2. Phosphogypsum is a by-product of phosphate fertilizer
plants and chemical industries for manufacture of phosphoric
acid by the action of sulphuric acid on the rock phosphate. It
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.
Due to its pozzolonic properties it can be used for partial
replacement of cement. The study aims to determine the
optimum amount of phosphogypsum that can give maximum
strength to the concrete.
3. Concrete as is well known heterogeneous mix of cement,
water and aggregates. The admixtures may be added in
concrete in order to enhance some of the properties desired
specially.
In India, demand for cement is more. Due to this
construction cost of the structure increases. The
phosphogypsum is an industrial waste by-product produced
in various industries like fertilizer industry, phosphate ore
and phosphoric chemical industry.
4. In order to overcome the scarcity of cement and decrease
the cost of concrete under these circumstances the use of
solid wastes, agricultural wastes, and industrial by-
products like phosphogypsum, fly ash, etc. came into use.
Utilization of industrial waste such as phosphogypsum not
only solves environmental problems but also provides a new
resource for construction industry.
The proper utilisation of phosphogypsum is needed to solve
environmental and disposal problems. In different countries
attempts have been made from time to time to find ways
and means of utilising phosphogypsum and therefore
disposing significant quantity of waste.
5. S.Venkatasubbaiah, Sri.V.K.Visweswararao (2017)
The present paper deals with the experimental
investigation on mechanical properties of partially cement
replaced phosphogypsum concrete using0%, 2.5%, 5%,
7.5%, 10%, 12.5%, 15%, 17.5%and 20% replacement with
M25 grade concrete with water-binder ratio of 0.48.
Koduru.Srinivasalu, P.Raghava (2017)
The experiment consists of testing concrete using 0%,
2.5%, 7.5%, 5%, and 10% replacement of phosphogypsum
for M20, M25, and M30 grades of concrete. It is observed that
cement can be replaced with phosphogypsum to develop to
good and hardened concrete to achieve economy.
6. Jahir Hussain .S , Jeyakumar (2016)
Most Concretes produced today contain materials in
addition to portland cement to help achieve the strength or
durability performance which includes fly ash, silica fume and
ground-granulated blast furnace slag used separately or in
combination. Phosphogypsum are used as admixture to improve
the performance of concrete. It is a waste material obtained
from fertilizer manufacturing.
S. Dhinakaran, R. Mercy Shanthi, (March 2015)
The experiment consists of testing partially replaced
phosphogypsum concrete using 0%, 2%, 4%, 6%, 8% and 10%
replacement of cement with phosphogypsum. The percentage
increase in compressive strength (at water- cement ratio 0.5) at
8% phosphogypsum content, when compared with plain
concrete is more then 20%
8. CEMENT
Portland cement is the basic ingredients of concrete, mortar
and most non speciality grout. The product obtained by
burning, then cooled and ground to the required fineness.
Ordinary Portland cement 53 grade conforming to IS code
was used. Different laboratory test were conducted on
cement to determine its standard consistency, Initial setting
time, final setting time and specific gravity.
9. FINE AGGREGATE
Sand is a natural granular material which is mainly
composed of finely divided rocky material and mineral particles.
The most common constituent of sand is silica (silicon dioxide,
or SiO2), usually in the form of quartz, because of its chemical
inertness and considerable hardness, is the most common
weathering resistant mineral. Hence, it is used as fine
aggregate in concrete. The Aggregate was tested for its physical
requirements such as gradation, fineness modulus, specific
gravity in accordance with IS 383-1970.
10. COARSE AGGREGATE
The shape and size distribution of the aggregate is very
important as it affect concrete by voids. Aggregate should
pass through 20mm sieve and retained on 10mm IS sieve.
Coarse aggregate should be hard, strong, dense, rough and
free from salt and organic matter. Well graded aggregate
provides denser concrete with fewer voids. The aggregates
were tested for their physical requirements such as
gradation, fineness modulus, specific gravity and bulk
density in accordance with IS 383-1970.
11. WATER
Water plays a vital role in achieving the strength of
concrete. It is practically proved that minimum water-cement
ratio 0.35 is required for conventional concrete. Water
participates in chemical reaction with cement and cement
paste is formed and binds with coarse aggregate and fine
aggregates. If more water is used, segregation and bleeding
takes place, so that the concrete becomes weak. If water
content exceeds permissible limits it may cause bleeding. If
less water is used, the required workability is not achieved.
Potable water fit for drinking is required to be used in the
concrete and it should have pH value ranges between 6 to 9.
12. PHOSPHOGYPSUM
Phosphogypsum refers to the calcium sulphate hydrate
formed as a by-product of the production of fertilizer
from phosphate rock. It is mainly composed of gypsum
(CaSO4·2H2O). The phosphogypsum known to have some of
the chemical impurities like phosphates and world-wide for
most of the applications as a binder or cements etc.
Chemical Constituents Percentage (%)
CaO 31.2
SiO2 3.92
SO3 42.3
R2O3 3.6
MgO 0.49
Phosphate, Fluoride 18.49
13.
14. CEMENT
Specific gravity of cement = 3.14
Fineness modulus of cement = 5.56%
The normal consistency of the given sample of cement = 36%
Initial setting time for the given cement = 35 minutes
FINE AGGREGATE
The specific gravity of fine aggregate = 2.56
Fineness modulus = 5.676%
TESTS ON MATERIALS
15. COARSE AGGREGATE
The specific gravity of coarse aggregate = 2.56
Water absorbed by the coarse aggregate = 1.5%
PHOSPHOGYPSUM
Specific gravity of phosphogypsum = 2.655
The percentage weight of residue over
the total sample = 6.66%
16. TARGET MEAN STRENGTH OF CONCRETE
The target mean strength for specified characteristics cube
strength at 28 days is given by,
f’ck = fck + ( t x s)
f’ck = 25 + (1.65 x 4) = 31.6 N/mm2
Water cement ratio = 0.40
Water content = 197.2 l/ m3
Cement = 197.2 /0.40 = 493.02 kg/m3
Mass of coarse aggregate =1023kg/m3
Mass of fine aggregate =627.45kg/m3
18. The phase I of this research work deals with the
experimental investigation of concrete by partially replacing
the cement by phosphogypsum with 7.5%, 10% , 12.5% and
15%. In the phase 1 of the project, the materials are collected
and various material tests were done. Mix design for M25
grade concrete is calculated.
19. The phase II of the project work involves testing of the
concrete specimens. The Fresh concrete as well as hardened
concrete properties of the phosphogypsum with different
percentages of replacement are needed to be tested with the
reference mix. The main aim of the project is to find the
optimal percentage of replacing cement with phosphogypsum.
20. IS 383-1970 Specification for coarse and fine aggregate from natural
sources for concrete.
IS 456-2000 Code of practice for plain and Reinforced concrete.
IS 10262:2009 Indian Standard Concrete Mix Proportioning-
Guidelines (First Revision).
IS 12269-1987 Specification for 53 grade ordinary Portland cement.
Chang.W, Engineering properties and construction application of
Phosphogypsum1990.
S.Venkatasubbaiah, Sri.V.K.Visweswararao, A Study on Replacement
of Phosphogypsumin Conventional Cement Concrete., International
Journal of Innovative Research in Science, Engineering and
Technology 2017.