Flow Sheet for 30/40 TPH
River sand, referred to as natural sand, had been one of the principal construction materials and remained as the key filler in bonding mixes for all masonry constructions, since ages. The scenario has changed globally in mid-20th century onwards. The river sand has become scarce, the principal reason being environmental protection laws enacted by the local governments, imposing a ban on river sand mining. This has led the construction aggregates industry worldwide, particularly that in India, to find a suitable substitute filler material to river sand. With continuing rapid growth in infrastructure construction sector, any substitute for river sand should obviously be available aplenty, should be able to be processed to the same physical characteristics of river sand and should be able to be sourced in final form in bulk quantities to meet the growing demand for fine aggregates in cement concrete & cement mortar production. The ideal substitute was found to be crushed sand derived by crushing hard-stone. The obvious source was zeroed on to existing and/or new aggregates plants that could produce and supply both fine aggregates and coarse aggregates. But the issue faced by quarry operators is that most of their existing plants deploy two-stage crushing with jaw + jaw or jaw + cone crusher, which work on principle of compression/pressure to break the hard-stone and do not yield a fine grain cubical product that could be termed as crushedsand, or M-Sand, with physical characteristics comparable, if not equivalent, to river-sand.
A solution is found by introducing VSI (vertical shaft impact) crushing technology for turning coarse aggregates into finer material of required particle size, shape and gradation. The quarry operators have and are quickly adopted/adopting to 3-stage crushing with a tertiary VSI crusher to produce fine aggregates along with coarser fractions. The VSI crusher that simulates nature’s way of generating river-sand, has helped the quarry operators to turn the so called 0-5 mm “crusher-dust”, hitherto rejected as a waste material, into a value-added product, that is universally termed as ‘MSand’.
Those quarry operators who got 3-stage VSI plant or added a tertiary VSI crusher station to their existing 2-stage plants are simultaneously producing 0-4.75 mm M-Sand as well as (less than) 22 mm quality-enhanced cubical shaped coarse aggregates. The additional VSI crusher station has also helped them in converting excess coarser products to M-Sand, making their operations more profitable.
The M-Sand produced in VSI crusher with ‘Rock-on-Rock’ crushing principle is proven to be of required cubical shape with consistent gradation and is found to yield good results as fine-aggregate in all cement concrete mixes, asphalt mixes and as dry mortar/plaster sand, depending on the stone characteristics. VSI-produced sand is accepted by concrete engineering fraternity round the globe as the right substitute to river sand and is extensively used in RMC and other cement concrete works. The benefit of using VSI crusher to produce M-Sand is twofold: 1) The quarry operator/crusher owner is able to convert 0-5 mm product to high value M-Sand making his aggregates production business more profitable and 2} The end user has found a single source for coarse aggregates as well as fine-aggregate product conforming to standard codes, deriving purchasing and logistic advantage
The fine aggregate means the natural sand or M-Sand which passes through 4.75 mm sieve. The IS: 383 – 1970 lays down four grading zones from coarse sand to fine sand specifying limits on range of percentage proportions of various fractions that fall between 4.75 mm down to zero, which is reproduced below:
| Sieve size | Zone-I | Zone-II | Zone-III | Zone-IV |
|---|---|---|---|---|
| 10 mm | 100% passing | 100% passing | 100% passing | 100% passing |
| 4.75 mm | 90-100% passing | 90-100% passing | 90-100% passing | 90-100% passing |
| 2.36 mm | 60-95% passing | 75-100% passing | 85-100% passing | 95-100% passing |
| 1.18 mm | 30-70% passing | 55-90% passing | 75-100% passing | 90-100% passing |
| 0.6 mm | 15-34% passing | 35-59% passing | 60-79% passing | 80-100% passing |
| 0.3 mm | 5-20% passing | 8-30% passing | 12-40% passing | 15-50% passing |
| 0.3 mm | 5-20% passing | 8-30% passing | 12-40% passing | 15-50% passing |
| 0.15 mm | 0-10% passing | 0-10% passing | 0-10% passing | 0-15% passing |
Concrete sands fall under Zone -II and dry mortar/plaster sands fall under Zone-III/Zone-IV. The admissible limit for M-Sands, on 0.15 mm (150-micron) is up to 20%.
Many comparisons of river sand and M-Sand gradations have confirmed that the M-Sands produced using vertical shaft impact (VSI). A typical comparison of river sand and M-Sand against Zone – II code is produced below:
| IS Sieve Designation | Zone II (IS:383) (% Passing) | River Sand (% Passing) | M-Sand (% Passing) |
|---|---|---|---|
| 4.75 mm | 90-100 | 100 | 100 |
| 2.36 mm | 75-100 | 99.5 | 91 |
| 1.18 mm | 55-90 | 90 | 66 |
| 600 microns | 35-59 | 61 | 40 |
| 300 microns | 8-30 | 17.5 | 25 |
| 150 microns | 0-20 | 3.5 | 12.5 |
| 75 microns | 15 max. | 5 | 15 max. |
Wherever required the gradation of M-Sand can be controlled in VSI crusher to meet the specified standards. In addition, the M-Sands provide cubicle particle and sans silt and any organic impurities.
YES provides complete crushing and screening solutions for aggregates industry. The present effort is to utilize its specialist knowledge in fine crushing and separation and provide an economical and compact sand production module that can be installed in existing plants. The excess produced products of 5-10 mm and 20-40 mm will be crushed to produce well-graded & quality M-Sand meeting IS code, and thereby creating a value addition to one’s existing operations. Also, the construction contractors can set up these compact modules quickly at their project sites to convert excess crushed stone, gravel, crusher waste to M-Sand to meet their project demand.
The above flow-sheets and plant layout are developed for production of construction sands meeting IS code. The crushing is accomplished in a VSI crusher (two different rotor sizes). The ‘Rock-on-Rock’ crushing principle of the VSI yields cubical shape particles and size distribution meeting required standard codes. The VSI works in closed circuit with a high performance vibrating screen to crush all feed material to < 5.0 mm product.
The VSI and vibrating screen are mounted on a composite, sturdy and compact steel fabricated skidframe. The material feeding arrangement will be designed to suit to the existing plant disposition and owners’ preferences. What is shown in the layout is a typical feeding arrangement consisting of a ground level feed-hopper fed by a front-end-loader. A belt conveyor below the hopper extracts and feeds the material to VSI crusher. A set of scissor conveyors are deployed to collect, transport and deliver the crushed material to the vibrating screen. The product fraction is delivered on to a stockpile conveyor and oversize is fed back to VSI crusher through a screen discharge chute arrangement.
The skid-module can be integrated with the existing 2-stage crusher plants as a third-stage crushing station to produce simultaneously M-Sand and cubical shaped coarse aggregates. By introducing a bigger size VSI crusher and a vibrating screen, the total 5-40 mm produce of secondary station will be fed to VSI, via a surge hopper, thereby produce all > 22 mm well-graded cubical premium fine and coarse aggregates that go into wet and dry concrete mixes.
The design of the of the skid-mount is compact, transport-friendly, enable quick installation & disassembling at project sites.
The unit is wired-up to an electrical control panel mounted on the skid. The purchaser would need to provide and connect up power source to the panel.
