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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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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

Lodha Signs Joint Development Agreement For Parel–Sewri Land

Deal covers 10 acres at Rs 3,640 million (mn)

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Lodha Developers has signed a joint development agreement with Sahana Group for a 10-acre parcel in the Parel–Sewri corridor of Mumbai. The agreement is valued at Rs 3,640 million (mn), reflecting the consideration reported for the transaction. The joint development arrangement will see the land owners and the developer collaborate on planning and construction while sharing development proceeds under the terms of the contract. The arrangement is subject to customary closing conditions and regulatory approvals.

The site in Parel–Sewri occupies a strategic location within central Mumbai and offers opportunities for urban redevelopment given its proximity to transport links and established neighbourhoods. The parties have agreed to pursue statutory approvals and detailed project planning before commencing construction activity. The arrangement is described as a long-term development collaboration focused on unlocking the value of the site. Stakeholders will monitor progress as statutory milestones are reached.

For Lodha Developers, the deal reinforces its pipeline of land parcels available for development in the Mumbai metropolitan area and is expected to expand its capacity to deliver built assets. For Sahana Group, partnering with a developer on a joint development agreement provides a route to monetise land holdings while retaining a share in future realisation. The structure aligns incentives to complete the project efficiently and to move through planning milestones. Market reception and execution pace will shape the ultimate returns for both parties.

The financial terms and timetable for completion will depend on regulatory clearances and market conditions, with returns to be realised as phases of development are sold or leased. Both parties will need to coordinate with municipal authorities and service providers to meet infrastructure and compliance requirements. The agreement signals continued investor interest in central Mumbai land parcels and may encourage further collaborative ventures between land owners and developers. Further disclosures will be issued.

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Concrete

Seppa Township Road Being Paved With Bituminous Concrete

Township road upgrade uses bituminous concrete

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Work is underway to pave the main township road in Seppa with bituminous concrete, marking a significant upgrade to the local transport network. The project is being overseen by the district administration and carried out by municipal contractors using mechanised laying equipment. The initiative aims to replace older surface material that had become potholed and dusty, and to improve all weather access for residents and public services. Local officials have coordinated traffic diversions and site safety measures to minimise disruption during construction.

The work includes preparing the base, applying a bituminous concrete layer and compacting the surface to enhance load bearing capacity. Engineers are ensuring proper drainage and edge sealing to extend pavement life and reduce water ingress. The choice of bituminous concrete reflects considerations of durability and ease of maintenance in the local climatic conditions. Equipment on site includes pavers, rollers and material stabilisers operated by trained crews.

Residents and business owners along the route are expected to benefit from smoother journeys and reduced vehicle operating costs once the surface is completed. The administration has scheduled work to avoid peak movement hours and has informed local transport operators about temporary changes in stops and routes. Environmental precautions have been put in place to control dust and run off during construction and to dispose of surplus material responsibly. The project has also provided short term employment opportunities for local labour.

Officials said routine maintenance will be scheduled to preserve the new surface and that monitoring will continue to assess performance and inform future works. The improved road is intended to support daily mobility, emergency access and the movement of goods, contributing to broader local development goals. Authorities will review the outcome of the works and plan any necessary follow up interventions to maintain serviceability. Community members expressed relief at the reduced dust and smoother travel that the pavement is expected to deliver.

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Gautam Adani Inspects Godda 2,300 MW Power Plant

Inspection follows MP request and points to cement plan

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Gautam Adani visited Godda on Sunday to carry out a first inspection of the power plant in the district, where electricity generation of 2,300 megawatts (MW) is being undertaken through five units. The visit involved a walkthrough of production areas and technical installations and included meetings with senior plant executives. The inspection was described by officials as focused on operational readiness and optimisation of output.

Officials said the establishment of the plant followed a request from the local member of parliament, who provided cooperation during project development, and indicated that plans to establish a cement plant in Godda are likely to materialise soon. The electricity produced at the facility is currently being supplied to Bangladesh, and officials confirmed that the possibility of exporting power to other neighbouring countries is under consideration. Company representatives indicated that the project aims to balance regional energy demand with commercial export obligations.

During the review of all units, plant leadership set out steps to accelerate commissioning and enhance maintenance regimes to ensure sustained generation. The commissioning of the power plant has already been credited with contributing significantly to the development of Godda, and the proposed cement plant is expected to add industrial capacity and create large-scale employment in the region. Local authorities are monitoring progress with a view to aligning infrastructure improvements and workforce development.

Stakeholders expect the visit to accelerate operational momentum at the site and to clarify timelines for further investment and local supply arrangements. The inspection was followed by technical briefings and an internal review of safety and environmental practices to support reliable operations. Officials said subsequent measures will focus on connectivity, logistics and community engagement to ensure the project delivers intended economic benefits.

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