Introduction to raw materials for small concrete blocks

Wenzhou Exmork Machinery Co.,Ltd.

At present, the small concrete blocks produced in my country are mainly hollow blocks, and the raw materials used are cement, ordinary sand and gravel, artificial light aggregates (such as expanded perlite ceramics, clay ceramics and fly ash ceramics), Natural aggregates (such as pumice, volcanic scoria and zeolite), industrial waste light aggregates (such as fly ash, coal slag, spontaneous combustion gangue, coke slag, calcium slag and expanded slag beads) and other light coarse aggregates.

 1. Cement: Use ordinary Portland cement with 32.5 or above, Portland cement (GB175-1999) and slag Portland cement (GB1596-91). Generally, slag Portland cement is used in summer production. It is not suitable to use pozzolanic Portland cement and fly ash Portland cement.

 2. Coal ash: Technical requirements are shown in the table below.

 It is required that the SiO2 content of all levels of ash is greater than 40%, the Al2O3 content is greater than 15%, the bulk density is 516~107kg/m3, and the particle density is 1800~2400kg/m3. Generally, low-calcium, dry-discharged fly ash should be used. Level I and II ash can be used for blocks with a strength level above 13MPa, while level III fly ash can only be used for blocks with a strength level no greater than 10MPa.

 3. Carbide slag: Carbide slag is the waste residue produced when producing acetylene from calcium carbide (CaC2). The composition and properties of carbide slag are similar to slaked lime, and the Ca(OH)2 content usually reaches 60%-80% (dry basis). In my country, wet processes are mostly used to produce acetylene. The moisture content of carbide slag is very high, and it can be used only after precipitation and concentration. Carbide slag is blue in color and has a slight odor but is harmless. If electroless stone slag can be replaced by fresh lime, slaked lime is generally not used. If it is quick lime block, it must be ground in advance, and the fineness should be 0.080mm, and the sieve residue should not be more than 25%. The effective calcium oxide content of quicklime is required to be no less than 70%, and the higher the better. If the CaO content is insufficient, the amount of quicklime can be increased. The MgO content in quicklime is less than 4%, otherwise the product will easily explode. Quicklime scraps or shell powder discharged from power plants and chemical plants can also be used to replace calcium carbide slag.

 4. Gypsum: dihydrate gypsum can be used, requiring the calcium sulfate content to be greater than 65%, or phosphogypsum (solid waste from the phosphate fertilizer industry, in which the P205 content is less than 3%) can be used instead.

 5. Slag: its main components are the same as fly ash, apparent density 600-900kg/m3, particle density 1100-1800kg/m3; loss on ignition ≤ 20%, MgO content less than 4%, CaO content less than 5%, SO3 The content is less than 4%, the volume stability test is qualified, the particle size is 0.16-10mm, and the fineness modulus should be between 2.4-4.2.

 6. Sand: According to the fineness modulus (Mx), it can be divided into coarse sand (Mx is 3.7-3.1), medium sand (Mx is 3.0-2.3), fine sand (Mx is 2.0-1.6) and extra-fine sand (Mx is 1.5-0.7). This product uses sand with a fineness modulus Mx between 3.7 and 1.6, and its mud content should be less than 3%. River sand should be used.

 7. Stone: gravel or pebbles, the particle size is greater than 5mm and less than 8mm.

 8. Industrial waste: including fly ash, steel slag, waste rock slag, tailings sand, slag, construction waste (red brick slag, concrete slag), coal gangue, etc. Various industrial waste residues can be used together, and the technical requirements are as follows: the loss on ignition of each waste residue is not more than 20%, SO3 ≤ 2%, the sanding particle size of each waste residue is 0.3-1.3mm, and the content of fine powder below 0.1mm is ≤20%. It can be used instead of sand; the gravel particle size of each waste residue is 3-15mm, and it can be used instead of gravel when the mud content is ≤3%. The weight loss of each waste residue after recycling is 13%.

 Coal gangue is the roof, floor and rock in the coal seam. Coal gangue is not a single rock, but a mixture of carbonaceous materials and rocks. It has unstable factors. Coal gangue must be used after spontaneous combustion or artificial calcination. The softening coefficient of spontaneous combustion gangue is not less than 0.8, and the boiling loss rate is not greater than 5. %, the loss on ignition is not more than 5%. The slag should be left for more than 6 months, the SO3 content should not exceed 1%, and there should be no garbage, weeds, etc.

 Calcified slag is a high-temperature liquid slag in the cyclone furnace. Its temperature is generally 1200-1400°C. When it overflows from the slag discharge port at the bottom of the furnace, it is quenched by water and bursts into a solid glass body of 2-10mm. It is then quenched and granulated. The slag is called calcium-enhanced slag or liquid slag, also called water quenching slag. The calcium-enhanced slag contains active ingredients such as CaO and has a high SiO2 content. After testing, it is determined that it is still an inactive material. After the calcium-increasing slag is quenched and rapidly cooled by water, there will be cracks and internal stress inside the particles. Large particles are fragile, but small particles are very strong, so the calcium-increasing slag must be broken when using it.

 9. Volcanic scoria: It is a material from volcanic eruptions. It has the characteristics of porous, light body and strong toughness. It has good thermal insulation, heat insulation and sound insulation effects. Natural bulk density 580-800kg/m3. The cylinder pressure strength is about 3Mpa.

 10. Pumice: It is a kind of natural light aggregate. The bulk density is 350-800kg/m3, and the cylinder compressive strength is 1.6Mpa. Since pumice itself has low cylinder compressive strength, pumice concrete has low strength, but its thermal insulation is good.

 11. Light aggregate: including clay ceramsite, fly ash ceramsite, perlite, floating beads, shale ceramsite, pumice, volcanic scoria, etc., complying with the regulations of (GB/T17431.1-1998), the largest particle size Diameter 10mm (fineness modulus 2.3-4.0 is appropriate) mud content <3%.