Sand and gravel, as important building materials and concrete raw materials, are widely used in the construction of buildings and road engineering, with a huge market demand. Manufactured sand, which is made by different types of rocks, is gradually becoming a substitute for natural sand, and the application of manufactured sand has become a global trend.
Compared with various natural sand such as river sand, sea sand and mountain sand, what are the advantages of manufactured sand?
Sand refers to rock debris with a particle size less than 5mm that forms and accumulates in natural conditions such as lakes, seas, rivers, and mountains. It can also be construction particles less than 4.75mm processed by mining machinery.
The thickness of sand is divided into four levels according to the fineness modulus:
Coarse sand: The fineness modulus is 3.7-3.1, and the average particle size is above 0.5mm.
Medium sand: The fineness modulus is 3.0-2.3, and the average particle size is 0.5-0.35mm.
Fine sand: The fineness modulus is 2.2-1.6, and the average particle size is 0.35-0.25mm.
Extra fine sand: The fineness modulus is 1.5-0.7, and the average particle size is below 0.25mm.
Natural sand: Rock particles with a particle size below 5mm, formed by natural conditions (mainly rock weathering), are called natural sand.
Manufactured sand: Rock, mine tailings or industrial waste particles with a particle size of less than 4.7mm made by mechanical crushing and screening after soil removal treatment, but excluding soft and weathered particles.
Manufactured sand (M-Sand) has low roundness and large edges, which is widely used in the aggregate market and effectively replaces river sand as the main source of sand and gravel. At present, the projects with large demand for sand and gravel are subway projects, libraries, parks, viaducts, squares, stadiums and other infrastructure construction, reinforced concrete high-rise buildings, roads, railways, bridges, etc., all the industries that need to use sand and natural sand, manufactured sand can be used in these places.
Manufactured sand is a sand and gravel material obtained after crushing by the applicable professional sand making equipment such as a suitable crusher. Compared with natural river sand, it has the characteristics of sharp edges and many needle-like shapes.
Distinguish manufactured sand and river sand from appearance:
River sand is directly excavated from the river channel, so it is mixed with small pebbles and fine sand. These small pebbles are subject to long-term erosion by the river, and their edges are relatively rounded.
The ruggedness and durability of manufactured sand has reached the index of excellent quality, and there is no problem in the use of ordinary concrete. However, in the use of concrete components that are often subjected to friction and impact, in addition to the use of admixtures, the cement sand ratio of the concrete, the crushing index of the sand, and the stone powder content should also be controlled.
The stone powder of machine made sand is a finely ground rock powder smaller than 0.075mm, which cannot react with cement hydration, but it has excellent connection with cement crystalline stone and plays a micro aggregate filling effect in the internal layout.
In fact, if the powder content of machine made sand does not exceed 20%, it has no adverse effects on the coagulation time and strength development of concrete, and has good performance in the workability, pumpability, strength, and other aspects of adding concrete mixtures.
The granularity of manufactured sand is irregular, and when using structural bonding such as cement, it often has better adhesion, greater pressure resistance, and longer service life.
Manufactured sand is generally made from a manually selected raw material, with uniform and stable materials. The mineral and chemical composition is consistent with the raw material, and it is not as complex as natural sand.
The fineness modulus of manufactured sand can be artificially controlled through production processes, and production can be organized according to user requirements, which natural sand cannot achieve.
In summary, manufactured sand not only has a wide range of sources, stable materials, easy operation and control, good performance, and can meet construction needs, but also is economically feasible. It is the development direction of the future construction market and is also very beneficial for the protection of the natural environment.
The production methods of manufactured sand are mainly divided into dry method and semi-dry method.
Dry production method means that in addition to spray dust removal water in individual process links, the process of the entire production line is basically water-free, mainly suitable for areas with cold weather, dry weather, serious lack of water resources, and soil in the ore raw materials can be screened out.
Semi-dry production method refers to no water before and in the crushing section, and washing with water after the crushing section, which is mainly suitable for areas with rich water resources or where the clay material included in the ore raw materials cannot be removed by dry screening. Of course, some areas with higher requirements for manufactured sand also can adopt wet production method.
The coarse crushing equipment is generally a jaw crusher, a two-chamber impact crusher (suitable for medium hardness or soft materials), or a gyratory crusher. If the production capacity requirement is high, greater than 1000t/h, gyratory crusher is recommended.
Primary & Medium Crushing
For medium& fine crushing, SBM provides cone crusher and impact crusher for customers to choose.
Cone crusher: Mainly suitable for crushing rocks with high hardness and high abrasiveness index, with fewer powdered products.
Impact crusher: Mainly suitable for crushing rocks with medium or low hardness and abrasiveness index, with more powdered products.
If there is less demand for powdered products, standard cone crushers can be used for medium crushing, and short head cone crushers can be used for fine crushing.
By circulating the material multiple times in the crushing chamber and undergoing multiple crushing and shaping under the action of the surrounding gas eddy, continuous crushing and shaping of the material is achieved, and the required finished sand is discharged from the lower part of the machine.
Screening equipment generally adopts linear vibrating screen or circular vibrating screen. . The circular vibrating screen is not too strict in screening accuracy, has a large amplitude and high screening efficiency, and is suitable for large-scale production use. Currently, it is the mainstream equipment for mining screening. And linear vibrating screen is suitable for screening with small processing capacity and small particle size, and can also be used for water content filtration.
When equipped with a pressure water spraying system on a circular vibrating screen, it can serve as stone washing equipment. With the help of water flushing, the stones roll and vibrate on the screen surface, making it easier to wash away the fine mud adhering to the surface.
For mud powder and stone powder in products with 0-4.75mm, it is generally adopt a spiral sand washing machine or a bucket wheel sand washing machine to obtain manufactured sand after washing.
After washing the sand and gravel aggregate, the mud containing wastewater after need to be treated to achieve discharge standard. After the investigation of the wastewater treatment equipment, we can adopt cyclone group, concentrator and filter press unit to treat the wastewater and mud, which can avoid the shortcomings of direct discharge of sludge waste into the sedimentation tank, such as large area and difficult to clean up the sedimentation tank.
The production investment of manufactured sand is inseparable from the support of various crushing and sand making equipment, the VSI5X and VSI6X series sand making machines developed by SBM, and the VU sand aggregate system are very common in the application of the industry, and the reputation is good. At present, thousands of manufactured sand production lines have been established in the world, you can make an appointment to the nearby production site.
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