Sand is generally divided into natural sand and artificial sand. Rock particles with a particle size less than 5mm formed under natural conditions (mainly rock weathering) are called natural sand. Artificial sand is made by crushing rocks, but it is generally not used because of its high cost and many flakes and powders.
Natural sand can be divided into river sand, sea sand and mountain sand according to its source. Mountain sand has rough surface, angular particles, high sediment concentration, many organic impurities and poor quality. The surface of sea sand and river sand is smooth, but the salt content of sea sand is high, which has certain influence on concrete and mortar. River sand is clean and has a wide range of uses.
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As a very old building material, sand was used by ancient Egyptians to build pyramids, and Mesopotamia used it to make the first glass. In India, sand is called "red gold". Moderate compression resistance, an important part of various basic building materials, the speed of urban expansion and the acceleration of infrastructure construction have driven the demand of sand market to soar. In just 20 16 a year, India's construction industry consumed 500 million tons of sand.
However, the serious shortage of market supply has caused the price of sand in India to soar rapidly. Take Jalandar, Punjab as an example, the local sand price per 2.8 cubic meters has risen from 2 100 rupees (1 RMB is about 9.3 rupees) to 2,600 rupees.
High profits attract a large number of sand miners, and all kinds of illegal activities derived from it not only seriously damage the ecological environment of river banks, but also reduce the stability of water potential, laying hidden dangers for flood control and navigation safety. Indian geologists found that the lower reaches of Ganges near Bangladesh are all a mixture of clay and silt, and even stones are rare.
People's Daily-People's Daily listens to foreign winds: When sand becomes a scarce resource,
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