Connect with us

Concrete

Technology plays a vital role in utilising alternative materials

Published

on

Rajpal Singh Shekhawat, Senior General Manager (Production and QC),JK Lakshmi Cement, stresses on the importance of the quality of alternative raw materials in order to maintain the quality of the output.

What are the core raw materials used in the production of cement?
The first step to manufacturing cement is manufacturing the clinker. The principle raw material required to make clinker is cement grade limestone. Other raw material requirements depend upon the quality of limestone and these could be iron ores like red ochre, blue dust, laterite, alumina ores like bauxite, China clay and siliceous materials like Marl and silica sand. As far as cement is concerned for Ordinary Portland Cement (OPC), clinker and
gypsum are used, for Pozzolana Portland Cement (PPC) clinker, gypsum and fly ash are used and for Portland Slag Cement (PSC) clinker, gypsum and slag are used.

What are the alternative raw materials that can be used in the production of cement? How does that impact the process of production?
Waste from the aluminium industry like red mud, waste from the marble industry like marble slurry and marble khanda, waste from the chemical industry like chemical sludge and ETP sludge, waste from the paper industry like paper sludge can be used in clinker manufacturing. For the cement manufacturing process, waste from chemical industry like chemical gypsum, waste from ceramic industry like mould gypsum, waste from zinc industry like jarosite and waste from the salt industry like marine gypsum can be used.
However, the quantity of alternative material or waste to be utilised depends a lot upon the quality of limestone and quality of other raw materials used in cement grinding. It varies from plant to plant and the quality of these alternative materials varies from source to source.

Can cement maintain its quality standard with inclusion of supplementary raw materials as against limestone?
Certainly, the quality of cement can be maintained by including these supplementary raw materials, however, the raw material proportion must be tweaked according to the quality of alternative raw material and the cost benefit analysis.

Explain the impact on carbon emission of the production unit when alternative raw materials are used in various proportions.
Carbon emission in cement manufacturing is mainly because of limestone, fuel burning, and electrical energy consumption. Majority of the CO2 emission in cement industry is from the decomposition of calcium carbonate and if we replace limestone by alternative raw material which contains calcium in any form other than carbonate, carbon emission can be reduced. For example, if we replace 1 per cent of CaO by other raw materials then around 5 kg CO2/ MT of clinker will be reduced.

How can the cost of production be reduced by using alternative or supplementary raw materials in cement production?
Cost of production depends on the plant location, limestone and raw material quality. The source of alternative raw materials for some plants are significant and in some instances because of high logistic cost economics do not work out. For example, if a cement plant is located near the industry where chemical gypsum is generated, there will be a significant gain to that particular cement plant.

What are the major challenges in using other cementitious materials?
Using alternative materials comes with their own set of challenges. Some of the challenges associated with them are high moisture content, material flowability, consistency in the material quality, chloride and sulphur content.

What role does technology play in deciding which materials can be used and incorporating them in the production process?
Certainly, technology plays a vital role in utilising alternative material, for example if drying technology is available at the plant like drier than even high moisture material can be used and handled otherwise only selected material with less moisture content are allowed.
Likewise in case of alternative fuel, if pre-processing facilities like separation of organic and combustion solid fraction, screening and pre-shredding is available then MSW can be directly used. However, when the pre-processing and shredding facility is not available at the plant then the plant requires shredded RDF <80 mm in case of in-line calciner and <40-50 mm in case of separate line calciner. Regarding utilisation of high chloride and high sulphur material if akali/chloride by-pass is installed then even high chloride/sulphur can be accepted based on the cost benefit analysis otherwise chloride input is to be restricted to 200-300gm/tonne of clinker.

Does your organisation manufacture a variant of cement made from alternative raw materials? Tell us more about its performance and use.
Yes, we are utilising various alternative raw materials like chemical gypsum, mould gypsum, ETP and phosphate sludges. Talking about chemical gypsum, its purity is more than natural gypsum. The performance of concrete made by the cement by utilising partial replacement of chemical gypsum is more cohesive than the cement made from natural gypsum. Moreover, the cement made by utilising chemical gypsum improves the workability of cement. Likewise, we utilise various alternative fuels at our premises and their consumption is being optimised looking into process and quality.
By utilising various alternative raw materials and fuels we are saving around 25 kg CO2/Mt of clinker and working on alternative materials and fuels that can reduce carbon footprints further.

How do you foresee future of production?
The per capita capital cement consumption in India is still much lower than the world average. Therefore, there is a huge potential for the industry to grow. There has been a continuous rise in the cost of fuel post covid and post the Russia-Ukraine engagement and still rising.
Owing to this, there is pressure on the industry to maintain the margins. Although, Indian cement industry is co-processing various alternative fuels and alternative raw materials to reduce its carbon footprint, it will in the future also put its focus on utilising alternative materials and fuels to bring down the cost of production.

-Kanika Mathur

Concrete

Precast use of concrete promotes sustainability

Published

on

By

Vijay Shah, Managing Partner, India Precast, advocates the use of precast concrete as he puts forth details about its manufacturing, uses and methods while emphasising the sustainability of the product.

Explain the process of casting concrete in shapes and what is the grade of concrete used for making these shapes?
Precast casting concrete elements are manufactured with the required steel reinforcement either in formwork, moulds or on steel plates with side shuttering etc. The concrete cast is made at a different location and is then transported to the site. Precast elements are made of minimum M20 to M50 grade of concrete.

What is the difference between precast and cast in-situ as uses of concrete?

  • The use of concrete in the precast method and the cast in-situ method differs widely based on many factors.
  • Precast concrete shapes are cast at a different location and are then transported to the site where construction work takes place while with the cast in-situ process, concrete is poured on-site.
  • Curing of precast concrete is fast as it takes place under ideal and controlled conditions while the cast in-situ concrete takes relatively longer to get cured but can be easily used for two-way structural systems.
  • For the precast concrete, the process is easy to do and is repeatable as the same moulds or framework can be used. This increases the value of construction and derives more value
  • while cast in-situ adapts building shapes and post tensioning.
  • The work and rework in the usage of precast shapes is less, thus, reduces cost at the site
  • while with the cast in-situ method there is a requirement of space allotment for concrete mix and necessary add-ins, that is added cost for the construction job.

Tell us about prestressed and reinforced concrete.
Prestressed concrete is a combination of high strength concrete and tensioned steel strands. This combination makes a strong structural unit that is useful in building roof slabs, bridge girders etc. Reinforced concrete is manufactured from a combination of high strength concrete and normal reinforcement bars.

Tell us more about the precast elements manufactured, their shapes and sizes.
Precast is one of the best ways to rapidly build industrial buildings, commercial buildings, affordable housing, mass, EWS, LIG housing, schools, hospitals, public buildings, agriculture railways, stadiums, sport centres, parking, bridges, airports etc. They have a higher productivity and quality set at industry level.
Various types of precast elements manufactures are:

  • Solid load bearing floor slabs, load bearing walls, facades, sandwich wall panels and cladding panels
  • Floor and roof slabs are made from prestressed load bearing hollow core concrete slab and ribbed slabs. They are also made from half floor slab or semi-finished floor slab with a lattice girder
  • Precast stair cases, balcony, toilet pods, lift shafts, water tanks
  • Prestressed lintel, frames, beams, columns and double-tee beams
  • Internal partition walls are made with light-weight hollow core wall panels instead of AAC blocks or bricks
  • Boundary walls, fencing poles, U-drainage or trenches, box culvert etc.

What is hollowcore concrete flooring and what is its lifespan?
Hollowcore slabs are precast, prestressed concrete elements that are generally used for flooring. Some of the advantages of using these flooring are longer lifespans and no propping, flexibility in designs, faster construction, lightweight structures, fire resistant structures, high load capacities and units manufactured specific to the project.
The maximum span of hollowcore floors will depend on the floor depth and the specific loadings imposed on the floor.

What are the quality standards followed while making precast shapes for any project?
Quality control is a very important aspect in the process of making precast concrete shapes. It is imperative to make precast shapes as per the exact requirement provided by the engineers and the construction party. To maintain the quality of product from our end,

  • We ensure there are quality control systems and procedures in place along with a quality assurance plan. Our programme consists of tests, trials, and general procedures for acceptance.
  • There is a laboratory and related facilities, which are required for the selection and control of the quality of materials and workmanship. The central quality laboratory is used for various quality control tests like cube test, workability test, slump test, sieve analysis etc. The materials used for making the final precast shapes also has to be shared for testing to various third-party laboratories with an advance intimation.
  • All the necessary tests are carried out in respective batching plants or sites depending on the use of concrete at our facility.
  • Documentation for all the tests conducted and their reports is maintained in records, for references and submission to the relevant authorities and the users of the same.

As precast use of concrete is conducted in a dedicated space and is in a monitored environment, it becomes easier to maintain high quality due to its repeatability factor. The necessary general precast machinery and moulds, steel tables, concrete batching and dispensing equipment, vibrating and finishing equipment and dedicated labour team help maintain the higher quality standards as compared to cast in-situ use of concrete.

How do you incorporate sustainability in the process of precasting?
Precast use of concrete promotes sustainability with its repeatability factor. There’s more planning involved in the process and equipment like the moulds, vibrating machine, finishing machine are all reusable elements of the process.
As mentioned, there is planning in precast use of concrete where only the required measure of concrete is mixed and poured into moulds that are made to precision as per the requirement of the project. The quantity is also previously defined, which means there is reduced to zero wastage of material.
This waste reduction leads to lesser needs of cleaning and clearing equipment, which may further be fueled by other energy sources. Thus, precast concrete, by large, is a sustainable means of building.

What are the advantages of using precast concrete?
There are multiple advantages of using a precast structure for any project like cost efficiency, speed, versatility, safety, sustainability and beauty.
This includes:

  • The use of precast improves the quality and lifespan of any building
  • It reduces the time of building, thus reducing the costs involved for all the other equipment and labour that goes in to the project, thus, proving to be cost effective
  • The maintenance of a precast is lower due to its high quality and durability that is ensured while it is cast
  • This method of using concrete is a sustainable option due to its repeatability

What are the major challenges you face in the process of making precast shapes and in their transportation?
The precast industry plays on volume and repetition. This is one of the major challenges as well.
The requirement of having to repeat the process
that contains a large volume of mixed concrete and getting the same perfection in the shapes is a cumbersome process.
The initial investment in setting up the precast plant and acquiring all equipment and moulds is high. With bulk shapes to be transported from one place to another and the requirement for site space and handling, this time of concrete use is more suitable for tier 2 and tier 3 cities.

How do precast elements or shapes help in the profitability of a construction activity?
As precast concrete is made at a different location than the construction site, the other jobs keep going on at the site and then the precast shapes are placed there. This reduces construction time to up to one-third to one-fifth as compared to cast in-situ concrete, thus, reducing cost of the construction.
Construction maintenance is reduced as the quality of their precast structures are monitored and carefully administered at the plant level. This means it adds to the reliability, durability, accuracy, and ability to produce architectural elements in any building adding to its quality and strength. Precast also provides insulation, thermal inertia and fire resistance and the possibility of integration with MEP (Mechanical, Electrical and Plumbing) from the start of the project.

How can precast concrete contribute towards affordable mass housing in India?
Defined shapes and technical requirements in precast concrete helps reduce the waste and increase the repeatability factor, thus, reduces the cost and time for any construction or building project. Higher control on quality, less time consumer leads to lesser need of labour and equipment on-site, which also adds to the profitability of the structure.
All factors combined bring down the overall cost of the project, leading to that benefit translating to the end consumer and bringing a surge of affordable mass housing in India.

-Kanika Mathur

Comparison Between Cast-in-situ (conventional method) versus Technology Drive Precast

Sr. No Criteria Conventional Construction Precast Construction 3D Modular/ Panel & Hollow Core Slab.
1 Natural resource consumption High 30 per cent saving
2 Labour Problem Heavy labour problem while work in progress Less labour required
3 Dependability on skilled labor 60 per cent Dependability
4 Time consuming Verv High Fast track
5 Initial investment Low High
6 Finishin Normal Excellent
7 Quality production Poor Excellent as factory based.
8 Material wastage High Least
9 Speed/ Productivity Low Excellent
10 Strength Good Excellent
11 Durability Low High
12 Structure weight/ Deed load Very heavy Reduced
13 Brick Block and Plastering Required No Need
14 Service like Electrical, plumbing & sanitary Break, Provide & Re-build Pre-embedded

Continue Reading

Concrete

The age of concrete blocks can be up to a 100 years

Published

on

By

Nikita George, Director Operations, APCO Concrete Blocks and Allied Products, takes us through the manufacturing process of concrete blocks and its composition and also specifically discusses their patented product – cellular blocks.

Tell us about the type of concrete blocks that your organisation manufactures.
We manufacture mainly solid and cellular concrete blocks. The cellular block is our patented product, which has become increasingly popular due to its high utility value in the construction process. We are also gearing up to launch our new line of pavers and kerb stones by the end of August.

What is the composition of each type of block and what are their strengths?
Blocks constitute of mainly three items:
Cement,

  • Manufactured Sand and Stone Aggregates Our patented cellular blocks have a vast set of benefits:
  • Lightweight: The cellular block is between 8 to 9 kg lighter than the solid block. This not only increases the productivity of the labour but also helps in reducing the overall steel requirement for the project.
  • Thermal insulation properties: With the erratic weather conditions in India today, cellular blocks help in maintaining thermal insulation properties within the building. In a recent experiment conducted on a building, which used the cellular blocks, a marked reduction in temperature by three degrees was recorded.
  • Sound insulation properties: Due to the hollow nature of these concrete blocks, the product is able to cut the decibel levels by 14 per cent.
  • Compressive strength and water absorption properties: The cellular blocks exceed the ISO parameters for compressive strength and water absorption.

How do you ensure quality standards for the concrete blocks manufactured?
With our 50 years of experience in the concrete blocks manufacturing industry, we have continually evolved and tried our best to stay relevant with the international quality standards. Quality control begins with procurement of good quality raw material. Fortunately, we have our own crushers to cater to our production units. This helps us negate undesirable raw materials. State of the art machinery and a strong base of SOP help mitigate errors. Above all, of these we have a skilled set of managers who have over 25 years of experience in the concrete blocks field.

Tell us about the sustainability and environmental benefit while manufacturing and while using these blocks in construction?
The blocks that we manufacture follow the highest quality parameters that give a very long life span. When used in building, the age of concrete blocks can be up to 100 years. The blocks used in these buildings at the time of demolition can be re-crushed and used to manufacture the same product again. And since concrete blocks are one of the strongest products available in the market, the on site damages are virtually zero. Unlike native methods of concrete production, we use only M-sand. There is no usage of river sand hence, safeguarding our environment. Also, as mentioned before, concrete blocks can be reused even after the lifespan of a building. This cuts down on further usage of raw materials.

What are the key benefits that any builder can get from using your concrete blocks?
The concrete blocks industry to a large extent can still be categorised in the unorganised sector. Due to this, there is a lot of disparity in pricing and quality in the market. At APCO, with our 50 years of experience, we have won the trust of our customers by consistently proving the highest quality of our products and on-time delivery.
With our 5 production units strategically located around Bangalore city, we have the capability of producing up to one lakh blocks per day. This allows us to consistently supply large quantities to our customers. Our customers can also be assured that the quantity of blocks that leave our plants is the same quantity that will be unloaded at the site.
Apart from this as mentioned in the earlier answers, our cellular blocks host a wide range of benefits during and even after the construction of a building.

How do these concrete blocks contribute to the profitability of construction?
When APCO came into the market in the early ’70s, the construction industry was heavily reliant on the traditional clay bricks. It took us about 10 years before we got our first big break. And since then, the construction market has not looked back. There have been multiple competitors in the walling solutions market but in terms of pricing and quality no other product comes close. Most people build a house once. At APCO, we believe in making that house a home. We provide unrivalled quality and a fair price to all our customers!

What does the near future hold for APCO Concrete Blocks and allied products?
We will be launching our new product line of pavers and kerb stones by August and we are working towards APCO being present in a few more states around India.

Kanika Mathur

Continue Reading

Concrete

Effects of Macronomics

Published

on

By

In any industry, it always helps to take into account the macro perspective as it aids one in navigating the broader economic trends. As per the assessments of the April-June quarter (Q1), India’s gross domestic product (GDP) increased 13.5 per cent, which was lower than RBI’s estimated 16.2 per cent. A fiscal deficit of Rs 3.41 trillion was noted during the April-July period this financial year.


Moody’s Investors Service has revised India’s economic growth projection for 2022 to a reduced 7.7 per cent. The downward revision is due to rising interest rates, an uneven monsoon and global demand slowdown, which is not surprising as the Russia-Ukraine war continues to cast its shadow. The eight core infrastructure sectors, including cement, slowed down to 4.5 per cent in July, which afforded the service sector to shine in the first quarter.


Taking a bird’s eye view of the cement sector, the upward moving trends are looking promising and that has kept optimism buoyed amongst the players. Monsoon is a tricky time for the cement industry as construction takes a backseat and price fluctuations in cement are rife.

As per Kotak Institutional Equities report, cement prices have declined about a percent sequentially in the second quarter. Cement price was recorded at Rs 384 per 50 kg bag in August pan-India. In spite of a sluggish season, the demand is likely to soar in the coming months, and the key players in the industry are anticipating robust growth.


There is a lot that’s underway for cement manufacturers in terms of alternative raw materials, energy efficiency and eco-friendly processes. Given the infrastructure and construction boom that India is witnessing today, the cement segment is likely to perform well. However, the challenges that the sector faces are unique to it, and it remains to be seen how cement brands will innovate to overcome them.

Continue Reading

Trending News

© COPYRIGHT 2021 ASAPP Info Global Services Pvt. Ltd. All Right Reserved.