Self Curing And Self Compacted Concrete

DEVELOPMENT OF SELF CURING SELF COMPACTED CONCRETE By VEKARIYA SANKETKUMAR M (120070720006)

PROF. NANAK J. PAMNANI Princiapal, H.b.patelpolytehnic, Limbodara, Lunawada, (dist. Mahisagar)

DR. DARSHANA R. BHATT Associate professor, Department of structural engineering Bvm engineering college, vvn

A Dissertation Phase-I (730003) Submitted to Gujarat Technological University In Partial Fulfillment of the Requirements for The Degree of Master of Engineering In Structural Engineering December 2013

BIRLA VISHVAKARMA MAHAVIDYALAYA ENGINEERING COLLEGE VALLABH VIDYANAGAR

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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 of Co-Guide

Signature

(PROF. NANAK J PAMNANI) BHATT)

(DR. DARSHANA R.

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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,

VishvakarmaMahavidyalayaEngineering andPROF.

A.K.VERMA,

Engineering,

Birla

Associate

College, Professor

and

Principal,

Birla

VallabhVidyanagar Head,

VishvakarmaMahavidyalayaEngineering

Structural 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

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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 4

2.2.3 L-box Test 2.2.4 U-box Test

2.3 2.4 2.5

5

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

6

LIST OF TABLE

Table-2.1

…

15 Table-2.2

…

16 Table-2.3

…16

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CHAPTER 1 INTRODUCTION 1.1 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”

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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

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molecules which in turn reduces the vapour pressure, thus reducing the rate of evaporation from the surface.

 a) b) c) 

Potential Materials for Internal Curing (IC) : Lightweight Aggregate (natural and synthetic, expanded shale) Super-absorbent Polymers (SAP) (60-300 nm size) 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



4

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 Literature pertaining to self curing, self-compacting concrete will be reviewed from published papers of journals and codes practice.

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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.

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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 Lbox 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 selfcompacting 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

DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE

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curing concrete is on par with 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.

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(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.

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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

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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.

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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 SelfCompacting 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.

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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 selfcompacting. 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: In this chapter include information about materials used for development of self curing, self compacting concrete

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3.2 MATERIALS USED IN CONCRETE: Concrete is a homogeneous mixture of cement, coarse aggregate, fine aggregate and water and admixtures cem ent

fly ash

aggreg ate

wat er

admixture & construction chemical

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, 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.

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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)

Table-4.1 Physical Properties of Portland cement

DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE

PROPERTY Specific Gravity Consistency Initial setting time Final setting time Compressive strength at 7 days N/mm2 Compressive strength at 28 days N/mm2

VALUE 3.15 28% 35min 178min 38.49 N/mm2 52.31 N/mm2

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IS CODE IS : 8112 - 1989 3.10-3.15 30-35 30min minimum 600min maximum 43 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:

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A F S C G ig a o r g n iu a e d r t v s e g le a t e 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 1 2 3 4 5 6

Particulars Source Zone Specific Gravity Fineness Modulus Bulk Density Colour

Value of Sand Bodeli, Gujarat Zone II 2.55 2.87 1776.29 kg/m3 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. 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 nonslip 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

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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 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 1 2

Particulars Source Specific Gravity

Value of Sand Sevalia, Gujarat 2.75

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3 4 5

Fineness Modulus Bulk Density Colour

19

5.76 1764.14 kg/m3 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 Sr.no 1 2 3 4 5

Particulars Source Specific Gravity Fineness Modulus Bulk Density Colour

Value of Sand Sevalia, Gujarat 2.65 7.73 1624.88 kg/m3 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!!

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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 1 2

Physical Properties Colour Specific Gravity Source: SICART lab, V.V.N

Test Result Grey 2.13

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. 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”

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Sr. No 1 2 3 4 5 6

Constituents Loss on ignition Silica (SiO2) Iron Oxide (Fe2O3) Alumina (Al2O3) Calcium Oxide (CaO)

21

Weight % by 4.17 69.40 3.44 28.20 2.23 1.45

Magnesium Oxide (MgO) 7

0.165 Total Sulphur (SO3)

8

Insoluble residue

9 ALKALIES

Sodium Oxide (Na2O)

0.58 1.26

Potassium Oxide (K2O) 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. 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

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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 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.

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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. 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

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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 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

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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 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

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improving the workability, entrains air also. As the entrainment of air reduces the mechanical strength, a good plasticizer is one which does not cause airentrainment 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 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 airentrainment. It is advised that users should follow the instructions of wellestablished 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

When plasticizers are used, they get adsorbed on the cement particles. The adsorption of charged polymer on the particles of cement creates particleto-particle repulsive forces which overcome the attractive forces. This

Fig. 4.2.Effect of surface-active agents on deflocculating of cement grains.

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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 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

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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. The superplasticizers also produce a homogeneous, cohesive concrete generally without any tendency for segregation and bleeding.

4.4.2.2CLASSIFICATION OF SUPERPLASTICIZER

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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.

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

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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° C Ph ≥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 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.

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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. 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

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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. 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.

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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 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

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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 Reflectance Drying time Water retention efficiency Curing efficiency

0.29% kg/m² as per ASTM 70 % as per ASTM C 309 : 06 < 90 min as per ASTM C 309 : 06 More than 90% 90%

4.5.4.2 ACRYLICBASED 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

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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 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

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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 selfdesiccation. 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 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

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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 watersoluble 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. TABLE 4.11 Physical and Chemical Properties of PEG’s 600 Physical State And

Liquid

Appearance Odor & Taste Molecular Weight Ph (1% Soln/Water) Specific Gravity Dispersion Properties Solubility

Not Available 1000 G/Mole 6 1.12 See Solubility In Water, Methanol, Diethyl Ether 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 selfdesiccation from occurring.

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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.

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CHAPTER4 METHEDOLOGY 5.1 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 selfcompacted concrete by mix design & trial mixes. 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.

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

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.

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

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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 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 1 2 3 4 5 6 7 8 9 10

Method Property Slump-flow by Abrams cone Filling ability T50cmslumpflow Filling ability J-ring Passing ability V-funnel Filling ability V-funnel at T5minutes Segregation resistance L-box Passing ability U-box Passing ability Fill-box Passing ability GTM screen Segregation resistance Orimet Filling ability Table 5.1List of test methods for workability properties of SCC For site quality control, two test methods are generally sufficient to monitor production quality. Typical combinations are Slump-flow and V-

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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 1 2 3 4 5 6 7 8 9 10

Method

Unit

Typical range of value Minimum Maximum Slump-flow by Abrams cone mm 600 800 T50cmslumpflow sec 2 5 J-ring mm 0 10 V-funnel sec 6 12 V-funnel at T5minutes sec 0 +3 L-box (h2/h1) 0.8 1.0 U-box (h2-h1) mm 0 30 Fill-box % 90 100 GTM screen % 0 15 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 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.

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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

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

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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.

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.

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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 The apparatus is shown in figure 5.1     

V-funnel Bucket ( ±12 litre ) Trowel Scoop Stopwatch

Procedure flow time

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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 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

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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 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.

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Equipment   

L box

of a stiff non absorbing material see figure 5.3. Trowel Scoop

Fig 5.3 L-box test

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.

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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.

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.

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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.

CHAPTER 5

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SCHEDULING OF WORK

S T E P 1 2 S T E P 3 4 S T E P 5 STEP6 

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. Adding different percentage of Admixtures by volume of cement. Decide optimum percentage of chemical admixture

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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) Ratio No. Of cube

0 3

0.3 3

0.4 3

0.5 3

0.6 3

0.7 3

0.8 3

Grade M30 SELF CURING SELF COMPECTED (GLYCOL – 1500) Ratio 0 0.3 0.4 0.5 0.6 0.7 0.8 No. Of cube 3 3 3 3 3 3 3

1 3

0 3

0.3 3

0.4 3

0.5 3

0.6 3

0.7 3

1 3

0 3

0.3 3

0.4 3

0.5 3

0.6 3

0.7 3

24

Tot al 0.8 3

1 3

Grade M30 SELF CURING NVC (GLYCOL – 1500) Ratio No. Of cube

24 Tot al

Grade M30 SELF CURING NVC (GLYCOL – 600) Ratio No. Of cube

Tot al

24 Tot al

0.8 3

1 3

24

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53

6.5SCHEDULING FOR TESTING OF CONCRETE BLOCK

Day 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

0 M36(24) M315(24) M36N(24) M315N(24)

3

compression test 7

28

M36(8) M315(8) M36N(8) M315N(8) M36(8) M315(8) M36N(8) M315N(8)

M36(8) M315(8) M36N(8) M315N(8)

TABLE: 6.3 SCHEDULING FOR TESTING OF CONCRETE BLOCK

CHAPTER 6 REFRENCES

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1. Raghavendra Y.B1 and Aswath M.” EXPERIMENTAL INVESTIGATION ON CONCRETE CURED WITH VARIOUS CURING METHODS”-international journal of advanced scientific research and technology issue 2, volume 3 (june2012) 2. A.Aielstein

Rozario

“EXPERIMENTAL

STUDIES

ON

EFFECTS

OF

SULPHATE RESISTANCE ON SELF-CURING CONCRETE” International Journal of Engineering Research & Technology (IJERT),Vol. 2 Issue 4, April – 2013 3. Roberto Troli, Enco, Engineering Concrete, “Ponzano Veneto (TV), ItalySELFCOMPACTING / CURING / COMPRESSING CONCRETE” 6th International Congress, Global Construction, Ultimate Concrete Opportunities, Dundee, U.K. – 5-7 July 2005 4. Raghavendra Y.B

“EXPERIMENTAL INVESTIGATION ON CONCRETE

CURED WITH VARIOUS CURING METHODS-A COMPARATIVE STUDY” international journal of advanced scientific research and technology issue 2, volume 3 (june- 2012) 5. Hannah Angelin M. “EXPERIMENTAL STUDIES ON OPTIMAL DOSAGE OF SELF CURING AGENT IN CONCRETE” International J. of Engg. Research & Indu. Appls. (IJERIA). ISSN 0974-1518, Vol.5, No. III (August 2012), pp. 143154 6. M.V.Jagannadha Kumar1,

“ STRENGTH CHARACTERISTICS OF SELF-

CURING CONCRETE” , M.V. JAGANNADHA KUMAR* et al ISSN: 2319 1163 Volume: 1 Issue: 1 7. A.M.M.Sheinn, C.T. Tam, F.L. Rodrigo "COMPARATIVE STUDY ON HARDENED PROPERTIES OF SELFCOMPACTING CONCRETE (SCC) WITH NORMAL SLUMP CONCRETE (NSC)" 29th Conference on OUR WORLD IN CONCRETE & STRUCTURES, Singapore (2004) 8. C. Selvamony, M. S. Ravikumar, S. U. Kanna& S. Basil Gnanappa "INVESTIGATIONS ON SELF-COMPACTED SELF-CURING CONCRETE USING LIMESTONE POWDER & CLINKERS"ARPN Journal of Engineering and Applied Sciences VOL. 5, NO. 3, ISSN 1819-6608, (2010)

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55

9. EFNARC 2002February. Specification and Guidelines for Self-Compacting concrete. EFNARC (European Federation of Producers and Applicators of Specialist Products for Structures). 10. Fareed

Ahmed

Memon,

MuhdFadhilNuruddin,

Samuel

Demie

and

NasirShafiq"EFFECT OF CURING CONDITIONS ON STRENGTH OF FLY ASH-BASED SELF-COMPACTING GEOPOLYMER CONCRETE"International Journal of Civil and Environmental Engineering 3:3 (2011) 11. K. Vijai, R. Kumutha and B. G. Vishnuram "EFFECT OF TYPES OF CURING ON STRENGTH OF GEOPOLYMER CONCRETE"International Journal of the Physical Sciences Vol. 5(9) , (2010) 12. Md. Safiuddin, S.N. Raman and M.F.M. Zain"EFFECT OF DIFFERENT CURING

METHODS

ON

THE

PROPERTIES

OF

MICROSILICA

CONCRETE"Australian Journal of Basic and Applied Sciences, 1(2): 87-95, ISSN 1991-8178, (2007) 13. M.V. Krishna Rao, P. Rathish Kumar, Azhar M. Khan "A STUDY ON THE INFLUENCE OF CURING ON THE STRENGTH OF A STANDARD GRADE CONCRETE MIX"Architecture and Civil Engineering Vol. 8, No 1, pp. 23 - 34, (2010) 14. M.V.Jagannadha

Kumar,

M.Srikanth,

Dr.K.JagannadhaRao

“STRENGTH

CHARACTERISTICS OF SELF-CURING CONCRETE” International Journal Of Research Engineering & Technology (IJRET),pp. 51-57, (2012) 15. N. Ganesan, P.V. Indira, P.T. Santhoshkumar "DURABILITY ASPECTS OF STEEL FIBRE-REINFORCED SCC", Indian Concrete Journal. pp. 31-37. (2006) 16. Nan su Kung-chunghsu, His-wen chai."A SIMPLE MIX DESIGN METHOD FOR SELF COMPACTING CONCRETE"Cement and Concrete Research. 31: 1799-1809. (2001) 17. Оkamura H. and Ouchi M."SELF COMPACTING CONCRETE" Journal of advanced Concrete Technology, Vol.1, No. 1 pp. 5–15, (2003)

DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE

56

18. P. Rathish Kumar"HIGH PERFORMANCE SUPERPLASTICIZED SILICA FUME MORTARS FOR FERROCEMENT WORKS"Architecture and Civil Engineering Vol. 8, No 2, pp. 129 - 134, (2010) 19. RužaOkrajnov-BajićDejanVasović"SELF-COMPACTING CONCRETE AND ITS APPLICATION

IN

CONTEMPORARY ARCHITECTURAL PRACTISE"

SPATIUM International Review No. 20, p. 28-34, (2009) 20. SahmaranChristiantoYaman"The effect of chemical admixtures and mineral additives on the properties of self-compacting mortars" Cement and Concrete Composites. 28: 432-440. (2006) 21. S. N. Tande, P. B. Mohite" APPLICATIONS OF SELF COMPACTING CONCRETE"32ndConference

on

OUR

WORLD

IN

CONCRETE

&

STRUCTURES, Singapore (2007) 22. V. M. MALHOTRA"RESULTS OF A LABORATORY STUDY SUPERPLASTICIZERS IN CONCRETE" PUBLICATION # C780142, (1978) 23. Weston T. Hester "HIGH-RANGE WATER-REDUCING ADMIXTURES IN PRECAST CONCRETE OPERATIONS" Precast/Prestressed Concrete Institute journal, (1978)

24.

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