NHAI Explores Use of Waste Materials for Ecologically Sustainable National Highway Infrastructure

NHAI and the Department of Fertilizers are conducting field trials to explore the use of Phosphor-Gypsum in National Highway construction to achieve a circular economy in the use of gypsum.

This by-product of fertilizer production was accredited by the Indian Road Congress for road construction for three years based on evaluations conducted by CRRI.

NHAI also encourages the use of waste plastic and fly ash in road construction as they have been proven to be durable, sustainable and economical. These initiatives are part of NHAI's commitment to reducing carbon footprint and promoting ecologically sustainable National Highway Infrastructure.

Phosphor-Gypsum

What is Phosphor-Gypsum?

Phosphor-gypsum is a by-product of the phosphate fertilizer industry, which is produced during the wet process of phosphoric acid production. It is a type of gypsum that contains high levels of phosphorus and other impurities, making it unsuitable for use in construction.

Composition and Characteristics:

Phosphor-gypsum is a white, powdery substance that is similar in appearance to regular gypsum. It typically contains between 10% and 25% phosphorus pentoxide (P2O5), as well as other impurities such as fluoride, silica, and heavy metals. Phosphor-gypsum is also slightly more soluble in water than regular gypsum, which can lead to environmental concerns if it is not properly disposed of.

Uses and Applications:

Phosphor-gypsum is not suitable for use in construction due to its high levels of impurities. However, it can be used as a soil amendment to improve the fertility of agricultural land. The phosphorus in phosphor-gypsum is readily available to plants, making it a valuable fertilizer. Additionally, phosphor-gypsum can be used in cement production as a substitute for natural gypsum. This can help reduce the environmental impact of cement production, as natural gypsum is a finite resource.

Environmental Concerns:

Phosphor-gypsum can pose environmental concerns if it is not properly disposed of. The high levels of phosphorus in phosphor-gypsum can lead to eutrophication of water bodies if it is discharged into rivers or lakes. Eutrophication occurs when excess nutrients, such as phosphorus, enter a body of water and stimulate the growth of algae and other aquatic plants. This can lead to oxygen depletion and the death of fish and other aquatic life.

Regulations:

In many countries, regulations have been put in place to control the disposal of phosphor-gypsum. For example, in the European Union, phosphor-gypsum is classified as a waste and must be disposed of in accordance with the Waste Framework Directive. In the United States, the Environmental Protection Agency (EPA) has established guidelines for the management of phosphor-gypsum, which include requirements for storage, transportation, and disposal.