There are many types of concrete admixtures, which can be divided into the following categories according to their chemical composition: inorganic admixtures, organic admixtures, and composite admixtures. Inorganic admixtures are mainly electrolyte salts; organic admixtures are mostly surface-active substances and some high molecular polymers, organic compounds, and double salts. Surfactant admixtures can be divided into three categories: anionic, cationic, and nonionic. Among them, anionic surfactants are currently the most used; composite admixtures are usually composed of inorganic and organic compounds and generally have a variety of functions.
Selection of admixtures
Faced with a wide variety of admixtures, choosing the different types according to additional technical requirements is essential. The steps are as follows:
a. Determine the primary purpose of selecting admixtures;
b. Select appropriate admixtures based on known cement varieties or select appropriate cement varieties based on determined admixture varieties;
c. According to the different properties and engineering requirements of the admixture, determine the dosage through experiments;
d. Determine the incorporation method of admixtures according to different construction plans, such as mixing, transportation, molding methods, maintenance conditions, and other processes;
e. Adjust the mixing ratio according to the purpose and amount of the admixture;
f. Take a test piece for the first product (in the third and fourth mixing) for a quick inspection to confirm or modify its blending amount or the process plan.
Incorporation method of admixtures
Admixture is a material with a small usage but a significant effect. Therefore, correct measurement is necessary when using admixtures. The allowable deviation of the measure is within 2%.
Based on forms, admixtures can be divided into powdery, colloidal, liquid, and solid. When using powdery admixtures, they should be weighed in advance according to the standard dosage for each mixing and kept in small packages for later use. When it is not needed, temporarily use a small spoon or measuring cup to replace the mass with volume; use gel, liquid, solid, and other dosage forms. When using additives, they must be diluted with water in proportion before use, and they must be stirred evenly before use.
