Introduction Of Naphthalene Series High-efficiency Water Reducer

Introduction of Naphthalene Series High-efficiency Water Reducer

Naphthalene-based high-efficiency water reducer (naphthalenesulfonic acid formaldehyde condensate) and some other chemical admixtures play an important role in modern concrete materials and technologies. It can improve various properties of concrete and promote the development of new concrete technologies. When used together with mineral admixtures (also known as mineral admixtures), it promotes the utilization of industrial by-products (such as ground slag and fly ash, etc.) in cementitious material systems, which helps to save resources and protect the environment. Under the trend of continuously exploring more low-cost, environmentally compatible materials and technologies, it can be expected that naphthalene-based superplasticizers will play an important role in future concrete production.

Naphthalene-based high-efficiency water reducer is a new type of chemical admixture, its performance is different from ordinary water reducer. It is characterized by a high water reducing rate, which is greater than 12% (the water reducing rate will increase with the increase of the dosage, and even reach more than 20%). Within the normal dosage range, there is generally no serious problem of retardation and excessive air-entrainment for concrete. Due to its unique physical and chemical properties, it has become the most widely used high-efficiency water reducer in China. According to the statistics of the Concrete Admixture Branch of China Building Materials Industry Association, in 2003, the total amount of various superplasticizers in my country was 936,600 tons, of which the naphthalene series superplasticizers reached 774,400 tons, accounting for 83% of the output of superplasticizers.

Naphthalene-based high-efficiency water reducers are generally produced from industrial naphthalene (sometimes refined naphthalene) as raw materials. The production process is as follows: naphthalene becomes a powder product through sulfonation, hydrolysis, condensation, neutralization, filtration, and spray drying. The production process of naphthalene-based high-efficiency water reducer is mature, and the product performance is stable. On the one hand, this product can be directly used in concrete. The performance of its superplasticizer concrete has been mastered by the majority of engineers, and the impact of excessive or insufficient addition on concrete performance can also be predicted; Water agent has good adaptability with other admixtures, and can be widely used as the composition of compound admixtures, such as pumping agent, water repellent, air-entraining water reducer, antifreeze, etc. Water agent; finally, its cost performance is relatively high, which can be accepted by the engineering field, so the naphthalene-based high-efficiency water reducer has become the mainstream product of high-efficiency water reducer in my country, and has become a variety with a large amount of use. Although the naphthalene-based high-efficiency water-reducing agent has many advantages, it also has some shortcomings, mainly because it has a poor effect on the plasticity of the concrete. Benchmark concrete; although the water-reducing rate is high, it is still difficult to meet the requirements of concrete with higher water-reducing rate requirements, and when used for high-strength high-performance concrete with low water-binder ratio, the viscosity of the concrete is relatively high , is not conducive to construction. In order to comprehensively improve the performance of the naphthalene-based high-efficiency water reducer, the following methods need to be adopted: add auxiliary admixtures (compounds) to the naphthalene-based high-efficiency water-reducer to alleviate its shortcomings. On the other hand, the naphthalene-based high-efficiency water reducer can be optimized by changing the molecular parameters (molecular weight, molecular weight distribution, sulfonation degree) or substituting part of naphthalene with other compatible monomers to form a copolymer. So far, naphthalene-based composite products have been widely used, that is, adding an appropriate retarder to the naphthalene-based superplasticizer to reduce the loss of concrete slump; using a copolymerization method to improve the performance of the naphthalene-based superplasticizer , is currently in the development phase.

The annual output of naphthalene-based superplasticizers in my country is 774,400 tons, which can be said to be the largest in the world. It takes about 310,000 tons of industrial naphthalene to produce such a quantity of high-efficiency water-reducers. It is worth noting that: the production of naphthalene Most of the chemical raw materials of superplasticizers are extracted from industrial by-products. Naphthalene is produced from alkyne tar or petroleum distillate; sulfuric acid is extracted from pyrite flue gas combustion or processing. Therefore, most of the raw materials consumed in the production of naphthalene-based superplasticizers are industrial by-products. This is very consistent with the current trend of saving resources, promoting the development of mixed cement, and reducing environmental impact. However, at present, the annual output of industrial naphthalene in my country is less than 300,000 tons, and it is difficult to meet the needs of the admixture industry alone; and industrial naphthalene is a raw material for various chemical industries, so the supply of naphthalene is quite scarce, and the price fluctuations are also quite large In 2002, the price of naphthalene rose from RMB 4,000/ton to RMB 5,000/ton to RMB 12,000/ton to RMB 13,000/ton. The sharp fluctuation of raw material prices had a great impact on the production and supply of naphthalene-based high-efficiency water reducers. In recent years, my country has imported more than 100,000 tons of industrial naphthalene from abroad every year. From 2004 to 2005, some new tar processing enterprises were put into production. The supply of naphthalene can increase by more than 100,000 tons per year on the original basis, but can it be guaranteed? The admixture industry's access to naphthalene raw materials with reasonable prices and sufficient supply is still a concern for admixture companies. In view of this situation, it is also an urgent task for the concrete admixture industry to actively develop high-efficiency water reducers that use non-naphthalene as raw materials. After the tight supply of naphthalene in 2002, the new high-efficiency water reducer developed with non-naphthalene as raw material has made gratifying progress.

(Reprinted from China Concrete and Cement Products Network, please indicate the source)