Cement grinding aid is a chemical additive. Adding a small amount in the cement grinding process can improve the grinding process. In order to improve grinding efficiency, reduce power consumption, improve the fineness of cement powder and cement strength, a small amount or a small amount of grinding AIDS are added in the grinding process without changing the existing process and equipment conditions of the factory, which affects the mechanical force of grinding operation.
Cement grinding aid is a small product in the cement industry chain, but it plays a very important role in increasing production and reducing consumption in the cement industry, which can bring tangible benefits to cement enterprises.
In the mid-1980s, China successfully developed three series of more than ten kinds of grinding AIDS, which are suitable for different kinds of cement grinding. Under the condition of constant specific surface area, the output of grinding machine increases10% ~ 20%; Mineralizer improves the yield and quality of clinker calcination; Retarder improves the quality and performance of cement and becomes an indispensable additive in cement production. With the improvement of construction engineering technology, ordinary concrete can no longer meet the needs of different construction technical conditions, and people have developed additives that can change various properties of concrete. Such as: preparing high-quality high-strength concrete, shortening the construction period, speeding up the construction, meeting the construction requirements under special conditions, realizing the horizontal and vertical pumping of concrete, and developing commercial concrete produced on a large scale by centralized industrialization, and so on; Admixtures make the workability of concrete arbitrary. Admixtures have become the fifth basic component after cement, sand, stone and water. The special research results of cement and concrete additives and their technical and economic significance, the implementation experience of factories and sites, the production process practice of cement enterprises after the implementation of new cement standards, the selection of some national standards and industry standards, etc. It will certainly play a positive role in promoting the correct and standardized understanding and use of additives for cement enterprises, cement products and construction departments in China.
function
1. Without changing the conditions of the cement mill, change the dispersity of materials in the mill, effectively eliminate the electrostatic adsorption and ball paste grinding of cement fine particles, and optimize the gradation of cement particles.
2. Under the condition of keeping the same cement strength grade, using the same cement clinker and admixture and adjusting their proportions appropriately, the cement clinker can generally be reduced by 6- 10% after adding cement grinding AIDS, and the total amount of admixture can be increased by 6- 10%.
3. Keeping the original mill output unchanged and improving the fineness and specific surface area of cement powder can increase the cement strength by 20% in 3 days and 10% in 28 days; Or keep the existing fineness and specific surface area of cement powder, which can improve the output of cement mill by more than 10%.
Cement grinding AIDS can also bring direct economic benefits to cement enterprises: electricity consumption per unit area of cement, grinding body consumption, mill liner consumption and maintenance costs are correspondingly reduced, productivity is improved, production scale of enterprises is expanded, and costs are reduced. At the same time, the use of cement grinding AIDS can improve the fluidity of cement, improve the efficiency of classifier, reduce the caking phenomenon of cement, and correspondingly reduce the time and cost of cement loading and unloading.
dosage
(1) All enterprises that use cement grinding AIDS know that each variety of cement grinding AIDS has its optimal dosage, and the dosage of liquid products is generally 0.03%-0. 15%, with a wide range of dosage and great price disparity; The dosage of powdered products is generally 0.5%- 1%, which is large in quantity and low in price. In fact, adding less grinding AIDS can't achieve good results, and adding more grinding AIDS can't increase much effect. Cement enterprises should pursue products with high cost performance. China's national standard "General Portland Cement" (GB 175-2007) was officially implemented on June 1 2007. The requirement that "grinding AIDS ≤0.5% are allowed to be used in cement production, and the chloride ion content in cement must be ≤0.06%" has been added to the new cement standard. The original dosage of grinding AIDS is about 0.8- 1.0%. If the content of NaCl is 30%, the addition of chloride ion in the grinding aid is 0. 15-0. 18%. Even if the dosage can be reduced to 0.5%, the dosage of chloride ion or sulfate ion in cement remains unchanged. Coupled with the chloride ion content in cement clinker and admixture, the chloride ion content in cement will far exceed the specified amount in the new cement standard.
(2) Alkali-aggregate reaction and alkali content limitation of cement. As we all know, alkali in cement can react with active aggregate to expand, and even lead to concrete cracking and damage. Therefore, in many major projects, the alkali content of cement used is limited to below 0.6%. The dosage of powdered grinding AIDS is about 0.8- 1.0%. When the content of NaCl is 30%, the addition of Na2O in the grinding aid is 0. 16-0.20%. If it still contains 30% Na2SO4, it will be further increased by 0. 10-0. 13. The United States paid little attention to alkali aggregate at the peak of construction. As a result, in the 1980s and 1990s, a large number of cases of concrete structure damage caused by alkali-aggregate reaction were found all over the country, and now everyone is "discoloring at the sight of alkali". Many investigation results show that aggregates in many areas of China have alkali activity, and cases of concrete structure damage caused by alkali-aggregate reaction are common. Therefore, when adding Na2SO4 to cement, the potential consequences should be considered.
(3) The phenomenon of pan-alkali is contrary to the strength of concrete.
Adding sodium sulfate to cement sometimes leads to alkali flooding, and when the dosage is high, it will also lead to strength for 28 days and beyond. Although there is no direct regulation on sodium sulfate in cement concrete, many countries, regions or engineering projects have strict regulations on alkali. The influence of sodium sulfate on the performance of concrete is various.
Type and model
Types of cement grinding AIDS
(1)ZM series grinding AIDS (Yiwu Anbao Company) use polymeric polyols instead of 50% triethanolamine. After compounding, the grinding aid has good strengthening effect and the cost is greatly reduced.
(2)XK series polymer polyol, mother liquor of grinding aids, grinding aids containing a large amount of limestone, grinding aids containing mineral powder, etc. (Shandong Linyi Shuangkai Grinding Aids R&D Co., Ltd.)
(3) CBA110 cement additive (Grace Company): CBA110 cement additive contains a very trace component CB 1 10. Soluble compounds composed of CB 1 10 and iron leave the surface of cement particles in aqueous solution and then are separated from B 1 10. Free CB 1 10 molecules return to the surface of cement particles and further combine with iron in C4AF hydrate. Therefore, as long as there is unhydrated C4AF phase and water, CB 1 10 will always promote the hydration reaction of cement, make the hydration of cement particles more complete and give full play to the strength of cement.
(4)TM grinding aid (South China University of Technology): It is mainly composed of three substances: A is a sodium salt with good grinding aid effect, B is a nonionic surfactant, and C is a salt with grinding aid enhancement effect. They are compounded according to a certain proportion, the concentration is 40%, the pH is 8 ~ 9, and the density is 1. 14g/cm3.
(5)CSA high-content limestone composite cement grinding aid (Beijing Zhongbo Juhe Technology Co., Ltd.): The introduction of special organic substances that greatly improve the later strength improves the comprehensive performance of composite cement after adding a large amount of limestone, and greatly reduces the cement production cost. At present, the maximum limestone content can reach 35%.
(6) Xinjiang Tianshan Cement Co., Ltd. uses CGA grinding AIDS.
(7) As a cement grinding aid (School of Chemistry and Chemical Engineering, Central South University): A new compound grinding aid with inorganic minerals as the carrier, consisting of triethanolamine and water reducer (modified lignin derivative).
(8)TM cement grinding aid (South China University of Technology): It is mainly composed of three substances: A- sodium salt, which has better grinding effect; B- nonionic surfactant; C salt, with grinding aid and strengthening effect. TM is composed of A, B and C in a certain proportion, with a concentration of 40% and a density of 1. 14g/cm3.
(9)LT2003 grinding aid (South China University of Technology): Surfactants A and B, industrial waste liquid C, acid and alkali are prepared according to a certain proportion and procedure, with a concentration of 40%, PH=8 and a density of 1. 12g/cm3.
(10)Mighty LF series grinding aids This product is derived from coconut oil and palm oil, and is a derivative of natural fatty alcohol. It does not contain chlorine salts that damage the durability of cement, and does not contain amines and aldehydes that are harmful to human body and environment. Effectively improve the specific surface area, fineness and particle distribution of cement, promote the hydration of iron salts in cement and improve the strength of cement at all ages.
(1 1)DF grinding aid (China Institute of Building Materials, Heep Company, USA)
(12)BD99 1 1 Series High Efficiency Cement Grinding Aids (Feili Company of Tianjin Cement Design and Research Institute)
(13)CD88 series grinding AIDS (Luoyang wanshun building materials co., ltd): mainly made of more than ten kinds of raw materials such as coal extract, vegetable oil and ethanolamine through emulsification and compounding. Raw materials of liquid cement grinding AIDS: triethanolamine, mother liquor of liquid grinding AIDS, polyalcohol amine, polymeric polyol, triisopropanolamine, ethylene glycol, propylene glycol, diethylene glycol, sugar ether (also known as molasses and orange water, which can be used to color or improve cement workability/adjust setting time and enhance it), sodium acetate (also known as sodium acetate), dodecyl benzene (increasing flow rate), aluminum sulfate, calcium chloride and sodium sulfate.
In recent years, polymer synthetic grinding AIDS, mainly polycarboxylic acids, have appeared, but the incompatibility between polycarboxylic acid grinding AIDS and naphthalene concrete additives has restricted its development. There is also a polymer synthetic cement grinding aid modified by triethanolamine, and the final step of the grinding aid product needs to be completed by compounding process.