The document summarizes a seminar presentation on using phosphogypsum in pavement construction. Phosphogypsum is a waste byproduct of fertilizer production that contains gypsum. It has several potential uses in road construction, such as soil stabilization, subgrade improvement, and as a base material or additive in asphalt. Experimental studies found that phosphogypsum has properties suitable for these uses, including adequate strength and permeability. While it poses disposal challenges due to potential radioactivity, utilizing phosphogypsum in pavement construction provides environmental benefits over disposal in landfills.

1. VISVESVARAYA TECHNOLOGICAL UNIVERSITY
Jnana Sangama Belagavi - 590018
Seminar Presentation on
“PHOSPHOGYPSUM IN PAVEMENT CONSTRUCTION”
Presented by: Seminar Guide Seminar Coordinators
Hruthik M K Mr. Suraj Shet Mrs. Megha Mayuri/
4MT19CV011 Assistant Professor Miss Prathiksha G
Assistant Professor
Department of Civil Engineering
MANGALORE INSTITUTE OF TECHNOLOGY & ENGINEERING
Accredited by NAAC with A+ Grade, An ISO 9001: 2015 Certified Institution
(A Unit of Rajalaxmi Education Trust®, Mangalore - 575001)
Affiliated to VTU, Belagavi, Approved by AICTE, New Delhi.
Badaga Mijar, Moodabidri-574225, Karnataka

2. CONTENTS
• INTRODUCTION
• MATERIALS
• WHAT IS PHOSPHOGYPSUM
• USAGE OF PHOSPHOGYPSM BY NHAI
• PHOSPHOGYPSM MANUFACTURE IN INDIA
• ADVANTAGES
• DISADVANTAGES
• SUMMARY

3. INTRODUCTION
• Phosphogypsum is a waste generated from fertilizer industry during the preparation of phosphoric acid. The production of phosphogypsum
is about 12 million tons/year in the country. Only about 40-50% is utilized for cement manufacturing, as fertilizer in agriculture and for the
manufacture of gypsum boards, etc. Remaining waste is dumped in a slurry form in a designated pond without any usage and is occupying
the costly land. The utilization of phosphogypsum in road construction has already been investigated by a number of researchers.
• Utilization of phosphogypsum for parking construction was investigated in Poland since 1970, and detailed research in road engineering
was carried out between 2007-09. (Research Report 1989). Paige-green and Gerber (2000) evaluated the feasibility of phosphogypsum as a
road pavement material.
• Based on geotechnical and strength tests, it was concluded that mixes of phosphogypsum-ash-binder mixes could be used for road
embankment and sub-base of road pavement. Dutta and Kumar (2016) investigated the suitability of fly ash-lime phosphogypsum
composite in road construction. It was concluded that 28 days cured sample could be used as a base/subbase material in road construction.

4. MATERIALS
• Gypsum is a rock like mineral commonly found in the earth's crust, extracted, processed
and used by Man in construction or decoration in the form of plaster and alabaster.
• During the time of the Pharaohs, Gypsum was used as mortar in the construction of the
Cheops Pyramid (3000 B.C.).
• Chemically it is CaS04.2H20 i.e. Calcium Sulphate Dihydrate.

5. WHAT IS PHOSPHOGYPSUM
• Phosphogypsum (PG) is 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).
• Although gypsum is a widely used material in the construction industry, phosphogypsum is usually not used, but
is stored indefinitely because of its weak radioactivity caused by the presence of naturally occurring uranium (U)
and thorium (Th), and their daughter isotopes radium (Ra), radon (Rn) and polonium (Po).
• The long-range storage of phosphogypsum is controversial.

6. USAGE OF PHOSPHOGYPSM BY
NHAI
• NHAI along with Department of Fertilizers, Ministry of Chemicals & Fertilizers is going to take up field trials on NHAI projects for
use of Phosphor-Gypsum in National Highway construction to achieve a circular economy in the use of Gypsum.
• The road was evaluated by Central Road Research Institute (CRRI) and based on their report, the Indian Road Congress
(IRC) has accredited neutralized Phosphor Gypsum waste material for road construction for a period of three years.

7. • The fertilizer company and CRRI have been asked to take up field trials on an NHAI project to evaluate performance of
Phosphor-Gypsum on a National Highway and to generate confidence among various stakeholders on use of Phosphor-
Gypsum waste material in Highway construction.
• NHAI is also encouraging use of waste plastic in road construction, which has already been tested very successfully.
Studies have established that roads built using plastic waste are durable, sustainable and increases life of the bitumen.
• Construction of one kilometer of 4-lane highway helps in disposal of approximately seven tons of plastic waste.
Similarly, NHAI has used ‘Fly Ash’ – fine residue of coal combustion in the Thermal Power Plants (TPPs) for
construction of Highways and flyover embankments.
• The 135 km long, six lane ‘Eastern Peripheral Expressway’, used 1.2 crore cubic meter of fly-ash in its construction.
NHAI has been encouraging the innovative use of new materials and is focused on reducing the carbon footprint,
enhancing durability and making construction more economical.

8. USAGE OF PHOPHOGYPSUM IN PAVEMENT
CONSTRUCTION
Phosphogypsum can be used as a material for pavement construction due to its ability to improve the properties of soil and provide
strength and stability to the pavement. Here are some ways in which phosphogypsum can be used for pavement construction:
1. Soil stabilization: Phosphogypsum can be used to stabilize soils by improving their physical and mechanical properties. It can
increase the strength and stability of soil, making it suitable for use as a base or sub-base material in pavement construction.
2. Subgrade improvement: Phosphogypsum can be used to improve the quality of the subgrade soil, which is the layer of soil
beneath the pavement. It can increase the strength and stability of the subgrade, which can help prevent pavement failure.
3. Base material: Phosphogypsum can be used as a base material for pavement construction. It can improve the strength and
stability of the pavement by providing a solid foundation.
4. Asphalt binder: Phosphogypsum can also be used as an additive in asphalt binder. It can improve the flow properties and stability
of the asphalt, which can help prevent cracking and other forms of pavement distress.

9. PHOSPHOGYPSUM MANUFACTURE IN
INDIA
Dhanlakshmi Chemicals offer high quality Phosphogypsum Chemical that contains minimum
90 % calcium sulphate. Our offered product finds its application in soil treatment industries
and helps in removing the Sulphur from the soil. Hence, choosing the right Gypsum Powder
Suppliers & Manufacturers in India is a must if you desire the standard excellence.
Phosphogypsum is radioactive due to the presence of naturally occurring and radium in the
phosphate ore.

10. ADVANATGES
1. Use as a soil conditioner: Phosphogypsum can be used as a soil amendment to improve soil structure, water-holding capacity, and
nutrient availability. It is an excellent source of calcium and sulfur, which are essential nutrients for plant growth.
2. Environmental benefits: By using phosphogypsum as a soil amendment, it helps to reduce the amount of waste that would otherwise be
sent to landfills. This reduces the environmental impact of waste disposal.
3. Cost-effective: Phosphogypsum is often available at low or no cost, as it is a waste product of the phosphate industry. This makes it an
affordable option for soil improvement.
4. Reduce soil erosion: The use of phosphogypsum in soil can help to reduce soil erosion by increasing the soil's ability to retain water
and nutrients.
5. Reduce the need for chemical fertilizers: Phosphogypsum is a good source of nutrients, particularly calcium and sulfur. Its use can help
reduce the need for chemical fertilizers, which can be costly and have negative environmental impacts.
Overall, the use of phosphogypsum has several benefits for agriculture and the environment, making it a valuable resource for sustainable
farming practices.

11. DISADVANTAGES
1. Radioactivity: Phosphogypsum can contain low levels of radioactivity due to the presence of naturally occurring radium in phosphate
rock. This can pose a risk to human health and the environment if not managed properly.
2. Environmental impact: The disposal of phosphogypsum can have a negative impact on the environment, particularly if it is not
properly managed. It can lead to the contamination of water sources and soil, and can harm wildlife and ecosystems.
3. Storage and transportation: Phosphogypsum is a bulky material that requires large amounts of storage space, and can be difficult and
expensive to transport. This can add to the cost and logistics of managing this waste product.
4. Regulatory compliance: In many countries, there are regulations governing the handling, storage, and disposal of phosphogypsum.
Companies that produce this waste must comply with these regulations, which can be time-consuming and costly.
5. Public perception: Due to concerns about radioactivity and environmental impact, some members of the public may be opposed to
the production and use of phosphogypsum. This can create challenges for companies that produce this waste, as they may face
opposition from local communities and environmental groups.

12. SUMMARY
Phosphogypsum waste material was evaluated for its geotechnical characteristics considering its possible utilization in the construction of
embankment, subgrade and subbase layer. A brief summary of the conclusions from the experimental study are given below:
1. The value of specific gravity of phosphogypsum is marginally low (2.5) as compared to soil due to its mineral composition.
2. It is a fine-grained material, no expansive, non-plastic and poorly graded.
3. The Maximum Dry Density (MDD) and Optimum Moisture Content (OMC) of phosphogypsum are observed to be 14.8 kN/m3 & 19.6
kN/m3 respectively. Compaction curve is flat in nature indicating insensitiveness of dry density with moisture content.
4. The average value of CBR is observed to be 26 %. The average coefficient of permeability is observed to be 1.45 x 10-7 m/sec which
indicates that phosphogypsum is fairly permeable material.
5. From the direct shear test, the shear strength parameters of phosphogypsum viz. angle of internal friction ( ) and cohesion (c) are observed
as 330 and 8 kN/m2 respectively.
6. Phosphogypsum is low compressible material and settlement is expected to be completed during the construction itself.
7. Factor of safety of 3m phosphogypsum embankment is observed to be more than 1.25 under critical water condition (sudden drawdown)
with seismic factor.

13. THANK YOU