River sand price skyrocketed, mechanism sand "popular", you do not understand can not
Recently, mechanism sand price rises all the way, in the past to gravel processing mainly manufacturers have also joined the ranks of mechanism sand, but before "into line" you still need to make clear these knowledge points!
1. What is mechanism sand?
According to the provisions of "construction sand" (GB/ t14684-2011) : rock, mine tailings or industrial waste slag particles with particle size less than 4.7mm made by mechanical crushing and screening after soil removal treatment, but excluding soft and weathered particles.
Extra-fine sand: natural river sand with fineness modulus of 0.7-1.5 obtained by testing according to the method specified in "construction sand" (GB/T14684).
Mixed sand: sand made by mixing mechanical sand with natural sand.
2. What is machine-made sand concrete?
Concrete prepared with mechanical sand as fine aggregate. At present, the annual production of mechanism sand in foreign countries is no less than 5 billion tons.
3. What kind of mechanical sand is qualified?
Mechanical sand that meets the national technical standards and has passed the factory inspection is qualified. Generally need to detect the items are: fineness modulus, particle size, stone powder content, apparent density, voidage, crushing value, methylene blue MB value.
4. Which rocks can be used for mechanical sand production?
Mechanism sand (gravel) sand-making raw materials are usually granite, basalt, river pebbles, pebbles, andesite, rhyolite, diabase, diorite, sandstone, limestone and so on. The machine-made sand also varies in strength and use by rock type.
5. Compared with natural river sand, what are the characteristics of mechanism sand?
1) compared with natural river sand, the mechanism sand has the characteristics of sharp edges and corners, more needle pieces and rough, which can be distinguished from the two in appearance;
2) the solidity of the mechanism sand is slightly worse than that of river sand;
3) high content of mechanical sand powder;
4) general natural sand, a fineness modulus, can have a variety of gradations, the fineness modulus of mechanical sand can be artificially controlled through the production process, according to user requirements to organize production, which is not natural sand can do;
5) mechanical sand has better adhesion, more compression resistance and longer service life;
6) the composition and chemical composition of placer minerals are consistent with the raw materials and are not as complex as natural sand.
6. Why is the quality of mountain sand and sea sand worse than that of river sand?
Generally, sand weathering is more serious, with more mud, more organic impurities and light substances; Sea sand often contains shell and other impurities, in addition to chlorine salt, sulfate, magnesium salt will cause the corrosion of steel reinforcement, these substances affect the performance of concrete, so the quality is worse than river sand.
7. What are the main sand standards in China?
GB/T14684 -- 2011 construction sand
Jgj52-2006 quality standards and inspection methods for sand and stone used for ordinary concrete
JGJ/ t241-2011 technical specification for application of artificial sand concrete
Db50/5030-2004 technical regulations for the application of machine-made sand mixed sand concrete (chongqing)
JT/ t819-2011 "mechanism sand for highway engineering cement concrete"
Dbj52-55-2008 technical specifications for highway mechanism sand high strength concrete in guizhou province
Jtge42-2005 "test code for highway engineering aggregate"
8. What are the technical quality indicators of mechanical sand?
The main technical indexes of the mechanism sand are: particle gradation, fineness modulus, stone powder content, voidage, apparent density, packing density, methylene blue (MB) value, crushing value index, mica content, light material content and other 16 technical indexes.
9. What are the gradation and fineness modulus of the mechanical sand particles?
Particle grading: refers to the proportion of particle size.
Fineness modulus: a technical index reflecting the fineness of mechanical sand particles. The larger the fineness modulus, the thicker the sand. The specifications of mechanical sand can be divided into four types according to the modulus of fineness (Mx) : coarse, medium, fine and extra-fine, among which:
1) the fineness modulus of coarse sand is 3.7-3.1, and the average particle size is over 0.5mm;
2) the fineness modulus of medium sand is 3.0-2.3, and the average particle size is 0.5mm -- 0.35mm;
3) the fineness modulus of fine sand is 2.2 -- 1.6, and the average particle size is 0.35mm -- 0.25mm;
4) the fineness modulus of extra-fine sand is 1.5-0.7, and the average particle size is less than 0.25mm.
10. The gradation index of mechanical sand particles is very critical. How can it be adjusted?
Mechanical sand particle gradation can be achieved by adjusting feed gradation, feed volume, crusher speed, screen size and other aspects.
11. What are needle and flake particles?
When the length of the sand particle is greater than 2.4 times the average particle size of the particle size, it is acicular. Those whose thickness is less than 0.4 times the average particle size are flake particles. The average particle size refers to the average of the upper and lower particle size of the particle size.
12, what is the mechanism of sand powder, stone powder content what requirements?
Stone powder refers to the particles with the particle size less than 75 m in the mechanism sand and the same as the processed parent rock. The content of stone powder is less than 10% for ordinary concrete and less than 5% for high-strength concrete.
13. What is sand aggregate?
Sand aggregate is a construction project in sand, egg (gravel) stone, gravel, stone, stone, stone and other materials collectively.
Aggregate with particle size greater than 4.75mm is called coarse aggregate, which is often referred to as gravel or gravel;
Aggregate with particle size less than 4.75mm is called fine aggregate, also known as sand or mechanism sand.
Sand aggregate is the main building material of concrete and piled stones in construction projects.
14. What are the mechanical sand production processes?
1) according to the separation method of stone powder, it can be divided into "wet sand", "dry sand" and "semi-dry sand";
2) according to the technological process, it can be divided into "separate sand making" and "combined sand making".
3) according to the structure form, it can be divided into "flat sand making" and "floor sand making".
15. What are the equipment for producing machine sand?
There are various crushing processes and equipment combinations for mechanical sand production, and the common ones are as follows:
A. Jaw crusher + impact crusher (common);
B. jaw crusher + cone crusher;
C. Jaw crusher + roller crusher;
D. Jaw crusher + impact crusher + impact sand shaping machine (common);
E. Jaw crusher + cone crusher + impact sand shaping machine or sand making system (common).
16. What is the basic technological process of machine-made sand production?
Mechanical sand production process is diverse, regardless of the size of equipment, but the basic production process can be generally divided into the following stages: mine stone → coarse crushing → medium crushing (part set screening) → fine crushing (shaping) → screening → dusting → mechanical sand.
17. There is a close relationship between mechanical sand particle shape and crushing equipment. What about the product particle shape of various crushing equipment?
In all kinds of crushing equipment, the vertical shaft impact crusher (barmack) is better in grain shape, the counter crusher second, cone crusher again, jaw crusher is worse.
18. Why particle shaping?
Common mechanism sand has many edges and corners, rough surface, irregular particles, and many needle pieces, which have adverse effects on concrete performance. The shaping of mechanism sand particles can effectively improve the above problems.
19. What are the common testing instruments in mechanical sand detection? 1
The basic instruments of mechanical sand test are standard square sifter, shaker, blast dryer, powder content tester, crushing index tester, electronic balance, saturated surface dry test mold, volumetric bottle, press, etc.
20. What are the main advantages of using and promoting mechanism sand?
1) quality advantages: fixed and stable material source, mechanized and industrialized production mode ensures stable, adjustable and controllable quality of mechanical sand products.
2) quality advantages: high surface energy and hydrophilicity; With complete gradation, mud content can be controlled; There are a variety of mineral components, physical properties to choose; The fineness modulus and particle gradation are relatively stable and adjustable. Grain shape can be improved.
3) management advantages: stable legal entity, mining license, fixed business site, factory and commercial operation.
4) resource advantages: various waste resources can be used to properly separate and process tailings, and many tailings can be made into artificial sand by mechanical sand equipment, which not only solves the problem of environmental pollution, but also improves the utilization rate of natural resources, fully meeting the requirements of circular economy and scientific development concept.
21. What are the problems facing the promotion and application of mechanical sand in terms of its quality and production?
At present, the main problems are:
1) poor grain shape and excessive needle flake, which are greatly restricted by rock material and equipment type;
2) poor particle gradation and large fineness modulus;
3) the content of stone powder is high, and the washing mud removal powder is faced with unreasonable gradation, coarse particles and other problems;
4) backward concept, some areas still use weathered sand and stone debris washed or simply processed as mechanism sand;
5) energy consumption and environmental protection pressure are still high in the production process.
22, the mechanism of sand shape is very important to the application of concrete, its impact mainly reflected in which aspects?
1) whether the grain shape is regular or not affects the packing density and voidage of the aggregate itself, thus affecting the volume of cement slurry filling the void of the aggregate;
2) the irregular granule has a larger specific surface area and requires more enveloping slurry;
3) affect the working performance of fresh concrete and its mechanical meshing force at the interface with cement slurry, etc.