paper which is unfavorable for the environment. This

 

paper done by, 1. Abdul Basit Khan ,2. Tushar
Raju, 3. Raunak Singh Suri

 

 

“1, 2- Students of S.I.R.T.S.  , 3.- Student of N.I.T.T.T.R.

 

Abstract — The concrete is made up the
combination of fine aggregate, coarse aggregate, cement and water. And is the
major part of construction. A large amount of
demolished waste is generated every year in India due to the rapid development
of infrastructure. Since a very small amount of this waste is recycled, so
placing this waste is a very serious problem because it requires a large amount
of space. This paper is a part of comprehensive program where the experimental are
carried out to evaluate the effect of partial replacement of coarse aggregate
by demolished waste concrete on compressive strength and workability of DAC
(Demolished Aggregate Concrete). For that 7, 14 and 28 days compressive
strengths were recorded. The earlier study on this project shows that the
compressive strength of the DAC (Demolished Aggregate Concrete) somehow
resembles with the conventional concrete if used in a proper amount up to 30%.
So in this study we have taken the demolished concrete aggregate 10%, 20%, 30%
by weight of the approved coarse aggregate and the concrete cubes were casted by
that demolished concrete aggregate then further tests conducted such as workability,
compressive strength for that DAC and the result obtained are found to be
comparable with the conventional concrete.

 

OVERVIEW

Due to development of
industries and urban areas waste generation is also increased, which is
unfavorable for the environment. This study deals with recycling and reusing of
waste concrete that is collected from buildings that are demolished and
collapsed. The main aim of this paper is to reduce the use of naturally
available river soil which is used as fine aggregate for producing concrete. There
is a shortage of about 55,000 million m3 due to
the construction of new infrastructure which shows that the demand of the
aggregates in future increases. 750 million m3 additional
aggregate is required to fulfill the demand of the road sector. There is a huge
gap between the demand and the During construction waste generated is about 40
kg per m2 to 60 kg per m2. Similarly, during renovation,
repair and maintenance work 40 kg/m2 to 50
kg/m2 waste is generated. The waste generated due to demolition of the
building is highest among all the wastes. If we demolish permanent building
about 300kg/m2 waste is generated and in case of demolition of semi-permanent
building 500kg/m2 waste is generated. The current concrete construction practice is
thought unsustainable because, not only it is consuming enormous quantities of
stone, sand, and drinking water, but also two billion tons a year of Portland
cement, which releases greenhouse gases. Experiments has been conducted for
waste materials like- rubber tires, e-waste, coconut shell, blast furnace slag,
waste plastic, demolished concrete constituents Environment must be protected
for the survival of the human beings and other lives on earth. So environment consciousness,
sustainable development and preservation of natural resources should be kept in
mind during the construction work and industrialization. At present, demolished
material are dumped on land or treated as waste, which means they cannot be
utilized for any purpose. If we put the demolished waste on land then the
fertility of the soil get decreases. 23.75 million tons of waste is generated annually
in India in the year of 2007 according to Hindu Online. According to CPCB
(Central Pollution Control Board) Delhi, 14.5 million tons out of 48 million waste
is generated from the construction waste from which only 3% is utilized in the
construction of the embankment. In 100 parts of the construction waste 40 parts
are of concrete, 30parts of ceramics, 5 parts of plastics, 10parts of wood, 5
parts of metal and 10 parts of some other mixed compounds. But the current
method adopted for the management of this waste are landfill mainly which
causes a giant amount of the construction and demolished waste deposition and
such huge amount affects the environment adversely. In India concrete, bricks,
sand, mortar and tile residues are the main materials found in the demolished
waste of buildings. This waste can be recycled or process in to the recycled
demolished aggregates which can be utilized in the concrete mixes. Demolished
concrete aggregate (DCA) is generally produced by the crushing of concrete
rubble, then screening and removal of contaminants such as plaster, paper, reinforcements,
wood, plastics. Concrete made with this type of recycled demolished concrete
aggregate is called Demolished aggregate concrete (DAC). The main purpose of

 

This study is to
determine the basic properties of DAC made of coarse recycled demolished
concrete aggregate then to compare them with the properties of concrete made
with natural aggregates concrete. Fine recycled aggregate cannot be applied in
the concrete which is used for structures so we can ignore its amount 70-75%
aggregates are required for the production of concrete. Out of this 60-67% is
of coarse aggregate & 33-40% is of fine aggregate. India is in the top 10 users
of the concrete due to rapid growth of infrastructure. As the demolished
aggregate is lighter than the natural aggregate so the concrete made from such
aggregate possesses low density but the water absorption of the demolished aggregate
is higher than the natural aggregate and the strength of the demolished
aggregates is somehow lesser than the natural aggregates. So concrete made from
these demolished aggregate can be utilized where more strength is not required e.g.
in low rising buildings, in reinforced concrete pavements etc.

 

 

MATERIALS
AND METHODOLOGY

Demolished waste: Demolished
concrete waste is collected from /residential building in Rajatnagar Bhopal
(m.p.). It is light grey in color.

 

 

 

Fig(a)
Demolished
Concrete Aggregate

 

 

 

Properties of
Demolished Aggregates:

 

i. Specific Gravity:

The crushed concrete is taken and
is sieved through 4.75mm sieve and the amount passed is taken for testing. The specific gravity in saturated surface dry condition of demolished
concrete aggregate was found from 2.45 which is less but satisfying the
results. If specific gravity is less than 2.4, it may cause segregation;
honeycombing & also yield of concrete may get reduced.

 

ii. Water Absorption:

The aggregate is
immersed in water for 24 hours and then the weight of the wet aggregate is
noted. The aggregate is

placed in an oven and
dried for 24 hours and the dry aggregate weight is noted. This gives the water
absorption of aggregate. The water absorption of aggregate is 1.8%, which is
comparatively more than that of the natural aggregates. The DCA from demolished
concrete be made of crushed stone aggregate with old mortar adhering to it.
Thus the water absorption results are satisfactory.

 

 

iii. Bulk Density:

The bulk density of
demolished aggregate is lower than that of natural aggregate, thus results are
not satisfactory;

due to low Bulk Density
the mix proportion gets affected.

 

iv. Crushing and Impact Values:

The demolished
aggregate is comparatively weaker than the natural aggregate against different
mechanical actions.

As per IS 2386 part
(IV), the impact and crushing values for concrete wearing surfaces should not
exceed 30% &

for other than wearing
surfaces 45% respectively. The crushing & impact values of recycled
aggregate satisfy

the BIS specifications
limit. From crushing and impact test it is found that use of recycled aggregate
is possible

for application other
than wearing surfaces.

 

 

 

 

 

 

 

 

 

 

 

MIX DESIGN

A mix design is a method of
calculating the amount of coarse aggregate, fine aggregate, cement content and
water content is calculated by using the experimental values obtained.

 

DESIGN STIPULATIONS:

 

Mix of concrete is M20

The fck valve is 20
N/mm2

Consider maximum aggregate size
is 20mm

Degree of workability = 0.90
(compaction factor)

Type of Exposure = Mild
exposure

 

 Test data of material
(to be determined in the laboratory):

 

Specific gravity of cement =
3.15

Specific gravity of CA = 2.63

Specific gravity of RFA = 2.84

 

Water absorption:

 

CA = 0.5 %

RFA (recycled fine aggregate) =
1.8 %

Free (surface) moisture:

 

CA = nil

RFA = 1%

Fine aggregates confirms to
zone 2 IS-383

 

MIX DESIGN CALCULATIONS:

 

TARGET STRENGTH:

 

Constant for 5% risk factor is
1.65. In this case standard deviation is taken from IS:456 against M 20 is 4.0.

ftarget =
fck + 1.65 x S

= 25
+ 1.65 x 4.0 = 31.6 N/mm2

Where,

S = standard deviation in N/mm2 =
4 (as per table -1 of IS 10262- 2009)

 

WATER CEMENT RATIO:

 

From Table 5 of IS 456,
(page no 20)

Maximum water-cement
ratio for Mild exposure condition = 0.55

Based on experience,
adopt water-cement ratio as 0.5.

0.5<0.55, hence OK. DETERMINATION OF COURSE AND FINE AGGREGATE:   CA = 1181.65kg FA = 579.80 Kg   Selection of Cement Content Water-cement ratio = 0.5 Corrected water content = 191.6 kg /m3 Cement content = From Table 5 of IS 456, Minimum cement Content for mild exposure condition = 300 kg/m3 383.2 kg/m3 > 300 kg/m3, hence, OK.

This value is to be checked for durability requirement from IS: 456.

In the present example against mild exposure and for the case of
reinforced concrete the minimum cement content is 300 kg/m3 which
is less than 383.2 kg/m3. Hence cement content adopted = 383.2 kg/m3.

As per clause 8.2.4.2 of IS: 456

Maximum cement content = 450 kg/m3

 

MIX RATIO:

 

The mix proportion of M25 found to be:

Cement                    replaced aggregate             coarse aggregates

372kg                             579.80
kg                           1181.65 kg

  1              :                       1.6                   :              
    3.2

Actual quantities required for the mix per bag of cement:

The mix is 0.50: 1: 1.6: 3.2 For 50 kg of cement, the
quantity of materials are worked out as below:

Cement = 50 kg

RFA = 77.5 kg

Coarse aggregates =159 kg

Water = 25 lit

 

Correction
due to absorbing / moist aggregate:-

Since the aggregate is saturated surface dry condition hence no
correction is required.

 

FRESH
CONCRETE TEST:

 

SLUMP CONE TEST:

 

This test is used to measure the properties of fresh concrete. This is an
empirical test that measures the workability of fresh concrete. It is used to
determine the consistency of the concrete.

True slump achieved. Slump 300mm Compaction factor 0.95. High workability
concrete, for sections with congested concrete, not normally suitable for
vibration,

Concrete Mixes

Conventional Cubes:

Volume of each cube = 3.375 x 10-3 m3

Volume of 3 cubes = 10.125 x 10-3 m3

Quantity of materials required (considering 10 % loss)

Cement = 5 kg

Sand = 7.7 kg

Coarse aggregates =15.7 kg

Water = 2.5 lit

The mix design is calculated and the amount of aggregate need for 9 cubes
is calculated. The mix is done by hand by adding water at different interval

COMPRESSIVE
STRENGTH:

 

The compressive strength of the concrete is tested for 7, 14 and 28 days
and the average value is taken. The compressive is done in compressive machine
and the values are plotted in a graph along with the corresponding strength of
conventional M20 grade concrete at the same days of curing.

 

 

Compressive
strength N/mm2

 

 

CONCLUSION:

 

Thus this paper clearly depicts the advantages of replacement of
aggregates with C&D waste concrete. The results of the compressive and
tensile strength are comparatively higher than the conventional concrete. Thus
by replacing the natural aggregate with the replaced waste can reduce the
amount of pollution as well as preserve nature at all cost. Further test are
being conducted for more research values. From the calculated results we can
conclude that whatever is destroyed can be reused in a more effective manner
without causing any damage to the environment. Demolished aggregate possess
relatively lower bulk

crushing, density and
impact standards and higher water absorption as compared to natural aggregate.
Tests conducted on demolished aggregates and results compared with natural
coarse aggregates are satisfactory as per IS 2386.The compressive strength of
demolished aggregate concrete is relatively lower up to 15% than natural

aggregate concrete. Using
demolished aggregate concrete as a base material for roadways reduce the
pollution involved in trucking material.

 

 

FUTURE
SCOPE

1. Sustainable
development of structures can be

achieved by using waste
demolished concrete

aggregate.

2. We can use the
plastic waste also as a coarse

aggregate in concrete.

3. Fine aggregate in the
demolished concrete can also

be utilized in future.

4. Demolished bricks and
stones possess the same

properties as coarse
aggregates.

 

 

 

 

 

 

 

III.
RESULTS AND DISCUSSION

Compressive strength is
the maximum compressive stress that, under a gradually applied load, a certain
solid material can carry on without fracture. Compressive strength of 3, 7 and
28 days of the DAC shown in the TABLE (III) for 0%, 10%, 20%, 30% replacement
of the coarse aggregate by demolished concrete aggregate for M-30 mix. Three
specimens for each proportion were cast and tested for comparative study. For 30%
replacement of coarse aggregate the 28 days compressive strength is 82.65% of
the compressive strength of conventional concrete. A concrete is termed as
workable if it is easily placed, transported, compacted, and finished without any
segregation. This property is tested by slump test. The results of slump test
are mentioned in TABLE (IV) for different percentages of demolished concrete
aggregate. The workability of the DAC is lower than the conventional concrete
because the rate of absorption of DA is higher than nominal aggregate.

 

REFERENCES

 

1 Katz, A. (2003), ”
properties of concete made with recycled aggregate from partially hydrated old
concete”, Cement Concrete Research, 33,703-11

 

2 “Demolition and
Reuse of Concrete and Masonry “, proceedings of Third International RELIMS
symposium,1993

 

3 Yuan, H. and Shen,
I. (2011), “Trend of the research on construction and demolition waste
management”, Waste Management 31 (4), 670- 679

 

4 Rao,A, Jha,K.N. and
misra S. (2005), “Use of aggregate from recycled construction and demolition
waste in concrete”, Recourses Conservation & recycling , 50(1)
71-81.

 

5 Padmini,A. K .,
Ramamurthy. K, and Mathews ,M.S (2008), ” Influence of parent concrete on the
properties of recycled aggregate concrete”, Construction and Building Material,
23 (2), 829-836.