Generally speaking, the development of superplasticizer can be roughly divided into three stages: the first generation of ordinary superplasticizer represented by lignocellulosic acid, the second generation of superplasticizer represented by naphthalene and the third generation of high performance superplasticizer represented by polycarboxylate. The first and second generation superplasticizers are restricted by the problems such as large amount of water reducing agent, insufficient water reducing, poor adaptability of cement, large slump loss and toxic materials as raw materials. Polycarboxylate superplasticizer, which appeared in the early 1980s, is considered as the third generation of superplasticizer. It is the latest generation of water reducer at home and abroad. With its excellent performance, it is becoming a worldwide research hotspot.
After the development of water reducer from lignosulfonates, naphthalene sulfonate condensates, trimethylamine formaldehyde condensates, aminosulfonates and polycarboxylic acids, the water reducing rate has also increased from 8% to about 30%. The application of high-performance water reducer means that 20% - 30% of cement can be saved, that is, 320-480 million tons of cement can be saved, It is close to China's annual cement production. Therefore, the use of water reducing agent, from the source of concrete energy saving, capital saving, pollution reduction and other clean production. In addition, the use of high-performance water reducer can make the concrete to meet the requirements of various properties, the maximum possible use of fly ash or other mineral admixtures, to achieve waste recycling, reduce the pollution of waste to the atmospheric environment, but also reduce the fact that waste occupies valuable land. With the continuous development of construction industry, the demand for water reducing agent is increasing every year in the world. At present, the world's demand for water reducer is about 4.8 million tons, and the annual demand for water reducer in China's construction industry exceeds 1 million tons. According to incomplete statistics in 2003, the total amount of superplasticizer in China is about 925000 tons, including 775000 tons of naphthalene and its derivatives, 95000 tons of amino acids, 36000 tons of aliphatic group, 4% of aliphatic group, 16000 tons of polyacrylic acid salts, 1.7% of polyacrylic acid salts, and 14000 tons of melamine series, 5%. So far, naphthalene superplasticizer still occupies the main position of superplasticizer.
Polycarboxylate superplasticizer not only has the functions of high performance water reducing (the highest water reducing rate can reach 35%), improving the pore structure and compactness of concrete, but also can control the slump loss of concrete and better control the air entrainment, retarding setting and bleeding of concrete. It has relatively good compatibility with different kinds of cement. Even at low content, it can make concrete have high fluidity, and has low viscosity and small slump change with time at low water cement ratio.
Therefore, it can be predicted that with the development of concrete technology, polycarboxylate superplasticizer with its excellent performance will get greater development and application.