1

CHAPTER 1

INTRODUCTION

In India, a huge quantity of construction and demolition wastes is produced

every year. These waste materials need a large place to dump and hence the disposal of

wastes has become a severe social and environmental problem. On the other hand

scarcity of natural resources like river sand is another major problem which results in

increasing the depth of river bed resulting in drafts and also changes in climatic

conditions. Hence it becomes necessary to protect and preserve the natural resources.

The possibility of recycling demolition wastes in the construction industry is thus of

increasing importance. In addition to the environmental benefits in reducing the

demand of land for disposing the waste, the recycling of demolition wastes can also

help to conserve natural materials and to reduce the cost of waste treatment prior to

disposal.

To minimize the waste generated from demolition process, the recycled concrete

wastes used as coarse aggregate in concrete. It is also used to reduce the construction

costs. To utilize the waste generated from structures. To use various waste materials in

construction units. To achieve the sustainable development of structural engineering.

To find the alternative of basic materials which are used in construction from past

many years. (Sherwood, 1995).The largest proportions of demolition waste are

concrete rubbles. It has been shown that the crushed concrete rubble, after separated

from other construction and demolition wastes and sieved, can be used as a substitute

for natural coarse aggregates in concrete or as a sub-base or base layer in pavements.

2

Successful application of recycled aggregate in construction projects has been

reported in some European and American countries, as reviewed by Desmysteret al.

(2000). The limited use of recycled aggregate in structural concrete is due to the

inherent deficiency of this type of material. In comparison with natural normal weight

aggregates, recycled aggregates are weaker, more porous and have higher values of

water absorption. The results of research studies by Hendrikset al. (1998) show that,

when recycled aggregates obtained from crushed concrete are used to replace up to

20% by weight of the coarse natural aggregate in concrete, little effect on the

properties of concrete is noticed.

The concrete strength decreases when recycled concrete was used and the

strength reduction could be as low as 40%. However, no decrease in strength was

reported for concrete containing up to 20% to 40%, but beyond these levels, there was

a systematic decrease in strength as the content of recycled aggregates increased. The

strength characteristics of concrete is affected by the quality of recycled aggregate at

high water/cement ratio, it was not affected when the water/cement ratio is low. This

study is carried out to determine the feasibility of using of recycled aggregate as

concrete. The concrete is expected to achieve its desired strength in stipulated period.

The effect of replacing the natural coarse aggregates with crushed concrete the

properties of concrete is reported.

3

1.1 NEED FOR STUDY

To utilize the waste generated from the structures. To use various waste

materials in construction units. To achieve the sustainable development of structural

engineering. To find the alternative of basic materials which are used in construction

from past many years.

1.2 IMPORTANCE OF STUDY

To reduce the dumping place required for disposal of solid waste. It enhancing

the combustible process of solid wastes. Due to scarcity of natural resources like river

sand, quarries etc. It needs to reduce the congestion due to demolition wastes at peak

places such as traffic areas, markets etc.

1.3 JUSTIFICATION

The study will carried out locally to check the feasibility of using recycled

aggregates in concrete. This study is taken to achieve the strength of recycled concrete

aggregate like as natural coarse aggregate. It leads to reduce an economical cost. And it

also used to reduce solid waste disposal.

4

CHAPTER 2

LITERATURY REVIEW

Madan MohanReddy.K, Bhavani.R, Ajitha. B (2012).In this study the use of

crushed construction and demolition waste as a Recycled Concrete Aggregate (RCA)

in the production of new concrete was investigated. They had tested Compressive

strength, Moister Content, Water Absorption, Specific Gravity, Abrasion Value,

Impact Value, Crushing Value, Bulk Density, Aggregate Thickness, Flakiness Index

and Slump Cone .The RCA were collected from local demolished structure. The study

was conducted with an M20 mix with the selected w/c ratio: 0.5 and the development

of compressive strength of the RAC and NAC at the age of 7 & 28 days were studied.

The performance of compressive strength produced by Recycled Aggregate Concrete

(RAC) and results are compared with the Natural Coarse Aggregate Concrete (NAC).

The result shows the compressive strength of RAC is on average 87% of the NAC and

the Slump of RAC is low and that can be improved by using Saturated Surface Dry of

RCA (SSD RCA). They conclude that the RAC specimen makes good quality

concrete.

S.K.Singh, P.C.Sharma (2013). They had tested Compressive strength, Flexural

strength, Moister content, Water absorption, Specific gravity, Modulus of elasticity,

Abrasion value, Impact value, Crushing value, Bulk density, Aggregate thickness,

Flakiness index and Slump cone. The recycled aggregate were collected from four

sources all demolished structures. The fine aggregate used in the concrete, i.e. recycled

and conventional is 100 percent natural. For both types of concrete i.e. M-20 and M-

25, 0.5 w/c ratio, maximum size of aggregate and mix proportion are kept constant.

The development of compressive strength of recycled aggregate concrete at the age of

5

1,3,7,14,28, 56, and 90 days; the development of tensile & flexural strength at the age

of 1,3,7,14 and static modulus of elasticity at the age of 28 days are investigated. This

study presents the experimental results of recycled coarse aggregate concrete and

results were compared with the natural crushed aggregate concrete. The results showed

the compressive, tensile and flexural strength of recycled aggregate are on average

85% to 95% of the natural aggregate concrete. The durability parameters were also

investigated for recycled aggregate concrete and are found to be in good quality

concrete.

Marco Pepe,Romildo D. Toledo Filho , Eduardus A.B. Koenders,EnzoMartinelli

(2010).As sustainability is becoming a fundamental requirement for all modern

industrial activities, upcoming environmental research efforts should be intended at

both enhancing the efficiency in the use of raw materials and reducing the carbon

footprint. They had tested Compressive strength and water absorption. The recycled

aggregate were collected from demolished structure. They found, Recycled concrete

aggregates (RCAs) present higher porosity than natural ones. The higher porosity of

RCAs results in a higher water absorption capacity. Autogenous cleaning process was

considered to reduce water absorption. The influence of the process duration on the

concrete properties is investigated. Both workability and strength are enhanced by the

process under consideration.

Prof. Chetna M Vyas, (Dr.) Darshana R Bhatt (2013). In this study of the result

and analysis, the experimental results showed that the early compressive strength of

concrete made of natural coarse aggregate and recycled coarse aggregate is

approximately same. The slump test indicates a decreasing trend of workability when

the percentage of recycled aggregate were increased. The target slump had been

achieved, where the range is from 75mm to 150mm. The workability was good and can

be satisfactorily handled for 0% recycled aggregate to 100% recycled aggregate. The

6

slump observed is less with more percentages of recycled aggregate concrete mixes.

The compression test result indicates an increasing trend of compressive strength in the

early age of the concrete specimens with minimum percentage of recycled aggregates.

The results also show that the concrete specimens with low % of replacement of

recycled aggregate get the highest strength when compared to the concrete specimens

with different higher percentage of recycled aggregate. From the obtained result, it is

possible to use minimum % of recycled aggregate for higher strength of concretes.

Hence the recycled aggregate can be used in concrete with minimum % of replacement

of natural coarse aggregate.

N.Sivakumar, S.Muthukumar,V.SivakumarD.Gowtham, V.Muthuraj(2014). The

aim for this study was to determine the strength and durability characteristics of high

strength structural concrete by using recycled coarse aggregates, which will give a

better understanding on the properties of concrete with recycled aggregates. The scope

of this study was to investigate the possibility of using low cost recycled coarse

aggregates as an alternative material to coarse aggregate in high strength structural

concrete. The experimental investigation were carried out using detailed strength and

durability related tests such as compressive strength test of cubes, split tensile strength

test of cylinders, modulus of elasticity tests acid resistance test, test for saturated water

absorption and porosity. The tests were conducted by replacing the coarse aggregates

in high strength concrete mixes by 0, 10, 20, 30, 40 and 50% of recycled coarse

aggregates. A 50% replaced mix with reduced w/c ratio was also tested. From the

experimental investigation it was found that recycled coarse aggregates can be used for

making high strength concretes by adjusting the w/c ratio and admixture contents of

the mix. When the percentage of RCA replacement was increased, compressive

strength gets reduced. However when water/cement ratio of mix was decreased, the

compressive strength increases. The target compressive strength (40MPa) can be

7

achieved for 30 to 40 % of RCA replacement by decreasing the water cement ratio and

adjusting the admixture content of mix. This is classified as high strength concrete and

can be applied in infrastructures, which need compressive strength up to 40MPa.

Another result found in this research is that when reducing the water cement ratio used

in recycled aggregate mixes, tensile strength and modulus of elasticity are also

improved. This will give an improvement in general strength characteristics of

structural building. The water absorption and porosity of RCA replaced mixes are

higher than normal mix but within the permissible limits. These properties can be

modified by reducing the w/c ratio and by incorporating admixtures.

Table no. 2.1 Literatury Review

sl.no Author Tests Result Conclusion

1

M.pepe,

R.D.Toledofilh

o, E.A.B.

Koenders,

E.Martinelli

Compressive

strength.

(M25, 28 days).

0% RCA =33.03Mpa

50%RCA without

autogenous process=

27.50Mpa.

50% RCA with

autogenous process=

29.92Mpa.

The compressive strength of

RCA increased, water

absorption and porosity

reduced by autogenous

cleaning process.

2 N.Sivakumar,

S.Muthukumar

, V.Sivakumar,

D.Goutham,

V.Muthuraj.

Compressive

strength.

(M40, 28 days).

Compressive

strength

With 0.4 w/c ratio

NCA= 37Mpa.

RCA= 27Mpa.

With 0.34 w/c ratio

RCA= 40Mpa.

The all strength of RCA

increased by adjusting the w/c

ratio.

8

3 Prof. chetna

M Vyas,

Prof.Dr.

darshana

R bhatt.

Compressive

strength.

(M20, M25,

M30, 28 days).

Compressive

strength

0%RCA= 38.1N/mm2.

40%RCA=

39.5N/mm2.

100%RCA=35.1 N/

mm2.

The compressive strength of

RCA concrete was reduced

while increasing the % of

RCA.

4 Madhanreddy.

k, Bhavani.R,

Ajitha.B

Compressive

strength

(M25, 28 days).

Compressive

strength

NCA= 28.18Mpa.

RCA= 25Mpa.

The result shows the

compressive strength of RAC

is on average 87% of the

NAC and the Slump of RAC

is low and that can be

improved by using Saturated

Surface Dry of RCA (SSD

RCA).

2.1 CONCLUSION FROM LITERATURY REVIEW

Therefore no decrease in strength in concrete containing up to 20% to 40% of recycled

aggregates, but beyond these levels, there was a systematic decrease in strength as the

content of recycled aggregates increased.

9

CHAPTER 3

MIX DESIGN

Mix design of concrete is the process of selecting the required ingredients of

concrete and finding their relative proportions with the aim of producing an

economical concrete of certain strength and durability. In order to test the specimen

using recycled aggregate we adopt M25 grade concrete. The mix proportion of M25

Grade is 1:1:2.The coarse aggregate used in this project is divided into two phase of

natural coarse aggregate and recycled concrete aggregate. The broken hardened

concrete, which passes through the 20mm sieve is used. We adopted the w/c as the

ratio of 0.5.

3.1 ORDINARY PORTLAND CEMENT

OPC 53 grade cement is used. This is the common type of cement which is used

for construction of many structures in the form of mortar and concrete. It is the one of

the binding material used in civil engineering constructions. It has high plastic

properties. It hardens in short time. Ordinary Portland (53 grade) Portland cement

available in the local market of standard brand was used in the investigation. Portland

cement is the most commonly used type of cement in the world today. Specific gravity

of cement = 3.15

10

3.2 COARSE AGGREGATE

Coarse aggregates are usually those particles which are retained on an I.S. 4.56

mm sieve. Generally for the concrete 20 mm size coarse aggregates are satisfied.The

aggregate should be clean and free from organic matter. For good concrete the value of

fineness modulus of coarse aggregate should be between 6 to8.The coarse aggregate of

20 mm size and angular in shape is used.

3.3 RECYCLED AGGREGATE

The demolished waste concretes were collected from different six sites.

Different kinds of concrete wastes are collected like plain cement concrete and

reinforced cement concrete. Totally 500 kg of waste concrete were collected. These

samples are broken down and sieved. The samples are sieved in 20mm sieve, these

samples taken for further use as provided by IS standards IS: 383-1970. The recycled

concrete aggregate must be clean and free from dust particles. The sample will satisfies

the following tests were taken to determine the properties of coarse aggregates like

Specific Gravity, Water absorption, Moister content, Impact value, Grading, Thickness

of concrete and Flakiness index. In six different sites, 4 sites waste materials not

satisfied the properties as provided by IS standards IS: 383-1970. Only two samples

satisfy the conditions, in it we took only one sample for further use for tests.

3.4 FINE AGGREGATE

Fine aggregate is sand which is usually obtained from rivers or lakes sometimes

beach sand is also used. The fineness modulus of sand should be around 2 to 3.2.For

this mix the fineness modulus is a size of 2.36mm. The locally available natural river

sand was used as fine aggregate. It was tested as per Indian Standard Specification IS:

383-1970.

11

3.4.1 Sieve analysis results

The sieve analysis done and reports located in below table.

Table no. 3.1 Sieve Analysis of Fine Aggregate.

Sieves Retained weight (g) % of Retained Cumulative % % of Finer

4.75mm 3 0.3 0.3 99.7

2.36mm 51 5.1 5.4 94.6

1.18mm 447 44.7 50.1 49.9

600 293 29.3 79.4 20.6

300 153 15.3 94.7 5.3

150 43 4.3 99.0 1

75 7 0.7 99.7 0.3

Pan 3 0.3 100 0

Total 1000 100 - -

Table no. 3.2 The Percentage of Finer Value Satisfy The Grade Zone – 1 From IS

383 – Part 1

Sieves % finer for grade zone – 1 from IS 383:part1 % finer obtained

4.75mm 90-100 99.7

2.36mm 60-95 94.7

1.18mm 30-70 49.9

600 15-34 20.6

300 5-20 5.3

150 0-10 1

12

3.4.2 Specific Gravity test

Empty weight of pycnometer, W1 = 678g

Weight of pycnometer wih 200g sand, W2 = 878g

Weight of pycnometer with 200g sand and full of water, W3 = 1634g

Weight of pycnometer with full of water alone W4 = 1518g

Specific gravity, (w2-w1)/ ((w2-w1)-(w3-w4) G = 2.66

3.4.2 Water Absorption test

Weight of dry sample, W1 = 1000g

Weight of sample after immersed in water for 24 hrs, W2 = 1012g

Percentage increase in weight, ((w2-w1)/w1) x100 = 1.2%

3.5 WATER

Water is an important ingredient of concrete. As a general guidance, if the water

is fit for drink it is fit for making concrete. However, some water containing a small

sum of salt is not suitable for concrete. Other yard-stick adopted is if the pH between 6

and 8 the water is accepted to be suitable. The best way is to use the water from a

particular source and concrete is made. The concrete is tested for 7 days and 28 days

strengths if 90% result is obtained it can be considered to be suitable.

The pH of the available water = 7.4

13

3.6 Concrete mix design for normal concrete

Grade designation : M25

Type of cement : OPC 53 grade

Maximum nominal size of aggregate : 20 mm

Maximum water-cement ratio : 0.5

Exposure condition : Severe

Degree of supervision : Good

Type of aggregate : Crushed angular aggregates

3.7 Test data for materials

Cement used : OPC 53 grade

Specific gravity of cement : 3.15

Specific gravity of

1) Coarse aggregate : 2.70

2) Fine aggregate : 2.66

Water absorption

1) Coarse aggregate : 0.54%

2) Fine aggregate : 1.2%

14

3.8 Target strength of mix proportioning

f’ck = fck + 1.65 s

f’ck = target average compressive strength at 28 days,

fck = characterastics compressive strength at 28 days, and s= standard

deviation.

From Table 1 of IS 10262-2009, Standard Deviation, s = 4 N/mm2

Therefore, target strength = 25 + 1.65 x 4 = 31.6 N/mm2

3.9 PERCENTAGE OF RCA AND SAMPLE DETAILS

The Recycled Concrete Aggregate is not added fully in specimens. The recycled

concrete aggregate is added in different ratios in a combination of natural coarse

aggregate and recycled concrete aggregate in the following method.

Table no. 3.3 Sample Details.

SAMPLE NAME % OF RCA

RCA1 0%

RCA2 20%

RCA3 40%

RCA4 60%

RCA5 80%

RCA6 100%

NCA - Natural coarse aggregate

RCA – Recycled concrete aggregate

15

CHAPTER 4

PROCESS

4.1. COLLECTION OF MATERIALS

The demolished concrete waste is collected from six different sites. First sample

collected from demolished residential building near Jaya Engineering College,

Thiruninravur, Chennai - 23. Second sample collected from demolished residential

building near Skywalk, Aminjikarai. Third sample collected from residential building

near Periyapalayam, Thiruvallur district. Fourth sample collected from demolished

commercial building near Arakkonam. Fifth sample collected from residential building

near Thiruvallur Railway Station. Sixth one collected from demolished residential

building at Avadi. Totally 1200 kg of waste concrete is collected from different sites

and taken through the casting site.

Figure no.4.1 Collection of Materials.

16

4.2. MANUAL CRUSHING

The waste concrete material is stored in the casting site. We would crush the

demolished concrete wastes. There are two types of crushing methods are available.

That are, i) MECHANICAL CRUSHING, ii) MANUAL CRUSHING. In this study we

crushed the concrete wastes manually. In manual crushing, different kinds of hammers

are used, like steel hammer, wood hammer and small size hammers. In this process,

nearby we crushed the waste concrete for required size and shapes. The crushed

concrete aggregates would be free from cement portions. Totally 800 kg of recycled

concrete aggregates separated from 1200 kg of crushed concrete.

Figure no.4.2 Manual Crushing of Waste Materials

17

4.3. SEGREGATION

The crushed concretes have not uniform in size. It has dust particles. Here

segregation is needed compulsory. The size of 20mm recycled concrete aggregates

would be segregated. The segregation of recycled concrete aggregate is of different

sizes and shapes for using it in making specimens. The recycled aggregate is sieved

through the 20mm sieve and the particles retained in 20mm sieve is taken and weighed.

Then a check for appropriate shape is also made. About 400 kg of recycled aggregate

is crushed and segregated which is to be used for making specimen samples. In this

process Sieve Analysis Flakiness Index and Aggregate Thickness were tested for

segregate the recycled aggregates.

Figure no.4.3 Segregation of Waste Materials.

18

4.4 BATCHING AND MIXING

After fixing the desired proportion the quantity of required ingredients, viz,

cement, coarse aggregate, fine aggregate and recycled aggregate, have to be measured

out in batches for mixing. This process of measuring out ingredients is called batching.

Batching may be done by weight or by volume.

In weight batching method all the ingredients of concrete are directly weighed in

kilogram. This is a slow process.

In volume batching method, two units of measurement, viz, liquids are measured

in liter and solid materials in cubic meter.

For example, in the M25 grade concrete for the specimen size of 15x15x15cm

cube with 20% of partial replacement of recycled aggregate needs, 2.1kg of cement,

2.1kg of sand, 3.36kg of natural coarse aggregate, 0.84kg of recycled concrete

aggregate and 1.1 liter of water.

For example, in the M25 grade concrete for the specimen size of 30x15co

cylinder with 20% of partial replacement of recycled aggregate needs, 3.4kg of cement,

3.4kg of sand, 5.44kg of natural coarse aggregate, 1.36kg of recycled concrete

aggregate and 1.7 liter of water.

19

4.5. MANUAL MIX

Mixing of concrete may be done by hand or by machine. Mixing should be done

thoroughly so as to have a uniform distribution of ingredients which can be judged by

uniform color and consistency of concrete. On a clean, hard and water tight platform

cement and sand are mixed dry using shovels until the mixture shows a uniform in

color. Then aggregate added and mixed uniformly. Based on the water cement ratio the

required quantity of water is added and mixed and placed or cast within 30 minutes.

The concrete mixed by man power. The grade of specimen used is M25. The material

is taken for M25 concrete is done using weight batching. The six type of specimen

were used in which ratio of natural coarse aggregate and recycled concrete aggregate

varies. The water cement ratio as adopted 0.5

Figure no.4.4 Manual Mixing of Concrete

20

4.6 CASTING AND CURING OF SPECIMEN

The cube specimen is of size 15cmx15cmx15 cm. the largest nominal size3 of

both aggregates does not exceed 20mm. The size of cylinder is 15cmx30cm.the moulds

are be of metal moulds, preferably of steel or cast iron. A tamping steel bar of 16 mm

diameter long 0.6m long with a bullet end is used for compacting. The concrete is

filled into the mould in 5m deep approximately. Each layer is compacted by tamping

rod or by vibration. After the top layer has been compacted the top of the mould is

leveled using a trowel. The top is covered with glass or metal plate to prevent

evaporation. The specimens are demoulded after 24 hours and submerged into clean

water for curing.

Figure no.4.5 Casting of Specimens

21

Figure no.4.6 Curing of Specimens.

22

CHAPTER 5

EXPERIMENTAL INVESTIGATION

Testing of concrete is used to determine the strength and properties of concrete.

The testing of both natural coarse aggregate and recycled aggregate were also

investigated. There are two types of testing of concrete i) Testing of Fresh concrete and

ii) Testing of Hardened concrete. The tests concerned with fresh concrete are to check

the workability of concrete. The hardened concrete is to find the strength, creep effects,

durability, etc.

5.1 MOISTURE CONTENT

The various moisture state in which an aggregate may exists being are

Damp or wet – aggregate in which the pores connected to the surface are filled

with water and with free water also on the surface.

Saturated surface dry – aggregate in which the pores connected to the surface are

filled with water but with no free water on the surface.

Air dry – aggregate that has a dry surface but contains some water in the pores.

Two of these, saturated surface dry and oven dry, are used as basis for specific

gravity calculations. Total moisture content was measured by measuring the mass of a

sample of the recycled concrete representative of moisture content in the collected

sample being tested, by drying the sample and obtained the mass again.

23

Table no.5.1 Determination of Moister Content of Recycled Concrete Aggregate

Sl.no Description Sample 1 Sample 2 Sample 3

1 Weight of recycled coarse

aggregate taken w1, (g) 500 550 600

2 Weight of oven dried after

24 hrs w2, (g) 480 525 575

3 Moister content 4.16% 4.76% 4.34%

4 Average moister content 4.42%

Table no.5.2 Determination of Moister Content of Natural Coarse Aggregate

Sl.no Description Sample 1 Sample 2 Sample 3

1 Weight of natural coarse

aggregate taken w1, (g) 500 550 600

2 Weight of oven dried

after 24 hrs w2, (g) 475 527 578

3 Moister content 5 % 4.6% 4.5%

4 Average moister content 4.7%

24

5.2 WATER ABSORPTION

The water absorption of the recycled concrete aggregate is measured in

accordance with Indian standards. Water absorption in computed as a percentage by

subracting the oven dry mass from the saturated surface dry mass, dividing by the oven

dry recycled concrete cubes and multiplying by 100.

Table no.5.3 Determination of Water Absorption of Recycled Concrete

Aggregate.

Sl.no Description Sample1 Sample2 Sample 3

1 Weight of recycled

concrete aggregate w1,

(g)

1000 1250 1500

2 Weight of saturated

surface dry w2, (g) 1005.6 1255.5 1506.4

3 % of water absorption 0.6% 0.57% 0.64%

4 Average % of water

absorption 0.62%

Table no.5.4 Determination of Water Absorption of Natural Coarse Aggregate.

Sl.no Description Sample1 Sample2 Sample 3

1 Weight of recycled concrete aggregate

w1, (g) 1000 1250 1500

2 Weight of saturated surface dry w2,

(g) 1006 1255.7 1505.9

3 % of water absorption 0.56% 0.55% 0.52%

4 Average % of water absorption 0.54%

25

5.3 SPECIFIC GRAVITY

DEFINITION –The specific gravity of a material is the mass of the material in

air divided by the mass of an equal volume of water. A material with s specific gravity

of 3.00 would be thus three times as heavy as that of water.

Each material particle is made up of solid matter and voids that may or may not

contain water. Since the material mass will vary with its moisture content, specific

gravity is determined at fixed moisture content. The various moisture states in which a

material may exist have been described previously.

The volume of the material particle is usually assumed to be the volume of solid

matter and internal pores. Two different values of specific gravity may be calculated

depending upon whether the mass is used as oven dry or a saturated surface dry (SSD)

mass. Bulk specific gravity is the oven dry mass divided by the mass of a volume of

water equal to the SSD material volume, while bulk specific gravity SSD is the SSD

mass divided by the mass of a volume of a water equal to the material volume.

TEST METHODS – The specific gravity of the recycled concrete aggregate is

measured in accordance with Indian standards. Recycled concrete aggregates, dried to

constant mass at 100ºc to 110ºc, cooled in air and immersed in water for 24 hrs. it is

then removed from the water and dried to a saturated surface dry state using with (dry

cloth) large absorbent cloth. The mass of a sample in air is determined and then it is

placed in a sample container of a perforated bucket for determination of its mass in

water. The mass of sample in water is less than that in air and the loss in mass is equal

to the mass of the water displaced. Therefore, the loss in mass is the mass of a volume

of water equal to the recycled concrete aggregate volume.

26

5.3.1 Specific gravity of natural coarse aggregate

Empty weight of pycnometer, W1= 678 g

Weight of pycnometer with 200 g blue metal, W2= 878 g

Weight of pycnometer with 200 g blue metal and full of water, W3= 1644 g

Weight of pycnometer with full of water alone, W4= 1518 g

Therefore, G = 2.70

5.3.2 Specific gravity of recycled concrete aggregate

Table no.5.5 Determination of Specific Gravity of Recycled Concrete Aggregate.

Sl.no Description Sample 1 Sample 2 Sample 3

1 weight of recycled concrete

aggregate w1, (g). 1000 1250 1500

2 Weight of saturated surface dry w2,

(g) 1050 1320 1575

3 Weight of perforated empty bucket

in submerged condition w3,(g). 600 600 600

4 Weight of perforated bucket and

sample in submerged condition w4,

(g).

1250 1275 1300

5 Submerged recycled concrete

aggregate weight w5, (g) 650 675 700

6 Specific gravity 2.65 2.60 2.69

7 Average specific gravity 2.63

27

5.4 IMPACT VALUE

Since the recycled concrete aggregates are soft materials when compared with

natural coarse aggregate used in concrete, in view of larger scale construction program

and for effecting economy in the cost of construction, soft aggregates having adequate

mechanical strength in terms of impact value may be made use of in the concrete.

Determination of recycled concrete aggregates impact value is measured in

accordance with Indian standards. The recycled concrete aggregate samples of which

passes through 12.5 mm IS sieve and retained on a 10 mm IS sieve had been taken for

this test. Tested recycled concrete aggregates are removed and the whole of it sieved

on the 2.36 mm IS sieve. The observation and the results are tabulated below as in

given table

5.4.1 Impact test for natural coarse aggregate

Weight of container with 10 mm aggregates, W1= 1217 g

Weight of container with sample passed through 2.36 mm sieve after W2= 968 g

Mean aggregate impact value = [(W1-W2) / W1] X 100

= [(1217-968) / 1217] X 100

=20.46 %

28

Table no.5.6 Determination of Impact Value of Recycled Concrete Aggregate.

Slno Description Sample 1 Sample 2 Sample 3

1 Weight of empty mould

w1,(g) 1875 1875 1875

2 Weight of mould + sample

w2, (g) 2375 2380 2365

3 Weight of sample w3, (g) 500 515 490

4 Weight of sample passed

through 2.36 mm IS sieve

w4 (g)

95 120 135

5 Weight of sample retained

on 2.36 mm IS sieve w5

(g)

405 395 355

6 Impact value 19% 23.33% 27.55%

7 Average impact value 23.5%

5.5 RECYCLED CONCRETE AGGREGATE THICKNESS

Recycled concrete aggregates are selected at random in different places and their

thickness are measured using vernier caliper at different locations in a recycle concrete

cubes itself, and then the average has been considered. The thickness of recycled

concrete aggregates are varied in the ranges from 20mm.

5.6 FLAKINESS INDEX

Referring the Indian standards, it is concluded that the flakiness index of the

recycle concrete aggregate is 100%.

29

5.7 GRADING

DEFINITION – Grading refers to the distribution of particle sizes present in a

material. The grading is determined in accordance with the Indian standars.

TEST METHODS – The recycled concrete aggregate sample weighs and

sieved successfully on the appropriate sieves starting with the largest. The number and

size of sieves selected for a sieve analysis in depends upon the particle sizes present in

the sample and the grading requirements. Each sieve was shaken separately over a

clean tray until not more than trace passes, for period of two minutes. The shaking of

sieve was done with a varied motion, backwards and forward, left to right, right to left,

circular clockwise and anti – clockwise, and with frequent jarring, so that the recycle

concrete aggregates are kept moving over the surface in frequently changing

directions. On completion of sieving, the mass of material retained on each sieve and

the pan was weighed and the results are given in table.

FINENESS MODULUS – Using the sieve analysis results, a factor called the

fineness modulus is computed. It is the sum of the total percentages retained on each of

specified series of sieves, divided by 100. Although fineness modulus is most

commonly computed for fine aggregates, the fineness modulus of coarse aggregate is

needed for some proportioning methods. Even though the 20mm sieve was used in the

sieve analysis, this is not included in the calculation. Since the total percent retained on

the 4.75mm sieve is 100%, 100% will also be retained on the smaller sieves specified

in the fineness modulus definition.

Based on this calculation if fineness modulus has been made here.

30

Table no.5.7 Fineness Modulus of Recycled Concrete Aggregates

Sl

no

Sieve size

(mm).

Mass

retained

(g)

%

retained

Cumulative

% retained

% passing Fineness

modulus

calculation

(total %

retained)

1 20 mm 35000.00 90.00 85.00 90.00 90.00

2 12.50 mm 19500.00 83.83 65.83 81.17 82.83

3 10.00 mm 12500.00 63.50 43.33 67.67 63.50

4 04.75 mm 6750.00 51.67 26.00 51.00 51.60

5 Pan 5000.00 41.00 100.00 38.00 41.00

6 Total 78750.00 100.00 100.00 100.00 -

7 02.36 mm 3100.00 25.00 35.00 28.00 22.00

8 01.18 mm 1400.00 15.00 25.00 21.00 15.00

9 600 µm 3500.00 8.00 15.00 10.20 08.50

10 300 µm - - - - 100

11 150 µm - - - - 100

12 Sum 674.43

13 Fineness modulus = 674.43/100 = 6.74

31

5.7.1 Sieve analysis for natural coarse aggregate

Table no.5.8 Sieve Analysis For Natural Coarse Aggregate.

Sieves Retaining

weight (in ‘g’) % retained

Cumulative

% % finer

25 mm 0 0 0 100.0

20 mm 231 23.1 23.1 76.9

12.5 mm 629 62.9 86.0 14.0

10 mm 125 12.5 98.5 1.5

Pan 15 1.5 100.0 0

Total 1000 100

% passed through 20mm sieve and retained in 12.5 mm sieve = 62.9 %

For good concrete the value of fineness modulus of coarse aggregate should be

between 6 to8.

32

5.8 SLUMP CONE TEST

The test can be conducted in the field or laboratory. This test is not suitable for

very wet and very fry concrete. The apparatus for conducting the slump test consist of

a metallic mould in the form of frustum of a cone with 20 cm bottom diameter, 10 cm

top diameter and 30 cm height. A steel tamping rod of 16mm diameter and 0.6 m long

with a bullet end is used for tamping. The internal surface of the mould is cleaned and

placed on a smooth non- absorbant surface. The mould is filled in four layers of equal

height. Each layer is compacted for 25 times. After filling the mould and rodded, the

excess concrete is stuck off and leveled. The mould is lifted upward from the concrete

immediately rising it slowly. This allows the concrete to subside. This subsidence is

referred as slump of concrete. The difference in height of themould and that of the

subside concrete is measured and reported in mm which is taken as the slump of

concrete.

Figure no.5.1 Slump Cone.

33

Table no.5.9 Slump Value

SLNO TYPE SLUMP (mm)

1 RCA1 61

2 RCA2 52

3 RCA3 45

4 RCA4 40

5 RCA5 39

6 RCA6 35

Figure no 5.2Comparison of Slump Value.

0

10

20

30

40

50

60

70

RCA%

SLU

MP

VA

LUE

(mm

)

PERCENTAGE OF RCA %

Slump Cone Test

RCA1-0%

RCA2-20%

RCA3-40%

RCA4-60%

RCA5-80%

RCA6-100%

34

5.9 COMPRESSIVE STRENGTH

The cube compressive strength for all the mixes at 14 and 28 days of curing is

presented in table 5.1. It is an easy and most common test. The tests are conducted in

cubes. The cube specimen is of size 15x15x15 cm. the largest nominal size3 of both

aggregates does not exceed 20mm. the moulds are be of metal moulds, preferably of

steel or cast iron. A tamping steel bar of 16 mm diameter long 0.6m long with a bullet

end is used for compacting. The concrete is filled into the mould in 5m deep

approximately. Each layer is compacted by tamping rod or by vibration. After the top

layer has been compacted the top of the mould is leveled using a trowel. The top is

covered with glass or metal plate to prevent evaporation. The specimens are

demoulded after 24 hours and submerged into clean water. The specimens are tested in

a compression testing machine at the completion of 14 and 28 days. Compression on

the cube undergoes lateral expansion.

Figure no.5.3Compressive Strength of Cube.

35

Table no.5.10 Compressive Strength of Concrete Cubes

SLNO TYPE COMPRESSIVE STRENGTH ( N/mm2)

14 DAYS 28 DAYS

1 RCA1 28.7 34.4

2 RCA2 30.5 36.8

3 RCA3 32.8 38.3

4 RCA4 27.9 33.1

5 RCA5 25.2 29.0

6 RCA6 20.3 25.8

Figure no.5.4 Comparison of Compressive Strength of Concrete Cubes

0

5

10

15

20

25

30

35

40

45

14 days 28 days

com

pre

ssiv

e st

ren

gth

n/m

m2

days

Compressive strength of cube

RCA1-0%

RCA2-20%

RCA3-40%

RCA4-60%

RCA5-80%

36

5.10 SPLIT - TENSILE STRENGTH

The size of cylinder is 15x30cm. This is the indirect tension test. In this test a

cylindrical specimen is placed horizontally between the loading surfaces of a

compression testing machine. The load applied until failure of the cylinder along the

vertical diameter. The main advantage of the test is the same compressive testing

machine and the same cylindrical specimen used for compression test may be used.The

split tensile strength of cylindrical specimen values shown in the below table 5.2.

Figure no.5.5 Split Tensile Strength of Concrete.

37

Table no 5.11Split Tensile Strength of Cylinder Specimen.

SLNO TYPE SPLIT TENSILE STRENGTH (N/mm2)

14 days 28 days

1 RCA1 2.11 2.57

2 RCA2 2.17 2.62

3 RCA3 2.26 2.73

4 RCA4 2.08 2.49

5 RCA5 2.02 2.40

6 RCA6 1.92 2.26

Figure no.5.6 Comparison of Split Tensile Strength of Cylinder.

0

0.5

1

1.5

2

2.5

3

14 DAYS 28 DAYS

split

ten

sile

str

en

gth

n/m

m2

days

split tensile test

38

5.11COMPARITIVE ANALYSIS

Test results of recycle concrete aggregate properties were compared with normal

coarse aggregates and they are presented in table here in.

Table no.5.12 Comparitive Analysis.

Sl no Physical and mechanical properties Natural

coarse

aggregate

Recycled

concrete

aggregate

1 Moister content 4.7% 4.42%

2 Water absorption 0.54% 0.62%

3 Specific gravity 2.70 2.63

4 Impact value 20.46% 23.5%

5 Fineness modulus 6 to 8 6.74

6 Aggregate thickness 20mm 20mm

7 Flakiness index 100% 100%

8 Compressive strength 34.4N/mm2

38.3N/mm2

9 Split tensile strength 2.57N/mm2

2.73N/mm2

10 Slump cone test 61mm 45mm

39

CHAPTER 6

RESULTS AND DISCUSSION

6.1 MOISTURE CONTENT

For the selected sample of recycled concrete cubes, the average moisture content

in the recycled concrete aggregates was found to be 4.42%.Each recycled concrete

specimens particles is made up of solid matter and voids that may or may not contain

water. Since the recycled concrete aggregate are basically wood based on organic

material and hence it is moister retaining capacity would be more compared with

normal aggregates. The moister content of samples may have some different with its

state existence. The recycled concrete aggregates usually carry some moister and that

becomes part of mixing water. With the different state of shells and its moister

contents, they will absorb some of the mixing water when it is used in concrete.

6.2 WATER ABSORPTION

For the selected sample of recycled concrete cubes, the average water absorption

in the recycled concrete aggregates was found to be 0.58%.Each recycled concrete

specimens particles is made up of solid matter and voids that may or may not contain

water. Since the recycled concrete aggregate are basically wood based on organic

material and hence it is water absorbing capacity would be more compared with

normal aggregates. The water absorption of samples may have some different with its

state existence. The recycled concrete aggregates usually carry some moister and that

becomes part of mixing water. With the different state of shells and its water

absorption, they will absorb some of the mixing water when it is used in concrete.

40

6.3 SPECIFIC GRAVITY

For the selected sample of recycled concrete aggregate, the average of specific

gravity was found to be as 2.63.The specific gravity of an aggregate used in mixture

proportioning calculation to find the absolute volume that a given mass of material will

occupy in the mixture. Absolute volume of an aggregate refers to the space occupied

by the aggregate particles excluding the voids between the particles. The specific

gravity for normal weight aggregate used in concrete ranges from 2.52 to 2.63.

6.4 IMPACT VALUE

The average impact value of the recycled concrete aggregates was found to be in

as 23.5%. The aggregate impact value gives relative measures of the resistance of an

aggregate to sudden impact or shock. The aggregate impact value should not be more

than 45% by the weight of aggregate used for concrete other than wearing surfaces and

30% by weight for concrete to be used as wearing surfaces, such as runways, road and

pavements.

6.5 AGGREGATE THICKNESS

The thickness of recycled concrete aggregates are varied in the ranges were

found to be from 20mm.

6.6 FLAKINESS INDEX

The flakiness index of the recycled coarse aggregate is 100% flaky material. Flat

particles in concrete aggregate will have particularly objectionable influence on the

workability, cement requirement, strength and durability, excessively flaky aggregate

makes very poor concrete.

41

6.7 GRADING

To grade the recycled coarse aggregate, the fineness modulus of the recycle

coarse aggregates were found to be and the average fineness modulus was 6.74,

fineness modulus will give some idea of the mean size particles in the entire body of

the aggregate. The limits of fineness modulus for aggregate are 1) for aggregate having

maximum size of aggregates in the range of 2 to 3.5, 2) for coarse aggregate having

maximum size of aggregate 20 mm is in the range of 6 to 8.

6.8 SLUMPCONE TEST

In case of dry sample, slump will be in the range of 25-50 mm that is 1-2 inches.

But in case of wet sample, the slump may vary from 150-175mm or say 6-7 inches. So

the slump is specifically mentioned along the mix design and thus it should be checked

as per your location. 20-50 is used for road work mass concrete and 50-100 and above

used for RC beams and slabs.

6.9 COMPRESSIVE STRENGTH

The cube compressive strength for all mixes at 14 and 28 days of curing and the

results show that the concrete specimen with more replacement of recycled concrete

aggregates have the lowest compressive strength when compared to the concrete

specimens with less recycled concrete aggregate for both 14 and 28 days of curing. The

compressive strength of the concrete specimens for 40% recycled concrete aggregate is

38.3 N/mm2 which met the target strength of 33.4 N/mm

2.

42

6.10 SPLIT TENSILE STRENGTH

The cylinder split tensile strength for all mixes at 14 and 28 days of curing and

the results show that the concrete specimen with more replacement of recycled

concrete aggregate have the lowest split tensile strength when compared to the

concrete specimens with less recycled concrete aggregate for both 14 and 28 days of

curing. The split tensile strength of the concrete specimens for 40% recycled concrete

aggregate is 2.73 N/mm2 which met the target strength of 2.57 N/mm

2.

43

CHAPTER 7

CONCLUSION

Research on the usage of waste construction materials is very important as the

quantity of waste materials is gradually increasing as result of increase in population

and increase in urban development. Furthermore, with the cheaper price of recycled

aggregates compared to natural aggregates, the builders can carry out the construction

task with lesser material cost. From the present experimental investigation it was found

that the recycled aggregates will influence much in hardened properties of concrete. As

the percentage of crushed concrete coarse aggregate increased, strength of the concrete

gets decreased

To achieve the strength of the concrete, use 100% of crushed coarse aggregate in

compression element like concrete blocks and concrete pavements. As there is

considerable reduction in compressive strength with recycled aggregate, further

research is needed to explore about the usage of recycled aggregates in combination

with different fibrous materials with special reference to its applications on structural

elements like concrete slabs, beams, columns and walls, Apart from this more studies

are required to understand the long term durability characteristics of concrete made

using recycled aggregates.

44

CHAPTER 8

REFERENCE

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