Keeping the multiple requirement of the Indian construction industry in view to have a reliable mixer to turn out desired strength of concrete, which is simple to operate, has good mobility and it facilitates speeder construction, the new Volumetric Mixers made in USA by M/s.International Mixers has been introduced for the first time in India by M/s.Elektromag Devices Pvt. Ltd.
The important working principles of the Mixer are that aggregate, cement, sand, flyash/slag and other additives are taken out from different hopper mounted on an automotive chasis through various calibrated gate valves and mixed in an Auger Style Mixer. Calibration could be done at the site by weight depending upon available materials and for various grades of concrete suggested mix is also available on a ticker.
A properly designed and maintained auger-style continuous mixer will actually deliver a quality mix superior to that of traditional methods. Most specifiers recognize and accept that when the fresher concrete is applied, it becomes stronger and the total quality will also be higher. With a volumetric mixer, the concrete is made “on demand” around or actually when needed, ensuring the freshest concrete possible.
The design and acceptability of the volumetric mixer has greatly improved since the technology was first introduced in 1966. Today, an ASTM specification has particularly been established for the volumetric mixer, ASTM C685 and it can be compared to C94 specification traditionally used in weight batching (central batch plant with delivery by rotating drum mixers). Indeed, the National Ready-Mixed Concrete Association (NRMCA) has internally established a bureau for volumetric mixer manufacturers. Today's Volumetric Mixer has earned a legitimate reputation for quality and reliability, and is recognized by every US State and federal Department of Transportation as an acceptable source for highways work.
Outstanding Mix Quality
The quality of concrete from a Volumetric Mixer is being recognized for long. Arguably, the fresher the concrete is, the higher and stronger its quality is. With a Volumetric Mixer, concrete is mixed and discharged as needed; the mixing process begins only when it is required at the actual site. There is no concern of hot loads and water tempering because fresh concrete is made on demand. Another important point is the flexibility of the Volumetric Mixer. A Volumetric Mixer can produce 0-250mm slump from the same load giving quality concrete on site to match a wide range of specifications and the calibrations can also be changed quickly to accommodate any new mix requirements. In a manner of minutes, a certain calibration can be set up to accommodate a different mix design. The new Volumetric Mixer is very user-friendly and quickly adaptable. These days, this is the most accurate machine in the Industry (0.5% to 1%).
Lower Equipment and Initial Investment Cost
The Volumetric Mixer solution normally requires less investment than traditional methods employing a central batch plant with supporting drum mixers. The return on investment when compared to cost and production does strongly favor Volumetric Mixer as the initial investments relatively low and the production rate performance is relatively high.
This is the only modular mixer in the market and its all units are bolted and separated. The best thing of this new innovation and addition is that it can be easily added for the future. Open concept allows for simple maintenance/ operations extending the life and limited downtime.
On Site Batch Plant or Mobile Delivery Versatility
The Volumetric Mixer can be used as a stationary unit with a local power source i.e diesel, electric or as a mobile unit serving on site batching plant or for a delivery to site solution. Where mobile delivery is best, time and distance limitations that may apply to traditional methods do not apply. Concern of “hot loads” and water tempering are not applicable to the Volumetric Mixer. A chassis or trailer mounted unit may be selected to best serve the mobile application. Efficient use of time and fuel can be greatly gained by using a Volumetric Mixer as an on site ‘batch plant’. Where material storage can be located at the job site, a Volumetric Mixer represents a true value in both cost and performance. In some situations, only one or two person could be employed to run the job, serving as loader and operator. In addition, the ability to coordinate labour and materials to construction sites is vastly improved. Waste is greatly reduced, cost overruns less likely when the VM is used for job site locations and or for difficult remote deliveries.
Simplicity of Operation
Today’s Volumetric Mixer is simple to operate and the operator can easily be trained, as the mixer has in most cases only four hydraulic levers to engage (auger mixer horizontal and height, mixer and conveyor engagement). In addition, they are operating the mixing process in full view of the control station and the flow of contents. One can easily adjust water and admix flow as may be needed. As long as the aggregate, sand, and cement bins are supplied, the Volumetric Mixer can produce concrete continuously at a normal rate of 50m3 per hour (Mixers can also be built to produce upto 80m3 per hour, depending upon the application).
As a standard feature, the Volumetric Mixer has a counter meter that can be interpolated to give exact volume or yield of concrete for separate deliveries to multiple job sites, regardless of the mix design. Additionally, where required, an electronic PLC metering device can be included to provide accurate details of the mix, very similar to that offered by central batch plants. Not only every job site delivery content will be recorded, but also can be set to total any specific day or time frame activity.
Cement Delivery System
An advantage of Volumetric Mixer is accuracy and performance of Volumetric Mixer’s cement delivery system. Volumetric Mixer incorporates a reversed flighting auger that brings cement contents laterally to center, where it is transferred to the metering auger for introduction to the mixing auger. Because of this design, Volumetric Mixer system is so accurate that it has even passed CALTRAN C 109 specification (cement content cannot be very more than a plus or minus 1/2% in four repeated tests). In addition, all cement contents can completely be emptied from the cement bin as may be required.
Advanced Mixing Auger
Volumetric Mixers solid flighting and shearing design enables machine to produce and deliver concrete at a high angle. Volumetric Mixer can produce concrete at a full rate of delivery when the mixing auger is at a 45 degree angle (2M discharge height), and it can do this at up to an 200mm slump. This is extremely important if the unit is required to feed a pumper, as no adjustments are needed to either terrain or the pumping equipment to accomm- odate full delivery from the system.
With the above features Indian construction Industry can reap full benefit and get value for its money.