Manufactured sand (M-Sand) is the way forward for India´s construction industry.
India is on a fast track to develop world-class infrastructure in the country. Commencing with road sector wherein a construction speed of 40 km a day has already been achieved, plans are afloat to take it to 100 km a day. Similar traction has begun in other construction sectors like canals and more will follow. The common ingredient for all construction is sand and if the estimates provided by the CPCB are considered, 135 billion tonne of crushed and screened aggregate will be required up to 2018, out of which approximately 20 per cent will be sand! Rest is only mathematics to determine the industry size.
Need for M-Sand
Infrastructure construction guzzles sand to produce concrete and other stone based aggregate mixes for the works at hand. Natural and river sand have been the most preferred sources of supply by the construction industry for ages. However, for reasons of environment protection and poor to low CSR strength of river sand has led to banning of natural sand mining and prohibition to use river sand, in most regions of India.
Further, the transportation cost of natural sand from source to job sites is prohibitive and severely impacts the economic viability of the project, many of which are located in far flung regions. At the same time the variations in the properties of natural are restricted only by the number of sources. Therefore, it is a marathon task for the mix designers, who are compelled to commence their design process from the basics every time followed by intense testing by the project owners prior to commencement of work. As result, there are project execution delays and inordinate costs incurred by the contractors.
Manufactured sand or M-sand is one of the best solutions to the above problems and when supported by the crushing and screening equipment manufacturers with the appropriate M-sand solution/s, it has emerged as the most technically and commercially viable solution for the construction industry.
Niraj Srivastava, Vice President, Technical Support, CSR, Metso India, comments, ´Rising concerns to the alarming situation, of negative environmental impact, has been strict measures making their way in the whole country. After banning mining of river sand and other minor minerals without the mandatory environment clearance, the National Green Tribunal (NGT) has also banned beach sand mining or removal of sand from river beds across the country without an environmental clearance. Yet, news about illegal sand mining keeps making its way to the national and regional dailies every now and then. The figure reported to have accounted for loss of minerals through such practices have run into multi-million tonnes.´
In fact, the 2011 sand policy encourages establishment of manufactured sand units by giving top priority while allotting quarries. So, manufactured sand is the option. As the natural sand is not replenished at the rate it is being used, the government has begun to promote manufactured sand. Experts vouch that manufactured sand is only a viable alternative to natural sand, but is superior in many ways. Tests have revealed that characteristics of mortars and concrete using manufactured sand as fine aggregate are superior when compared to the natural sand as fine aggregate. Demand for manufactured fine aggregates for making concrete is increasing day by day as river sand cannot meet the rising demand. Because of its limited supply, the cost of natural river sand has sky rocketed and its consistent supply cannot be guaranteed. Under this circumstances use of manufactured sand becomes inevitable.
Key deliverables by OEMs
Compressive strength of sand is the main parameter considered by the designers. It is a combination of the shape, size grading and moisture content which impacts the strength of M-sand in addition to the properties of the available quarry material. The Figure 1 explains the key deliverables, which are of essence for the equipment solution providers in the words of Srivastava.
´The major performance parameters considered by customers are capacity and final product size, as these are directly related to the customer´s revenue. Apart from this, the quality of machines, wear and tear, ease of maintenance, design and execution capability, service and spare back-up available in close proximity are other important factors impacting the choice of partner for customers,´ says Sivasubramanian Natarajan, Managing Director, thyssenkrupp Industries India.
Equipment solutions on offer
Shape is a major issue. This is where the crushing equipment´s role is critical to ensure an acceptable shape and size. Says Srivastava, “Cone crushers like the Metso Nordberg® HP Series™ and GP Series™, enable the production of finer products together with coarser aggregates. They also lower the initial capital investment and save energy, due to the fewer crushing stages. They give the producers high energy efficiency and capacity, good product gradation, a high reduction ratio. Cavity design for cone crushers should be optimized to ensure that crushing occurs along the full length of the crushing zone between the liners. This causes inter-particle crushing to occur, leading to the highest possible generation of the required fines and cubically shaped products. Advances in high-speed cones with high clamping forces offer the opportunity to produce well-graded and shaped <20 mm product including well graded manufactured sand.“
Studies show that the best end product for various purposes can be achieved with high-velocity impact crushing. The Metso Barmac® VSI vertical shaft autogenous impactor improves the soundness and shape of the material and produces a quality that is very close to natural sand. Unlike cones, VSI shaping is not influenced by the closed side setting (CSS), and shaping occurs throughout the product curve. The sand produced from rock-on-rock crushing is proven to have sound performance in concrete and mortar products. Such sand is well known for its cubical shape and consistent gradation. The gradation and quality of the product from the VSI does not tail off with increased wear on parts. This leads to the highest possible quality of performance in concrete and mortar mixes leading to reduced production costs. Screens and Classifiers are then used to remove the needed amount of fine particles and dust. “Metso´s triple slope screen (TS Screen) is used for final screening for manufactured sand as well as for plaster sand to take 2.36 mm down product. Metso air classifiers, which are environmentally friendly and economical to use, produce consistent sand quality,“ explains Srivastava.
Dual bearing TS screen ensures capacity and efficiency due to multi-slope profile with elliptical vibrating motion, 20-40 per cent more capacity compared to conventional inclined screen. Elliptical motion forwards at feed end and backward at discharge end - particle retention time on screening surface more for efficient screening. Superior for aggregate and fines´ screening, screening area varies from 7.6 to 25 sq m in double and triple deck option.
Metso´s air classification technology offers dry classification solutions to produce manufactured sand. The dry separation process separates fine and coarse particles. This allows a reduced percentage of super fines in manufactured sand. Classified manufactured sand for concrete has particles of equi-dimensional shape, an “even” type particle size distribution, thereby meeting specifications and achieving quality products.
Metso offers two classifier options to aggregate producers. The gravitational inertial classifier is typically fed 0/4 mm or less and makes separations between 300 microns (50#) and 63 microns (230#). These units are ideal for use in the manufacturing of concrete and asphalt sands that typically require a reduction in the amount of 63 microns (230#) present. This unit is designed with an internal re-circulating function that allows the efficiency of the separation to be adjusted depending on the desired grading curve. When finer separations are required, the centrifugal classifier can make separations of between 100 microns (140#) and 20 microns (625#). This makes these units suitable for the production of very fine products such as lime, fly ash and fertilisers.
Thyssenkrupp is a major player that offers aggregate crushing solutions for M-sand manufacturing. Sivasubramanian states, “thyssenkrupp Industries India is a part of global conglomerate with a proven track record of excellent quality engineering products having a presence in the Indian market for the last several decades. thyssenkrupp has world-class design and manufacturing facility to construct machines suitable for aggregate crushing and produce M-sand. These machines based on proven design comprising jaw crusher, cone crusher and VSI produce excellent quality sand suitable for construction purposes. We cater to all requirements of the aggregate crushing market. We have various sizes of all crusher models suitable for capacities varying from 100 tph to 500 tph. Depending on individual customer needs, machines can be supplied to suit final product size and capacity.“
The noticeable effects on environment and the ecosystem caused by sand mining, together with the growing demand of aggregates to fulfill the construction requirements of the urban world has made it imperative to look for alternate solutions to the concern. That´s the reason; operators now wish to produce high-quality manufactured sand.
Manufactured sand is defined as a purpose-made crushed fine aggregate produced from a suitable source material. Production generally involves crushing, screening and separation into discrete fractions, recombining and blending may be necessary. Manufactured sand has a more predictable product consistency than natural sand variation. There are two main drivers.
Firstly, there is a lack of natural sand reserves. Urban expansion, local legislation and environmental constraints have made the extraction of natural sand and gravel an expensive activity. Application processes for greenfield sand and gravel extraction are often long, expensive affairs with a high chance of site applications being rejected. The increasing difficulty in extraction has had a negative effect on the bottom line for many producers. In many regions of the world, the extraction of sand and gravel is heavily taxed or banned completely to try to preserve remaining deposits. The industry must find alternatives to meet the growing demand for fine aggregates.
The second driver is purely economic. A growing number of quarry operators have found that processed, high-quality Manufactured sand can improve their bottom line and significantly reduce the percentage of waste and low-value by-products. Customer requirements for production less than 20 mm, especially for 5/20 mm, mean that significant amounts of 0/5 mm are produced as a by-product.
By utilising the correct process equipment, low-value crusher dust can be processed into a high-value, premium product. Concrete, mortar and asphalt sand production is possible depending on the material characteristics and regional regulations.
Sivasubramanian elaborates on the demand drivers, “Increased thrust in road building (40 km/day) is a major opportunity for the crushing business. With added focus on urban infrastructure development such as Smart Cities, Metro Projects and mega power projects, we are seeing financial institutions coming forward to refinance stalled projects, which is a big positive for this sector. Power plants, coal mining and such sectors have also shown tremendous potential for growth.“
Aftermarket support: Key differentiator
Says Srivastava, “Our competence and expertise are at your service around the clock, 365 days a year. You can count on Metso´s highly trained, certified field service teams to maximise your equipment and plants´ availability. With over 1,500 Metso service technicians in the field and an extensive distributor and partner network, we are there to support our customers 24x7. We understand that speed of response is critical. Only Metso provides true global support with 20+ factory hubs, 40 service centres and more than 1,500 service technicians in the field to support our customers. Metso has an extensive partner network of 150+ distributors with whom we work closely to deliver the service levels you have come to expect.“
Sivasubramanian elaborates on his company´services, “thyssenkrupp Industries India has been present in India since 1957, and is equipped with excellent infrastructure and resources. It has a large service department with more than 200 employees, including service engineers who can cater to customer needs across India on short notice. We also ensure availability of spares in close proximity to customers and are setting up warehouses in the regions where customer clusters are prominent. The key to success for any business is satisfied customers and we at thyssenkrupp lay a lot of emphasis on this aspect. Our focus on high quality products at optimum prices with world-class in-house manufacturing facilities, excellent service standards and spare back-up in close proximity of our customers are our key strengths to ensure satisfied customers.“
Srivastava says, “Metso has years of know-how in different solutions for sand processing and a good portfolio of related equipment.“ He adds, “Crushing equipment´s role is critical to ensure an acceptable shape and size. Cone crushers, like the Metso Nordberg® HP Series™ and GP Series™, enable the production of finer products together with coarser aggregates. They also lower the initial capital investment and save energy, due to the fewer crushing stages. Metso´s HRC™ high-pressure grinding roll technology lends itself especially well to the production of sand.
The inter-particle commendation method makes the cubical/angular product shape under the correct operating conditions.“
Studies show that the best end product for various purposes can be achieved with high-velocity impact crushing. “The Metso Barmac® VSI vertical shaft autogenous impactor improves the soundness and shape of the material and produces a quality that is very close to natural sand,“ says Srivastava. He further adds, “Most other VSI crushers use metallic parts to crush rock, but the Barmac VSI uses the rock fed into the machine to crush itself. The better the end-product grain shape, the better its performance in concrete, asphalt and base mixtures. The rock-on-rock crushing and grinding action also provides the lowest cost per ton of any impact crushing method. Classifiers are then used to remove the needed amount of fine particles and dust. Metso static Air Classifiers, which are environmentally friendly and economical to use, produce consistent sand quality.“
“Backed by proven design and total manufacturing under close quality monitoring, we are one of the top bracketed manufacturers of aggregate crushing machines,“ states Sivasubramanian. He adds, “Safety, maintenance-friendly and simplicity of design and high performance are the hallmarks of thyssenkrupp worldwide. User-friendly operation is our prime focus. Many features like automatic grease lubrication system, automatic hydraulic system and compressed air system, adjustable bushing offering four eccentricities for our high-end crushers make our design not only robust but also convenient for end-users from a maintenance point of view.“
According to Srivastava, the change in trends and size of the market will depend on the decision of industry regulatory bodies about environment protection and announcements of new projects by government authorities. He elaborates, “As always, Metso has maintained its market leadership by introducing modern cutting edge technology in crushing and screening segment globally as well as locally. And will certainly introduce something novel and suitable for Indian market.“ Sivasubramanian is positive on the growth opportunities in sand manufacturing segment. “With the strong focus on infrastructure spending by the Government of India and the state governments, we are confident that the market will have a healthy growth going forward,“ he observes.
The market for the standard crushing and screening equipment to produce larger sized aggregates in the range 5 to 55 mm along with other finer sizes will continue to grow in line with the projected infra developments spread over the incoming decades. However, the same equipment category, when configured and customised to produce M-sand will have the additional distinction of protecting the environment while servicing the user requirements. As a result, while piggybacking the success story of the mainstream equipment, M-sand equipment may emerge as a stand alone entity of infrastructure equipment.
Rounded shape, smooth surface texture, and grading have a significant effect on the performance of fresh concrete.
Aggregate when blends with well-shaped, rounded, and smooth Sand particles require less paste for a given slump than blends with flat, elongated, angular and rough particles, reduces inter-particle friction in the fine aggregate component of the concrete mix grading.
Optimized M-sand with uniform grading results in aggregate blends with high packing and with low water demand.
As a result, they are less expensive and will have less durability problems caused by the paste such as heat generation, porosity, and drying shrinkage.
Producer secures new product offerings and reduces low-value product
Customer has access to a secure supply of sand with a stable grading curve.