Saritha Report

8/10/2019 Saritha Report

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ABSTRACT


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ABSTRACT

In India, about 6 million tons of waste gypsum such as phosphogypsum,

flourogypsum etc., are being generated annually. Phosphogypsum is a by-product in the wet process

for manufacture of phosphoric acid (ammonium phosphate fertilizer) by the action of sulphuric acid

on the rock phosphate. It is produced by various processes such as dihydrate, hemihydrate or

anhydrite processes. The other sources of phosphogypsum are by-products of hydrofluoric acid and

boric acid industries. The disposal of phosphogypsum is a serious environmental problem. This

problem along with scarcity of cement, environmental pollution associated with the manufacture of

cement and its increased cost can be solved to some extent by replacing certain quantity of cement

in concrete with phosphogypsum. Our present study deals with the experimental investigation oncompressive strength, and splitting tensile strength of phosphogypsum concrete. The study aims to

determine the optimum amount of phosphogypsum that can give maximum strength to concrete. The

experiment consists of testing partially replaced phosphogypsum concrete using 0%, 10%, 20% and

30% replacement of cement with phosphogypsum at two different water cement ratios (0.4 &0.5).

Based on the experimental investigation conducted and the subsequent analysis of test results, the

following conclusions are drawn. With 10% replacement of cement with phosphogypsum, the

compressive strength and splitting tensile strength at 28 days increased commendably. However,

further replacement of cement with phosphogypsum lead to drastic reduction not only in the

compressive strength but also the split-tensile strength. Even though an industrial waste like

phosphogypsum impairs the strength development of calcined products, it can be used as a partial

replacement of cement in concrete, to achieve economy. Thus the method is important in

engineering, environmental and economic point of view and the strength and durability of concrete

can be further increased by FRP bars. The use of fibre reinforced polymer (FRP) has become a very

popular all over the world in civil and structure engineering applications due to its great advantages

such as high corrosion resistance, greatly improving the stiffness and strength of an existing

structural element with minimal effects to the surrounding environment, and high strength-to-weight

ratio instead of steel reinforcement bars.


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CHAPTER 1

INTRODUCTION

1.1.GENERAL

Difficulty in disposing waste is one of the serious problems faced by our country. A

large amount of money is being used for waste disposal. Today, it is a new trend to study the

potential utilization of the different waste materials in various fields. If the addition of these

materials can make any positive changes in the field in which it is applied, it is an added advantage

along with the waste disposal. In the field of concrete technology, various researches are frequently

done to improve its properties. This includes the research on utilizing the materials like rice husk

ash, fly ash, etc in concrete. Though a large amount of waste gypsum is generated in India, it is not

used effectively. This is a serious matter of concern. As we give more emphasis to sustainable

development, effective utilization of waste materials like phosphogypsum deserves importance.

Scarcity of cement leads to its increased cost, which causes problems in the construction sector. At

the same time, reduction in the cement production and usage has environmental benefits also. Thus

utilization of phosphogypsum in concrete gives multiple advantages, as it leads to a solution to

problems related to waste disposal and reduction in the usage of cement in concrete, thereby

reducing its cost. With the advancement of technology and increased field application of concrete

and mortars, the strength, workability, durability and other characteristics of the ordinary concrete is

continually undergoing modifications to make it more suitable for any situation. The growth ininfrastructure sector led to scarcity of cement because of which the cost of cement increased

incrementally. In India, the cost of cement during 1995 was around Rs. 1.25/kg and in 2005 the

price increased approximately three times. In order to combat the scarcity of cement and the

increase in cost of concrete under these circumstances the use of recycled solid wastes, agricultural

wastes, and industrial by-products like fly ash, blast furnace slag, silica fume, rise husk,

phosphogypsum, etc. came into use. The use of above mentioned waste products with concrete in

partial amounts replacing cement paved a role for (i) modifying the properties of the concrete, (ii)

controlling the concrete production cost, (iii) to overcome the scarcity of cement, and finally (iv) the

advantageous disposal of industrial wastes. The use of particular waste product will be economically

advantageous usually at the place of abundant availability and production. Much of the literature is

available on the use of fly ash, blast furnace slag, silica fume, rise husk, etc. in manufacture of

cement concrete. However, the literature on the use of phosphogypsum in construction industry is in


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the budding stage. This paper tries to focus on the use of phosphogypsum in partial replacement of

cement in concrete.

1.2. PHOSPHOGYPSUM

Phosphogypsum refers to the gypsum formed as a by-product of processing

phosphate ore into fertilizer with sulphuric acid. Phosphogypsum is produced from the fabrication of

Phosphoric acid by reacting Phosphate ore with Sulphuric acid. Phosphogypsum can be gainfully

utilized in cement and building materials industries. It needs beneficiation before use because of the

presence of deleterious constituents like P2O5 and fluoride. The process of generation of

Phosphogypsum can be represented by the following equation:

Ca3(PO4)2CaF2 +10H2SO4+20H2O 6H3PO4 + 10CaSO4.2H2O+ HF

(Phosphoric acid) (Phosphogypsum)

Fig 2.1. Phosphogypsum

Phosphogypsum is generally found in wet powder with moisture content ranging from 10% to

25%.Its pH varies from 2.7 to 6.4.It is produced from anhydrate, dehydrate and hemihydrates

processes. Phosphogypsum in dehydrate form, generally contains more than 90% CaSO4.2H2O and

contains impurities like P2O5, residual fluoride and free acid. The small amount of impurities inphosphogypsum (traces of free acids, acidic phosphate and silica fluoride) affect the quality of

gypsum. Phosphogypsum is also produced as a by-product of hydrofluoric acid and boric acid

industries. Current worldwide generation of phosphogypsum is 100 million tons per year. In India,

about 6 million tons of waste gypsum such as phosphogypsum, fluorogypsum, etc are produced

annually.


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1.2.1. Composition of phosphogypsum

Phosphogypsum, which has an average particle diameter of less than 0.2 mm, is

primarily calcium sulfate dihydrate, CaSO4.2H2O, in association with varying amounts of silicon,

phosphate and fluoride. Phosphogypsum is only slightly soluble in water, about 2g per litre.

Phosphogypsum contains appreciable quantities of radium-226, uranium, and other uranium decay

products. This is due to the high uranium concentration in phosphate rock which was discussed in

Section 2.1.1. The radionuclides of significance are: uranium-238, uranium-234, thorium-230,

radium-226, radon-222, lead-210, and polonium-210. When the phosphate rock is processed

through the wet process, there is a selective separation and concentration of radionuclides. Most of

the radium-226, about 80 percent, follows the phosphogypsum, while about 86 percent of the

uranium and 70 percent of the thorium are found in the phosphoric acid (Gu75).

1.2.2 The Wet Process

In general, the wet process for manufacturing phosphoric acid involves four primary

operations: raw material feed preparation, phosphate rock digestion, filtration, and concentration.

The phosphate rock is generally dried in direct-fired rotary kilns, ground to a fineness of less than

150 /tm for improved reactivity, and digested in a reaction vessel with sulphuric acid to produce the

product, phosphoric acid, and the byproduct, phosphogypsum. Specific wet-acid processes used

include the classic Prayon and Nissan-H processes which generate a dihydrate form of

phosphogypsum (CaSO4.2H2O), and the Central-Prayon and Nissan-C processes which generate a

hemihydrate form of phosphogypsum (CaS(VteH2O) (EPA90). The processes that'generate the

hemihydrate form results in phosphoric acid concentrations of 40 to 50 percent without evaporation,

as opposed to the 30 to 35 percent normally produced by the dihydrate processes. It is uncertain

which of the above processes are used by each of the phosphoric acid facilities; however, indications

are that only two or three facilities use one of the processes which generate the

hemihydratephosphogypsum while the large majority of the facilities use one of the processes which

generate the dihydrate phosphogypsum . All four processes generate two special wastes: process

wastewater and phosphogypsum.

The phosphogypsum is transferred as slurry to onsite disposal areas referred to as phosphogypsum

stacks. These stacks are generally constructed directly on unused or mined-

out land with little or no prior preparation of the land surface. Gypsum is dredged from the pond on

top of the stack and used to increase the height of the dike surrounding the pond. The


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phosphogypsum stacks become an integral part of the overall wet process. Because the process

requires large quantities of water, the water impounded on the stack is used as a reservoir that

supplies and balances the water needs of the process. Thus, the stack is not only important as a

byproduct storage site, but also contributes to the production process.

1.2.3. Uses of phosphogypsum

Phosphogypsum is currently being used in several commercial applications with

additional research being conducted, primarily by the Florida Institute of Phosphate Research

(FIPR), in order to identify new applications and expand existing ones. Currently, applications

include:

1) Fertilizer and conditioner for soils where peanuts and a variety of other crops are grown;

2) Backfill and road-base material in roadway and parking lot construction;

3) Additive to concrete and concrete blocks;

4) Mine reclamation; and

5) Recovery of sulfur.

1.2.4. Purification of phosphogypsum

The major disadvantage to the commercial use of phosphogypsum is the presence of

potentially hazardous concentrations of radium-226. Research is being conducted in the United

States and in other countries to reduce or remove the radium from raw phosphogypsum to ensure its

safe use in the agriculture and construction industries. Methods for the removal of radium include

hydrocycloning, a physical separation process, and calcining raw phosphogypsum into the

hemihydrate form which eliminates most of the radium.

The physical process involves the use of a hydrocyclone to separate the smaller phosphogypsum

crystals (less than 30 ^m) which contain the greatest portion of the radionuclides from the rest of the

phosphogypsum (Pe85). Although this process has proven effective in reducing radium

concentrations by factors of 2 to 5, it does not remove all of the radium from the phosphogypsum.

A new process, which shows promise of producing phosphogypsum of a much lower radioactive

content, involves calcining the raw phosphogypsum into the hemihydrate form (CaSO4.1/2H2O)

and dissolving the hemihydrates in water (Mo90). The solution is quickly filtered and the radium

salts are collected on the filter media.

Although the hemihydrate process generates a relatively low volume of waste, it is concentrated in

radium-226, up to 600 pCi/g, and may pose disposal problems that are equal to or even greater than

those associated with the original phosphogypsum (EPA90). No information is available on the


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volume or radium-226 concentration of the waste resulting from the physical separation method,

but it would probably produce wastes with relatively high concentrations of radium-226. This

waste disposal problem will need to be resolved if the purification of phosphogypsum is to become

viable.

1.2.5. Phosphogypsum stabilisation

The stabilisation and solidification of a phosphogypsum with low radionuclide

activity using sulphur polymer concrete allows the disposal of both sulphur and Phosphogypsum.

This could help to reduce the environmental impact of Phosphogypsum land disposal, eliminating

the potential for further contamination. The S/S process has permitted the obtainment of monoliths

with good mechanical properties. Compared to the reference samples, the mechanical properties of

the monoliths incorporating up to 10% Phosphogypsum do not seem to be affected. Determination

of the natural radionuclide content before and after the treatment indicates that the S/S process

allows a considerable reduction of the radionuclide content in the stabilised materials. In general

terms, the results obtained are promising and may help to improve the performance and

understanding of the radionuclide immobilisation process, with a view to increasing the

Phosphogypsum content in SPC-PG samples and extending the application of this procedure to

Phosphogypsum with a higher radionuclide activity.


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CHAPTER 2

AIM AND OBJECTIVE

2.1. AIM

(1)To determine the compressive strength, splitting tensile strength and modulus of elasticity of

concrete with 0%, 10%, 20% and 30% replacement of cement with phosphogypsum and water-

cement ratios 0.4 and 0.5.

(2)To study the effect of adding phosphogypsum to concrete

(3)To find the optimum percentage of phosphogypsum which give maximum strength to concrete.

(4)To understand the effectiveness of FRP in strength enhancement of concrete

2.2. OBJECTIVE

(1) The disposal of phosphogypsum is a important techno-economical problem. Finding out a long

lasting solution to that problem is our primary objective.

(2) The scarcity of cement and increased cost creates problem in construction industry.Finding out a

way to make concrete more economical is our another objective.

(3) There is an increasing need to improve the strength characteristics of concrete. Promoting the

use of materials like phosphogypsum that can improve the properties of concrete is also one of our

objectives.

(4) Promoting sustainability in construction field is our key objective.


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CHAPTER 3

LITERATURE REVIEW

3.1. GENERAL

The project deals with the experimental investigation on compressive strength,

splitting tensile strength and modulus of elasticity of phosphogypsum concrete. Some attempts have

been made to utilize phosphogypsum as base and filler materials (in the form of cement-stabilized

phosphogypsum mix) in the construction of highways, runways, etc. In other attempts,

phosphogypsum was recycled for manufacture of fibrous gypsum boards, blocks, gypsum plaster,

composite mortars using Portland cement, masonry cement, and super-sulphate cement. In some

other attempts phosphogypsum was also used as a soil conditioner for calcium and sulphur deficient

soils, as it has fertilizer value due to presence of ammonium sulphate. Recently, the effect of

phosphoric and fluorite impurities present in waste phosphogypsum on the setting time, strength

development and morphology of selenite gypsum plaster have been studied. Also, the techno

economic feasibility of beneficiating phosphogypsum has been studied, wherein the beneficiated

phosphogypsum was used for making Portland cement and Portland slag cement and the results

favoured use of phosphogypsum as an additive cement clinker in place of natural gypsum. However,

a very few attempts have been made to study the usability of phosphogypsum as partial replacement

to cement, whose use in cement and concrete will be a significant achievement in the development

of concrete technology in the coming few decades.3.2. CURRENT RESEARCHES

The project to find out the effect of phosphogypsum in concrete has been done by

different agencies. Some of their important observations are as follows.

3.2.1. A study of strength characteristics of phosphogypsum concrete

(1)The important findings of th study are as follows

The compressive strength at 7 days increased significantly (around 20% increase) at water-binder

ratio 0.50 and marginally (around 1-10% increase) at other water-binder

Ratios;

(2)The compressive strength at 28 days increased significantly (around 25% increase) at water-

binder ratio 0.45 and marginally (around 1-3% increase) at other water-binder ratios;

(3)The compressive strength at 90 days increased significantly (around 19% increase) at water-

binder ratio 0.65 and marginally (around 1-10% increase) at other water-binder ratios;


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(4) The split-tensile strength at 28 days increased marginally (around 3-10% increase) at different

water-binder ratios.

However, further replacement of cement with phosphogypsum lead to drastic reduction not only in

the compressive strength but in the split-tensile strength also. From Table 1 it is noted that the

flexural strength not only decreased significantly with higher replacement of cement with

phosphogypsum but with increase in water-binder ratio also. From the flexure test we observe that

as the replacement of phosphogypsum increases, the beam fails at lower load. And as the percentage

of replacement increases the deflection of the beam also increases. From the crack patterns it is

observed that the width and number of cracks increased with the increase in replacement of

phosphogypsum beyond 10%. As we aimed at the target mean strength of 40 N/mm2, 20%

replacement can be taken as the optimum possible replacement of cement with phosphogypsum with

water-binder ratios 0.40 and 0.45 respectively, because the strength in such a case of replacement is

more than 40N/mm2. Similarly if we aim at the target mean strength of 30 N/mm2, 30%

replacement can be taken as the optimum possible replacement of cement with phosphogypsum with

water-binder ratios 0.40 and 0.45 respectively, or 20% replacement with water-binder ratio 0.55, or

10% replacement with water-binder ratios 0.60 and 0.65 respectively, because the strength in such a

case of replacement is more than 30 N/mm2. Similarly if we aim at the target mean strength of 20

N/mm2, 30% replacement can be taken as the optimum possible replacement of cement with

phosphogypsum with water-binder ratio 0.55, or 20% replacement with water-binder ratios 0.60 and

0.65 respectively, because the strength in such a case of replacement is more than 20 N/mm2.

However, it is noted from Table 1 that 40% replacement of cement with phosphogypsum lead to

decrease in the compressive strengths by approximately one-third the original compressive strengths

without any addition of phosphogypsum. From Table 1 it is also noted that for preparations of

standardconcrete with grade designations M 25, M 30, M 35 and M 40 (as per IS 456 -2000) we

can use any appropriate replacement of cement with phosphogypsum in the range of 10-30% with

appropriate water-binder ratio of 0.40-0.65, and for ordinate concrete with grade designations M

10, M 15 and M 20 we can use any appropriate replacement of cement with phosphogypsum in the

range of 10-30% with appropriate water-binder ratio of 0.55-0.65.

3.2.2. A demonstration project:Roller compacted concrete Utilizing phosphogypsum

This demonstration project indicates that phosphogypsum based RCC is suitable for

the construction of parking facilities. The advantages of using phosphogypsum in RCC pavement

are described as follows:


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1. Phosphogypsum provides additional fines for better compatibility and surface finish without

impairing long term durability.

2. It compensates for some of the dry shrinkage to limit the extent of cracking.

3. It retards setting joints is assured.

Quality of aggregates time so that continuity at the cold play an important role on strength properties

of RCC and concrete in limestone may not be suitable for projects where strength in general. Central

Florida's excess of 2500 psi is needed. Moisture content in the mixture is very critical in the paving

operation. High moisture content in the mixtures will result in water flowing up to the top surface,

therefore, hindering the compactive effort.

3.2.3. Phosphogypsum based cement Formulation in agreement with Standard Portland

cement in the Framework of a concrete code policy For thermal and energetic efficiency Of

the building

The performance appraisal of the industrial and laboratory tests allow appreciating

the capacity of the phosphogypsum to replace the gypsum, as a regulator of hardening. Water-binder

ratio 0.45 With the report that the standards were respected for the resistance and for the sulphating.

The addition of the phosphogypsum in variable percentages in the laboratory and industrial tests

allowed seeing the influence of the product, on the parameters illustrating the quality of the cements.

All the parameters are in accordance with the standards, the phosphogypsum appears as a substitute

of the gypsum at level of 3 to 4.5% of constituents. Nevertheless, times of hardening are high

comparatively to those whom we usually obtain with the gypsum; but corresponding to the

Senegalese standards. This rise is due to the presence phosphate.

3.2.4. The use of cement-stabilized phosphogypsum mixes in road construction

The performance of cement-stabilized phosphogypsum mixes is strongly influenced

by cement content and curing time. Increases in cement content and curing time lead to higher

values of unconfined compressive strength and initial tangent modulus. For curing periods of less

than 14 days, the UCS and E0 presents a steeper gradient. Up to this period, the mixtures reached,

on the average, 79% of the resistance and 85% of the E0 obtained for an 84-day curing time. The

samples tested under soaked conditions reached UCS values 8% and E0 values 3,2% lower than

those observed in samples tested under unsoaked conditions. The moisture content causes little

influence on the unconfined compressive strength and initial tangent modulus. It was not possible to

determine a unique pattern to describe the behavior of cement-stabilized phosphogypsum mixes

with the compaction moisture content.


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CHAPTER 4

METHODOLOGY

COLLECTION OF MATERIALS

TESTING OF MATERIALS

MIX DESIGN

MIXING WITH SPECIFIC

PROPORTION

MOULDING OF SPECIMEN

DEMOULDING OF SPECIMEN

CURING FOR 7,14,28,56 DAYS

TESTING OF SPECIMEN

ANALYSIS AND CONCLUTION


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CHAPTER 5

TESTS ON CEMENT AND PHOSPHOGYPSUM

5.1. FINENESS OF CEMENT

Fineness is the measure of the total surface area of cement. For finer cements, surface

area will be more. Fineness influences the rate of hydration, rate of strength development, shrinkage,

cracking, bleeding and also the cost of cement. Firstly, breakdown any air lumps present in cement

sample with fingers. Weight accurately 100g of cement, place it on a standard IS. 90 micron sieve,

and sieve continuously until no more fine materials passes through it. Weight the residue. The

observations of the test are shown in the table 3.1.

Table.5.1. Observations of fineness test of cement

Sample No. Weight of sample,

W1(gm)

Weight of residue,

W2(gm)

Fineness=

(W2/W1)x

100%

1 100 8 8

2 100 7 7

3 100 5 5

Calculation

Fineness of cement by dry sieving=(W2/W1)x100

=(7/100)x100=7%

5.2. SPECIFIC GRAVITY OF CEMENT

Specific gravity is defined as the ratio between the weight and volume of a given

quantity of the material, and it is needed in mix proportions calculations. Dry the Le Chatelier flask

and fill with kerosene oil or naphtha to a point on the stem between zero and one ml. Dry inside of

flask above the level of liquid. Immense the flask in a constant temperature water bath maintained at

room temperature for sufficient time. Record the level of kerosene oil in the flask as initial reading.

Introduce about 64 gm of cement into the flask so that the level of kerosene rises above the bulb

portion. Cement should not be allowed to adhere to the sides of the flask above the liquid. Insert the

stopper into the flask and roll it gently in an inclined position. Expel the air from cement until no

further air bubbles rise to the surface of the liquid. Note down the level of kerosine in the flask.

Readings observed are shown below.


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Observation

Weight of cement used=64 gm

Initial reading= 0.6 ml

Final reading= 19.9 ml

Calculation

Volume of cement=Initial reading-final reading= 19.9-0.6= 19.3

Specific gravity=Weight of cement in g/Displaced volume of kerosine in ml

=64/19.3=3.316

5.3.CONSISTENCY OF STANDARD CEMENT PASTE

Since different batch of cement differ in fineness, pastes with same water content may

differ in consistency when first mixed. For this reason the consistency of the paste is standardized

by varying the water content until the paste has a given resistance to penetration. Standard

consistency is defined as that consistency which will permit the vicat plunger to penetrate to a point

5mm to 7mm from the bottom of the Vicat mould when the cement paste is tested. The observations

of the test are shown in the table 3.2.

Table 5.2. Observations of consistency test of cement paste

Wt of dry

cement,W1(gm)

Wt of water added,

W2(gm)

Penetration from

bottom of

mould(mm)

Percentage of water for

standard consistency

(W2/W1)x100

400 110 18 27.5

400 120 10 30

400 130 5 32.5

Calculation

Percentage of water for standard consistency=32.5 %

5.4. INITIAL AND FINAL SETTING TIMES OF CEMENT

When cement is mixed with sufficient water, hydration occurs.In the beginning, the

paste loses its fluidity and within a few hours,noticeable stiffening results. This is called initial set

and is measured by the ability of the paste to withstand a certain arbitrary pressure.Further build-up

hydration products is followed by commencement of the hardening process, responsible for the


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strength of concrete, which is known as final set. The time from the addition of water to dry cement

to the initial and final set are known as the initial setting time and final setting time respectively.

Cement should not set too rapidly or too slowly. The initial setting time must allow for handling and

placing the concrete before stiffening. The maximum final setting time is specified and measured to

ensure normal hydration.Readings observed are shown below.

Observations

Initial setting time= 40 minutes

Final setting time= 9 hours 10 minutes

5.5.FINENESS OF PHOSPHOGYPSUM

Fineness of phosphogypsum is tested in the same way as that of cement. . Firstly,

breakdown any air lumps present in phosphogypsum sample with fingers. Weight accurately 100g

of phosphogypsum, place it on a standard IS. 90 micron sieve, and sieve continuously until no more

fine materials passes through it. Weight the residue. The observations of the test are shown in the

table 3.3.

Table.3.1. Observations of fineness test of phosphogypsum

Sample No. Weight of sample,

W1(gm)

Weight of residue,

W2(gm)

Fineness=

(W2/W1)x

100%

1 100 8 8

2 100 7 7

3 100 5 5

Calculation

Fineness of phosphogypsum by dry sieving=(W2/W1)x100

=(7/100)x100=7%

5.6. INITIAL SETTING TIME OF PHOSPHOGYPSUM ADDED CEMENT

The procedure for determining the initial setting of phosphogypsum added cement is

same as that of cement. Here, 10% of cement is replaced with phosphogypsum for doing the test.

Initial setting time of phosphogypsum added cement = 60 minutes


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5.7. RESULTS

Fineness of cement =7%

Specific gravity of cement= 3.316

Percentage of water for standard consistency of cement paste=32.5%

Initial setting time of cement=40 minutes

Final setting time of cement= 9 hours 10 minutes


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CHAPTER 6

TESTS ON AGGREGATES

6.1. PARTICLE SIZE DISTRIBUTION

Particle size distribution, also called gradation ,refers to the proportions (by mass) of

aggregates distributed in specific particle ranges. It is an important property that affects mix

proportions, workability,porosity, durability, shrinkage and economy.Generally aggregates passing

through 4.75mm sieve is called fine aggregate and those retained on 4.75mm sieve is called coase

aggregate.

6.1.1. Particle size distribution of Coarse aggregate

The observations of the test are shown in the table 4.1.

Table 6.1. Observations of particle size distribution of coarse aggregate

IS Sieve

No.

Sieve

Size(mm)

Weight

retained in

each

sieve(gm)

Percentage

weight

retained

Cumulative

weight

retained

Percentage

weight

passing

80 80 0 0 0 100

63 63 0 0 0 100

50 50 0 0 0 100

40 40 0 0 0 100

31.5 31.5 0 0 0 100

25 25 0 0 0 100

20 20 214 11.088 11.088 88.912

16 16 553 28.652 39.74 60.26

12.5 12.5 769 39.844 79.584 20.416

10 10 307 15.906 95.49 4.51

6.3 6.3 55 2.849 98.339 1.6614.75 4.75 25 1.295 99.634 0.366

Pan 7 0.3626 100 0

Draw a semi-logarithmic graph with percentage passing on Y axis and log sieve opening on X axis.

From the grading cure D60 and D10 are noted, where D60 is the sieve opening corresponding to

60% passing and D10 for 10% passing.


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Fig 6.2. Particle size distribution curve of coarse aggregate

Fineness modulus=Sum of cumulative percentage of weight retained/100 = 523.875/100=5.238

Uniformity coefficient=D60/D10= 16/11= 1.45 Effective size=D10= 11

6.1.2. Particle size distribution of fine aggregate

The observations of the test are shown in the table 4.2.

Table 6.2. Observations of particle size distribution of fine aggregate

Sieve

Size(mm)

Weight

retained in

each sieve(gm)

Percentage

weight retained

(%)

Cumulative

weight retained

Percentage

weight

(%)assing

4.75 6 0.3 0.3 99.7

3.25 0 0 0.3 99.7

2.36 39 1.95 2.25 97.75

1.18 1000 50 52.25 47.74600 402 20.1 72.35 27.65

300 216 10.8 83.75 16.25

150 200 10 93.05 6.95

75 42 2.1 95.25 4.75

Pan 95 4.75 100 0

0

20

40

60

80

100

120

1 10 100

Weightpassing(%)

Sieve size(mm)


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Fig. 6.3. Particle size distribution curve of fine agggregate

Fineness modulus= Sum of cumulative percentage of weight retained/100=499.5/100=4.995

Uniformity Coefficient=D60/D10=1.5/1.2=7.5

Effective size=D10=0.2

6.2. SPECIFIC GRAVITY OF AGGREGATESIn Connection with the concrete mix design, it is necessary to know the space

occupied by the aggregate particles within the concrete.Specific gravity is defined as the ratio of

weight in air of given volume of air at the standard temperature to the weight in air of equal volume

of water at that temperature.

5.2.1. Specific Gravity of Coarse aggregate

Observation

A=Weight of the container +aggregate +water=8.450 Kg

B=Weight of the container+ water= 5.556 Kg

C=Weight of the surface dried aggregate= 4.414 Kg

D=Weight of the oven dried aggregate= 4.385 Kg

Calculation

Specific gravity=D/[C-(A-B)] = 4.385/[4.414-(8.450-5.550)]= 2.896

Apparent specific gravity=D/[D-(A-B)]=4.385/[4.835-(8.450-5.550)]= 2.498

0

20

40

60

80

100

120

0.01 0.1 1 10

Weightpassing()%

Sieve size (mm)


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6.4. RESULTS

Fineness modulus of coarse aggregate= 5.238

Uniformity coefficient of fine aggregate= 1.45

Effective size of fine aggregate = 11

Specific gravity of coarse aggregate= 2.896

Apparent specific gravity of coarse= 2.498

Water absorption of coarse aggregate 0.6613

Bulk density of coarse aggregate=1.5379

Void ratio of coarse aggregate =0.7058

Porosity of aggregate=0.4137

Fineness modulus of fine aggregate=4.995

Uniformity Coefficient of fine aggregate=7.5

Effective size of fine aggregate=0.2

Specific gravity of fine aggregate= 2.208

Apparent specific gravity of fine aggregate=2.789

Water absorption of fine aggregate= 9.433%


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CHAPTER 7

PREPARATION OF CONCRETE SPECIMENS

7.1. MATERIALS REQUIRED

Cement: Ordinary Portland cement of grade 53 is used for the investigation. Different

tests are carried out to find the properties of cement as per IS 4031-1988.The properties of cement

obtained from the tests are: fineness-7%, normal consistency-32.5%, specific gravity-3.316, initial

setting time-40 minute, final setting time-9hours 10 minutes. From the tests, it is proved that the

cement satisfies requirements as per IS 12269-1987.

Fine Aggregate: The properties of the fine aggregate obtained as per the test result are: Fineness

modulus-4.995 and specific gravity-2.896.The fine aggregates satisfy the requirements as per IS

2386-1963.

Coarse Aggregate: Aggregate with 20mm nominal size is used. The properties obtained from the

tests are-Fineness modulus-5.238, specific gravity-2.896, bulk density-1.58, void ratio-0.705 and

porosity-0.414.The coarse aggregate satisfies the results as per IS 2386-1963.

Phosphogypsum: The phosphogypsum is collected from Fertilizers And Chemical Travancore

Limited (FACT), Aluva.

Water: The water used for preparing concrete is clean and free from acids and organic substances.

7.2. STEPS INVOLVED

7.2.1. Estimation of ingredients

For every type of concrete 4 cubes are prepared for testing compressive strength and

a total of 3 cubical specimens are prepared for testing splitting tensile strength. Specimens are

prepared for 0%, 10%, 20% and 30% phosphogypsum content with water cement ratios 0.4 and

0.5.The size of cubical specimen is 150mmx150mm and size of cylindrical specimen is 150mm

diameter and 300mm height. The total number of specimens is 56.Quantities of materials required

for preparing concrete specimens are prepared by absolute volume method. While doing the

estimation 20% extra is added to the total quantity. To prepare 4 cubical and 3 cylindrical specimens

of 10% cement replacement at water-cement ratio 0.4, the quantity of ingredients required are-

cement-13.14kg, fine aggregate-21.89kg, coarse aggregate-43.99kg, phosphogypsum-1.46kg, water-

5.84kg.


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Calculation

Mix proportion: cement: FA: CA: water=1:1.5:3:0.5

Specific gravity of cement=3.14

Specific gravity of Fine aggregate=2.65

Specific gravity of Coarse aggregate=2.65

Specific gravity of water=1

Cube

Volume of cube=15x15x15= 3375cm^2

Volume of concrete obtained per z gram= (1/3.14) + (1.5/2.65) + (3/2.65) + (0.5/1)=2.52

Weight of cement required for 1 concrete cube=3375/2.52=1339g=1.339kg

Weight of cement required for 4 concrete cubes with 0% phosphogypsum=4x1.339=5.356kg

Weight of cement required for 4 concrete cubes with 10% phosphogypsum=4x (1.339-

0.1x1.339)=4.8204kg


0.2x1.339)=4.2848kg


0.3x1.339)=3.7492kg

Total weight of cement required for 4+4+4+4=16 specimens=5.356+4.8204+4.2848+3.7492=

15.21154kg

We are testing specimens with 2 water cement ratios. Therefore total weight of 16+16=32

specimens=2x15.21154=30.423kg

Weight of phosphogypsum required for 10% cement replacement=10% x 1.339=0.1339

Weight of phosphogypsum required for 4 specimens=4 x 0.1339=0.5356kg

Weight of phosphogypsum required for 20% cement replacement=20% x 1.339=0.2678kg




Weight of phosphogypsum required for 4+4+4=12 specimens=0.5356+1.0712+1.6078=3.2136kg

We are preparing specimens with 2 water contents. Therefore total weight of phosphogypsum

required for 12+12=24 specimens=2 x 3.2136=6.4272kg


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Cylinder

Volume of cylinder=3.14xR2xH= 3.14x7.5^2x30=5301.437cm^2

Volume of concrete obtained per z gram=(1/3.14)+(1.5/2.65)+(3/2.65)+(0.5/1)=2.52

Weight of cement required for 1 concrete cylinder=5301.437/2.52=2103.7g=2.1037kg

Weight of cement required for 3 concrete cylinders with 0% phosphogypsum=3x2.1037=6.3111kg

Weight of cement required for 3 concrete cylinders with 10% phosphogypsum=3x (2.1037-

0.1x2.1037)=5.6799kg


0.2x2.1037) =5.0488kg


0.3x2.1037) =4.4177kg

Total weight of cement required for 3+3+3+3=12 specimens=6.3111+5.6799+5.0488+4.4177=

21.4575kg

We are testing specimens with 2 water cement ratios. Therefore total weight of 12+12=24

specimens=2x21.4575=42.915kg

Weight of phosphogypsum required for 10% cement replacement=10% x 2.1037=0.21037






Weight of phosphogypsum required for 3+3+3=9

specimens=0.63111+1.26222+1.89333=3.78663kg

We are preparing specimens with 2 water contents. Therefore total weight of phosphogypsum

required for 9+9=18 specimens=2 x 3.78663=7.5733kg

Result

Total weight of cement required=30.423+42.915=73.338kg

Total weight of phosphogypsum required=7.5733=14kg

Total weight of fine aggregate required=1.5 x 73.338=110.007kg

Total weight of coarse aggregate required=3x 73.338=220.014kg


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7.2.2. Weighing and batching

The proportioning of ingredients-cement, fine aggregate, coarse aggregate,

phosphogypsum and water are done by mass. The mass of each material is taken accurately to keep

the correct proportion.

7.2.3. Mixing of concrete

For preparing phosphogypsum concrete, the first step is to mix the weighed quantity

of cement and phosphogypsum till it become a homogenous mixture. Then fine aggregate and

coarse aggregate are added to it and is mixed well. Thereafter, add water uniformly and continue

mixing till a homogenous mass is obtained.

Thorough mixing is essential for the production of uniform, high quality concrete. For this reason

equipment and methods should be capable of effectively mixing concrete materials containing the

largest specified aggregate to produce uniform mixturesof the lowest slump practical for the work.

Separate paste mixinghas shown that the mixing of cement and water into a paste before combining

these materials withaggregates can increase thecompressive strength of the resulting concrete. The

paste is generally mixed in a high-speed, shear-type mixer at aw/cm(water to cement ratio) of 0.30

to 0.45 by mass. The cement paste premix may include admixtures such as accelerators or retarders,

superplasticizers,pigments,orsilica fume.The premixed paste is then blended with aggregates and

any remaining batch water and final mixing is completed in conventional concrete mixing

equipment.[19]

High-energy mixed (HEM) concrete is produced by means of high-speed mixing of cement, water

and sand with netspecific energy consumption of at least 5 kilojoules per kilogram of the mix.

Aplasticizer or asuperplasticizer is then added to the activated mixture, which can later be mixed

with aggregates in a conventionalconcrete mixer. In this process, sand provides dissipation of

energy and creates high-shear conditions on the surface of cement particles. This results in the full

volume of water interacting with cement. The liquid activated mixture can be used by itself or

foamed (expanded) for lightweight concrete.[20]

HEM concrete hardens in low and subzero

temperature conditions and possesses an increased volume of gel, which drastically

reducescapillarity in solid and porous materials.
http://en.wikipedia.org/wiki/Construction_aggregatehttp://en.wikipedia.org/wiki/Compressive_strengthhttp://en.wikipedia.org/wiki/Water-cement_ratiohttp://en.wikipedia.org/wiki/Plasticizerhttp://en.wikipedia.org/wiki/Pigmenthttp://en.wikipedia.org/wiki/Silica_fumehttp://en.wikipedia.org/wiki/Concrete#cite_note-18http://en.wikipedia.org/wiki/Concrete#cite_note-18http://en.wikipedia.org/wiki/Concrete#cite_note-18http://en.wikipedia.org/wiki/Energy_densityhttp://en.wikipedia.org/wiki/Energy_densityhttp://en.wikipedia.org/wiki/Plasticizerhttp://en.wikipedia.org/wiki/Superplasticizerhttp://en.wikipedia.org/wiki/Concrete_mixerhttp://en.wikipedia.org/wiki/Concrete#cite_note-19http://en.wikipedia.org/wiki/Concrete#cite_note-19http://en.wikipedia.org/wiki/Concrete#cite_note-19http://en.wikipedia.org/wiki/Capillarityhttp://en.wikipedia.org/wiki/Capillarityhttp://en.wikipedia.org/wiki/Concrete#cite_note-19http://en.wikipedia.org/wiki/Concrete_mixerhttp://en.wikipedia.org/wiki/Superplasticizerhttp://en.wikipedia.org/wiki/Plasticizerhttp://en.wikipedia.org/wiki/Energy_densityhttp://en.wikipedia.org/wiki/Concrete#cite_note-18http://en.wikipedia.org/wiki/Silica_fumehttp://en.wikipedia.org/wiki/Pigmenthttp://en.wikipedia.org/wiki/Plasticizerhttp://en.wikipedia.org/wiki/Water-cement_ratiohttp://en.wikipedia.org/wiki/Compressive_strengthhttp://en.wikipedia.org/wiki/Construction_aggregate


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7.2.4. Placing of concrete in moulds

The concrete is placed in cubical and cylindrical moulds in 3 equal layers by tamping

each layer with an iron rod.

7.2.5. Curing

Concrete specimens prepared are immersed in water for 24 hours after placing the

concrete. The curing is done for 28 days.

In all but the least critical applications, care needs to be taken to properly cureconcrete, to achieve

best strength and hardness. This happens after the concrete has been placed. Cement requires a

moist, controlled environment to gain strength and harden fully. The cement paste hardens over

time, initially setting and becoming rigid though very weak and gaining in strength in the weeks

following. In around 4 weeks, typically over 90% of the final strength is reached, though

strengthening may continue for decades. The conversion ofcalcium hydroxide in the concrete

intocalcium carbonate from absorption ofCO2over several decades further strengthen the concrete

and making it more resilient to damage. However, this reaction, calledcarbonation,lowers the pH of

the cement pore solution and can cause the reinforcement bars to corrode.

Hydration and hardening of concrete during the first three days is critical. Abnormally fast drying

and shrinkage due to factors such as evaporation from wind during placement may lead to increased

tensile stresses at a time when it has not yet gained sufficient strength, resulting in greater shrinkage

cracking. The early strength of the concrete can be increased if it is kept damp during the curing

process. Minimizing stress prior to curing minimizes cracking. High-early-strength concrete is

designed to hydrate faster, often by increased use of cement that increases shrinkage and cracking.

Strength of concrete changes (increases) up to three years. It depends on cross-section dimension of

elements and conditions of structure exploitation.

During this period concrete needs to be kept under controlled temperature and humid atmosphere. In

practice, this is achieved by spraying or ponding the concrete surface with water, thereby protecting

the concrete mass from ill effects of ambient conditions. The pictures to the right show two of many

ways to achieve this, ponding submerging setting concrete in water and wrapping in plastic to

contain the water in the mix. Additional common curing methods include wet burlap and/or plastic

sheeting covering the fresh concrete, or by spraying on a water-impermeable temporary curing

membrane.
http://en.wikipedia.org/wiki/Calcium_hydroxidehttp://en.wikipedia.org/wiki/Calcium_carbonatehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbonationhttp://en.wikipedia.org/wiki/Carbonationhttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Calcium_carbonatehttp://en.wikipedia.org/wiki/Calcium_hydroxide


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Properly curing concrete leads to increased strength and lower permeability and avoids cracking

where the surface dries out prematurely. Care must also be taken to avoid freezing, or overheating

due to theexothermic setting of cement. Improper curing can causescaling, reduced strength,

poorabrasion resistance andcracking.

7.2.6. Testing of specimens

After 28 days of curing, the specimens prepared are tested. Compressive strength test, splitting

tensile strength test are done with the prepared specimens.
http://en.wikipedia.org/wiki/Exothermichttp://en.wikipedia.org/wiki/Spalling#Spalling_in_mechanical_weatheringhttp://en.wikipedia.org/wiki/Abrasion_(mechanical)http://en.wikipedia.org/wiki/Fracturehttp://en.wikipedia.org/wiki/Fracturehttp://en.wikipedia.org/wiki/Abrasion_(mechanical)http://en.wikipedia.org/wiki/Spalling#Spalling_in_mechanical_weatheringhttp://en.wikipedia.org/wiki/Exothermic


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CHAPTER 8

TESTING OF CONCRETE SPECIMENS

8.1. COMPRESSIVE STRENGTH OF CONCRETE

Compressive strength is the most important property of hardened concrete and is

generally considered in the design of concrete mixes. Many other properties of concrete depend on

its compressive strength.The procedure of the test is as follows. Take out the specimens from the

curing tank and clean its surface. Measure the dimensions to 0.2 mm and note its weight. Place the

specimen in the machine in such a manner that the load is applied to opposite side of the cubes as

cast. The load is applied without shock and increased continuously at a rate of approximately 14

N/mm per minute. Record the maximum load taken by each specimen.From the values of maximum

load of different specimens, characteristic compressive strength is determined

Sample calculation(for concrete with 0% phosphogypsum)

Compressive strength(from table 6.1.)=Maximum load/areaof specimen

=810000/(149x150)=36 N/mm2

Table 8.1. Observations of compressive strength of concrete cubes

Sl No. Dimension Maximum Load(N) Compressive

Strength(N/mm2)

1 150x150 940000 41.77

2 151x150 935000 41.28

3 151x149 650000 28.89

4 149x151 810000 36.00

8.2. SPLITTING TENSILE STRENGTH OF CONCRETESplitting tensile test is an indirect method to determine the tensile strength of

concrete (it yields strength values which are higher than the true tensile strength). In this test, the

cylindrical specimen is subjected to a uniform line load along the length of the specimen. The

tensile strength is calculated using the load at which the specimen splits into two. The procedure is

as follows. Cast the cylinder of size 150 x 300mm from the mix and cure for 28 days. Note the


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diameter and length of specimen. Centre one of the plywood strips along the centre of lower plate

and place the second plywood strip lengthwise on the top of the cylinder. Apply the load without

shock and increase continuously at a nominal rate within the range 1.2 N/mm2 per minute. Maintain

the rate until failure. Note the load applied.

Sample Calculation(for concrete with 0% phosphogypsum content)

Load observed, P= 166 KN

Diameter of specimen, D=150mm

Length of specimen, L= 300mm

Splitting tensile strength= 2P/(DL)=2X166000/(x150x300)=2.348N/mm2


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CHAPTER 9

RESULTS OF THE EXPERIMENTAL INVESTIGATION

9.1. COMPRESSIVE STRENGTH

The compressive strength of concrete is found to increase with the addition of

phosphogypsum up to 10% replacement of cement with phosphogypsum. The increase in

compressive strength is more at a water cement ratio of 0.4.The percentage increase in compressive

strength(at water-cement ratio 0.4) at 10% phosphogypsum content , when compared with plain

concrete is 3.63%.But the compressive strength of concrete(at water -cement ratio 0.5) at 10%

replacement is slightly less when compared to plain concrete. There is a significant reduction in the

compressive strength at 20% and 30% phosphogypsum content. Thus the optimum amount of

phosphogypsum in concrete is found to be 10%.For M20 concrete, the compressive strength should

be greater than 20 N/mm2.All the concrete specimens except the one which is prepared with 30%

phosphogypsum and 0.4 water cement ratio, satisfies this criteria.

Table 9.1. Comparison of compressive strengths of concrete

Replacement of cement,% Water-cement ratioCompressive strength,

N/mm2

00.4 36.88

0.5 36

10 0.4 38.22

0.5 35.55

200.4 21.11

0.5 22.22

300.4 18.66

0.5 20


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Fig 9.1. Variation of compressive strength with phosphogypsum addition

9.2. SPLITTING TENSILE STRENGTH

Splitting tensile strength values also show similar trend as in the case of compressive

strength. The splitting tensile strength is found to be maximum at 10% phosphogypsum content with

water-cement ratio 0.4. The percentage increase in the splitting tensile strength of concrete (0.4

water cement ratio) at 10% phosphogypsum content is 9.39%. But splitting tensile strength (0.5

water cement ratio) at 10 % phosphogypsum content is less compared with plain concrete. There is a

very significant reduction in the compressive strength at 20% and 30% replacement.

Table 9.2. Comparison of splitting tensile strength of concrete

Replacement of cement,% Water-cement ratio Splitting tensile

strength,N/mm2

0 0.4 2.263

0.5 2.348

10 0.4 2.475

0.5 2.178

20 0.4 2.065

0.5 1.839

30 0.4 1.641

0.5 1.697

0

5

10

15

20

25

30

35

40

45

0 10 20 30 40

Compressivestren

gth,N

/mm2

Replacement of cement,%

w/c 0.4

w/c 0.5


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Fig 9.2. Variation of splitting tensile strength with phosphogypsum addition

.

9.4. INFERENCE OF RESULTS

From the above results it can be inferred that the strength characteristics increases

with the increase in the amount of phosphogypsum in concrete up to 10 % replacement.Compressive strength, splitting tensile strength and modulus of elasticity shows similar behavior

though there is minor variation in the trend.If we aim at a target compressive strength of 30

N/mm2,it is feasible to do upto 10% replacement. Similarly, if the target compressive strength is 20

N/mm2, it is feasible to use concrete with 20 % replacement of cement with phosphogypsum. Even

20% replacement of cement in concrete with phosphogypsum gives compressive strength of 20

N/mm2. The compressive strength at 20% and 30% replacement of cement with phosphogypsum

gives lower values of compressive strength than ordinary concrete. But , if these replacements

ensure a compressive strength , which is more than the target, it is better to use concrete with 20 and

30% phosphogypsum content, there by making concrete more economical.

0

0.5

1

1.5

2

2.5

3

0 10 20 30 40

Splittingtensilestrength,N

/m

m2

Replacement of cement,%

w/c 0.4

w/c 0.5


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CHAPTER 10

ADVANTAGES AND LIMITATIONS

10.1. ADVANTAGES

(1) In India, about 6 million tons of waste gypsum such as phosphogypsum, flourogypsum etc, are

being generated annually. This is an important waste disposal problem. Using phosphogypsum in

concrete is a feasible solution to this problem.

(2) The growth of infrastructure industry led to scarcity of cement because of which the cost of

cement increase incremently. Partial replacement of cement in concrete with phosphogypsum

reduces the cost of concrete.

(3) The strength characteristics of concrete increases with the partial replacement of cement upto

10%.Therefore it improves the properties of concrete.

(4) The setting time of cement increases with the addition of phosphogypsum

10.2. LIMITATIONS

(1) It contain small quantities of impurities like silica , fluorine and phosphate and fuel is required to

dry it before it could be processed for some applications as a substitute for natural gypsum, which is

a material of higher purity.

(2) Phosphogypsum contains certain amount of slightly radioactive elements

(3) The quality of phosphogypsum deteriorates with its aging. Therefore strength characteristics of

concrete reduce with aging of phosphogypsum used in it.10.3. FUTURE SCOPE OF THE PROJECT

There is scope for future extention of the project for determining the more accurate

percentage replacement of phosphogypsum. It may be most probably between 10% and 20%. The

reactions of phosphogypsum with cement can also be examined. The extent of radioactivity of

phosphogypsum is an important aspect to be studied.


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CHAPTER 11

CONCLUSION

11.1. GENERAL

From the experimental investigation of phosphogypsum concrete we can arrive at the

following conclusions-

1. Addition of phosphogypsum to concrete affects the strength characteristics of concrete

2. Compressive strength, splitting tensile strength and modulus of elasticity has its maximum value

at 10% replacement of cement with phosphogypsum, it reduces if the percentage replacement is

more than 10%.Thus the optimum amount of phosphogypsum to be added to concrete is 10%.

3. There will be significant reduction in the cost of concrete if phosphogypsum is added to it. The

scarcity of cement and its increased cost are serious problems faced by construction industry. Use

of phosphogypsum in concrete will be an appropriate solution to these problems.

4. The stacks of phosphogypsum dumped by the fertilizer plants is a serious waste disposal problem.

Effective utilization of phosphogypsum in concrete reduces the intensity of problems caused by its

dumping.

Thus phosphogypsum which is a by-product of fertilizer plant and chemical industries can be

effectively utilized by partial replacement of cement in concrete with phosphogypsum. This method

is surely a step toward sustainable development and is important in engineering, environmental and

economic point of view.


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PHOTOS

COMPRESSIVE STRENGTH TEST


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SPLIT TENSILE STRENGTH TEST


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REFERENCES

1. Central Pollution Control Board Assessment of Utilization of Industrial Solid Wastes in

Cement Manufacturing,Programme Objective Series PROBES/103/2006-2007.

2.IS: 10262-2009, Concrete Mix Proportioning-Guidelines, Bureau of Indian Standards, New Delhi,

2009

3. IS: 456-2000, Plain and reinforced Concrete - Code of Practice, Bureau of Indian Standards,

New Delhi, 2000.

4. Marcelo C. Takeda and Alexandre B. ParreiraThe Use of Cement-Stabilized Phosphogypsum

Mixes in Road Construction, University of Sao Paulo, Sao Carlos, Brazil.

5.Rafat A. Huwait, M.A., Aly A. Aly Abdo, Muhammed H. Hassan, and S.A. Elmongy(1999)

An assessment of radioactivity of selected industrial wastes, 16th National Radio Science

Conference, Ain Shams University, Cairo, Egypt.

6. Shetty M.S., Concrete Technology-Theory and Practice, S.Chand &Company Ltd, New Delhi,

2009

7. Siva Sankar Reddy T, D. Rupesh Kumar, and H.Sudarsana Rao (2010) A Study on Strength

Characteristics of Phosphogypsum Concrete, Asian Journal of Civil Engineering (Building and

Housing) Vol.11.No.4.Pages 411-420

8. Tara Sen and Umesh Mishra (2010) Usage of Industrial Waste Products in Village RoadConstruction,International Journal of Science and Development. Vol.1. No.2.

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