Economy & Market
AAC production in cement plant
Published
12 years agoon
By
admin
Cement companies can manufacture AAC blocks and can compete with stand alone AAC units in the country.
The raw materials required for AAC production are readily available in any cement manufacturing plant. The process does not require installation of a steam boiler or a power plant and can utilise the waste-heat from the clinker cooler exhaust gases for steam curing of aerated concrete. The method also earns carbon credits not only for the green product being made, but also for waste-heat utilisation. Although, there are more than 35 standalone AAC manufacturing units in India, very limited attempts have been made to manufacture AAC by the cement plants. One reason behind this is the lack of awareness about the new technologies that were developed recently in this field. DS Venkatesh elaborates on the technology offered by Cemeng for AAC production in a cement plant.
What is AAC
AAC is lightweight autoclaved aerated concrete, which is completely cured, inert and stable form of calcium silicate hydrate. It is a structural material, approximately one quarter in weight of the conventional concrete. It is composed of minute cells/air pockets, which give the material its lightweight and high thermal insulation characteristics. It is available as blocks and as pre-cast reinforced units for building floors, roofs, walls and lintels.
Raw material
Raw materials for AAC vary with the manufacturer and the location. The kinds of materials that could be used are detailed in the ASTM C1386 specifications. They include some, or all, of the following: fine silica sand; Class F fly ash; hydraulic cements; calcined lime; gypsum; expansive agents such as finely ground aluminium powder or paste; and water.
AAC is produced by mixing quartz sand and/or pulverised fly ash (PFA), lime, cement, gypsum/anhydrite, water and aluminium and is hardened by steam-curing in autoclaves. The silica is obtained from silica sand, fly ash (PFA), crushed silica rock and/or stone. It is possible to obtain silica as a by-product coming from other processes such as foundry sand or burgee from glass grinding; although, it can be used only if the levels of alkali or other impurities are not too high. The calcium is obtained from quick lime, hydrated lime and cement. Gypsum acts as a catalyst and enhances the properties of AAC. Careful regulation of the amount of aluminium powder gives accurate control over the density of the final product.
Cement with the least per cent of clinker would be the cheapest and suitable, e.g., Portland limestone cement. If milling of siliceous material is required, Cemeng suggests grinding of a composite mix of siliceous materials together with cement clinker, lime and gypsum/anhydrous. The ground material can be stored in a single bin. It also eliminates the need for multiple handling of individual constituents and weigh batchers. Cemeng employs a PSRG mill function in open circuit to produce the desired fineness of the composite mix.
Process flow
Cemeng has simplified the process flow to minimise the number of equipment and material handling requirements in mini AAC plants. The process gets rid of ?wet cutting? the green cake as it is possible only if the plant is involved in exclusive production of smaller blocks. Other AAC products with or without reinforcement certainly require ?dry milling? of cured cakes for profiling. Cemeng moulds for AAC are wheel-mounted units with a base plate and sliding sidewalls. There is no need for rotation or dismantling and re-assembling of side plates. Loaded moulds are transferred directly into the autoclaves for steam curing. Cemeng autoclaves generate the required steam in the autoclave itself. Separate boiler is not required. For mini AAC plants, Cemeng suggests after-cutting/milling of cured blocks for economic benefits.
The important unit operations involved in AAC production are gravimetric proportioning and mixing of constituents with water to form the slurry. This is followed with secondary mixing with expansive agents, pouring the slurry into casting moulds and then allowing sufficient time for initial hydration. Once the material is hydrated it gains enough strength to support its own weight and can undergo de-moulding/cutting. The cakes are then transferred into autoclave for high pressure steam curing. Once cooled, the autoclaved blocks are ready for after-cutting/milling as per the required profile. The AAC cost depends mainly on the cost of mineral binders and the expansive agents used. The cost of silica can vary from location to location.
Cement plant and Cemeng mini AAC production line
Cemeng mini AAC production line can be installed in an existing cement plant. Cement plants are already processing and handling both siliceous and mineral binder constituents, except for lime and sand. Also, ground raw meal, preheater ESP dust, pre-calcined meal from bottom most stage of preheater can partially or wholly replace lime. Sand may be replaced by ground slag and cinder. Clinker dust from cooler ESP and gypsum can replace cement. Besides, clinker cooler exhaust air may be effectively utilised for production of steam required for autoclaving, thus eliminating the need for a separate boiler set up.
AAC production capacity, on a thumb rule basis, can be considered as twenty cubic meter per day for every 100 tpd production capacity of the clinkerisation unit. This is based on steam production using gases only from the from clinker cooler exhaust.
Manufacturing process
To make AAC, sand is ground to the required fineness in a ball mill and is stored along with other raw materials. The raw materials are then batched by weight and are delivered to the mixer. Measured amounts of water and expansive agent is added to the mixer to prepare a cementitious slurry.
Preparation of slurry
Slurry preparation is a batch process. When AAC is being made from dry constituents, Cemeng employs separate weighbin augur dosers for each constituent the Cemeng weighbin augur doser, which uses a combination of weight and volumetric filling. A vertical auger looks like a corkscrew. The auger rotates in the hopper filled with lose powder. As it turns, it drives the powder through the bottom of the hopper into a narrow tube, where the powder is drawn down by a turning screw. The auger runs through the narrow tube, creating a tight fit. As the screw turns, it pulls the prescribed amount of powder down the tube. The agitator keeps the feed flowing to the centre of the auger. You can control the amount of powder delivered by setting the number of revolution made by the auger.
The augur screw discharges into a tubular disc conveyor for conveying and transferring directly into the AAC mixer. Subsequently, aluminium paste is added, secondary mixing is carried out and the final slurry is discharged into the AAC moulds.
Casting in moulds
Steel moulds are prepared to receive fresh AAC. If reinforced AAC panels are to be produced, steel reinforcing cages are secured within the moulds. After mixing, the slurry is poured into the moulds. The expansive agent creates small, finely dispersed voids in the fresh mixture, which increases the volume by about 50 per cent within three hours. The moulding of AAC in the mould box, holding for initial strength and de-moulding prior to autoclaving is an important step in reducing the material handling. Conventionally, the base of the moulds-box and three sides are welded together with only one side plate of mountable type. This calls for mould rotation to load the green mould on to the mountable side plate.
Cemeng moulds for AAC are trolley-mounted units with a base plate and sliding sidewalls. During casting, the sidewalls are slided inwards to form a box holding the slurry. The sidewalls keep space all around the green cake for the passage of steam. No rotation or dismantling of the side plates and reassembling are required. After curing in autoclaves, the cake is picked up by a grab and is transferred to the trolley.
Cemeng also offers ?FlexiMold? wherein rectangular shaped pre-stitched permeable cloth bags with open top are held at the base of the trolley. The flexibag is filled half with slurry and the top half is left empty to allow for expansion. As the green cake attains strength, it attains the shape of the flexibag. The telescopic brackets are then lowered. The bracket is held in its lowest position when the trolley is moved into the autoclave. The green cake along with FlexiMold is left undisturbed. After curing, the trolley is moved out and the cured cake in the moulding bag is lifted and transferred to storage. FlexiMold serves as a protective cover for cured block and it is also disposable. The size of the green cake can be set as required and several green cakes can be mounted on a single trolley.
Autoclaving
Autoclaving is steam curing at high temperature and pressure. It is required to achieve the desired structural properties and dimensional stability. The chemical reactions that produce the final calcium silicate hydrate structure happen in the autoclave. The process takes about eight to 12 hours under pressure of about 174 psi (12 bar) and a temperature of about 360?F (180?C), depending on the grade of material produced. Preferably, two autoclaves are used with the casting and precuring section in between. The mixing station is located near the discharge end of the autoclave. The thermic fluid reservoir is located at the feed end of the autoclave. This permits the precuring shed to store the cast moulds for the required duration. The waste heat from grate cooler exhaust is utilised for the heating the thermic fluid in a simple heat exchanger. It is estimated that at least 350-400 kg/hr of steam could be generated per 100 tpd production capacity of clinkerisation unit. To initiate the curing cycle, the thermic fluid, heated to 205?C, is passed through the coils in the reservoir at the bottom of each autoclave to generate steam. The hot steam pressure rises up to 1.75Mpa.
After-cutting/milling of cured AAC Blocks
Steam cured AAC blocks can be transported directly to the marketing yards. After-cutting can be carried out by the stockists or at the construction site itself. Existing granite/stone cutting and polishing units at different cities in the marketing zone can be used to saw the AAC blocks to the required size/dimensions. It is always possible to saw cut the large size AAC blocks to the required size at the construction site. Any broken pieces could be used as lightweight filler, thus nothing is wasted.
Conclusion
Every cement plant has to take green initiatives to safeguard sustainability. Using waste-heat for steam generation is highly cost effective and adds to the profits of AAC production. Besides, the plant will also be a captive consumer of cement. Every cement plant can produce AAC at considerably lower cost and can compete with standalone AAC units. AAC products can save time, labour, cement and sand during construction.
References
Eco-Care Building products: www.primeaac.com
Raw material formulae: Dearye Brick machine
Silica, calcium joined in premium products, by Sandy Herod Pit and Quarry Dec 1987 Pg.72 – 74
Brick manufacture in a Cement Plant by DS Venkatesh, Cemtec Engineering, Secunderabad. Indian Cement Review May 1989, Pages ICR-19 to ICR-25 Green Concrete by Yuvraj Patil, Flycrete. Indian Cement Review, May 2014 ?Let us employ PSRG Milling Technology? by DS Venkatesh, Indian Cement Industry Desk Book, March 2014. www.victoryenergy.com
DS Venkatesh,
Freelance Industrial Consultant
Email: dsvenkatesh40@gmail.com
Former CEO and Director of Cemtec Engineering at Secunderabad, DS Venkatesh is currently working as a freelance industrial consultant. He started as a Design Engineer at ACC and later had a long stint at Holtec-India holding several responsible positions. He has been one of the lead consultants to many rotary based mini cement plants and expansions.
DS Venkatesh has provided technical know-how, design and manufacturing drawings for cement production machinery to many Indian machinery manufacturers. Re-engineering and retrofitting of plant/machinery for enhanced productivity is his forte. His work has helped in enhancement of PSRG milling technology applied in media grinding.
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Dalmia Bharat Acquires Jaiprakash Associates Cement Assets for ₹2,850 Crore
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Dalmia Cement executed a Business Transfer Agreement with Jaiprakash Associates and Adani Infra, to acquire 5.2 MnTPA of cement capacity across Madhya Pradesh and Uttar Pradesh.
Dalmia Cement (Bharat) announced on May 22, 2026 that it had signed a Business Transfer Agreement with Jaiprakash Associates Limited and Adani Infra (India) Limited for the acquisition of cement plants located at Rewa in Madhya Pradesh and Churk, Chunar and Sadwa in Uttar Pradesh. The deal was struck at an enterprise value of ₹2,850 crore and is expected to close within two weeks of execution.
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The transaction has a long backstory. Dalmia Cement had originally entered into a framework agreement with Jaiprakash Associates in December 2022, covering the sale of these business assets along with a long-term clinker supply arrangement. However, before the deal could be completed, Jaiprakash Associates was admitted to insolvency proceedings under the Insolvency and Bankruptcy Code. The earlier agreements could not be consummated as a result.
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Following the approval of Adani Group’s resolution plan for Jaiprakash Associates under the IBC framework, Dalmia approached the new management to revive discussions. The fresh Business Transfer Agreement was executed to settle all pending disputes, legal proceedings, and arbitration matters arising from the original framework agreement with Jaiprakash Associates.
Expanding market reach
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Filtration Technology is Critical for Efficient Logistics
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May 15, 2026By
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Niranjan Kirloskar, MD, Fleetguard Filters, makes the case that filtration technology, which has been long treated as a routine consumable, is in fact a strategic performance enabler across every stage of cement production and logistics.
India’s cement industry forms the core for infrastructure growth of the country. With an expected compound annual growth rate of six to eight per cent, India has secured its position as the second-largest cement producer globally. This growth is a result of the increasing demand across, resulting in capacity expansion. Consequently, cement manufacturers are now also focusing on running the factories as efficiently as possible to stay competitive and profitable.
While a large portion of focus still remains on production technologies and capacity utilisation, the hidden factor in profitability is the efficiency of cement logistics. The logistics alone account for nearly 30 per cent to 40 per cent of the total cost of cement, making efficiency in this segment a key lever for profitability and reliability.
In the midst of this complex and high-intensity ecosystem, filtration often remains one of the most underappreciated yet essential enablers of performance.
A demanding operational landscape
Cement production and logistics inherently operate in some of the harshest industrial environments. With processes such as quarrying, crushing, grinding, clinker production, and bulk material handling expose the machinery to constant high temperatures, heavy loads, and dust, often the silent destructive force for engines.
The ecosystem is abrasive, and often one with a high contamination index. These challenging conditions demand equipment such as the excavators, crushers, compressors, and transport vehicles to perform and perform efficiently. The continuous exposure to contamination across every aspect like air, fuel, lubrication, and even hydraulic systems causes long-term damage. Studies have also shown that 70 to 80 per cent of hydraulic system failures are directly linked to contamination, while primary cause of engine wear is inadequate air filtration.
For engines as heavy as these, even a minor contaminant has a cascading effect; reducing efficiency, performance and culminating to unplanned downtime. Particles as small as 5 to 10 microns, far smaller than a human hair (~70 microns), can cause significant damage to critical engine components. In an industry where margins are closely linked to operational efficiency, such disruptions can significantly affect both cost structures and delivery timelines.
Dust management: A persistent challenge
Dust is a natural by-product in cement operations. From drilling and blasting in the quarries to packing in plants, this fine particulate matter does occupy a large space in operations. Dust concentration levels in quarry and crushing zones often create extremely high particulate exposure for equipment. These fine particles, when enter the engines and critical systems, accelerates the wear and tear of the component, affecting directly the operational efficiency. Over time every block fall; engine performance declines, fuel consumption rises, and maintenance cycles shorten. In this case, effective air filtration is the natural first line of defence. Advanced filtration systems are designed to capture high volumes of particulate matter while maintaining consistent airflow, ensuring that engines and equipment operate under optimal conditions.
In high-dust applications, as in cement production, even the filtration systems are expected to sustain performance over extended periods without the need of frequent replacement. This becomes crucial in remote quarry locations where access to frequent maintenance may be limited.
Fluid cleanliness and system integrity
Beyond air filtration, fluid systems also play a crucial role for equipment reliability in cement operations. Fuel systems are required to remain free from contaminants for efficient working of combustion and injection protection. Additionally, lubrication systems also need to maintain the oil purity to reduce friction and prevent any premature wear of moving parts. The hydraulic systems, which are key to several heavy equipment operations, are especially sensitive to contamination.
If fine particles or water enters these systems, it can lead to reduced efficiency, erratic performance, and eventual failure of the system. Modern filtration systems are designed with high-efficiency media capable of removing extremely fine contaminants, with advanced fuel and oil filtration solutions filtering particles as small as two to five microns. Multi-stage filtration systems further ensure that fluid performance is maintained even under challenging operating conditions.
Another critical aspect of fuel systems is water separation. Removing moisture helps prevent corrosion, improves combustion efficiency and enhances overall engine reliability. Modern water separation technologies can achieve over 95 per cent efficiency in removing water from fuel systems.
Ensuring reliability across the value chain
Filtration plays a critical role across every stage of cement logistics:
• Quarry operations: Equipment operates in highly abrasive environments, requiring strong protection against dust ingress and hydraulic contamination.
• Processing units: Crushers, kilns, and grinding mills depend on clean lubrication and cooling systems to sustain continuous operations.
• Material handling systems: Pneumatic and mechanical systems rely on clean air and fluid systems for efficiency and reliability.
• Transportation networks: Bulk carriers and trucks must maintain engine health and fuel efficiency to ensure timely deliveries.
Across these operations, filtration plays a vital role; as it supports consistent equipment performance while reducing the risk of unexpected failures.
Effective filtration solutions can reduce unscheduled equipment failures by 30 to 50 per cent across heavy-duty operations.
Uptime as a strategic imperative
In cement manufacturing, uptime is currency. Downtime not only delays the production, but it also greatly impacts the supply commitments and logistics planning. With the right filtration systems, contaminants are kept at bay from entering the
critical systems, and they also significantly extend the service intervals.
Optimised filtration can extend service intervals by 20 to 40 per cent, reducing maintenance frequency while maintaining consistent performance across demanding operating conditions. Filtration systems designed for heavy-duty applications sustain efficiency throughout their lifecycle, ensuring reliable protection with minimal interruptions. This leads to improved equipment availability, lower maintenance costs, and more predictable operations, with well-maintained systems capable of achieving uptime levels of over 90 to 95 per cent in challenging cement environments.
Supporting emission and sustainability goals
With the rising environmental awareness, the cement industry too is aligning with the stricter norms and sustainability targets. In this scenario, the operational efficiency is directly linked to emission control.
Air and fuel systems that are clean enable
much more efficient combustion. They also reduce emissions from both the stationary equipment and transport fleets. Similarly, with a well-maintained fluid cleanliness, emission systems function better. Poor combustion due to contamination can increase emissions by 5 to 10 per cent, making clean systems critical for compliance.
Additionally, efficient and longer lasting filtration systems significantly reduce any waste generation and contribute to increased sustainable maintenance practices. Extended-life filtration solutions can reduce filter disposal and maintenance waste by 15 to 20 per cent. Smart and efficient filtration in this case plays an important role in meeting the both regulatory and environmental objectives within the industry.
Advancements in filtration technology
Over the years, there has been a significant evolution in the filtration technology to meet the modern industrial applications.
Key developments include:
• High-efficiency filtration media capable of capturing very fine particles without restricting flow
• Compact and integrated designs that combine multiple filtration functions
• Extended service life solutions that reduce replacement frequency and maintenance downtime
• Application-specific engineering tailored to different stages of cement operations
Modern multi-layer filtration media can improve dust-holding capacity by up to two to three times compared to conventional systems, while maintaining consistent performance. These advancements have transformed filtration from a basic maintenance component into a critical performance system.
Adapting to diverse operating conditions
The cement industry of India operates across diverse geographies. Spanning across regions with arid regions with higher dust levels, to the coastal areas with higher humidity, challenges of each region pose different threats to the engines. Modern filtration systems are thus tailored to address these unique challenges of each region.
Indian operating environments often range from 0°C to over 50°C, with some of the highest dust loads globally in mining zones.
Additionally, filtration technology can also be customised to variations which then align the system design with factors like dust load, temperature, and equipment usage patterns. Equipment utilisation levels in India are typically higher than global averages, making robust filtration even more critical. This approach ensures optimal performance and durability across different operational contexts.
Impact on total cost of ownership
Filtration has a direct and measurable impact on the total cost of ownership of equipment.
Effective filtration leads to:
• Lower wear and tear on critical components
• Reduced maintenance and repair costs
• Improved fuel efficiency
• Extended equipment life
• Higher operational uptime
Effective filtration can extend engine life by 20 to 30 per cent and reduce overall maintenance costs by 15 to 25 per cent over the equipment lifecycle. These benefits collectively enhance productivity and reduce lifecycle costs. Conversely, inadequate filtration can result in frequent breakdowns, increased maintenance expenditure, and reduced asset utilisation.
Building a more efficient cement ecosystem
With the rising demand across various sectors, the cement industry is expected to expand at an unprecedented rate. This growth is forcing the production to move towards a more efficient and resilient system of operations. This requires attention not only to production technologies but also to the supporting systems that enable consistent performance. Filtration must be viewed as a strategic investment rather than a routine consumable. By ensuring the cleanliness of air and fluids across systems, it supports reliability, efficiency, and sustainability.
The road ahead
The future of cement logistics will be shaped by increasing mechanisation, digital monitoring, and stricter environmental standards. The industry is also witnessing a shift towards predictive maintenance and condition monitoring, where filtration performance is increasingly integrated with real-time equipment diagnostics.
In this evolving landscape, the role of filtration will become even more critical. As equipment becomes more advanced and operating conditions more demanding, the need for precise contamination control will continue to grow. From quarry to construction site, filtration technology underpins the performance of every critical system. It enables equipment to operate efficiently, reduces operational risks, and supports the industry’s broader goals of growth and sustainability. In many ways, it is the unseen force that keeps the cement ecosystem moving, quietly ensuring that every link in the value chain performs as expected.
About the author
Niranjan Kirloskar, Managing Director, Fleetguard Filters, is focused on driving innovation, operational excellence, and long-term business growth through strategic and people-centric leadership. With a strong foundation in ethics and forward-thinking decision-making, he champions a culture of collaboration, accountability, and technological advancement.
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