Concrete water reducing agent is the most common water reducing agent. Since the 1940s, the design, planning and research of lignocellulosic water-reducing agents and various types of water-reducing agents with the same functions have been transformed. In the early 1960s, the first type of water-reducing agent was represented by naphthalene-based water-reducing agents. The third generation of high-efficiency water-reducing admixtures came out, and in the 1980s, the second-generation performance model water-reducing admixture represented by polycarboxylic acid-based water-reducing admixtures appeared. As an ideal upgrade product for third-generation water-reducing agents such as naphthalene series, the performance improvement of polycarboxylic acid-based high-efficiency water-reducing agents is comprehensive, and there are often qualitative leaps in terms of water-reducing effect and process performance. This article carefully compares the differences in water-reducing rates between naphthalene-based superplasticizers and polycarboxylic acid-based superplasticizers and their different impacts on concrete properties through experiments.
The water reduction rate of polycarboxylic acid-based water-reducing agents for Portland cement and general Portland cement is significantly better than that of naphthalene-based water-reducing agents. When the polycarboxylate water-reducing agent is used in Portland cement, it always has a significant water-reducing effect when the dosage is 0.5%. As the dosage increases, the water-reducing rate increases again, but when the dosage is increased to 1.0% The improvement in water-reducing effect is not necessarily obvious, but the water-reducing rate of naphthalene-based water-reducing agent still increases with the increase in dosage. When the polycarboxylic acid-based water-reducing agent is used in ordinary Portland cement, the water-reducing rate increases with the increase in the dosage. After the dosage exceeds 1.6%, the increase tends to slow down. The water-reducing rate of the naphthalene-based water-reducing agent increases with the dosage. The dosage increases but the slowness increases.
Specifically, the water-reducing rate of polycarboxylic acid-based water-reducing agents is much higher than that of naphthalene-based water-reducing agents, and is used in general Portland cement. It can achieve a much higher water reduction rate than that used for Portland cement.
(1) The water-reducing effect of polycarboxylic acid-based water-reducing agent is significantly better than that of naphthalene-based water-reducing agent. When the polycarboxylic acid-based water-reducing agent is used in Portland cement, the increase in water-reducing rate tends to slow down after the dosage is increased to 1.0%; when the polycarboxylic acid-based water-reducing agent is used in ordinary Portland cement, the dosage increases. After reaching 1.6%, the increase in water reduction rate tends to slow down.
(2) The addition of polycarboxylic acid-based water-reducing agents and naphthalene-based water-reducing agents is beneficial to improving the tensile strength of concrete at different ages. .
(3) Both polycarboxylic acid-based water-reducing agents and naphthalene-based water-reducing agents can improve the waterproofing, cold resistance and carbonization resistance of concrete. , listing the two effects as equal in improving cold resistance; for improving the waterproof concrete property and carbonization resistance, the effect of polycarboxylate water-reducing agent is more obvious.
(4) Polycarboxylic acid-based water-reducing agent is beneficial to reducing the shrinkage value of concrete, and can have a very good effect on improving the volumetric reliability, and mixed with The final shrinkage value of concrete containing naphthalene-based superplasticizer exceeds that of standard concrete and cannot have the effect of reducing shrinkage.
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