High range water reducer (high range water reducer), also known as super plasticizer, refers to the admixture which can greatly reduce the water consumption of the mixture under the condition of keeping the concrete slump basically the same. The main components of superplasticizer are almost all polymer electrolytes, which have high dispersing effect on cement and concrete, and can better maintain the slump of concrete. Adding this kind of admixture can greatly improve the fluidity of concrete mixture, or greatly reduce the water consumption of concrete mixture while maintaining the same fluidity High durability. Compared with superplasticizer, high performance water reducer not only has high water reducing rate, but also requires concrete admixtures with certain air entrainment, high slump retention and good water retention. [1-3]
High performance concrete (HPC) was formally proposed by the United States in 1990, and immediately attracted the attention of the whole world, known as "21st century concrete". At present, the requirements of high performance concrete are not only high strength, but also pay more attention to the long-term and super long-term durability of this structural material, as well as the dense, stable and excellent construction performance on the basis of high-strength. In the technical measures for the preparation of high-performance concrete, in addition to the high requirements for cement and aggregate, the most important feature is still in the mixing When ultra-fine powder admixtures (ground slag, silica fume, fly ash, etc.) and chemical admixtures are used, especially the high-performance water reducer, the concrete mixture has good uniformity, cohesiveness, fluidity, filling and plasticity retention, which greatly improves the mechanical properties, volume stability and durability of hardened concrete. Therefore, it can be said that high performance water reducer is the key to prepare high performance concrete.
At present, naphthalene series superplasticizer is widely used in China. Naphthalene water reducer plays an important role in improving the quality and service life of buildings, reducing energy consumption, saving cement and reducing environmental pollution. However, the development of naphthalene water reducer in recent decades has also exposed some natural difficulties Questions. With the vigorous construction of domestic large-scale projects such as hydropower stations, high-speed railways and sea crossing bridges, naphthalene based superplasticizer has been difficult to meet the performance requirements of these concrete projects. Therefore, foreign countries actively study and open up non naphthalene superplasticizer, until Japan successfully developed polycarboxylate superplasticizer for the first time, and then European and American countries began to turn to polycarboxylate superplasticizer Since then, polycarboxylate superplasticizer has been applied.
Polycarboxylate superplasticizer is a kind of polymer surfactant with comb shaped molecular structure and multi carboxyl groups. It can greatly reduce the water consumption of concrete and significantly improve the strength of concrete without changing the construction performance of concrete under low water binder ratio, or significantly change the workability of concrete at low water binder ratio, and the slump loss is small over time. Its low content, high water reducing rate, high slump retention performance, low shrinkage rate of concrete, good compatibility with cement, strong adjustability in molecular structure, high potential of high performance and environmental protection make it more and more concerned by civil researchers.