Why does concrete need to add water reducing agent? What will happen if you don't add it? What are the consequences?

Water reducer is usually called concrete water reducer, which is an additive in concrete. Water reducers are added in concrete construction, do you know why water reducers are added to concrete? What happens if you don't add it? What are the consequences? Let's find out together.

Why does concrete need to add water reducing agent? There are several main functions, namely:

01 Water reduction effect

After adding water reducer to concrete, it can significantly reduce the water-cement ratio while maintaining fluidity. The water reducing rate of high-efficiency water reducing agent can reach 10%~25%, while that of ordinary water reducing agent is 5%~15%. The reason why the water can be reduced is mainly because of the adsorption and dispersion of the concrete on the water reducing agent.

02 Lubrication

The polar hydrophilic group of the water reducer is directional adsorbed on the surface of cement particles, and is easy to combine with water molecules in the form of hydrogen bonds. The strength of this hydrogen bond association is much greater than the molecular attraction between water molecules and cement particles. The hydrogen bond association between water molecules makes the surface of cement particles form a layer of stable solvated water film, which acts as a three-dimensional protection, prevents direct contact between cement particles, and acts as a lubricant between them effect.

03 Plasticization

Adding water reducing agent to concrete can increase the fluidity without changing the water-cement ratio. The general water reducing agent can increase the slump of fresh concrete by more than 10cm while keeping the amount of cement constant, which can reduce water. The agent can prepare concrete with a slump of 25cm.

04 Humidification

After cement is mixed with water, the particle surface is wetted by water, and the degree of wetting has a great influence on the performance of fresh concrete. When this type of diffusive wetting occurs naturally, the amount of surface free energy reduction can be calculated from the equation proposed by Glbbs.

What will happen if there is no water reducer in concrete? What are the consequences?

Of course, concrete can also choose not to add a water reducing agent. The water reducing agent is a concrete admixture that can be formed without adding a water reducing agent. However, the density of concrete without water reducing agent will be relatively low, and the anti-seepage and so on will be correspondingly lower than those with water reducing agent. Water reducing agent has become the fifth necessary material for concrete besides cement, coarse and fine aggregate, admixture and water.

At present, in the process of building construction, water reducing agents will be added, especially in some demanding building construction scenes, the use of high-efficiency water reducing agents will be required.