The water-reducing agent should be used with concrete admixture, which will reflect the water-reducing effect. Cement quality is therefore a direct factor of the water reducing agent.
When dealing with different types of “problem” cements, different strategies are required.
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 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 crystalline structures and improving the fluidity of the cement mortar.
Low-alkali sulfur-deficient cement
Low alkali-sulfur cement is a cement with a lower sulfate level than normal cement. Ordinary cement is high in sulfate. It reacts with water and the sulfate forms crystals that cause cracking.
Reduced sulfate cement reduces the impact of the Alkali-aggregate Reaction (Alkali-Silica reaction) in Concrete by reducing its sulfate contents. The alkali silica reaction is a reaction between the alkalis of the cement and the silicates found in the aggregate. It causes concrete to expand, 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 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 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 containing high C3A has a higher adsorption rate of water-reducing agents. This will result in fewer fluidities and slumps 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 kinds of products that reduce water: a water-reducing naphthalene agent and a water-reducing polycarboxylic agent. The main difference in water reduction is that naphthalene has a higher efficiency. Polycarboxylic Acid is more efficient. For general foam concrete, naphthalene adds a few hundred to a kilogram of cubic volume, whereas polycarboxylic is only a few grams.