The website of the Ministry of Commerce announced that it has decided to suspend the export of natural sand to Taiwan on August 3. The relevant measures will be implemented from August 3, 2022. Affected by this news, natural sand has gained widespread attention.
Many netizens are curious: We all know citrus fruits, what is this natural sand? Where is it important, is it irreplaceable?
What is natural sand?
Simply put, natural sand is formed due to natural action (mainly rock weathering), and rock particles with a particle size of less than 5 mm mainly include river sand, sea sand, quartz sand, etc.
Let's talk about the river sand first, it is produced by the repeated collision and friction of natural stone under the action of water for a long time in the natural state. The composition of river sand is relatively complex, the surface has a certain smoothness, and it is a non-metallic ore with a high content of impurities.
River sand is widely used in construction, concrete, cementitious materials, road construction materials, artificial marble, etc. It can also be used for sand cleaning, rust removal, strengthening in foundry, metallurgy, building, bridge and other fields, forming, stress relief and surface cleaning and coating of various profiles.
Taking the most familiar concrete as an example, the traditional concrete uses the most river sand, which accounts for about 20% to 40% of the concrete volume and is the main material of concrete.
Sea sand is similar to river sand. Sea sand is washed, rolled, collided, and polished by seawater. Its particle size is relatively large, generally in centimeters (smaller particle size is sand, usually in millimeters).
Generally speaking, river sand is often used in engineering, because most of the sea sand contains excessive chloride ions, which will corrode the steel bars in the reinforced concrete, and eventually lead to the destruction of the building structure, which will shorten the safe service life of the building to a certain extent. If the sea sand must be used, it can be inspected according to the technical requirements.
Finally, let's talk about quartz sand. Natural quartz sand mostly comes from quartz deposits, with high silica content (above 90%), low mud content, uniform and reasonable particle size composition, round particles, smooth surface and good fluidity.
Quartz sand can form a strong bonding force with cement slurry and enhance the flexural and compressive strength of slurry. In addition, glass, casting, ceramics and refractory materials, metallurgy and other industries, as well as artificial field covers such as modern track and field fields, football fields, golf courses, etc., are also indispensable for quartz sand.
More than 90% of Taiwan's natural sand imports come from the mainland, and Taiwan's sand and gravel also depend on imports: A report from the island's media China Times News in December 2017 revealed that at that time, imported sand and gravel accounted for about 40% of the construction market in northern Taiwan, almost 90% depend on the mainland.
Natural sand is a non-renewable resource, it will be gone when used up. Illegal sand mining and indiscriminate mining will affect the stability of rivers and rivers, and threaten the safety of water engineering and water ecology such as flood control, navigation, bridges and docks, because river sand and gravel are an important part of the riverbed and the basic element to maintain the stability of the river. Therefore, with the continuous development of the machinery technology industry, a substitute has now been developed: machine-made sand. The machine-made sand processing equipment refers to the equipment for the production of machine-made sand aggregates. Since the speed of natural sand mining has been unable to meet people's daily needs, the shortage of sand and gravel aggregates has made machine-made sand into people's attention. More and more people are starting to produce machine-made sand. The following are some commonly used sand making equipment and common process flow of machine-made sand:
1. Jaw crusher
2. Impact crusher
3. Cone Crusher
4. Sand making machine
5. Common process flow of sand making
Both machine-made sand and natural sand belong to construction sand. The difference is that machine-made sand is made by sand production line, which is a kind of artificial sand; Natural sand is naturally formed and can be directly mined and used.
Which is better, natural sand or machine-made sand?
The source of machine-made sand is mainly limestone, followed by granite, basalt, etc. These rock resources are widely distributed in most parts of my country. It can be said that the source of machine-made sand is not limited by regions and seasons, and can be obtained locally, thereby greatly reducing the mechanism the cost of sand.
Even better, machine-made sand can effectively utilize a large amount of waste rock resources (such as waste concrete and other renewable solid waste construction waste), which can reduce environmental pollution and protect natural resources.
Some scholars have conducted a comparative study on the properties of machine-made sand and natural sand, and the results have found that under the conditions of the same ratio of cement to sand and consistency of cement, the compressive strength of the cement block made of machine-made sand is higher than that of the natural sand test block. 86% and the flexural strength is 50% higher.
At present, the application of machine-made sand in my country has been relatively common. According to the news of China Sand and Stone Network, the amount of machine-made sand in the domestic sand and gravel market accounts for more than 90%. Needless to say, since 2011, the mining volume of machine-made sand in my country has exceeded that of natural sand and gravel.
It is understood that in addition to being used in the construction field, sand does have many uses. These all use sand, like smartphones, laptops, glass bottles used in new crown vaccines, and even chip manufacturing. It is understood that sand is an important source of silicon materials - the industrial field uses carbon and silicon dioxide to react at high temperature to produce silicon, which is then used to produce solar cells, integrated circuit chips, etc.
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