Concrete

Durable Concrete

Published

6 months ago

June 14, 2024

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Benefits of using ternary blend-cement, flyash and GGBFS.

Cement is the prime ingredient in concrete. One tonne of cement produces around 0.8 to 1 MT of carbon dioxide. It’s worth noting that efforts are being made to reduce the carbon footprint of cement production by using supplementary cementitious materials such as flyash and GGBS in concrete. In case of ternary blended concrete, supplementary cementitious materials flyash, GGBS are used in addition to cement, sand, aggregate, water and admixture.
To evaluate the percentage of replacement of cement with flyash and GGBS, one needs to understand the properties of concrete mixed with flyash, GGBS as ingredient, structure strength, stripping time, durability requirements.
Flyash: Pulverised coal is used in thermal power plants for electricity generation. A by-product of this combustion reaction is flyash. The electrostatic precipitators (ESPs) used inside chimneys of the power plants remove flyash before ejecting out the combustion gases into the atmosphere. Flyash is a very fine particle like residue, which has pozzolanic properties. Hence, it is often blended with cement and also used as partial replacement of cement.
Flyash consists of silica (SiO2), alumina (Al2O3) and calcium oxide (CaO) as its major components.

Due to the spherical shape of flyash, water demands in concrete are reduced and concrete becomes more cohesive.
Silica in flyash reacts with calcium hydroxide released from cement to form CSH Gel.
Formation of CSH Gel leads to increase in strength of concrete further and makes the concrete dense and durable.
35 per cent of cement can be replaced with flyash according to IS specification.
Early strength is observed to be less for flyash concrete. Due to slow development of strength of concrete, stripping time gets delayed.

Ground granulated blast furnace slag (GGBFS): Blast furnace slag is a by-product of iron ore during the iron extraction process. Amongst all mineral admixtures, blast furnace slag has the highest specific gravity (2.8 to 3.0). The slag fineness is slightly more than that of the cement.
There are various types of slag available like air cooled slag, expanded or foamed slag, granulated slag. GGBFS possesses both cementitious and pozzolanic properties. An activator is needed to hydrate the slag.

GGBFS increases the initial setting time of the concrete. But it does not alter the workability of the concrete much because its fineness is almost the same as that of the cement.
The early rate of strength gain in concrete is diminished by replacement of cement in the concrete with GGBFS.
The final strength is improved by slag cement and the durability of the concrete is increased.
Concrete uses in marine construction are highly prone to chemical attack and corrosion. GGBFS as a concrete ingredient increases resistance against sulphate and chloride attack.
Normally concrete tends to segregate with GGBS as an ingredient.

Ternary blend: Ternary blended concrete is observed to be more cohesive and workable due to presence of flyash in concrete. Early strength gain can be achieved by using both cement and GGBS in concrete. Concrete with ternary blend is a win-win situation in terms of good product quality, optimising the cost of concrete, durability and resistance against chemical attack. Additionally, the use of SCMs in concrete can contribute to sustainability efforts by minimising the cement content which is associated with significant carbon dioxide emission during its manufacturing process. The hydration process of ternary blended concrete is divided into primary reaction by OPC and GGBS, pozzolanic reaction of GGBS and flyash as the secondary process. Both materials react with Calcium hydroxide produced by cement hydration to form CSH gel which gives denser microstructure than conventional OPC concrete. The dense structure improves the durability properties of ternary blended concrete. Process yields to minimise penetration of aggressive chemicals such as sulphate, chloride as compared to conventional concrete mix.

– Nagesh Veeturi and Sumanta Sahu

(Communication by the management of the company)

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Concrete

Jefferies’ Optimism Fuels Cement Stock Rally

The industry is aiming price hikes of Rs 10-15 per bag in December.

Published

3 weeks ago

December 4, 2024

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Cement stocks surged over 5% on Monday, driven by Jefferies’ positive outlook on demand recovery, supported by increased government capital expenditure and favourable price trends.

JK Cement led the rally with a 5.3% jump, while UltraTech Cement rose 3.82%, making it the top performer on the Nifty 50. Dalmia Bharat and Grasim Industries gained over 3% each, with Shree Cement and Ambuja Cement adding 2.77% and 1.32%, respectively.

“Cement stocks have been consolidating without significant upward movement for over a year,” noted Vikas Jain, head of research at Reliance Securities. “The Jefferies report with positive price feedback prompted a revaluation of these stocks today.”

According to Jefferies, cement prices were stable in November, with earlier declines bottoming out. The industry is now targeting price hikes of Rs 10-15 per bag in December.

The brokerage highlighted moderate demand growth in October and November, with recovery expected to strengthen in the fourth quarter, supported by a revival in government infrastructure spending.
Analysts are optimistic about a stronger recovery in the latter half of FY25, driven by anticipated increases in government investments in infrastructure projects.
(ET)

Concrete

Steel Ministry Proposes 25% Safeguard Duty on Steel Imports

The duty aims to counter the impact of rising low-cost steel imports.

Published

3 weeks ago

December 4, 2024

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The Ministry of Steel has proposed a 25% safeguard duty on certain steel imports to address concerns raised by domestic producers. The proposal emerged during a meeting between Union Steel Minister H.D. Kumaraswamy and Commerce and Industry Minister Piyush Goyal in New Delhi, attended by senior officials and executives from leading steel companies like SAIL, Tata Steel, JSW Steel, and AMNS India.

Following the meeting, Goyal highlighted on X the importance of steel and metallurgical coke industries in India’s development, emphasising discussions on boosting production, improving quality, and enhancing global competitiveness. Kumaraswamy echoed the sentiment, pledging collaboration between ministries to create a business-friendly environment for domestic steelmakers.

The safeguard duty proposal aims to counter the impact of rising low-cost steel imports, particularly from free trade agreement (FTA) nations. Steel Secretary Sandeep Poundrik noted that 62% of steel imports currently enter at zero duty under FTAs, with imports rising to 5.51 million tonnes (MT) during April-September 2024-25, compared to 3.66 MT in the same period last year. Imports from China surged significantly, reaching 1.85 MT, up from 1.02 MT a year ago.

Industry experts, including think tank GTRI, have raised concerns about FTAs, highlighting cases where foreign producers partner with Indian firms to re-import steel at concessional rates. GTRI founder Ajay Srivastava also pointed to challenges like port delays and regulatory hurdles, which strain over 10,000 steel user units in India.

The government’s proposal reflects its commitment to supporting the domestic steel industry while addressing trade imbalances and promoting a self-reliant manufacturing sector.

(ET)

Concrete

India Imposes Anti-Dumping Duty on Solar Panel Aluminium Frames

Move boosts domestic aluminium industry, curbs low-cost imports

Published

3 weeks ago

December 4, 2024

admin

The Indian government has introduced anti-dumping duties on anodized aluminium frames for solar panels and modules imported from China, a move hailed by the Aluminium Association of India (AAI) as a significant step toward fostering a self-reliant aluminium sector.

The duties, effective for five years, aim to counter the influx of low-cost imports that have hindered domestic manufacturing. According to the Ministry of Finance, Chinese dumping has limited India’s ability to develop local production capabilities.

Ahead of Budget 2025, the aluminium industry has urged the government to introduce stronger trade protections. Key demands include raising import duties on primary and downstream aluminium products from 7.5% to 10% and imposing a uniform 7.5% duty on aluminium scrap to curb the influx of low-quality imports.

India’s heavy reliance on aluminium imports, which now account for 54% of the country’s demand, has resulted in an annual foreign exchange outflow of Rupees 562.91 billion. Scrap imports, doubling over the last decade, have surged to 1,825 KT in FY25, primarily sourced from China, the Middle East, the US, and the UK.

The AAI noted that while advanced economies like the US and China impose strict tariffs and restrictions to protect their aluminium industries, India has become the largest importer of aluminium scrap globally. This trend undermines local producers, who are urging robust measures to enhance the domestic aluminium ecosystem.

With India’s aluminium demand projected to reach 10 million tonnes by 2030, industry leaders emphasize the need for stronger policies to support local production and drive investments in capacity expansion. The anti-dumping duties on solar panel components, they say, are a vital first step in building a sustainable and competitive aluminium sector.