Why We Use Plasticizers in Concrete

Concrete admixtures are an important part of concrete technology. Ordinary concrete may not provide the properties required for various projects, such as durability, strength, machinability, etc. In this case, it is necessary to use concrete admixtures to improve the performance of ordinary concrete. For example, large-scale concrete pouring, concrete pouring in narrow space, concrete that needs to reduce water use in water-deficient areas, concrete that needs to remove formwork early, concrete pouring near coastal areas, etc. Nowadays, concrete admixtures have become more and more important components of concrete. They are harmless to concrete structures, but ultimately improve the performance of fresh and hardened concrete.

Concrete admixtures are divided into many different types, among which the most widely used is a concrete plasticizer. Concrete plasticizers can improve the strength and workability of concrete without using too much water. Polycarboxylate ether superplasticizer in concrete is currently the most widely used concrete plasticizer because of its good water-reducing effect.

The strength of concrete is determined by the water-cement ratio. The higher the water content in fresh concrete, the lower the strength of the concrete. In general, workers add more water to concrete in order to make it more fluid, improve its workability during construction, and make it easier to pour. However, if excessive water is added during construction, the homogeneity of the concrete mixture will decrease and the strength of the concrete will decrease, which may result in segregation or seepage of the concrete.

Adding plasticizers to concrete can solve this problem. A concrete plasticizer has the effect of surface activity. Adding it in concrete can reduce the water content of concrete and enhance the strength of concrete. It can also save the use of cement, improve the concrete plasticizing performance. The intrinsic effect of plasticizer is generated by adsorption, dispersion, lubrication, wetting, water reduction, enhancement, and inhibition of slump loss.

Dispersion: After the cement is mixed with water, due to the molecular gravitational effect of the cement particles, the cement slurry forms a flocculation structure, so that 10%-30% of the mixing water is wrapped in the cement particles, which cannot participate in free flow and lubrication, thereby affecting the mobility of concrete mixture. When the water reducing agent is added, since the water reducing agent molecules can be adsorbed on the surface of the cement particles, the same charge is formed on the surface of the cement particles to form an electrostatic repulsion, which causes the cement particles to disperse. And the flocculation structure is destroyed to release the wrapped portion of water to participate in the flow, which effectively increases the fluidity of the concrete mix.

Lubrication: The hydrophilic group in the water reducing agent is very polar, so the water reducing agent adsorption film on the surface of the cement particles can form a stable solvated water film with the water molecules. This water film has a good lubricating effect, which can effectively reduce the sliding resistance between the cement particles, thereby further improving the fluidity of the concrete.

Steric effect: The branch having hydrophilicity in the structure of the water reducing agent extends in the aqueous solution to form a hydrophilic stereoscopic adsorption layer having a certain thickness on the surface of the adsorbed cement particles. When the cement particles are close, the adsorption layers begin to overlap, which creates a steric hindrance between the cement particles. The more overlap, the greater the repulsion of the space, and the greater the hindrance to the coagulation between the cement particles, so that the slump of the concrete remains good.

Slow-release of graft copolymerization branch: In the preparation process, the novel water reducing agent grafts some branches on the molecules of the water reducing agent. This branching can provide a steric hindrance effect, and in the high alkalinity environment of cement hydration, the branch is even slowly cut off, thereby releasing a polycarboxylic acid having a dispersing action. This can increase the dispersion of cement particles and control the slump loss.

Because plasticizer has a great impact on the performance of concrete, so choosing the right plasticizer in engineering construction is particularly important. Kingsun is a professional concrete admixtures manufacturer & supplier. Welcome to visit our website: https://kingsunconcreteadmixtures.com/ to get more information.