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.
It is important to adopt different strategies for different types of “problem” cement.
High alkali cement
A cement that contains a lot of alkali is called high-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. Moreover, high-alkali Cement can increase the fluidity of Concrete, 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 containing 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 crystalline structures and improving 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-aggregate Reaction (Alkali-silica Reaction) in concrete. Alkali and silicate react in concrete to produce expansion and cracking. 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 be ineffective. Instead, it is recommended to choose a water reducing agent that contains sulfate.
High C3A Content Concrete
Cement with a high C3A-content is one that contains a large amount of C3A. C3A is a mineral found in cement which reacts to water and forms an expansive substance. Cements with a high C3A percentage have a faster setting time and higher early strength. They are ideal for projects that need 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 with high C3A will have a greater ability to bind water-reducing agents. This will result in a reduction of the fluidity of concrete and its slump. If you are using water water-reducing agents, choose a water reducer containing high sulfate content or a slowing agent with hydroxycarboxylate in order to reduce C3A adsorption and improve concrete fluidity.
There are two kinds of products that reduce water: a naphthalene-based water-reducing product and a polycarboxylic-acid-based water-reducing product. The main difference in water reduction is that naphthalene has a higher efficiency. Polycarboxylic Acid is more efficient. For general foam concrete, the naphthalene cubic addition is between a few hundred g to a kilogram.