Connect with us

Concrete

Concrete Making Materials

Published

on

Shares

Cement is never used as cement alone but is always converted to a value-added product in practice. Therefore application of cement becomes extremely important. The cement producers have a dedicated department that looks into the applications of product. Now onwards, we shall try and cover it through a series of articles in a structured way.
Construction aggregate, or "aggregate", is a broad category of coarse to medium grained particulate material used in construction that includes sand, gravel, crushed stone, slag, and recycled concrete and geosynthetic aggregates. Aggregates are the most mined materials in the world.
Cement concrete is a cement and water paste in which aggregate particles are embedded. Aggregate usually occupies approximately 60 to 75 per cent of the volume of concrete. Besides reducing volume changes due to drying shrinkage of the cement-water paste, aggregate is inexpensive filler that reduces the cost of the concrete. Aggregate properties significantly affect the workability of plastic (concrete in the wet stage) concrete and the durability, strength, thermal properties, and density of hardened concrete. Types of rocks
Aggregates are generally sourced from natural materials or from industrial by products. Natural aggregates come from rock, of which there are three broad geological classifications. Igneous rock: These rocks are primarily crystalline and are formed by the cooling of molten rock material beneath the earth’s crust (magma).Sedimentary rocks: These rocks are formed from deposited insoluble material (e.g., the remains of existing rock deposited on the bottom of an ocean or lake). This material is transformed to rock by heat and pressure. Sedimentary rocks are layered in appearance and are further classified based on their predominant mineral as calcareous (limestone, chalk, etc.), siliceous (chert, sandstone, etc.) or argillaceous (shale, etc.).Metamorphic rock: These are igneous or sedimentary rocks that have been subjected to heat and/or pressure great enough to change their mineral structure so as to be different from the original rock.
Natural sands and gravels are the product of weathering and the action of wind or water, while stone sands and crushed stone are produced by crushing natural stone. Screening and washing may be used to process aggregates from either of these categories. Aggregates may be produced from igneous, sedimentary, or metamorphic rocks, but the presence or absence of any geological type does not, by itself, make an aggregate suitable or unsuitable for use in concrete. The acceptance of an aggregate for use in concrete on a particular job should be based upon specific information obtained from tests used to measure the aggregate quality, or upon its service record, or both. Synthetic aggregates may be either by products of an industrial process, such as blast-furnace slag, or products of processes developed to manufacture aggregates with special properties, such as expanded clay, shale or slate that are used for lightweight aggregates. Some lightweight aggregates such as pumice or scoria also occur naturally. Other classifications of aggregates may be based upon bulk density and particle shape, but these, as well as the ones previously discussed, serve mainly as aids in describing an aggregate. To understand the role played by aggregate in the performance of concrete, it is necessary to define specific aggregate properties and show their effect on concrete properties.Aggregates generally divided into two groups: Fine and Coarse aggregates.
Fine aggregates or natural or manufactured of particle size ranging from 10 mm to 0.075 mm. Coarse aggregates size ranging from 10 mm to 80 mm. The most commonly used maximum size of aggregate is 20 or 25 mm.Fine & Coarse aggregates
– IS-383 – 2016 Specification for concrete
– IS-2386 Part – I to VIII – Method of testWhy use aggregates?
We use aggregates mainly to reduce the cost of the concrete. Roughly aggregates would cost between 12 to 25 per cent of the cement price. Use of aggregate reduces thermal cracking. About 100 kg of OPC produces about 12o C temperature rise. Aggregates can reduce shrinkage, 10 percent of reduction in aggregate volume can double the shrinkage of concrete. High aggregate to cement ratio is desirable as it mainly influences cement content in concrete. Effect of aggregate size: Larger the (maximum) size; increases strength, decrease total surface area of aggregate that decreases required cement content. Improves rut resistance but increases problem with segregation of particles. Smaller maximum size can reduce segregation, reduces road noise, decreases tyre wear specially while transporting of ready mixed concrete. Why to specify sizes?
The foremost reason for specifying the size of aggregates is to control the cost of concrete, have a homogenous mix with higher bulk density, effectively use the water content and control the consumption of cement and other cementious
materials. By playing with the size of aggregates one can modify workability, pumpability, porosity and shrinkage of concrete.
Fine aggregates are nothing but the sand used in concrete. The size is down 4.75 mm to 0.075 mm and the content is usually 35 per cent to 45 per cent by mass or volume of total aggregate. Grading of aggregates: Grading is nothing but the particle-size distribution of an aggregate as determined by a sieve analysis using wire mesh sieves with square openings. As per IS:2386 (Part-1) for fine aggregate, 6 standard sieves with openings from 150 ?m to 4.75 mm. (150 ?m, 300 ?m, 600 ?m, 1.18 mm, 2.36 mm, 4.75mm) are used. For coarse aggregates , 5 sieves with openings from 4.75 mm to 80 mm. (4.75 mm, 10 mm, 12.5 mm, 20 mm, 40 mm and may be onwards). ?m is microns and 1 micron (?m) is 0.001 mm.
Grain size distribution for concrete mixes should be such that it will provide a dense strong mixture. Ensure that the voids between the larger particles are filled with medium particles. The remaining voids are filled with still smaller particles until the smallest voids are filled with a small amount of fines.
Generally in the city of Mumbai and around three type of aggregates are used which are termed as CA I( coarse aggregate),CA II and FA fine aggregates. For coarse aggregates the sizes vary from 20-25mm for CAII and 10-12 mm for CAI, the remaining third is Fine aggregate or Sand. The proportion of sand in concrete being 35 to 45 per cent, availability and price of sand has a direct impact on the production of concrete.
Fineness Modulus (FM) is a result of aggregate sieve analysis is expressed by a number called Fineness Modulus. It is obtained by adding the sum of the cumulative percentages by mass of a sample aggregate retained on each of a specified series of sieves and dividing the sum by 100. This measurement is important while designing concrete mixes with given materials at site.
Sand or fine aggregates is further graded in three categories and the following limits may be taken as guidance:Fine sand : Fineness Modulus : 2.2 – 2.6Medium sand : F.M. : 2.6 – 2.9Coarse sand : F.M. : 2.9 – 3.2
Sand having a fineness modulus more than 3.2 will be unsuitable for making satisfactory concrete.Colour of aggregates: Normally the colour of aggregates depend on the source of rock from which it is derived. The colour of aggregates that we see in Karnataka, Maharashtra and in the Northen part of India is much different. However colour has hardly any influence on the properties of concrete. But in case of decorative concretes the colour needs to satisfy the designer’s requirements. Tests on Aggregates: Fine aggregates
These are summarised as Grading, Silt & Clay content, Specific Gravity, Water absorption & moisture content, Soundness, Alkali Aggregate Reactivity, Organic Impurities and Soft Particles, Bulkage. We shall cover some of the important ones.
Impurities in fine aggregate and its effect: Clay particles, Shale, Mica, Weathered agate, Organic impurities-humus, sugar etc. These impurities lead to High water absorption, Low strength, High shrinkage, Retardation. (Slow strength gain for concrete).
Estimation of stilt content and organic impurities is very simple and can be easily carried out at site laboratory. It is recommended that every site laboratory must carry out these tests to ascertain the suitability of fine aggregates. Tests on Coarse aggregates:
– Specific gravity
– Dry Loose Bulk Density/Dry Relative Bulk Density
– Absorption & Surface moisture
– Shape
– Soundness
(Test methods – IS 2386 Part I to VIII)Tests on Coarse aggregates:
– Aggregate Crushing Value
– Aggregate Impact Value
– Aggregate Abrasion Value
– Alkali Aggregate Reactivity
(Test methods – IS 2386 Part I to VIII)Mechanical properties
Aggregate Crushing Value: Not more than 45 percent for other than wearing, surface and 30 percent for wearing surface.
Aggregate Impact Value: Not more than 45percent for other than wearing, surface and 30 percent for wearing surface.
Aggregate Abrasion Value: Not more than 50 per cent for other than wearing surface and 30 percent for wearing surface.
Aggregate Elongation & Flakiness: Not more than 40 percent (combined)
Soundness: (Loss after 5 cycles)
For fine aggregate: maximum 10 percent with sodium sulphate and 15 percent with magnesium sulphate.
For Coarse aggregate: maximum 12 percent with sodium sulphate and 18 percent with magnesium sulphate.
We thankfully acknowledge for making the articles available to us originally written by Suhas Dhuri and S Krishnan of e cube consultants, Thane and Prof. Gaurav H Tondan published on Linked in.Compilation by Vikas Damle Ex. Editor of ICR.

Continue Reading
Click to comment

Leave a Reply

Your email address will not be published. Required fields are marked *

Concrete

India Sets Up First Carbon Capture Testbeds for Cement Industry

Five CCU testbeds launched to decarbonise cement production

Published

on

By

Shares
The Department of Science and Technology (DST) recently unveiled a pioneering national initiative: five Carbon Capture and Utilisation (CCU) testbeds in the cement sector, forming a first-of-its-kind research and innovation cluster to combat industrial carbon emissions.
This is a significant step towards India’s Climate Action for fostering National Determined Contributions (NDCs) targets and to achieve net zero decarbonisation pathways for Industry Transition., towards the Government’s goal to achieve a carbon-neutral economy by 2070.
Carbon Capture Utilisation (CCU) holds significant importance in hard-to-abate sectors like Cement, Steel, Power, Oil &Natural Gas, Chemicals & Fertilizers in reducing emissions by capturing carbon dioxide from industrial processes and converting it to value add products such as synthetic fuels, Urea, Soda, Ash, chemicals, food grade CO2 or concrete aggregates. CCU provides a feasible pathway for these tough to decarbonise industries to lower their carbon footprint and move towards achieving Net Zero Goals while continuing their operations efficiently. DST has taken major strides in fostering R&D in the CCUS domain.
Concrete is vital for India’s economy and the Cement industry being one of the main hard-to-abate sectors, is committed to align with the national decarbonisation commitments. New technologies to decarbonise emission intensity of the cement sector would play a key role in achieving of national net zero targets.
Recognizing the critical need for decarbonising the Cement sector, the Energy and Sustainable Technology (CEST) Division of Department launched a unique call for mobilising Academia-Industry Consortia proposals for deployment of Carbon Capture Utilisation (CCU) in Cement Sector. This Special call envisaged to develop and deploy innovative CCU Test bed in Cement Sector with thrust on Developing CO2 capture + CO2 Utilisation integrated unit in an Industrial set up through an innovative Public Private Partnership (PPP) funding model.
As a unique initiative and one of its first kind in India, DST has approved setting up of five CCU testbeds for translational R&D, to be set up in Academia-Industry collaboration under this significant initiative of DST in PPP mode, engaging with premier research laboratories as knowledge partners and top Cement companies as the industry partner.
On the occasion of National Technology Day celebrations, on May 11, 2025 the 5 CCU Cement Test beds were announced and grants had been handed over to the Test bed teams by the Chief Guest, Union Minister of State (Independent Charge) for Science and Technology; Earth Sciences and Minister of State for PMO, Department of Atomic Energy, Department of Space, Personnel, Public Grievances and Pensions, Dr Jitendra Singh in the presence of Secretary DST Prof. Abhay Karandikar.
The five testbeds are not just academic experiments — they are collaborative industrial pilot projects bringing together India’s top research institutions and leading cement manufacturers under a unique Public-Private Partnership (PPP) model. Each testbed addresses a different facet of CCU, from cutting-edge catalysis to vacuum-based gas separation.
The outcomes of this innovative initiative will not only showcase the pathways of decarbonisation towards Net zero goals through CCU route in cement sector, but should also be a critical confidence building measure for potential stakeholders to uptake the deployed CCU technology for further scale up and commercialisation.
It is envisioned that through continuous research and innovation under these test beds in developing innovative catalysts, materials, electrolyser technology, reactors, and electronics, the cost of Green Cement via the deployed CCU technology in Cement Sector may considerably be made more sustainable.
Secretary DBT Dr Rajesh Gokhale, Dr Ajai Choudhary, Co-Founder HCL, Dr. Rajesh Pathak, Secretary, TDB, Dr Anita Gupta Head CEST, DST and Dr Neelima Alam, Associate Head, DST were also present at the programme organized at Dr Ambedkar International Centre, New Delhi.

Continue Reading

Concrete

JK Lakshmi Adopts EVs to Cut Emissions in Logistics

Electric vehicles deployed between JK Puram and Kalol units

Published

on

By

Shares
JK Lakshmi Cement, a key player in the Indian cement industry, has announced the deployment of electric vehicles (EVs) in its logistics operations. This move, made in partnership with SwitchLabs Automobiles, will see EVs transporting goods between the JK Puram Plant in Sirohi, Rajasthan, and the Kalol Grinding Unit in Gujarat.
The announcement follows a successful pilot project that showcased measurable reductions in carbon emissions while maintaining efficiency. Building on this, the company is scaling up EV integration to enhance sustainability across its supply chain.
“Sustainability is integral to our vision at JK Lakshmi Cement. Our collaboration with SwitchLabs Automobiles reflects our continued focus on driving innovation in our logistics operations while taking responsibility for our environmental footprint. This initiative positions us as a leader in transforming the cement sector’s logistics landscape,” said Arun Shukla, President & Director, JK Lakshmi Cement.
This deployment marks a significant step in aligning with India’s push for greener transport infrastructure. By embracing clean mobility, JK Lakshmi Cement is setting an example for the industry, demonstrating that environmental responsibility can go hand in hand with operational efficiency.
The company continues to embed sustainability into its operations as part of a broader goal to reduce its carbon footprint. This initiative adds to its vision of building a more sustainable and eco-friendly future.
JK Lakshmi Cement, part of the 135-year-old JK Organisation, began operations in 1982 and has grown to become a recognised name in Indian cement. With a presence across Northern, Western, and Eastern India, the company has a cement capacity of 16.5 MTPA, with a target to reach 30 MT by 2030. Its product range includes ready-mix concrete, gypsum plaster, wall putty, and autoclaved aerated fly ash blocks.

Continue Reading

Concrete

Holcim UK drives sustainable construction

Published

on

By

Shares

Holcim UK has released a report titled ‘Making Sustainable Construction a Reality,’ outlining its five-fold commitment to a greener future. The company aims to focus on decarbonisation, circular economy principles, smarter building methods, community engagement, and integrating nature. Based on a survey of 2,000 people, only 41 per cent felt urban spaces in the UK are sustainably built. A significant majority (82 per cent) advocated for more green spaces, 69 per cent called for government leadership in sustainability, and 54 per cent saw businesses as key players. Additionally, 80 per cent of respondents stressed the need for greater transparency from companies regarding their environmental practices.

Image source:holcim

Continue Reading

Trending News

SUBSCRIBE TO THE NEWSLETTER

 

Don't miss out on valuable insights and opportunities to connect with like minded professionals.

 


    This will close in 0 seconds