1, the surface of stone chips is rougher than sand, angular, and contains more stone powder with particle size less than 0. 16mm;
2. Stone chips contain both large particles and powder particles. This graded mixture has high strength and good adhesion with cement.
3. Gravel processed in the stone chip quarry.
Stone powder is made of alkaline stone such as limestone, and its particle size is less than 0.075 mm.
1, the particle size of stone powder is smaller than that of stone chips, therefore, when backfilling the trench, stone chips cannot be backfilled with stone powder;
2. Cement and stone chips are mixed into 5% cement stone chips. Because of its good gradation, the strength after molding is high. However, if cement stone powder is used, the adhesion between cement and stone will be reduced due to the simple gradation, thus reducing its overall strength.
In a broad sense, stones refer to white stones, colored stones, black stones, crushed stones, gravels and pebbles. You can choose according to your own needs. Generally, white stone, colored stone and black stone have smaller particle sizes and are used for decoration projects, while crushed stone, gravel and pebbles are suitable for structures, municipal administration, highways and railways.
Gravel that meets the engineering requirements is an angular granular material that is mined and processed according to a certain size. Gravel is a necessary material for concrete. Generally, the particle size of concrete is graded, 5-25mm.
Graded macadam is a mixture composed of fine aggregate, coarse aggregate and stone chips in a certain proportion. When its particle composition meets the requirements of dense gradation, it is called graded macadam. Graded macadam is a flexible material. As a base, it has the advantages of suppressing reflection cracks, improving the temperature and humidity of upper and lower materials, being easy to maintain and low in cost, but as a loose material, it has the disadvantages of low stiffness and poor integrity. Generally, it is only applicable to the road base with less traffic or the cushion of heavy traffic roads.
1, graded macadam is generally composed of several kinds (such as four kinds) of macadam with different particle sizes.
2. Graded macadam can also be made of unscreened macadam and stone chips. Unscreened crushed stone shall be crushed by a stone crusher after only controlling the maximum particle size (only passing through the sieve with the specified mesh number). Stone chips refer to the undersize residue with a pore size of 5mm in the gravel field, and its actual particle composition is often 0- 100mm, with good gradation. When the stone chips are insufficient, fine gravel or coarse sand can also be added, but its strength and stability are not as good as those of stone chips graded gravel.
3. The raw materials of graded macadam cushion are mainly composed of coarse aggregate and fine aggregate. The quality control index of coarse aggregate is mainly the crushing value and particle composition of crushed stone. Generally, the crushing value of coarse aggregate is not more than 30%, and the content of needle-like particles is not more than 20%. Fine aggregate mainly controls the particle composition, silt content and the dosage of stone chips to ensure continuous gradation.
Graded aggregate is a mixture of aggregates with different particle sizes and fractions. When its particle composition meets the requirements of dense gradation in technical specifications, it is called graded aggregate.
1. Graded aggregate, including graded crushed stone, graded crushed gravel (mixture of crushed stone and gravel, usually crushed to form crushed gravel with gravel) and graded gravel (or graded gravel), with a particle size composition of 0-100 mm.
2. The graded aggregate base structure is built according to the principle of dense mixture, and its strength is formed by the friction between aggregates and the cohesion of fine-grained soil, which is compacted and connected. In order to ensure that this structure has enough strength, it is necessary to make the aggregates that make up the mixture have the best gradation and good particle shape. After fully mixing, aggregates at all levels are evenly distributed and compacted, otherwise the strength of the structural layer will be affected.
3. Graded aggregate can be used as base and subbase of asphalt pavement and cement concrete pavement, and can also be used as subgrade improvement layer, especially in wet and rainy areas.
Sand and gravel are mixed in a certain proportion, which is also called graded sand. Generally used for ground cushion, foundation cushion and road cushion.
Stone slag is light gray fine-grained slag discharged during the reaction of calcium carbide with water to produce acetylene, that is, one or more residual stones with different specifications, which are mainly in powder form and mainly composed of calcium hydroxide.
1. Calcium carbide slag mainly comes from the production of PVC and vinyl acetate by calcium carbide method. Every production of 1 ton of PVC consumes about 1.45 tons of electricity, and every ton of calcium carbide hydrolyzes to produce 1 ton of calcium carbide slag, so every production of 1 ton of PVC needs to discharge more than 2 tons of calcium carbide slag. Calcium carbide slag has a large amount, high alkali content and harmful substances such as sulfur and arsenic. If discharged without treatment, it will block sewers, deposit riverbeds and endanger fishery production. Stacking on land will occupy land and pollute the environment.
2. Mortar production: The chemical composition of carbide slag meets the second-class low-magnesium lime standard, and can be mixed with cement and sand to form masonry mortar, which is called carbide slag cement mortar. Its compressive strength, frost resistance, cohesive force and softening coefficient all meet the specified requirements.
3. Cement production: firstly, the ferrosilicon blocks in the carbide slag are removed by water washing, and then the clear water in the upper layer is removed by sedimentation, and the water content of the thick slurry in the lower layer is about 66-70%. Coal, loess and iron slag are sent to a refiner according to the weight ratio of 16: 16:5, and water is continuously added during grinding to prepare slurry with water content of 54-98%. Then, calcium carbide slag and mud are evenly mixed into slurry containing 48 1% calcium oxide, which is dehydrated, dried and crushed, then shaped into balls with a certain size, sent to a vertical kiln for calcination and crushing, and then ground into cement.
Ballast, that is, the size and specification of the same material are within the specified range. It is often used as backfill in engineering construction.
Gravel: Fragments of rock, coal, etc.
Small stones used as subgrade on the railway. The traditional railway track usually consists of two parallel rails fixed on sleepers, and the bottom is ballast paved with small gravel. Ballast and sleeper can increase the stress surface, disperse the train pressure, help the rail bear the load, and prevent the rail from falling into the soil due to excessive pressure.
Gravel, a shapeless stone, is in a natural state after mining.
1. Gravel is a rock with irregular shape after blasting. The irregular shape is called random rubble, and the two sides are roughly parallel to each other. The gravel is irregular in shape. Generally, it is required that the thickness of the middle part of the stone is not less than 150mm, the length is 300 ~ 400 mm, and the mass is about 20 ~ 30 kg. Its strength should not be less than 10MPa and its softening coefficient should not be less than 0.75.
2. The main difference between crushed stone and slag is that the former is big and the latter is small.
Sweet potato stone is rectangular or irregular limestone, granite and other rocks commonly used as cushion, with specifications ranging from 100 mm to 200 mm. It is rectangular or irregular stone, such as limestone, which is used for cushion and paving subgrade. When laying, insert them vertically into the ground and lay them, pour concrete on them, vibrate and compact them, and the cracks in the sweet potato stones will be laid.
Decorative stone (also called lath stone) is a regular hexahedral stone made of dense sandstone, limestone and granite, which is used in architecture.
1. According to the regularity of processing shape, it can be divided into four types: original stone, coarse stone, semi-fine stone and fine stone.
2. According to the shape, it can be divided into strip stone, square stone and arch stone.
3. Original stone: The appearance is roughly square, and it is generally not processed or slightly adjusted. The width and thickness of stone should not be less than 200mm, and the length should not exceed 4 times the thickness. The depression depth of lap joint and joint surface is not more than 25mm, and the compressive strength is not less than 30mpa.
4. Coarse aggregate stone: the specifications and dimensions are the same as above, and the depression depth of lap joint and joint surface is not more than 20mm；; The depth of the depression on the exposed surface and the surrounding surface shall not exceed 20mm.
5. Fine aggregate stone: after finishing, the specifications and dimensions are the same as above, the depression depth of lap joint and joint surface is not more than 10mm, and the depression depth of exposed surface and surrounding area is not more than 2 mm. ..
Note: the surface around the joint refers to the part within the range of 20~30mm where the overlapping surface, joint surface and exposed surface intersect.
Gravel, a mixture of sand and gravel, pebbles and boulders (a kind of rock eroded by water or weather), is also called gravel, which has high density and good stability and is often used for paving road bases.
Sand refers to a loose mixture of sand. Geologically, minerals or rock particles with a particle size of 0.074~2mm are called sand, and those with a particle size larger than 2mm are called gravel or breccia (the difference between them lies in their smoothness). If the gravel in the gravel is mostly gravel, it is called gravel. In daily life, some people call sandstone sandstone.
1, sand: a general term, tiny sand, the main component of which is silica.
2. Sand: soil term, mainly composed of seasonal or mineral particles. Good permeability, poor water and fertilizer retention capacity and low mineral nutrient content.
3. Gravel: A geographical term referring to a mixture of sand and gravel. Smaller than rock particles and coarser than silt. The diameter of powder particles is between 0.06 and 2.0 mm, which is formed by weathering and erosion of rocks, and the main component is silicon dioxide.
4. Gravel: engineering term, referring to the mixture of sand and gravel or pebbles and boulders (a kind of rock eroded by water or weather). The diameter is more than 2 mm, which is larger than the diameter of gravel. Can be used for paving road base.
5. Sand (mainly silica) is mostly artificial or polished stones. The particles are relatively larger and have a stronger sense of fullness. You can clearly feel the existence of particles when you hold them in your hand.
1, gravel, gravel, the largest, with a diameter greater than 2mm；;
2, sand, secondly, the diameter is less than 2 mm;
3, silt, silt, third, the diameter is less than one sixteenth of a millimeter;
4. clay, the smallest, with a diameter less than 256th of a millimeter.
The difference between stone powder and river sand is that stone powder is made of stone, while river sand is natural. Grab a handful of river sand. If there is white limestone powder on your hand, you can judge that the river sand contains stone powder.
Sand with a particle size of 0.25-0.35 mm is fine sand, medium sand with a particle size of 0.35-0.5 mm and coarse sand with a particle size greater than 0.5 mm; The fineness of stone powder can be changed at will, depending on the grinding fineness of ball mill. (Commonly, bicarbonate of soda) becomes CaCO3, and when hydrochloric acid is added dropwise, carbon dioxide will be generated, and carbon dioxide will react violently to generate bubbles. Stone powder is opaque, white to blue-gray, and cubic. River sand is translucent and irregular (it needs to be observed with a magnifying glass or microscope). It is the most scientific to detect calcium content if conditions permit. The calcium content of pure stone powder is 35-38%, and river sand is almost 0%.
Due to the differences in physical properties such as gradation and fineness modulus between stone powder sand and natural river sand, the following points should be paid attention to during construction:
1. The mixing, transportation and pouring requirements of stone powder sand concrete are the same as those of natural sand concrete construction.
2. Take measures to ensure the stability of the quality of stone powder sand, and strengthen the regular detection of the gradation, fineness modulus, stone powder content and MB value of stone powder sand.
3, stone powder sand stacking, transshipment should pay attention to prevent mixing soil.
4. Set up the warehouse to be inspected and adjust the proportion appropriately according to the quality situation.
5. Strengthen the mixing of stone powder sand concrete mixture. Compared with river sand concrete, the mixing time should be appropriately extended for 30s~60s.
6. Regularly calibrate the measuring equipment and strictly control the dose accuracy.
7. Prevent vibration leakage, under vibration and over vibration.
8. Strengthen early health care and extend the health care time appropriately.
In the production of ready-mixed concrete, it is generally not appropriate to simply use stone chips (except artificial sand produced by sand making machine) instead of fine aggregate to prepare concrete.
Through the comparative analysis of experiments, the optimum mixing range of stone chips in mixed sand is 30-40%, and it should not exceed 40% for medium sand. For fine sand, it is 30-50%. It can be seen that the ratio of stone chips to sand of 30:70 is more suitable for medium sand; For fine sand, it is best to use the ratio of stone chips to sand of (30-35): (70-65).
Stone chip concrete uses stone chips and sand to mix concrete. On the one hand, the advantages of good adhesion and high strength between stone chips and cement slurry are fully utilized; On the other hand, the water retention and good smoothness of sand are utilized, and the two materials complement each other.
The simplest method is to put the stone chips containing stone powder and mud powder into a transparent container, add water to stir, and add water to ensure that the stone chips can settle freely in the water. After settling for 30 minutes, the bottom is stone chips, the top is stone powder, and the mud powder floats in the water.
Stone chips are by-products of adding gravel. Due to the external force, its strength will be lower than that of gravel, its flaky content and impurities (such as stone powder, soil, etc.). ) it will be high. Irregular particle shape and obvious edges and corners reduce the workability of concrete.
Natural sand generally refers to river sand, its cleanliness is generally higher than stone chips, its strength is also higher, and its particle shape is round, which is conducive to increasing the workability of concrete.
Sandstone weathered to form primitive mountain sand, washed, transported and collided by rain to form river sand, which is natural sand. As a result of natural selection, the composition of natural sand is relatively simple, with less individual structure and less impurities. Therefore, it has large porosity and high strength, which is more than cement. Under the same conditions, the strength of concrete is higher. Stone chips are the smallest part under the sieve when crushing stones, with diverse components, soil and other impurities, as well as many individual structures. Their porosity and strength are small, and their ratio is smaller than that of cement. Under the same conditions, the strength of concrete is low.
In C30 concrete production, it is necessary to determine the proportion of stone chips instead of natural sand through experiments. There are shortcomings in making concrete with stone chips, but the shortcomings of stone chips can be reduced by increasing the proportion of cement, and the strength of concrete can be increased, thus reaching the standard of C30 concrete.
Cement stabilized macadam takes graded macadam as aggregate, fills the gaps of aggregate with a certain amount of cementing material and sufficient mortar volume, and spreads and compacts according to the principle of embedding and squeezing.
Cement stabilized macadam material is mainly composed of granular materials and mortar volume. The granular material is graded macadam, and the mortar volume includes water and cementitious materials, and consists of cement and mixed materials.
Mixed materials can be divided into two categories: active and inactive. Active substances refer to substances such as fly ash that can react with calcium oxide precipitated in cement. Inactive materials refer to artificial or natural mineral materials with no activity or low activity. The quality requirements for this kind of materials are fine and free from harmful components.
Therefore, stone powder should be used as a mixture to fill it, and some stone chips can also be added appropriately.