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Changing normal concrete into durable concrete for tunnelling application

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In this second part of the two-part series paper, the author EugenKleen of Mc-Bauchemie Mueller GmbH and Co.KG looks at the materials required to change normal concrete to durable media resistant concrete for use in tunnelling application.The main materials, which can help change normal concrete to durable aggressive media resistant concrete, are:??New generation PCE based admixtures??Condensed silica fume or microsilica slurry or??Latest generation aluminosilicatePCE based admixturesMost of the new generation superplasticizers are from the Acrylic Polymer (AP) family. Polycarboxylate is a common term for the substances that are specifically used as Polyacrylate or Polycarboxylate ether (PCE). The PCE based Super Plasticizers are by far superior to the conventional once with respect to initial slumping as well as slump retention with time. The efficient working of these plasticizers is due to the new type of molecule designs. PCE based superplasticizers produce excellent properties when used with cementitious materials. The disadvantages associated with longer setting times of conventional superplasticizers is offset by PCE based super plasticizer and therefore its use in concrete can also attain high early strengths. The development of highly effective superplasticizers with long and consistent duration of action is therefore an important precondition for the production durable concrete, due to low water contents and high early strength requirements.Concrete additives based on PCE offer advantages like:Significant reduction of the water demand of the mix??Little loss of consistency??Short setting times??High early strengths??Low tendency to segregationThe advantages of these new generation polymers are very clear, not only in terms of performance but also in terms of the dosages used for similar conditions and this factor balances the disadvantages in economy, as new generation superplasticizers are relatively expensive per unit price.Condensed Silica Fume/Microsilica:The term ‘microsilica’ is adopted to characterise the silica fume, which is used for the production of concrete. Microsilica or Condensed Silica Fume (CSF) is a by-product resulting from reduction of high purity quartz with coal in the electric arc furnaces used in manufacture of silicon, ferrosilicon and other alloys of silicon.There are three main reasons for the incorporation of silica fume as an additive for HPC. Microsilica has a filter effect i.e. very fine particle distributed itself in the space between the materials in the concrete in a homogenous way to give rise to more dense concrete. Silica fume improves the strength of the transition zone between cement paste and aggregates. CSF is highly pozzolanic in combination with Portland cement.During cement hydration there is surplus of calcium hydroxide. The added condensed silica fume’s SiO2 reacts with surplus of calcium hydroxide, which are greater amounts of calcium silicate hydrate, which are denser and stronger than calcium hydroxide. The pozzolanic reaction and the filler-effect lead to a compaction of the cement paste and the conversion of CH crystals into CSH gel leads to homogenous paste. The phenomenon of dense packing in the interface zone of aggregates also contributes to increase the strength of the concrete on account of aggregates fully contributing their strength of concrete with silica fume is greater than those of the matrix, indicating the contribution of the aggregate of microsilica (50:50 with water) have all the benefits in transportation, dispensing methods, mixing times and dispersions to get the desired effect in durable concrete for tunnelling segments.New Generation Aluminosilicates:New generation aluminosilicates based on special nano-crystalizers have been developed. These new materials improve the properties that are crucial for the durability of high performance concrete. In addition to reducing chloride migration, an exceptional chemical and resistance to aggressive media of the concrete can be achieved with aluminosilicates. The concrete structure is simultaneously reinforced right down to nanoscale, density is improved and compressive and flexure strength as well as abrasion resistance of the high-performance concrete is increased. There is also a significant reduction of micro-crack formation, which makes it particularly suitable for the production of tunnelling concrete. Aluminosilicate reduce the proportion of portlandite by way of a pozzolanic reaction that changes it into the aluminosilicate crystals into calcium silicate hydrate. In addition to the unique resistance against acids a crystalline micro-reinforcement within the concrete structure is achieved. This reduces the risk of micro-crack formation, rendering concrete impermeable.Due to high homogeneity and reduced tackiness compared with microsilica based concrete, workability is improved significantly. In many instances this enables the production of high-performance concrete that can be pumped. In addition, a distinct improvement of the building structure’s aesthetics is gained due to the fair appearance of the concrete surface. Aluminosilicates perform over some of the disadvantages of microsilica:??Graded for dispersion in concrete??Graded particle size??Optimises mixing time within concrete??Good dispersion reduces unreacted material in the mix and increases passivation by C-S-H gel on aggregate surface??Material if agglomerated improve strength of the mix??Reduces risk of alkali silica reaction by agglomeration of aluminosilicate particles.All in all, the use of PCE admixtures and microsilica or aluminosilicate slurries in addition to the standard ingredients in concrete, plus excellent mix-design practices can facilitate the production of high performance concretes resistant to aggressive media, suitable for use in tunnelling applications.

Key difference between Microsilica and Aluminosilica


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false

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Microsilica

Aluminosilica

1

By-product of
ferrosilicium and silicium production, not specifically produced for concrete

1

Manufactured product. It
is only produced for use as concrete additive

2

Quantities are depending
on the metal industry and the economic development

2

Quantities are not
depending on other industries and are unlimited, therefore reliable
availability

3

Quality of the product
has a higher deviation because it is only a by-product

3

High quality standards
for end product because every step in production is controlled




























































































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Concrete

JK Cement marks 140 years of innovation and leadership

JK is one of India’s leading manufacturers of Grey Cement in India

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JK Cement Ltd. a leading building material company, one of India’s leading manufacturers of Grey Cement in India and one of the largest White Cement manufacturers in the world, celebrated 140 years of JK Organisation’s remarkable legacy at a grand event in the capital. The event honoured the group’s rich history, its significant contributions to multiple sectors of the Indian economy, and the unwavering dedication of its employees and partners.

The celebration gathered dignitaries, industry leaders, employees, and key stakeholders to reflect on JK Organisation’s journey from its inception to its present status as a global leader. Lieutenant Governor of New Delhi, VK Saxena, who himself started his career at JK Cement, along with Rajeev Shukla, Member of Rajya Sabha, graced the occasion. Key leaders of the JK Organisation, including Dr. Nidhipati Singhania, Vice President, JK Organisation, Dr. Raghavpat Singhania, Managing Director, JK Cement, and Madhavkrishna Singhania, Joint MD and CEO, JK Cement, were present to mark this significant milestone.

CEO’s from various known business houses both Indian and Multinational companies across sectors graced the occasion.

Reflecting on the organization’s journey, Dr. Nidhipati Singhania, Vice President, JK Organisation, said, “As we celebrate 140 years of JK Organisation, we are filled with immense pride and gratitude for our legacy, which is rooted in values of innovation, quality, and service to the nation. Our journey has been as much about business success as about driving positive change in the communities and industries we serve. The milestones we have achieved reflect our continuous efforts in advancing India’s infrastructure and industrial landscape.”

One of the key highlights of the evening was the recognising the long-serving employees and partners who have dedicated decades to JKCement. Their enduring loyalty underscores JK Organisation’s foundational values of trust and collaboration, which have been pivotal to the organisation’s success.

Addressing the guests at the event, Dr. Raghavpat Singhania, Managing Director, JK Cement, said, “This year along with the 140 years milestone, also marks two significant milestones for us: 50 years of grey cement business and 40 years of white cement business, affirming our leadership in the industry. Our recent expansion into coal mining underscores our commitment to vertical integration and sustainable resource management. We are dedicated to not only adapting to the evolving landscape but also driving positive change and creating lasting value for all our stakeholders and the nation.”

Emphasising the company’s commitment to innovation and progress, Madhavkrishna Singhania, Joint MD and CEO, JK Cement, said, “Our journey has been marked by resilience, adaptability, and a constant drive to exceed expectations. We’re committed to leveraging cutting-edge technology and sustainable practices to not only maintain our market leadership but also to contribute significantly to India’s progress. The trust of our stakeholders and the dedication of our team members have been instrumental in our success, and they will continue to be the pillars of our future endeavors.”

The event celebrated JK Organisation’s visionary outlook, showcasing its commitment to sustainable growth, technological innovation, and its influential role in driving India’s economic advancement.

VK Saxena, Lieutenant Governor, New Delhi, who was invited as the Chief Guest said “It’s an honour for me to be part of this landmark celebration for a company where I started my career as an Assistant Officer in Gotan, Rajasthan and worked for 11 years in different capacities with its White Cement plant. This exposure gave me insights of a corporate working, faster decision making and team work, which has helped me throughout my various stints thereafter. I wish all the best to JK Cement for all their Future endeavors in Nation Building”

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Concrete

Steel Ministry Proposes Rs.23.52 Lakh Crore for Decarbonisation

Steel Ministry unveils massive decarbonisation plan.

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Decarbonisation Proposal:
The Steel Ministry has outlined a substantial Rs.23.52 lakh crore proposal aimed at decarbonising the steel industry. This initiative is part of the broader sustainability and environmental goals set by the Indian government.

Objective and Goals:
The primary objective of the proposal is to reduce carbon emissions significantly and enhance the environmental performance of the steel sector. This aligns with India’s commitment to climate action and green growth.

Investment Focus:
The proposal will channel funds into advanced technologies, energy-efficient processes, and renewable energy sources. Key areas of investment include electrification, hydrogen-based steelmaking, and carbon capture technologies.

Expected Benefits:
Implementing this plan is expected to lead to major reductions in carbon emissions, improve air quality, and contribute to sustainable development. It will also bolster India’s position as a global leader in green steel production.

Industry Impact:
The steel industry, being a major emitter of greenhouse gases, will undergo a transformation. This shift will require industry-wide adaptation and could influence global steel market trends.

Government Support:
The Indian government is committed to providing policy support, incentives, and regulatory frameworks to facilitate this transition. This includes subsidies for green technologies and research and development funding.

Timeline and Phases:
The implementation will be carried out in phases over the coming years. Short-term goals will focus on immediate emission reductions, while long-term goals will target more comprehensive technological advancements.

Stakeholder Involvement:
Collaboration with industry stakeholders, technology providers, and research institutions will be crucial. Engagement with local communities and environmental groups will also play a role in ensuring the success of the proposal.

Challenges:
The initiative may face challenges such as high costs, technological barriers, and regulatory hurdles. Addressing these challenges will be essential for the successful execution of the decarbonisation plan.

Future Outlook:
The proposal positions India as a key player in the global movement towards sustainable steel production. It sets a precedent for other sectors to follow and supports the country’s broader climate goals.

Conclusion:
The Steel Ministry’s proposal for a Rs.23.52 lakh crore decarbonisation plan represents a significant step towards reducing carbon emissions in the steel industry. With substantial investment in green technologies and strong government support, this initiative aims to drive sustainable growth and position India as a leader in environmental stewardship.

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Concrete

New home prices in China fall 5.3% in August 2024

New home prices were down 5.3% from a year earlier.

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Official data revealed that China’s new home prices had fallen at their fastest rate in over nine years in August, as supportive measures failed to induce a significant recovery in the property sector. The data showed that new home prices were down 5.3% compared to the previous year, marking the sharpest decline since May 2015, compared to a 4.9% drop in July, based on calculations by Reuters from National Bureau of Statistics (NBS) data. Monthly figures indicated that new home prices had fallen for the fourteenth consecutive month, decreasing by 0.7%, which was the same drop recorded in July.

The property market in China continues to struggle with deeply indebted developers, incomplete apartments, and declining buyer confidence, which is putting a strain on the financial system and threatening the 5% economic growth target for the year. A Reuters poll had forecast that home prices in China would decline by 8.5% in 2024 and by 3.9% in 2025 as the sector struggles to stabilise.

Zhang Dawei, chief analyst at property agency Centaline, mentioned that the property market is still gradually bottoming out, with home buyers’ demand, income, and confidence expected to take some time to recover. He noted that the market was anticipating a stronger policy response. According to the official data released on Saturday, property investment had fallen by 10.2% and home sales had dropped by 18.0% year-on-year in the first eight months of the year.

Chinese policymakers have stepped up efforts to support the property sector, including reducing mortgage rates and lowering home buying costs. These measures have partially revitalised demand in major cities, while smaller cities, which have fewer home purchase restrictions and high levels of unsold inventory, are particularly vulnerable. This situation underscores the difficulties faced by authorities in balancing demand and supply across different regions.

In a research note on Friday, Nomura indicated that with the growth slowdown worsening under new headwinds in the second half of the year, Beijing might eventually need to step in as the “builder of last resort” by directly providing funding to delayed residential projects that have already been pre-sold. According to Bloomberg News, China may cut interest rates on over $5 trillion in outstanding mortgages as early as this month.

To support these mortgage rate cuts, economists at ANZ suggested that a reduction in the five-year Loan Prime Rate was likely in September, along with a 20 basis point cut to the medium-term lending facility (MLF) and a 50 basis point cut to the reserve requirement ratio (RRR).

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