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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
false
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

NDMC Rolls Out Intensive Sanitation Drive Across Lutyens Delhi

Municipal body intensifies cleaning and monitoring across the capital

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The New Delhi Municipal Council has launched an intensive sanitation drive across Lutyens’ Delhi, aiming to raise cleanliness standards in the capital’s central precincts. The programme will combine enhanced manual sweeping with mechanised cleaning and systematic waste removal to cover parks, heritage precincts and prominent thoroughfares. Authorities described the initiative as a sustained effort to improve public hygiene and reduce environmental hazards while maintaining the area’s civic image.

Operational teams have been instructed to prioritise drain clearing and litter hotspots, with special attention to markets and transit nodes that attract heavy footfall. Coordination with city utilities and waste processing units will be stepped up to ensure timely collection and disposal, and supervisory rounds will monitor adherence to cleaning schedules. Officials also intend to use data-driven planning to deploy resources efficiently and to identify recurring problem areas.

The council plans to engage resident welfare associations and business stakeholders to foster community participation in maintaining cleanliness and to support behavioural change campaigns. Public communication will be amplified through notices and outreach to encourage responsible waste handling and to inform residents about collection timings and segregation norms. Enforcement measures for littering and unauthorised dumping will be reinforced as part of a broader strategy to deter violations and sustain cleanliness gains.

The move reflects a focus on urban sanitation that officials link to public health priorities and to the city administration’s commitment to maintaining civic amenities. Monitoring mechanisms will include regular reporting and inspections to review outcomes and to recalibrate operations where necessary, according to municipal sources. The council emphasised that continued community cooperation will be essential for the drive to deliver lasting improvements in the appearance and hygiene of the capital’s core areas.

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Concrete

UltraTech Appoints Jayant Dua As MD-Designate For 2027

Executive named to succeed current managing director in 2027

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UltraTech Cement has appointed Jayant Dua as managing director (MD) designate who will take charge in 2027, the company announced. The appointment signals a planned leadership transition at one of the country’s largest cement manufacturers. The board has set a clear timeline for the handover and has framed the move as part of a structured succession plan.

Jayant Dua will be referred to as MD after assuming the role and will be responsible for overseeing operations, strategy and growth initiatives across the company’s network. The company said the designation follows established governance norms and aims to ensure continuity in executive leadership. The appointment is expected to allow a phased transfer of responsibilities ahead of the formal changeover.

The decision is intended to provide strategic stability as UltraTech Cement navigates domestic infrastructure demand and evolving market dynamics. Management will continue to focus on operational efficiency, capacity utilisation and cost management while aligning investments with long term objectives. The board will monitor the transition and provide further information on leadership responsibilities closer to the effective date.

Investors and market observers will have time to assess the implications of the announcement before the change is effected, and analysts will review the company’s outlook in the context of the succession. The company indicated that it will communicate any additional executive appointments or organisational changes as they are finalised. Shareholders were advised to refer to formal filings and company releases for definitive details on governance or remuneration.

The leadership change will be managed with attention to stakeholder interests and operational continuity, and the company reiterated its commitment to delivery on ongoing projects and customer obligations. Senior management will engage with employees and partners to ensure a smooth handover while maintaining focus on safety and compliance. Further updates will be provided through official investor communications in due course.

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Merlin Prime Spaces Acquires 13,185 Sq M Land Parcel In Pune

Rs 273 crore purchase broadens the developer’s Pune presence

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Merlin Prime Spaces (MPS) has acquired a 13,185 sq m land parcel in Pune for Rs 273 crore, marking a notable expansion of its footprint in the city.

The transaction value converts to Rs 2,730 mn or Rs 2.73 bn.

The parcel is located in a strategic area of Pune and the firm described the acquisition as aligned with its growth objectives.

The deal follows recent activity in the region and will be watched by investors and developers.

MPS said the acquisition will support its planned development pipeline and enable delivery of commercial and residential space to meet local demand.

The company expects the site to provide flexibility in product design and phased development to respond to market conditions.

The move reflects an emphasis on land ownership in key suburban markets.

The emphasis on land acquisition reflects a strategy to secure inventory ahead of demand cycles.

The purchase follows a period of sustained investor interest in Pune real estate, driven by expanding office ecosystems and residential demand from professionals.

MPS will integrate the new holding into its existing portfolio and plans to engage with local authorities and stakeholders to progress approvals and infrastructure readiness.

No financial partners were disclosed in the announcement.

The firm indicated that timelines will depend on approvals and prevailing market conditions.

Analysts note that strategic land acquisitions at scale can help developers manage costs and timelines while preserving optionality for future projects.

MPS will now hold an enlarged land bank in the region as it pursues growth, and the acquisition underlines continued corporate appetite for measured expansion in second tier cities.

The company intends to move forward with detailed planning in the coming months.

Stakeholders will assess how the site is positioned relative to existing infrastructure and connectivity.

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