Water-reducing admixtures are widely accepted in the concrete industry and have received increasing attention from researchers and users of concrete admixtures at home and abroad. The reason is that compared with traditional water-reducing agents naphthalene sulfonic acid and sulfonated melamine condensate, they can give concrete high dispersion, fluidity and high dispersion system stability to prevent slump loss at low dosages. At present, the main components of high-efficiency air-entraining water-reducing agents commonly used in Japan are transitioning from naphthalene sulfonates plus reactive polymers to systems. European and American countries are also following suit. The editor will take you to understand the application of system water-reducing agents in various industries. Industry application.
In order to further improve the performance of the water-reducing agent and reduce the cost of use, it is best to combine the high-performance water-reducing agent with other admixtures. The current problem is that most admixtures are not compatible with the water-reducing agent. , manifested in the fact that the products are insoluble in each other or have no superposition effect after mutual dissolution, which sometimes reduces the fluidity or slump retention of high-performance water-reducing agents, and sometimes increases the bleeding and segregation of concrete.
1. Used as cement grinding aid
In the cement production process, grinding aids are commonly used when grinding clinker to reduce the grinding time required to obtain particles of a certain fineness. energy consumption. Commonly used grinding aids include alkanolamines (ie triethanolamine, or triisopropanolamine) and polyethylene glycols (PEGs), because the latter is the side chain of the water reducing agent. Adding liquid water-reducing agent during the grinding process can not only increase the production capacity of the mill, but also reduce the water demand for cement production using this method. Some cement manufacturers have already conducted trials using this process. After three years of testing, different test results have been obtained. In some cases, the use of water-reducing admixtures can achieve very high production, while in some factories the production increase effect is not obvious or has no effect at all. The reasons for these differences remain unclear and require research. The information currently disclosed is that laboratories and cement plants use liquid admixtures with a concentration of 40%. When PCE is mixed with commonly used alcoholamine grinding aids, the best PCE effects can be obtained. Generally, 250 to 500 grams of water-reducing agent/ton of clinker can be added as a grinding aid. The plasticizing effect of the water-reducing agent is not observed; when the dosage is quite high (≥1 kg/ton of clinker) When used, it will be found that the water consumption of cement can be significantly reduced, thus obtaining higher strength. This method is particularly beneficial for mixing cement.
If the use of water-reducing admixtures as cement grinding aids can be successful, it will provide a new large demand for water-reducing admixtures. On the one hand, it is necessary to fully understand the surface chemical phenomena that occur during the grinding process through research and experiments. On the other hand, the requirement to reduce energy consumption costs in the future will also play a key role in this application.
2. Used in the production of water-reducing agents for gypsum board
Water-reducing agents can also be used in large quantities to produce gypsum wallboards. Here, the water-reducing agent can further reduce the water demand of the gypsum slurry and reduce the energy consumption required for drying the gypsum board, thereby reducing costs. Therefore, the main driving force for using water-reducing admixture products is to reduce energy consumption costs, followed by increasing strength. For this application, foreign countries have designed specific water-reducing agent products for gypsum boards.
3. Used in sprayed commercial concrete
Another important and newer application of water-reducing agents is the sprayed commercial concrete used in tunnel projects, in which water-reducing agents can be used to reduce water The gray ratio is reduced to a lower value, which is very necessary for spraying commercial concrete. Because ordinary shotcrete commercial concrete has a late-stage strength ratio of less than 100% due to the self-crystallization of cement hydrate induced by the accelerator, showing poor strength growth. The use of commercial sprayed concrete with water-reducing admixtures can help effectively achieve the predetermined later strength.
4. Powdered products are used for dry mortar
Although the output of water-reducing agents in our country is large at present, the output of powdered products is very small, and only a few companies produce it, which limits the It is the application of water reducing agent products in dry mortar and other industries that require powdery products.
Two issues should be paid attention to when producing powdery superplasticizer products. The first is the safety issue during the drying process. Usually in order to reduce energy consumption, powdered products are produced by spray drying mother liquor with the highest possible solids content. It should be noted that water-reducing agent powder products (liquid products are non-flammable and have flame retardant effects) are flammable organic substances and will spontaneously ignite at lower temperatures. Therefore, explosions and fires may occur during the production of powder products. It is now recognized that the safe production of powdered water-reducing admixture products can be effectively ensured by adding some substances that can significantly reduce the auto-ignition point.
Another issue that needs attention is that powdery products are sticky due to oily or waxy EO side chains. Due to the increase in the length of the side chain, the density of the side chain and the inclusion of PEG/MPEG mixture in the superplasticizer mother liquor, the tendency of the product to become dense and agglomerated is increased. In order to avoid this phenomenon, an inorganic carrier material with a very large specific surface area can be added during the spray drying process. This measure helps to form a non-dense powdery product. The self-flowing properties of this loose powdery product are beneficial to the production of powdery superplasticizer products.
Summary of the industry situation
1. The admixture industry is booming and has gradually formed a situation with complete varieties, increasing scale, continuous growth in production and sales, and continuous improvement in product performance. In 2013, the total output of commercial concrete admixtures reached 12.2525 million tons, equivalent to an additive sales value of 49.661 billion yuan.
2. Water reducing agents have grown significantly, naphthalene seriesThe output of high-efficiency water-reducing admixtures and aliphatic superplasticizers has also increased. The output in 2013 was 4.9781 million tons, 3.5759 million tons and 681.7 thousand tons respectively.
3. The proportion of synthetic water-reducing admixtures in the total amount of synthetic water-reducing admixtures continued to increase from 14.6% in 2007 to 52.2% in 2013. Its growth is affected by factors such as product performance, cost performance and raw materials. Recently, my country has sufficient supply of polyether raw materials.
4. The research and development of water-reducing agents in the future can be developed in several directions such as cement grinding aids, gypsum board water-reducing agents, sprayed commercial concrete and powdered products.
5. The admixture industry is still in an unstable dynamic development stage, and the problem of uneven regional distribution has improved. The western region and overseas construction are new sales markets for the commercial concrete admixture industry. </p
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