour Greyish Black
3.4.2.2 COURSEAGGREGATE (GRAVEL) (IS: 383 – 1989)
A granular material which can be of almost any rock type. It is usually
between 60mm and 2mm in size which may be rounded, if from a marine or fluvial
source, or angular if a quarried and crushed product. Gravels are sold in mixed sizes,
e.g. 20-5mm or closely graded to a specific size, such as 10mm.
The advent of modern blasting methods enabled the development of quarries,
which are now used throughout the world, wherever competent bedrock deposits of
aggregate quality exist. In many places, good limestone, granite, marble or other
quality stone bedrock deposits do not exist. In these areas, natural sand and gravel
are mined for use as aggregate. Where neither stone, nor sand and gravel, are
available, construction demand is usually satisfied by shipping in aggregate by
rail, barge or truck. Additionally, demand for aggregates can be partially satisfied
through the use of slag and recycled concrete. However, the available tonnages and
lesser quality of these materials prevent them from being a viable replacement for
mined aggregates on a large scale.
TABLE 4.5 Properties of Gravel or Course Aggregate
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 19
Sr.no Particulars Value of Sand
1 Source Sevalia, Gujarat
2 Specific Gravity 2.65
3 Fineness Modulus 7.73
4 Bulk Density 1624.88 kg/m3
5 Colour Greyish Black
3.5 FLY ASH
The Fly Ash story begins 2000 years ago...
When the Romans built the Colosseum in the year 100 A.D. - that still
stands the test of time!!
The ash generated from Volcanoes was used extensively in the
construction of Roman structures. Colosseum is a classic example of
durability achieved by using volcanic ash. The building constructed 2000
years ago and still standing today!
Only difference is, Fly Ash is generated in artificial volcanoes - non
other than coal fired.
TABLE 4.6 Physical Properties of fly ash “CLASS C”
Sr.no Physical Properties Test Result
1 Colour Grey
2 Specific Gravity 2.13
Source: SICART lab, V.V.N
3.5.1 So what is so special in fly ash that makes our concrete so durable?
Fly ash has a high amount of silica and alumina in a reactive form.
These reactive elements complement hydration chemistry of cement. Let us
take a quick tour through this exciting world of hydration chemistry.
When cement reacts with water, we say that hydration of cement has
begun.
On hydration, cement produces C-S-H Gel.
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 20
This C-S-H Gel binds the aggregates together and strengthens our concrete!
However, one more compound is produced on hydration that is so
different in behaviour. It is non-other than the Calcium Hydroxide Ca(OH)2.
In our construction industry, it is generally referred to as Free Lime.
Aggressive environmental agents like water, sulphates,CO2 attack this
free lime leading to deterioration of the concrete.
3.5.2 FROM MASS CONCRETE TO MASS APPLICATIONS
In the beginning of the twentieth century, fly ash was used only for the
mass concrete applications—to delay the heat of hydration. However, in the
early 80’s, with the advent of the high strength cements, the undesirable side
effects of free lime started surfacing.
TABLE 4.7Chemical Properties of fly ash “CLASS C”
Sr. No Constituents Weight % by
1 Loss on ignition 4.17
2 Silica (SiO2) 69.40
3 Iron Oxide (Fe2O3) 3.44
4 Alumina (Al2O3) 28.20
5 Calcium Oxide (CaO)
2.23
6 Magnesium Oxide (MgO)
1.45
7 Total Sulphur (SO3) 0.165
8 Insoluble residue -
9ALKALIES
Sodium Oxide (Na2O)
Potassium Oxide (K2O)
0.581.26
Source: SICART lab, V.V.N
3.5.3 IS FREE LIME REALLY BAD FOR CONCRETE?
No a certain amount of free lime is necessary to keep our concrete
alkaline.
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 21
The problem arises when our new generation - 53 grades - cements
produce excessive lime which leads to the deterioration of concrete,
leading to corrosion.
The cement technologists observed that the reactive elements present
in fly ash convert the problematic free lime into the beneficial C-H-S Gel.
Ca(OH)2 + SiO2 => C-S-H Gel
Ca(OH)2 + Al2O3 = C-Al-H Gel
OR
Problem + Fly Ash => Durable Concrete
The analysis on fly ash production from coal based thermal power
stations indicates that 82 power stations, as of today, produce about 175
million tons per year by 2012 A.D. with 15% annual rise in the thermal power
generation slated for the decade.
In India, it is estimated that 125-145 million tons of fly ash is
generated by 70 major thermal power plants of which only 6-10 % is utilized
by cement, construction and road industries.
3.5.4 WHAT MAKES FLY ASH SO DURABLE?
Fly ash has a high amount of silica and alumina in a reactive form.
These reactive elements complement hydration chemistry of cement.
Hydration chemistry of Cement: When cement reacts with water, the
hydration of cement begins. On hydration, cement produces C-S-H Gel. This
C-S-H Gel binds the aggregates together and strengthens the concrete.
However, one more compound is produced on hydration that is so different in
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 22
behaviour. It is none other than the Calcium Hydroxide Ca(OH)2. In
construction industry, it is generally referred to as Free Lime. Aggressive
environmental agents like water, sulphates, CO2 attack this free lime leading to
deterioration of the concrete.
It is not only the chemistry provided by fly ash that compliments
chemistry of cement, but also the physical properties of fly ash improve the
rheology and microstructure of concrete by a great extent. Fly ash, on itself,
cannot react with water, it needs free lime, produced on hydration of Portland
cement, to trigger off its Pozzolanic effect. Once it is triggered, it can go on
and on. In simple words, it means a much longer life for concrete structure.
Specific benchmarks have been set up to evaluate the performance of
concrete with respect to durability - mainly Strength and Permeability. This
means to produce a durable and long lasting concrete, it must possess: High
strength and Low permeability.
3.5.6 Fly ash makes concrete denser, and hence less permeable, mainly
by:
Reducing water demand in concrete
Improving microstructure of concrete
At the same time, fly ash improves long term strength of concrete due
to the continued Pozzolanic reaction as discussed earlier.
3.5.7 BENEFITS OF USING FLY ASH
It delays the heat of hydration and hence reduces the thermal cracks
in concrete.
It improves the workability of concrete.
It makes the mix homogeneous and hence reduces segregation and
bleeding.
The concrete finish is improved due to perfectly spherical fly ash
particles.
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 23
The concrete permeability is substantially reduced which enhances
the life of the structure.
Fly ash contributes to the long term strength in concrete.
3.6 ADMIXTURES
GENERAL: Admixture is defined as a material, other than cement, water and
aggregates, which is used as an ingredient of concrete and is added to the
batch immediately before or during mixing. Additive is a material which is
added at the time of grinding cement clinker at the cement factory.
Plasticizer
Superplasticizer
Retarders and Retarding Plasticizers
Accelerators and Accelerating Plasticizer
Air-entraining Admixtures
Damp-proofing and Waterproofing Admixtures
Gas forming Admixture
Workability Admixture
Grouting Admixture
Bonding Admixture
Colouring Admixture
3.6.1 PLASTICIZER
Requirement of right workability is the essence of good concrete.
Concrete in different situations require different degree of workability. A high
degree of workability is required in situations like deep beams, thin walls of
water retaining structures with high percentage of steel reinforcement, column
and beam junctions, tremie concreting,pumping of concrete, hot weather
concreting, for concrete to be conveyed for considerable distance and in ready
mixed concrete industries. The conventional methods followed for obtaining
high workability is by improving the gradation, or by the use of relatively
higher percentage of fine aggregate or by increasing the cement content. There
are difficulties and limitations to obtain high workability in the field for a
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 24
given set of conditions. The easy method generally followed at the site in most
of the conditions is to use extra water unmindful of the harm it can do to the
strength and durability of concrete.
The harmful effect of using extra water than necessary. It is an abuse, a
criminal act, and unengineering to use too much water than necessary in
concrete. At the same time, one must admit that getting required workability
for the job in hand with set conditions and available materials is essential and
is often difficult. Therefore, engineers at the site are generally placed in
conflicting situations. Often he follows the easiest path and that is adding extra
water to fluidise the mix. This addition of extra water to satisfy the need for
workable concrete is amounting to sowing the seed of cancer in concrete.
Today we have plasticizers and superplasticizers to help an engineer
placed in intriguing situations. These plasticizers can help the difficult
conditions for obtaining higher workability without using excess of water. One
must remember that addition of excess water, will only improve the fluidity or
the consistency but not the workability of concrete.
The excess water will not improve the inherent good qualities such as
homogeneity and cohesiveness of the mix which reduces the tendency for
segregation and bleeding. Whereas the plasticized concrete will improve the
desirable qualities demanded of plastic concrete. The practice all over the
world now is to use plasticizer or superplasticizer for almost all the reinforced
concrete and even for mass concrete to reduce the water requirement for
making concrete of higher workability or flowing concrete. The use of
superplasticizer has become almost an universal practice to reduce
water/cement ratio for the given workability, which naturally increases the
strength. Moreover, the reduction in water/cement ratio improves the
durability of concrete. Sometimes the use of plasticizers is employed to reduce
the cement content and heat of hydration in mass concrete.
The organic substances or combinations of organic and inorganic
substances, which allow a reduction in water content for the given workability,
or give a higher workability at the same water content, are termed as
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 25
plasticizing admixtures. The advantages are considerable in both cases : in the
former, concretes are stronger, and in the latter they are more workable.
3.6.1.1 THE BASIC PRODUCTS CONSTITUTING PLASTICIZERS:
(i) Anionic surfactants such as lignosulphonates and their modifications
and
derivatives, salts of sulphonates hydrocarbons.
(ii) Nonionic surfactants, such as polyglycol esters, acid of hydroxylated
carboxylic
acids and their modifications and derivatives.
(iii) Other products, such as carbohydrates etc.
Among these, calcium, sodium and ammonium lignosulphonates are
the most used. Plasticizers are used in the amount of 0.1% to 0.4% by weight
of cement. At these doses, at constant workability the reduction in mixing
water is expected to be of the order of 5% to 15%. This naturally increases the
strength. The increase in workability that can be expected, at the same w/c
ratio, may be anything from 30 mm to 150 mm slump, depending on the
dosage, initial slump of concrete, cement content and type.
A good plasticizer fluidizes the mortar or concrete in a different
manner than that of the air-entraining agents. Some of the plasticizers, while
improving the workability, entrains air also. As the entrainment of air reduces
the mechanical strength, a good plasticizer is one which does not cause air-
entrainment in concrete more than 1 or 2%.
One of the common chemicals generally used, as mentioned above is
Lignosulphonic acid in the form of either its calcium or sodium salt. This
material is a natural product derived from wood processing industries.
Admixtures based on lignosulphonate are formulated from purified product
from which the bulk of the sugars and other interfering impurities are removed
to low levels. Such a product would allow adsorption into cement particles
without any significant interference with the hydration process or hydrated
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 26
Fig. 4.2.Effect of surface-active agents on deflocculating of cement grains.
products. Normal water reducing admixtures may also be formulated from
wholly synthetic raw materials. It is also observed that at a recommended
dose, it does not affect the setting time significantly. However, at higher
dosages than prescribed, it may cause excessive retardation. It must be noted
that if unrefined and not properly processed lignosulphonate is used as raw
material, the behavior of plasticizer would be unpredictable. It is sometimes
seen that this type of admixture has resulted in some increase in air-
entrainment. It is advised that users should follow the instructions of well-
established standard manufacturers of plasticizers regarding dosage
3.6.1.2 ACTION OF PLASTICIZERS
The action of plasticizers is mainly to fluidify the mix and improve the
workability of concrete, mortar or grout. The mechanisms that are involved
could be explained in the following way:
Tendency to flocculate in wet concrete. These flocculation entraps
certain amount of water used in the mix and thereby all the water is not freely
available to fluidify the mix.
Sources: Concrete Technology Book by M.S.Shetty
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 27
When plasticizers are used, they get adsorbed on the cement particles.
The adsorption of charged polymer on the particles of cement creates particle-
to-particle repulsive forces which overcome the attractive forces. This
repulsive force is called Zeta Potential, which depends on the base, solid
content, quantity of plasticizer used. The overall result is that the cement
particles are deflocculated and dispersed. When cement particles are
deflocculated, the water trapped inside the flocs gets released and now
available to fluidify the mix. Fig. 4.1 explains the mechanism.
RETARDING EFFECT: It is mentioned earlier that plasticizer gets
adsorbed on the surface of cement particles and form a thin sheath. This thin
sheath inhibits the surface hydration reaction between water and cement as
long as sufficient plasticizer molecules are available at the particle/solution
interface. The quantity of available plasticizers will progressively decrease as
the polymers become entrapped in hydration products.
Many research workers explained that one or more of the following
mechanisms may take place simultaneously:
Reduction in the surface tension of water
Induced electrostatic repulsion between particles of cement.
Lubricating film between cement particles.
Dispersion of cement grains, releasing water trapped within cement
flocs.
Inhibition of the surface hydration reaction of the cement particles,
leaving more water to fluidify the mix.
Change in the morphology of the hydration products.
Induced steric hindrance preventing particle-to-particle contact.
It may be noted that all plasticizer are to some extent set retarders,
depending upon the base of plasticizers, concentration and dosage used.
4.4.2 SUPERPLASTICIZERS (High Range Water Reducers) HRWR
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 28
Superplasticizers constitute a relatively new category and improved
version of plasticizer, the use of which was developed in Japan and Germany
during 1960 and 1970 respectively. They are chemically different from normal
plasticizers. Use of Superplasticizers permits the reduction of water to the
extent up to 30 per cent without reducing workability in contrast to the
possible reduction up to 15 per cent in case of plasticizers.
The use of superplasticizer is practiced for production of flowing, self
levelling, self-compacting and for the production of high strength and high
performance concrete.
The mechanism of action of superplasticizers is more or less same as
explained earlier in case of ordinary plasticizer. Only thing is that the
superplasticizers are more powerful as dispersing agents and they are high
range water reducers. They are called High Range Water Reducers
(HRWR) in American literature. It is the use of superplasticizer which has
made it possible to use w/c as low as 0.25 or even lower and yet to make
flowing concrete to obtain strength of the order 120 Mpa or more. It is the use
of superplasticizer which has made it possible to use fly ash, slag and
particularly silica fume to make high performance concrete.
The use of superplasticizer in concrete is an important milestone in the
advancement of concrete technology; it is widely used all over the world.
India is catching up with the use of superplasticizer in the construction of high
rise buildings, long span bridges and the recently become popular Ready
Mixed Concrete Industry. Common builders and Government departments are
yet to take up the use of this useful material.
4.4.2.1 SUPERPLASTICIZERS CAN PRODUCE:
at the same w/c ratio much more workable concrete than the plain
ones,
for the same workability, it permits the use of lower w/c ratio,
As a consequence of increased strength with lower w/c ratio, it also
permits a reduction of cement content.
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 29
The superplasticizers also produce a homogeneous, cohesive concrete generally without any tendency for segregation and bleeding.
4.4.2.2CLASSIFICATION OF SUPERPLASTICIZER
Following are a few polymers which are commonly used as base for superplasticizers.
Sulphonatedmalanie-formaldehyde condensates (SMF)
Sulphonated naphthalene-formaldehyde condensates (SNF)
Modified lignosulphonates (MLS)
Acrylic polymer based (AP)
Copolymer of carboxylic acrylic acid with acrylic ester (CAE)
Cross linked acrylic polymer (CLAP)
Polycarboxylateethers (PCE)
Multicarboxylatethers (MCE)
Combinations of above.
Out of the above new generation superplasticizersbased on carboxylic
acrylic ester (CAE) andmulticarboxylatether (MCE).
As far as our country is concerned, at present (2000 AD), we
manufacture and use the first four types of superplasticizers. The new
generation superplasticizers have been tried in recent projects, but it was not
found feasible for general usage on account of
high cost. The first four categories of products differ from one another
because of the base component or on account of different molecular weight.
As a consequence each commercial product will have different action on
cements. Whilst the dosage of conventional plasticizers do not exceed 0.25%
by weight of cement in case of lignosulphonates, or 0.1 % in case of
carboxylic acids, the products of type SMF or NSF are used considerably
high dosages (0.5% to 3.00%), since they do not entrain air.
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 30
FIG 4.3: Effect of 3rd generation PCE based super-plasticizer
The modified lignosulphonate (LS) based admixtures, which have an
effective fluidizing action, but at the relatively high dosages, they can produce
undesirable effects, such as accelerations or delay in setting times. Moreover,
they increase the air-entrainment in concrete.
Super plasticizer has been procured from BASF chemical (india) Pvt.
Ltd. With the brand name Glanium B276 Suretec (polycarboxylic either base).
The properties aregiven in TABLE 4.7.
TABLE 4.8 Properties of “GLANIUM B276 SURETEC”Aspect Light brown liquid
Relative Density 1.10 ± 0.02 at 25° CPh ≥6
Chloride ion content <0.2%
Plasticizers and superplasticizers are water based. The solid contents
can vary to any extent in the products manufactured by different companies.
Cost should be based on efficiencies and solid content, but not on volume or
weight basis. Generally in projects cost of superplasticizers should be worked
for one cubic meter of concrete.
4.4.2.3EFFECTS OF SUPERPLASTICIZERS ON FRESH CONCRETE
It is to be noted that dramatic improvement in workability is not
showing up when plasticizers or superplasticizers are added to very stiff or
what is called zero slump concrete at nominal dosages. A mix with an initial
slump of about 2 to 3 cm can only be fluidised by plasticizers or
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 31
superplasticizers at nominal dosages. A high dosage is required to fluidify no
slump concrete. An improvement in slump value can be obtained to the extent
of 25 cm or more depending upon the initial slump of the mix, the dosage and
cement content. It is often noticed that slump increases with increase in
dosage. But there is no appreciable increase in slump beyond certain limit of
dosage. As a matter of fact, the over dosage may sometime harm the concrete.
A typical curve, showing the slump and dosage is shown in Fig. 4.2.
Fig 4.4, Sources: Concrete
Technology Book by M.S.Shetty
4.4.2.4 COMPATIBILITY OF SUPERPLASTICIZERS AND CEMENT
It has been noticed that all superplasticizers are not showing the same
extent of improvement in fluidity with all types of cements. Some
superplasticizers may show higher fluidizing effect on some type of cement
than other cement. There is nothing wrong with either the superplasticizer or
that of cement. The fact is that they are just not compatible to show maximum
fluidizing effect. Optimum fluidizing effect at lowest dosage is an economical
consideration. Giving maximum fluidizing effect for a particular
superplasticizer and cement is very complex involving many factors like
composition of cement, fineness of cement etc.
Although compatibility problem looks to be very complex, it could be
more or less solved by simple rough and ready field method. Incidentally this
simple field test shows also the optimum dose of the superplasticizer to the
cement. Following methods could be adopted.
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 32
Marsh cone test
Mini slump test
Flow table test
3.7 CONSTRUCTION CHEMICALS
Discussed the materials that are used as admixtures to modify the
properties of concrete. There are other chemicals not used as admixtures but
used to enhance the performance of concrete, or used in concrete related
activities in the field of construction. Such chemicals are called construction
chemicals or building chemicals. The following is the list of some of the
construction chemicals commonly used.
Concrete Curing Compounds
Polymer Bonding Agents
Polymer Modified Mortar for Repair and maintenance
Mould Releasing Agents
Protective and Decorative Coatings
Floor Hardeners and Dust-proofers
Ready to use Plaster
4.5.1 GENERAL CHARACTERISTICS
The clear or translucent compounds shall be colorless or light in color.
If the compound contains fugitive dye, it shall be readily distinguishable on
the concrete surface for at least 4 hours after application, but shall become
inconspicuous within 7 days after application, if exposed to sun light.
The white-pigmented compound shall consist of finely divided white
pigment and vehicle ready mixed for immediate use as it is. The compound
shall present in uniform white appearance where applied at the specified rate.
The liquid membrane forming compounds shall be of such consistency
that it can be readily applied by spraying, brushing or rolling at temperature
above 4°C.
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 33
The liquid membrane-forming compounds are generally applied in two
coats. If need be more than two coats may be applied so that the surface is
effectively sealed. The first coat shall be applied after the bleeding water, if
any, is fully dried up, but the concrete surface is quite damp. In case of formed
surfaces such as columns and beams etc., the curing compound shall be
applied immediately on removal of formwork.
The following types of compounds are included:
Clear or translucent without dye
Clear or translucent with fugitive dye
White pigmented.
4.5.2 MEMBRANE FORMING CURING COMPOUNDS
In view of insufficient curing generally carried out at site of work, the
increasing importance of curing for around good qualities of concrete, in
particular, strength and durability, the need for conservation of water and
common availability of curing compounds in the country, it is felt that detail
information is required on this vital topic - curing of concrete by membrane
forming curing compounds.
Availability of enough moisture in concrete is the essence for
uninterrupted hydration process. In fresh concrete, the moisture level in
concrete is much higher than the relative humidity of atmosphere. Therefore,
evaporation of water takes place from the surface of concrete. To recoup the
loss of water from the surface of concrete and to prevent the migration of
water from the interior of concrete to surface of concrete, that is to retain
adequate moisture in the concrete, certain measures are adopted. Such
measures taken are generally called curing of concrete.
4.5.3DRYING BEHAVIOUR
Drying behavior of concrete depends upon air temperature, relative
humidity, fresh concrete temperature and wind velocity.
4.5.4TYPES OF CURING COMPOUNDS
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 34
Liquid membrane forming curing compounds are used to retard the
loss of water from concrete during the early period of setting and hardening.
They are used not only for curing fresh concrete, but also for further curing of
concrete after removal of form work or after initial water curing for one or two
days. In the case of white pigmented curing compound it also reduces the
temperature rise in concrete exposed to radiation from sun. Curing compounds
are made with the following bases.
Synthetic resin based
Waxbased
Acrylicbased
Chlorinated rubberbased
4.5.4.1 SYNTHETIC RESIN & WAX BASED
Resin and wax based curing compounds seals the concrete surface
effectively. With time their efficiency will get reduced and at about 28 days
they get disintegrated and peel off. Plastering can be done after about 28 days.
If plastering is required to be done earlier, the surface can be washed off with
hot water. As per one set of experiments it has been revealed that the typical
curing efficiency was 96% for 24 hours, 84% for 72 hours 74% for 7 days and
65% for 14 days and the average efficiency of resin and wax based membrane
forming curing compound can be taken as about 80%.
Curing Compound has been procured from FAIR MATE chemical Pvt.
Ltd. With the brand name FAIRCURE WX WHITE (wax based). The
properties are given in TABLE 4.8.
TABLE 4.10FAIRCURE WX White Properties
Water retention 0.29% kg/m² as per ASTM
Reflectance 70 % as per ASTM C 309 : 06
Drying time < 90 min as per ASTM C 309 : 06
Water retention efficiency More than 90%
Curing efficiency 90%
4.5.4.2 ACRYLICBASED
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 35
Acrylic based membrane forming curing compound has the additional
advantage of having better adhesion of subsequent plaster. The membrane
does not get crumbled down or it need not be washed with hot water. In fact
on account of inherent characteristics of acrylic emulsion the bonding for the
plaster is better.
4.5.4.3CHLORINATED RUBBERBASED
Chlorinated rubber curing compounds not only form a thin film that
protects the concrete from drying out but also fill the minute pores in the
surface of concrete. The surface film will wear out eventually.
4.5.5APPLICATION PROCEDURE
The curing compound is applied by brush or by spraying while the
concrete is wet. In case of columns and beams the application is done after
removal of formwork. On the horizontal surface, the curing compound is
applied upon the complete disappearance of all bleeding water. In case of road
and Air field pavements where texturing is required, the curing compound is
applied after texturing. In case of Pune-Mumbai express highway, the
pavement is cast by slip form paver. In this process concrete is finished,
texturing is done and curing compound is sprayed all by mechanical means.
The young concrete is covered by tents to protect green concrete from hot sun
and drying winds. In the above express highway it is specified that the
concrete is also water cured after one day using wet hessian cloth. Water
curing over membrane curing is seemingly superfluous, but it may be helpful
in keeping the temperature down.
In case the concrete surface has dried, the surface should be sprayed
with water and thoroughly wetted and made fully damp before curing
compound is applied. The container of curing compound should be well stirred
before use.
At present we do not have Bureau of Indian Standard Specification and
Code of Practice for membrane forming curing compounds. It is under
preparation. Since curing compounds are used very commonly in our country
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 36
in many of the major projects, such as SardarSarovar dam projects, express
highway projects, etc., a brief description in respect of ASTM: C 309 of 81,
for "Liquid Membrane-forming Compounds for Curing concrete" and ASTM
C 156 of 80 a for "Water Retention by concrete Curing Materials"
SCOPE: The specification covers liquid membrane forming compounds
suitable for retarding the loss of water during the early period of hardening of
concrete. The white pigmented curing compound also reduces the temperature
rise in concrete exposed to radiation from sun.
4.6SELF-CURING
Today concrete is most widely used construction material due to its
good compressive strength and durability. Depending upon the nature of work
the cement, fine aggregate, coarse aggregate and water are mixed in specific
proportions to produce plain concrete. Plain concrete needs congenial
atmosphere by providing moisture for a minimum period of 28 days for good
hydration and to attain desired strength. Any laxity in curing will badly affect
the strength and durability of concrete. Self-curing concrete is one of the
special concretes in mitigating insufficient curing due to human negligence
paucity of water in arid areas, inaccessibility of structures in difficult terrains
and in areas where the presence of fluorides in water will badly affect the
characteristics of concrete.
Proper curing of concrete structures is important to meet performance
and durability requirements. In conventional curing this is achieved by
external curing applied after mixing, placing and finishing. Self-curing or
internal curing is a technique that can be used to provide additional moisture
in concrete for more effective hydration of cement and reduced self-
desiccation.
4.6.1 MECHANISM OF SELF–CURING
Continuous evaporation of moisture takes place from an exposed
surface due to the difference in chemical potentials (free energy) between the
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 37
vapour and liquid phases. The polymers added in the mix mainly form
hydrogen bonds with water molecules and reduce the chemical potential of the
molecules which in turn reduces the vapour pressure, thus reducing the rate of
evaporation from the surface, When the mineral admixtures react completely
in a blended cement system, their demand for curing water (external or
internal) can be much greater than that in a conventional ordinary Portland
cement concrete. When this water is not readily available, significant
autogenously deformation and (early-age) cracking may result. Due to the
chemical shrinkage occurring during cement hydration, empty pores are
created within the cement paste, leading to a reduction in its internal relative
humidity and also to shrinkage which may cause early-age cracking.
4.6.2 METHODS OF SELF-CURING
There are two major methods available for internal curing of concrete.
The first method uses saturated porous lightweight aggregate (LWA) in order
to supply an internal source of water, which can replace the water consumed
by chemical shrinkage during cement hydration. The second method uses
poly-ethylene glycol (PEG) which reduces the evaporation of water from the
surface of concrete and also helps in water retention.
Lightweight aggregate (LWA)
Poly-ethylene glycol (PEG)
4.6.2.1POLYETHYLENE GLYCOLS (PEG)
Polyethylene glycol is a condensation polymer of ethylene oxide and
water with the general formula H(OCH2CH2)nOH , the abbreviation (PEG) is
termed in combination with a numeric suffix which indicates the average
molecular weights. One common feature of PEG appears to be the water-
soluble nature. Polyethylene glycol is non-toxic, odorless, neutral, lubricating,
non-volatile and non-irritating and is used in a variety of pharmaceuticals.
PEG's below 700 molecular weight occur as clear to slightly hazy, colorless,
slightly hygroscopic liquids with a slight characteristic odour. PEG's Between 700-900
are semi-solid. PEG's over 1000 molecular weight are creamy white waxy solids,
flakes, or free-flowing powders. We are using PEG’s 600.
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 38
TABLE 4.11 Physical and Chemical Properties of PEG’s 600
Physical State And
Appearance
Liquid
Odor & Taste Not Available
Molecular Weight 1000 G/Mole
Ph (1% Soln/Water) 6
Specific Gravity 1.12
Dispersion Properties See Solubility In Water, Methanol, Diethyl Ether
Solubility Easily Soluble In Cold Water, Hot Water. Soluble In Methanol,
Diethyl Ether
Advantages of Internal Curing
Internal curing (IC) is a method to provide the water to hydrate all
the cement, accomplishing what the mixing water alone cannot do.
Provides water to keep the relative humidity (RH) high, keeping self-
desiccation from occurring.
Eliminates largely autogenous shrinkage.
Maintains the strength of concrete at the early age (12 to 72 hrs.)
above the level where internally & externally induced strains can
cause cracking.
Can make up for some of the deficiencies of external curing, both
human related (critical period when curing is required in the first 12
to 72 hours) and hydration.
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 39
CHAPTER4
METHEDOLOGY5.1 MIX DESIGN AND TRIAL MIXES
The proposed study is being carriedout to develop self-compacting
concrete using fly ash andcement in varying combinations for use in the Indian
conditions.Following guidelines of ‘European Federation of National
Associations Representing producers and applicators of specialist building
products for Concrete’ EFNARC. To identify the property of fresh self-
compacted concrete by mix design & trial mixes.
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 40
5.1.1 GENERAL
Mix design selection and adjustment can be made according to the procedure
show:
• Set required performance
• Select materials
• Design and adjust mix composition
• Verify or Adjust performance in laboratory
• Verify performance in concrete
5.1.2 TRIAL MIXES
There is no standard method for SCC mix design and many academic
institutions, admixture, ready-mixed, pre cast and contracting companies have
developed their own mix proportioning methods.Based on ‘European
Federation of National Associations Representing producers and applicators
of specialist building products for Concrete’ EFNARC specifications, was
adopted for mixed design. Different mixes were prepared by varying the
amount of coarse aggregate, fine aggregate, water powder ratio &
superplasticizers. After several trials, SCC mix satisfying the test criteria was
obtained.
To develop self-compacting concrete using cement with various
quantity of fly ash from partially replacing fine and coarse aggregate.
Following steps are followed to achieve the SCC.
Quantity of cement and amount of fly ash to be added are determinate
by EFNARC.
Fixing optimum dosage of Superplasticizer by Marsh cone test on
cement slurry.
After fixing W/P ratio and optimum dosage of Superplasticizer with
given content and fly ash, aggregate quantities are found out and mix is
done to verify the fresh properties of SCC.
Cubes, Cylinders & Beams are cast and checked for its strength by
performing destructive tests.
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 41
5.1.3 MIXING PROCEDURE
There is no requirement for any specific mixer type. Forced action
mixers, including paddle mixers, free fall mixers, including truck mixers, and
other types can all be used. The mixing time necessary should be determined
by practical trials. Generally, mixing times need to be longer than for
conventional mixes Time of addition of admixture is important, and
procedures should be agreed with the supplier after planttrials. If the
consistence has to be adjusted after initial mixing, then it should generally be
done with theadmixtures.
All concrete batches were prepared in rotating drum mixture. First, the
aggregate are introduced and then one-half of the mixing water was added and
rotated for approximate two minutes. Next, the cement and fly ash were
introduced with HRWR admixture already mixed in the remaining water.
Most manufactures recommend at least 5minutes mixing upon final
introduction of Admixtures.
Once, the mix was determined to have sufficient visual attributes of
SCC, the rheological tests were performed in quick succession.
5.2 REQUIREMENTS FOR SELF-COMPACTING CONCRETE
SCC may be used in pre-cast applications or for concrete placed on
site. It can be manufactured in a site batching plant or in a ready mix concrete
plant and delivered to site by truck. It can then be placed either by pumping or
pouring into horizontal or vertical structures. In designing the mix, the size
and the form of the structure, the dimension and density of reinforcement and
cover should be taken in consideration.
Due to the high content of powder, SCC may show more plastic
shrinkage or creep than ordinary concrete mixes. These aspects should
therefore be considered during designing and specifying SCC. Current
knowledge of these aspects is limited and this is an area requiring further
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 42
research. Special care should also be taken to begin curing the concrete as
early as possible.
The workability of SCC can be characterized by the following properties:
1) Filling ability
2) Passing ability
3) Segregation resistance
A concrete mix can only be classified as Self-compacting Concrete if
the requirements for all three characteristics are fulfilled.
5.2.1 TEST METHOD
Many different test methods have been developed in attempts to
characterize the properties of SCC. So far no single method or combination of
methods has achieved universal approval and most of them have their
adherents. Similarly no single method has been found which characterizes all
the relevant workability aspects so each mix design should be tested by more
than one test method for the different workability parameters.
NO Method Property
1 Slump-flow by Abrams cone Filling ability
2 T50cmslumpflow Filling ability
3 J-ring Passing ability
4 V-funnel Filling ability
5 V-funnel at T5minutes Segregation resistance
6 L-box Passing ability
7 U-box Passing ability
8 Fill-box Passing ability
9 GTM screen Segregation resistance
10 Orimet Filling ability
Table 5.1List of test methods for workability properties of SCC
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 43
For site quality control, two test methods are generally sufficient to
monitor production quality. Typical combinations are Slump-flow and V-
funnel or Slump-flow and J-ring. With consistent raw material quality, a single
test method operated by a trained and experienced technician may be
sufficient.
NO Method Unit Typical range of valueMinimum Maximum
1 Slump-flow by Abrams cone mm 600 800
2 T50cmslumpflow sec 2 5
3 J-ring mm 0 10
4 V-funnel sec 6 12
5 V-funnel at T5minutes sec 0 +3
6 L-box (h2/h1) 0.8 1.0
7 U-box (h2-h1) mm 0 30
8 Fill-box % 90 100
9 GTM screen % 0 15
10 Orimet sec 0 5
Table 5.2Acceptance criteria for Self-compacting Concrete
5.2.1.1SLUMP FLOW TEST AND T50cm TEST
Introduction
The slump flow is used to assess the horizontal free flow of SCC in the
absence of obstructions. It was first developed in Japan for use in assessment
of underwater concrete. The test method is based on the test method for
determining the slump. The diameter of the concrete circle is a measure for the
filling ability of the concrete.
Assessment of test
This is a simple, rapid test procedure, though two people are needed if
the T50 time is to be measured. It can be used on site, though the size of the
base plate is somewhat unwieldy and level ground is essential. It is the most
commonly used test, and gives a good assessment of filling ability. It gives no
indication of the ability of the concrete to pass between reinforcement without
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 44
blocking, but may give some indication of resistance to segregation. It can be
argued that the completely free flow, unrestrained by any boundaries, is not
representative of what happens in practice in concrete construction, but the test
can be profitably be used to assess the consistency of supply of ready-mixed
concrete to a site from load to load.
Fig 5.1 Slump flow test
Equipment
The apparatus is shown in figure 5.1
Mould in the shape of a truncated cone with the internal dimensions
200 mm diameter at the base, 100 mm diameter at the top and a height
of 300 mm.
Base plate of a stiff non absorbing material, at least 700mm square,
marked with a circle marking thecentral location for the slump cone,
and a further concentric circle of 500mm diameter.
Trowel
Scoop
Ruler
Stopwatch
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 45
Procedure
About 6 litre of concrete is needed to perform the test, sampled
normally. Moisten the base plate and inside of slump cone, Place base plate on
level stable ground and the slump cone centrally on the base plate and hold
down firmly. Fill the cone with the scoop. Do not tamp, simply strike off the
concrete level with the top of the cone with the trowel. Remove any surplus
concrete from around the base of the cone. Raise the cone vertically and allow
the concrete to flow out freely. Simultaneously, start the stopwatch and record
the time taken for the concrete to reach the 500mm spread circle. (This is the
T50 time). Measure the final diameter of the concrete in two perpendicular
directions. Calculate the average of the two measured diameters. (This is the
slump flow in mm). Note any border of mortar or cement paste without coarse
aggregate at the edge of the pool of concrete.
Interpretation of result
The higher the slump flow (SF) value, the greater its ability to fill
formwork under its own weight. A value of at least 650mm is required for
SCC. There is no generally accepted advice on what are reasonable tolerances
about a specified value, though ± 50mm, as with the related flow table test,
might be appropriate.
The T50 time is a secondary indication of flow. A lower time indicates
greater flow ability. The research suggested 3-7 seconds is acceptable for civil
engineering applications, and 2-5 seconds for housing applications.
In case of severe segregation most coarse aggregate will remain in the
centre of the pool of concrete and mortar and cement paste at the concrete
periphery. In case of minor segregation a border of mortar without coarse
aggregate can occur at the edge of the pool of concrete. If none of these
phenomena appear it is no assurance that segregation will not occur since this
is a time related aspect that can occur after a longer period.
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 46
5.2.1.2V-funnel TEST:
Introduction
The V-funnel test was developed in Japan and used by Ozawa, et al 5.
The equipment consists of a V-shaped funnel, shown in Figure 5.2. The funnel
is filled with concrete and the time taken by it to flow through the apparatus
measured. This test gives account of the filling capacity (flowability). The
inverted cone shape shows any possibility of the concrete to block is reflected
in the result.
Assessment of test
Though the test is designed to measure flowability, the result is
affected by concrete properties otherthan flow. The inverted cone shape will
cause any liability of the concrete to block to be reflected in theresult – if, for
example there is too much coarse aggregate. High flow time can also be
associated withlow deformability due to a high paste viscosity, and with high
inter-particle friction.While the apparatus is simple, the effect of the angle of
the funnel and the wall effect on the flow ofconcrete is not clear.
Fig 5.2, V-funnel test equipment (rectangular section)
Equipment
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 47
The apparatus is shown in figure 5.1
V-funnel
Bucket ( ±12 litre )
Trowel
Scoop
Stopwatch
Procedure flow time
About 12 litre of concrete is needed to perform the test, sampled
normally.Set the V-funnel on firm ground.Moisten the inside surfaces of the
funnel.Keep the trap door open to allow any surplus water to drain.Close the
trap door and place a bucket underneath.Fill the apparatus completely with
concrete without compacting or tamping,simply strike off the concretelevel
with the top with the trowel.Open within 10 sec after filling the trap door and
allow the concrete to flow out under gravity.Start the stopwatch when the trap
door is opened, and record the time for the discharge to complete (theflow
time). This is taken to be when light is seen from above through the
funnel.The whole test has to be performed within 5 minutes.
Procedure flow time at T5 minutes
a
Do NOT clean or moisten the inside surfaces of the funnel again.Close
the trap door and refill the V-funnel immediately after measuring the flow
time.Place a bucket underneath.Fill the apparatus completely with concrete
without compacting or tapping, simply strike off the concretelevel with the top
with the trowel.Open the trap door 5 minutes after the second fill of the funnel
and allow the concrete to flow out undergravity. Simultaneously start the
stopwatch when the trap door is opened, and record the time for the
dischargeto complete (The flow time at T5 minutes). This is taken to be when
light is seen from above through the funnel.
Interpretation of result
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 48
This test measures the ease of flow of the concrete; shorter flow times
indicate greater flow ability. ForSCC a flow time of 10 seconds is considered
appropriate. The inverted cone shape restricts flow, andprolonged flow times
may give some indication of the susceptibility of the mix to blocking.After 5
minutes of settling, segregation of concrete will show a less continuous flow
with an increase inflow time.
5.2.1.3L BOX TEST METHOD
Introduction
This test, based on a Japanese design for underwater concrete, has been
described by Petersson. The test assesses the flow of the concrete, and also the
extent to which it is subject to blocking byreinforcement. The apparatus is
shown in figure 5.3
The apparatus consists of a rectangular-section box in the shape of an ‘L’, with
a vertical and horizontalsection, separated by a moveable gate, in front of
which vertical lengths of reinforcement bar are fitted.The vertical section is
filled with concrete, then the gate lifted to let the concrete flow into the
horizontalsection. When the flow has stopped, the height of the concrete at the
end of the horizontal section isexpressed as a proportion of that remaining in
the vertical section (H2/H1in the diagram). It indicates theslope of the
concrete when at rest. This is an indication passing ability, or the degree to
which thepassage of concrete through the bars is restricted.The horizontal
section of the box can be marked at 200mm and 400mm from the gate and the
times taken to reach these points measured. These are known as the T20 and
T40 times and are an indicationfor the filling ability.The sections of bar can be
of different diameters and spaced at different intervals: in accordance
withnormal reinforcement considerations, 3x the maximum aggregate size
might be appropriate.The bars can principally be set at any spacing to impose
a more or less severe test of the passing abilityof the concrete.
Assessment of test
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 49
This is a widely used test, suitable for laboratory, and perhaps site use.
It assesses filling and passingability of SCC, and serious lack of stability
(segregation) can be detected visually. Segregation may alsobe detected by
subsequently sawing and inspecting sections of the concrete in the horizontal
section.Unfortunately there is no agreement on materials, dimensions, or
reinforcing bar arrangement, so it isdifficult to compare test results. There is
no evidence of what effect the wall of the apparatus and theconsequent ‘wall
effect’ might have on the concrete flow, but this arrangement does, to some
extent,replicate what happens to concrete on site when it is confined within
formwork.
Two operators are required if times are measured, and a degree of
operator error is inevitable.
Equipment
L box of a stiff non absorbing material see figure 5.3.
Trowel
Scoop
Fig 5.3 L-box test
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 50
Procedure
About 14 litre of concrete is needed to perform the test, sampled
normally.Set the apparatus level on firm ground, ensure that the sliding gate
can open freely and then close it.Moisten the inside surfaces of the apparatus,
remove any surplus waterFill the vertical section of the apparatus with the
concrete sample.Leave it to stand for 1 minute.Lift the sliding gate and allow
the concrete to flow out into the horizontal section.Simultaneously, start the
stopwatch and record the times taken for the concrete to reach the 200 and
400mm marks.When the concrete stops flowing, the distances “H1” and “H2”
are measured.Calculate H2/H1, the blocking ratio.The whole test has to be
performed within 5 minutes.
Interpretation of result
If the concrete flows as freely as water, at rest it will be horizontal, so
H2/H1 = 1. Therefore the nearerthis test value, the ‘blocking ratio’, is to unity,
the better the flow of the concrete. The EU research teamsuggested a
minimum acceptable value of 0.8. T20 and T40 times can give some
indication of ease offlow, but no suitable values have been generally agreed.
Obvious blocking of coarse aggregate behindthe reinforcing bars can be
detected visually.
5.3COMPRESSIVE STRENGTH TEST
150 mm × 150 mm × 150 mm concrete cubes are cast. Specimens with
ordinary Portland cement (OPC) and OPC replaced with and fly ash. the
specimens is remove from the mould and subjected to water curing for up to
90 days. After curing, the specimens are tested for compressive strength using
a calibrated compression testing machine of 2,000 KN capacities.
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 51
PROCEDURE:
The 3 days, 14 days, 28 days& 90 days compressive strength of cube
were tested in the following manner.
After cleaning the bearing surface of the compression testing machine,
the concrete cube was placed on its smooth face side. The axis of the
specimen was carefully aligned with the centre of the lower pressure
plate of compression testing machine. Then an upper pressure plate
was lowered till the distance between pressure plate and the top surface
of the specimen achieved. No packing used between face of the
pressure plates and cube.
The load was applied without shock and increased gradually at the rate
of kg/cm2/min until the specimen was crushed.
The compressive strength calculated in kg/cm3 from the max. Load
sustained by the cube before failure.
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 52
Fig 5.4 compression testing
Compressive strength= P/A load
Where, P = failure load
A=cross sectional area
Average of three values was taken for determining compressive
strength of concrete.
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 53
CHAPTER 5
SCHEDULING OF WORK
Identify appropriate admixtures and its proportion to achieve self
curing property and self compactibility of concrete.
Mix-design for M30 grade Self Compacted Concrete (SCC).
Mix-design for M30 grade Self Compacted Concrete (NVC).
To identify admixtures for Self-curing of SCC.
STEP 1 DETERMINE RESEARCH SCOPE AAND OBJECTIVES
STEP 2 DETERMINE RESEARCH METHODOLOGY
STEP 3 LITERATURE REVIEW
STEP 4 TRIAL MIX FOR SCC AND NVC
STEP 5 CASTING AND TESTING OF CONCRETE BLOCK
STEP 5 ANALYZE THE RESULT
STEP 6 DOCUMENTATION
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 54
Adding different percentage of Admixtures by volume of cement.
Decide optimum percentage of chemical admixture
WORK TO BE DONE IN NEXT PHASE II
Future scope of work
Testing the Concrete cubes at different interval of days with some
tests and prepares the documentation on it.
Then comparison between self curing SCC and self curing NVC
Decide optimum percentage of chemical admixture
I have completed my research work up to step-4 Trial Mix.
Preparing Scheduling for casting and testing of Self Curing Self
Compacted Concrete.
SCHEDULING FOR CASTING OF CONCRETE BLOCK
Grade M30 SELF CURING SELF COMPECTED (GLYCOL – 600) Total Ratio 0 0.3 0.4 0.5 0.6 0.7 0.8 1No. Of cube 3 3 3 3 3 3 3 3 24
Grade M30 SELF CURING SELF COMPECTED (GLYCOL – 1500) Total Ratio 0 0.3 0.4 0.5 0.6 0.7 0.8 1No. Of cube 3 3 3 3 3 3 3 3 24
Grade M30 SELF CURING NVC (GLYCOL – 600) Total Ratio 0 0.3 0.4 0.5 0.6 0.7 0.8 1No. Of cube 3 3 3 3 3 3 3 3 24
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 55
Grade M30 SELF CURING NVC (GLYCOL – 1500) Total Ratio 0 0.3 0.4 0.5 0.6 0.7 0.8 1No. Of cube 3 3 3 3 3 3 3 3 24
6.5SCHEDULING FOR TESTING OF CONCRETE BLOCK
compression testDay 0 3 7 28
1 M36(24) 2 M315(24) 3 M36N(24) 4 M315N(24) M36(8) 5 M315(8) 6 M36N(8) 7 M315N(8) 8 M36(8) 9 M315(8)
10 M36N(8) 11 M315N(8) 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 M36(8)29 M315(8)30 M36N(8)31 M315N(8)
TABLE: 6.3 SCHEDULING FOR TESTING OF CONCRETE BLOCK
DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 56
CHAPTER 6
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