Controlled thermal cracking
Replacing most of the cement slashed the heat of hydration, so the massive RCC sections could cure without the thermal cracking that plagues mass concrete.
The Ghatghar pumped-storage scheme in Maharashtra — India's first roller-compacted-concrete (RCC) dam — was built with fly ash replacing up to 60–70% of the cementitious binder. It remains a landmark case for high-volume fly ash concrete.
In mass concrete, the enemy is heat. As cement hydrates it releases heat; in a large pour the core warms, expands, and then cracks as it cools. The classic fix is to replace much of the cement with a pozzolan — and few projects have pushed that further than Ghatghar.
Commissioned by the Water Resources Department of the Government of Maharashtra, the Ghatghar Hydro-Electric Project is a pumped-storage scheme with two 125 MW units, built across three roller-compacted-concrete dams — an upper dam, a lower dam and a saddle dam. It was India's first RCC dam.
RCC is placed as a stiff, near-dry mix, spread and compacted in continuous 300 mm layers by vibratory rollers — fast, but only workable with a very high proportion of fines. Fly ash supplied those fines. Where a typical blend keeps fly ash near 35% of the binder, Ghatghar ran it at 60% by weight, and in places up to 70% — combating the alkali–silica reaction and holding down the heat of hydration in both structural and mass concrete.
At peak, the contractor consumed on the order of 3,000 tonnes of fly ash a day, drawn from NTPC's nearby Nashik thermal plant — turning a power-station by-product into a dam.
Replacing most of the cement slashed the heat of hydration, so the massive RCC sections could cure without the thermal cracking that plagues mass concrete.
High-volume fly ash binds free alkalis, mitigating the expansive alkali–silica reaction in both the structural and mass concrete — protecting a 100-year asset.
Fly ash gave the fines RCC needs to be rolled in continuous lifts — quicker construction and a lower binder cost than a conventional concrete gravity dam.
“For the first time, the Ghatghar project used 60 percent fly ash in the fly-ash-plus-cement mixture — later raised to 70 percent — with the contractor consuming around 3,000 tonnes of fly ash a day.”
— Reported from the Ghatghar RCC dam project
Fly ash was used in Indian construction for the first time at the Rihand irrigation project in Uttar Pradesh, replacing cement by roughly 15% — the earliest proof of pozzolanic replacement at scale here.
India's first RCC dam pushed replacement to 60–70%, showing that fly ash could be the dominant binder in a durable, mass-concrete structure — not just a minor additive.
Studies converge on 15–30% replacement for optimal early and target strength, with higher dosages giving long-term strength and durability gains — the basis for PPC, ready-mix and block work nationwide.
If a dam ran at 60%, a 15–35% ready-mix replacement is a conservative starting point. What Ghatghar demonstrates is what was achieved on that project, with its own binder, aggregates and mix design — it does not establish that our Grade I will replace 60–70% of binder in yours. Project-specific replacement levels require their own mix design and performance testing.
High-volume mixes only work with a classified, lot-tested feed. That is exactly what we supply — a signed certificate against every dispatch.
Lower heat, suppressed alkali–silica reaction and reduced permeability arrive together with the cost and carbon cut — not as a trade-off against them.
This is an industry case study, not a Nagesh Trading supply reference: figures are drawn from the public sources above and are presented for illustration, and Nagesh Trading was not a supplier to this project. The 60–70% replacement reached at Ghatghar is a project outcome, not a specification for our product. Project-specific replacement levels require their own mix design and performance testing.
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