sand

sand

Sand refers to small stone particles or things shaped like sand. It also refers to imperfect defects.

On August 19, 2019, according to a recent review published by Nature magazine, the speed of sand and gravel excavation has exceeded the speed of natural recovery.

Word concept

essential information

Sand refers to 0.074-2mm particle size material which is washed by rain or rolled by rock after weathering.

There are many kinds of sand, such as river sand, sea sand, metal sand, natural sandstone, and so on. Say deviate a bit, still have emery cloth. The main component of ordinary river sand is silica (SiO 2).

Sand generally contains a small amount of soil, which is limited by the level of buildings.

The apparent density of construction sand is more than 2500kg / M & sup3;, and the loose bulk density is more than 1350kg / M & sup3;.

Sand is one of the main components of concrete and mortar, and is the bulk material of civil engineering.

Sand is generally divided into natural sand and artificial sand. Natural sand is formed by the action of natural conditions (mainly rock weathering) and its particle size is less than 5mm. Artificial sand is made of crushed rock. It is usually not used because of its high cost and many flakes and powders.

According to its source, natural sand can be divided into river sand, sea sand and mountain sand. The surface of mountain sand is rough, the grain is angular, the sand content is high, the content of organic impurities is also high, and the quality is poor. The surface of sea sand and river sand is smooth, but the salt content of sea sand is high, which has a certain impact on concrete and mortar. River sand is clean and widely used.

The fineness of sand refers to the average fineness of sand particles with different sizes mixed together. Generally, there are coarse sand, medium sand and fine sand. The grain gradation of sand refers to the proportion of sand size particles. As can be seen from the figure, if the sand is of the same thickness, the void is the largest. When two kinds of sand are combined, the void is reduced, and when three kinds of sand are combined, the void is smaller. It can be seen that the porosity of sand depends on the matching degree of different particle sizes. Graded sand can not only save cement, but also improve the compactness and strength of concrete and mortar. The thickness of sand is expressed by fineness modulus MX. The larger the fineness modulus is, the coarser the sand is. According to the range of fineness modulus, sand is divided into coarse sand, medium sand, fine sand and extra fine sand.

Medium sand should be preferred in concrete preparation. When coarse sand is used, the sand ratio should be increased and enough cement consumption should be kept; when fine sand is used, the sand ratio should be reduced appropriately. The sand used for masonry mortar shall meet the technical property requirements of concrete sand. Due to the thin mortar layer, the maximum particle size of sand should be limited. For sand used in rubble masonry, the maximum particle size shall be less than one fourth to one fifth of the thickness of the mortar layer. For brick masonry, medium sand should be used, and the particle size should not be greater than 2.5mm. For smooth plastering and pointing mortar, fine sand shall be used.

Citation explanation

1. The sixth chapter of the story of heroes and Heroines: "although the ferocious monk is fierce, he is also a flesh man. The meat man's eyes need to wear this kind of clothes

It's probably better than kneading a piece of sand into it. It only hurts him so much that he says "ouch" and pours back. " Yang Mo's song of youth Part 1 Chapter 3: "her hair is stained with a lot of fine sand, but she doesn't feel it at all."

2. Refers to something shaped like sand. Such as: iron sand.

3. Metaphor refers to imperfect defects. There is no room for sand in my eyes.

Basic meaning

After weathering, the rocks are transported by wind or current. The small ones are carried away and deposited to form soil plain, while the medium ones are carried away. When the wind speed or velocity decreases, the rocks are deposited to form sand beach (the soil is carried to a farther place when the carrier speed drops lower, and the gravel is deposited in advance), and the large ones are left in situ to continue weathering. The end result is to become soil, which is how the earth is formed. Of course, there is also the phenomenon of magma erupting to form rocks, although the volcanoes in the 21st century are far less than those in ancient times. The sand used in the 21st century is transported from the sand field, the gathering place of sand.

The most common component of sand is silica, usually in the form of quartz, which is resistant to weathering due to its stable chemical properties and hard texture.

The main component of sand is silica (SiO2), and the density of silica is 2.65g/cm ^ 3, that is 2.65t/m ^ 3.

Sand is made up of minerals and tiny pieces of rock. Rock fragments are formed by erosion and weathering of rock. The composition of the sand varies from place to place, depending on the source and condition of the local rocks.

In inland (such as desert) and non tropical coastal (such as beach) environments, the most common component of sand is silicon dioxide (SiO2). Usually, silicon exists in the form of quartz.

Arkose is a kind of sand or sandstone with high content of feldspar (aluminum silicate), which is usually formed by weathering and erosion of nearby granite.

The fine white sand found in coral reefs is aboveground coral (limestone), which can pass through parrot fish's digestive system.

In some places, the sand contains magnetite, clay, chlorite, glauconite or gypsum. Magnetite rich sand is dark black. Sand containing chlorite and glauconite is generally green. Gypsum dunes at the White Sands National Museum in New Mexico are famous for their white color.

In some areas, the sand contains garnet and other corrosion-resistant minerals, such as some gem ores.

Discrimination method

In order to judge the grading of sand, screening test must be done.

Screening tests will show two different types of results.

1、 Know the cumulative residue percentage of each sieve.

2、 Fineness modulus.

These two results are obtained by comparing or calculating the cumulative sieve residue percentage.

Screening test, first to pass the 9.5mm sieve, take about 500g to do the test.

Set screen 4.752.361.180.60.30.150.075 and screen bottom.

Algorithm of fineness modulus fineness modulus: M = (a2.36 + a1.18 + a0.6 + a0.3 + a0.15-5a4.75) / (100-a4.75)

Among them, a0.15, a0.3 ~ ~ ~ a4.75 are the cumulative percentage of residue on the corresponding screen respectively.

Thus, the fineness modulus can be obtained, which can determine whether it is primary sand, medium sand or fine sand. Medium sand is used on the construction site.

Coarse sand 3.7-3.1, medium sand 3.0-2.3, fine sand 2.2-1.7, from which we can judge the sand, and then we can see the grading range.

It is also based on the requirements of the sieve percentage is not within the scope.

Sand is mostly made by hand or polished from some stones. The particles are larger and fuller. You can clearly feel the presence of particles in your hands.

The main purpose of making sand is to grind tools, make noises, or use it as a timer.

Sand is also ground by stone, but it is made by the power of nature after thousands of years of grinding. It is very small and soft, suitable for loading into some soft articles.

The biggest difference is that the sand is divided into different colors and different types are produced in different places. Take a handful of sand in your hand, you can't feel the existence of particles, but if you take a bath with sand, you can remove the dead skin on the skin surface and smooth the skin.

So, sand has many uses. However, the sand is single in variety and rough in appearance, and no more useful advantages have been found except for grinding.

purpose

Sand (sand) has a wide range of uses: it is not only used in construction, road construction, filtration, breeding and beautification, but also the main material for making glass. It contains silicon. In sports, it can also be used as sandbags for boxing and flood control! In daily life, it plays the charm of cleaning: factory workers wash hands and feet of sand, wash wine bottles, porcelain, metal tableware, jade, silver, etc. can use the master of young sand! Sandpaper of bright and smooth metal and wood! With volcanic ash or hot spring mud, it's a beauty pet! If there is oil on the ground, use sand to spread the machine oil, clean up the sand as soon as it is sprinkled, use it more to clean up traffic accidents, sand bombs for hunting, sand used to be grenades in the past, sandbags used in battlefield and rake yard, sandbags have many uses. The last funeral of the dead: Sasha is also it.

reduce

On August 19, 2019, according to a recent review published by Nature magazine, the speed of sand and gravel excavation has exceeded the speed of natural recovery.

It is reported that sand and gravel are the first class of raw materials with the largest amount of excavation. About 32 billion to 50 billion tons of sand are used every year in the world, mainly for manufacturing cement, glass and electronic products. Although deserts account for 20% of the earth's land surface, the sand in deserts is too smooth to use. Most of the angular sand suitable for industrial use comes from rivers - less than 1% of the earth's surface area.

Chinese PinYin : Sha Zi