Concrete

The Future of Gypsum

Published

4 years ago

July 15, 2022

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ICR charts out the evolution of gypsum and the role it plays in manufacturing in a bid to understand the economics of sustainability in cement production.

The word gypsum is derived from the Greek word ‘gypsos’ meaning ‘plaster.’ The quarries of the Montmartre district of Paris have long furnished burnt gypsum (calcined gypsum) used for various purposes, this dehydrated gypsum became known as plaster of Paris. The ability to harden or set when added with water makes it a very useful mineral for construction. In the mid-18th century, Gypsum was found to have great capabilities as a fertiliser. It is this connection as a fertiliser that today the world over phospho gypsum is now available aplenty as a by-product from fertiliser plants, and which can be gainfully used as an additive in the cement making process, replacing mineral gypsum.
The production of phosphate fertilisers requires breaking down calcium-containing phosphate rock with acid, producing calcium sulphate waste known as phospho-gypsum (PG). Similar is the case with the desulphurisation process of flue gas (to take out the SOx from the emissions) from power plants when natural limestone is used for this process resulting in FGD gypsum as the bi-product. This product is pure enough to replace natural gypsum in a wide variety of fields including drywalls, water treatment and cement set retarder.

Sustainability ahead
As a sustainability initiative, replacing natural gypsum scores better, but first let us understand the role of gypsum in the cement to concrete process.
The main purpose of adding gypsum in the cement is to slow down the hydration process of cement once it is mixed with water. The process involved in hydration of cement is that, when the water is added into cement, it starts reacting with the C3A (tricalcium aluminate, which is the main component of Portland cement) and hardens. The time taken in this process is very less, which doesn’t allow time for transporting, mixing and placing. When gypsum is added into the cement and water is added to it, reaction with C3A particles takes place to form ettringite. This ettringite is initially formed as very fine-grained crystals, which form a coating on the surface of the C3A particles. These crystals are too small to bridge the gaps between the particles of cement. The cement mix therefore remains plastic and workable. The time allowed for mixing, transporting and placing plays an important role in strength, composition and workability of concrete. As gypsum retards the process of hydration, it is termed as retarding agent of cement.
The role of gypsum in concrete making can be summarised as follows:

Gypsum prevents flash setting of cement during manufacturing.
It retards the setting time of cement.
Allows a longer working time for mixing, transporting and placing.
When water is mixed to cement aluminates and sulphates react and evolve some heat but gypsum acts as coolant and brings down the heat of hydration.
Gypsum cements possess considerably greater strength and hardness as compared to non-gypsum cement.
Water required in gypsum based cement for the hydration process is less.
The use of gypsum as an additive in cement ranges from 2.5 to 5 per cent.
In its natural form, gypsum can be found as thick layers in shale and as attractive crystals. No gypsum deposits are 100 per cent pure. It is usually found with deposits of a combination of the following: limestone, sand, shale, anhydrite and sometimes rock salt. To be a commercial deposit, gypsum content should be at least 75 per cent. But as mines get old the percentage of gypsum could be as low as 45 per cent in many of the natural deposits.

Logistically speaking
Gypsum mines or deposits can be found all over the world, but Spain, Thailand, United States, Turkey, Russia, UAE, Oman and Chile are the leading producers. India has deposits mainly in Rajasthan and that makes the logistics cost play an important role in the use of gypsum in cement and concrete in India. There are two components to be seen, the percentage of gypsum in the mineral (purity) that one is transporting and therefore total cost of moving it when compared with other forms of gypsum, which could be non-mineral, from synthetic or anhydrous to simply the spent acid or other forms of industrial or chemical waste.
The desulphurisation process itself now being made mandatory for all coal fired power plants creates an enormous opportunity for non-mineral gypsum to be used in cement. But the economics could be very tricky. Let us see the cost dynamics in some details as this could be the most sustainable way for producing gypsum for cement and concrete.
It is calculated that a 500 MW power plant would need 40,000T of limestone annually to take care of the SOx emissions through the desulphurisation process. This would amount to about 12 million tonne of limestone consumption (less than 3 per cent of the total limestone use per year) for the entire power generation of India. But the economics would lie in transportation. Even if limestone is available free of cost, the transportation cost including handling and royalty beyond 250 km could rise to Rs 1000/T as the landed cost at the power plant. The FGD gypsum after production would need to be transported to the cement grinding unit, which if more than 250 km would again cost the same. Thus the FGD gypsum would then compete with phospho gypsum, which is available aplenty in fertiliser or phosphate plants.
As these options compete with each other, use of natural gypsum would subside as the
enormous logistics cost of either importing it or transporting it across India would not be sustainable in the future.

–Procyon Mukherjee

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Star Cement Named Preferred Bidder For Boro Lakhindong Block

Preferred bidder for limestone mining lease in Assam

Published

18 hours ago

June 29, 2026

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Star Cement has been declared the preferred bidder for the mining lease for Boro Lakhindong West Block following e-auctions conducted by the Government of Assam. The block is located in Boro Lakhindong Village, Umrangso Tehsil, Dima Hasao District, Assam, and extends over an area of 123 hectares. The estimated limestone resource is 207.822 million (mn) tonnes (t), a quantity that will supply raw material for cement production and support the company’s manufacturing operations in the region.

The company is engaged in the manufacturing and selling of cement clinker and cement and distributes products across the north-eastern and eastern states of India. Star Cement operates plants and logistics networks that procure and process limestone to produce clinker for cement, and the addition of Boro Lakhindong is presented as a strategic enhancement of feedstock availability. The preferred bidder status secures rights to the specified lease area under the terms of the auction process.

Financial results for the company in the fourth quarter of fiscal year 2026 showed a consolidated net profit rise of 20.24 per cent to Rs 1,481.0 mn on an 11.54 per cent increase in revenue to Rs 11,735.5 mn compared with the corresponding quarter of the previous year. Those results reflected higher sales volumes and revenue growth in the company’s primary markets and are cited in company disclosures accompanying the lease announcement. The reported performance provides context to the company’s ability to pursue and finance new mining lease opportunities.

Market reaction to the declaration was modest, with the scrip rising zero point thirty six per cent to trade at Rs 212 on the BSE. The award of the Boro Lakhindong lease concludes the e-auction process for the west block and assigns operational rights to Star Cement as the preferred bidder, subject to completion of statutory and contractual formalities.

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KERC Proposal To Cut Rooftop Solar Export Tariff Raises Concern

Consumers and advocates urge regulator to reconsider change

Published

18 hours ago

June 29, 2026

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The Karnataka Electricity Regulatory Commission (KERC) has proposed a reduction in the tariff paid for surplus electricity that rooftop solar installations export to the grid, prompting concern among consumers, renewable energy advocates and industry specialists. The proposal arrives while the Central government and state governments are promoting clean energy adoption and offering subsidy schemes to encourage rooftop solar deployment. Thousands of households in Karnataka, particularly in Bengaluru, have invested substantial sums in rooftop systems to reduce reliance on conventional power and support state renewable targets.

Stakeholders have raised questions about the implications of a lower export tariff for the financial attractiveness of rooftop solar investments and the pace of the state transition to renewables. Industry analysts warned that a reduction in compensation for excess generation could discourage new installations and extend payback periods for existing systems. Current messaging from authorities, which simultaneously promotes adoption while proposing lower export rates, has been described by user groups as creating contradictory signals for consumers.

Experts argued that policy measures should focus on grid modernisation rather than reducing consumer benefits, with investments in transmission and distribution networks needed to manage higher volumes of distributed solar generation. Consumer groups and renewable advocates are preparing written submissions to the regulator and are urging retention of incentives that support household adoption of rooftop systems. KERC has invited public objections and suggestions as part of a consultation process that will determine the final tariff framework.

The outcome of the consultation is expected to influence the future growth of rooftop solar across the state and shape investor confidence in small-scale renewable projects. Residents who have already installed rooftop panels are monitoring developments closely because changes to compensation mechanisms may affect household finances and the speed of return on investment. Observers noted that coherent policy, aligned incentives and grid upgrades would be essential to sustain momentum in the rooftop solar sector.

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Indian Railways Plans Green Fly Ash Transport Network

Published

3 days ago

June 27, 2026

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Specialised rail logistics will move fly ash from power plants to infrastructure industries.

New Delhi

Indian Railways is planning a large-scale green logistics initiative to transport fly ash from thermal power plants to industries where it can be reused in infrastructure and construction activities.

The initiative was discussed during a review meeting chaired by Union Minister for Railways Ashwini Vaishnaw. Union Ministers of State for Railways V Somanna and Ravneet Singh Bittu were also present.

India generates nearly 340 million tonnes of fly ash every year from thermal power plants. The proposed initiative aims to create an efficient rail-based transport system using specialised containers and dedicated logistics arrangements to move fly ash safely from power plants to end-use industries.

Fly ash is widely used in road construction, cement manufacturing, brick production, concrete, blocks and boards. By improving its movement through the railway network, the initiative is expected to support better utilisation of this industrial by-product while reducing environmental concerns linked to storage and disposal.

The move also aligns with India’s circular economy goals by converting waste from thermal power generation into a useful raw material for the construction and infrastructure sectors. Wider availability of fly ash can help reduce material costs in areas such as bricks and cement, supporting more affordable infrastructure and housing development.

Through this initiative, Indian Railways aims to provide a cleaner, safer and more organised transport solution for fly ash, turning an environmental challenge into an infrastructure resource.