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The water-reducing agent should be used with concrete admixture, which will reflect the water reduction effect. Cement quality is therefore a direct factor of the actual effect water-reducing agents.
The following strategies are to be used when encountering “problem” cements:
High alkali cement
High-alkali is a cement type with a large amount of alkali. Alkali in high-alkali is usually higher than that of conventional cement.
The high-alkali cements have a high degree of alkalinity. This can impact the performance. High-alkali Cement can encourage the setting reaction, which is beneficial to the early development of strength in concrete. High-alkali Cement can also increase the fluidity of cement, making it more workable and easier to pump.
But there are also some issues with high-alkali clinkers. As an example, high alkali cements can reduce the efficiency of water-reducing agents and cause concrete to lose its slump faster. High-alkali cement may also lead to corrosion and carbonation problems in the concrete.
High-alkali Cement can benefit from water-reducing agents that contain a higher content of sodium sulfate. High-alkali cement contains a high amount of alkali, which accelerates C3A’s dissolution. Sodium sulfate reacts with C3A, forming AFt crystals. This improves the fluidity of the cement mortar.
Low-alkali sulfur-deficient cement
Low alkali-sulfur cement has less sulfate in it than normal cement. Ordinary cement is high in sulfate. It reacts with water and the sulfate forms crystals that cause cracks and expand the concrete.
Reduced sulfate cement helps reduce the impact of the Alkali-Silica reaction in concrete (also called the Alkali-Aggregate reaction). Alkali and silica react in concrete, causing cracking and expansion. The use of low-alkali cements that are sulfur-deficient can help reduce this reaction, and increase the durability and life of the concrete.
Due to the lower sulfate contents, water reducers work less well with low alkali-sulfur cement. Water-reducing agents can cause concrete to lose slump quickly if they are used in excess. In this case, the conventional method of using water-reducing agents may not work. Instead, it is best to choose a water reducing agent that contains sulfate.
High C3A cement content
Cement with a high C3A-content is one that contains a large amount of C3A. C3A is a mineral found in cement which reacts with the water to produce an expansive substance when it hydrates. Cements with high C3A contents have a faster setting time and higher early strength. They are ideal for projects requiring rapid strength development and rapid setting.
Cement with high C3A levels can cause some problems. C3A and sulfate react to form sulphoaluminate. This can cause concrete to expand or crack. In humid environments, cements high in C3A are susceptible to producing corrosive calcium-sulfate precipitates, which can have a negative impact on the durability of concrete and steel structures.
Cement containing high C3A has a higher adsorption rate of water-reducing agents. This will result in fewer fluidity and slump properties of concrete. If you are using a water water-reducing Agent, choose a water-reducing Agent containing high Sulfate content or a retarder that has hydroxycarboxylate in order to reduce C3A adsorption and improve concrete fluidity.
There are two types of products that reduce water: naphthalene-based water-reducing agents and polycarboxylic-based water-reducing acids. The main difference in water reduction is the naphthalene. It is high-performance, whereas the polycarboxylic is high-efficiency. For general foam concrete, the naphthalene cubic addition is between a few hundred grams and a kilogram.