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The future shall demand less energy intensive greener cements

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Dr Sujit Ghosh, Executive Director – New Product and R&D, Dalmia Cement (Bharat), discusses the alternative raw materials that can be used in the production of cement and its impact on carbon emissions while underscoring the major challenges faced in using other cementitious materials.

What are the core raw materials used in the production of cement?

The core raw materials used in the production of cement are limestone (calcium carbonate) and clay (a source of silica). First, the limestone is roasted/calcined to create activated lime (CaO) in a calciner and then the activated lime along with siliceous clay is proportioned along with some other minor ingredients into a raw mix design and charged inside a kiln to form cement clinker; which is basically made of complex compounds of calcium-silica-oxides primarily, which when mixed with water, reacts, to form a cementitious gel paste that binds all aggregates together and when dried up provides strength to the concrete/plaster, made with cement and the aggregates.

Limestone (calcium carbonate) and clay (silica), which are both available in nature, are inert materials. Only when they are heat-treated at temperatures above 900oC, they become activated lime (CaO) and activated/amorphous silica (SiO2), and fuse inside the cement kiln in liquid form to form complex calcium-silica-oxides, that is cement or cement clinker.

What are the alternative raw materials that can be used in the production of cement? How does that impact the process of production? 

As explained in the previous paragraph, any activated lime (CaO) and/or activated/amorphous silica (SiO2), could be potential sources of cementitious material.  These could be alternative raw materials for cement production. Thus far, the most widely found and used sources of alternative materials are primarily ‘fly ash’ and ‘blast furnace slag’. Fly ash is a waste product from the burning of coal (as in a thermal power plant etc). It primarily contains amorphous/activated silica (SiO2), but very little active lime (CaO) in the Indian context. So, it is not reactive on its own, it needs activated lime (CaO) to become cementitious – which is available from cement clinker, when the two are co-processed in a cement manufacturing plant. Blast furnace slag likewise is a waste product from the steel manufacturing process and does contain some activated silica and activated lime, but again, not in the proportion/concentration to itself become cementitious. It also has to be co-processed with a cement clinker in a cement manufacturing plant. Overall, these alternative or supplementary cementitious materials, which are other industry wastes, due to the need for co-processing with cement clinker, may add some costs to the production process, but since the use of such alternative raw materials, reduces the dependence on highly energy-intensive clinker, they are welcome by the cement manufacturing fraternity, that helps lower the carbon footprint of production. These cements are called ‘blended cements’ – either fly ash blended (popularly known as PPC) or slag blended (popularly known as PSC) or fly ash + slag blended (popularly known as PCC).

How can the cost of production be reduced by using alternative or supplementary raw materials in cement production?

Since the use of alternative / supplementary cementitious materials has been prevalent in the world and in India, for blended cement production, for the last couple of decades, the demand for such other industry wastes (primarily from thermal power plant or steel plant) has been increasing steadily. This has led to a steep increase in prices for these industry wastes (mainly slags from steel plants) which otherwise were previously dumped in landfills, by opportunistic players and profiteering groups. Also, since steel plants and thermal power plants are not co-located with cement plants geographically, transportation costs of such bulky waste materials have also been increasing. Cost of blended cement production has to reduce or at least maintain at par, as well as, at the same time assist the nation in beneficially getting rid of other-industry-wastes. Cement players can do justice to climate-change by producing less energy intensive blended cements that are in no way inferior in quality to pure-clinker cements. Transport subsidies should also be provided to cement manufacturers by the government as well as at the same time try and administer some polluter-to-pay mechanism (so that these wastes are not conveniently dumped away in nearby landfills by the relevant industries).

Kanika Mathur

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Concrete

Star Cement Named Preferred Bidder For Boro Lakhindong Block

Preferred bidder for limestone mining lease in Assam

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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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Concrete

KERC Proposal To Cut Rooftop Solar Export Tariff Raises Concern

Consumers and advocates urge regulator to reconsider change

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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

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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.

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