plasticizer, also known as water reducers, are additives used in the manufacture of high-strength concrete. plasticizers are chemical compounds that enable the production of concrete with approximately 15% lower water content. Super plasticizers reduce water by 30%. These additives are only used in a few percent by weight. Hence, plasticizers and super-plasticizers improve the performance of concrete and increase its working time.
plasticizers and super-plasticizers are used to improve the flow (rheology) of suspended particles in concrete. Adding them to concrete or mortar reduces the water-cement ratio without negatively affecting the performance of the mixture and enables the production of self-compacting concrete (SCC) and high-performance concrete (HPC). They also increase the strength of concrete by reducing the water-cement ratio.
The first generation of concrete plasticizer is lignosulfonate, it is one of the types of plasticizers that is added to the concrete mixing plan to achieve efficiency and reduce concrete water. Lignosulfonate-based concrete plasticizer additive is an additive with multiple functions, which, in addition to reducing the water content of concrete, will maintain concrete efficiency and delay setting. The standard definition of the concrete plasticizer additive is such that the water-reducing concrete plasticizer is a product that significantly reduces the amount of water in the concrete mixture without changing the fluidity or without changing the amount of slump water or fluid flow, increase or create both effects for concrete at the same time. The mechanism of concrete plasticizer effect on cement particles is in such a way that the negative charges of lignosulfonate-based concrete plasticizer additive particles cause it to be absorbed by positive calcium ions on the surface of the cement particles. So, the dispersion of the cement particles takes place through two mechanisms of electrostatic repulsion and spatial hindrance. Also, the concrete plasticizer additive has a favorable effect on cement agglomeration. With the formation of cement agglomerates, water gets trapped in the cement and finally the effectiveness of the concrete mixture decreases compared to the state where the cement particles are separated. By adding concrete plasticizer based on lignosulfonate to concrete, these agglomerates break apart and spread cement particles. In this way, the cement grains will be present in the mixture in a separate and non-adherent form, which will make the movement of the particles and flow of the concrete mixture easier. The mentioned mechanism will not change the volume of concrete and will only release the water trapped in the cement. In this case, the contact between cement particles is reduced and the existing cement is used more efficiently.
Superplasticizers based on polycarboxylate usually act through electrostatic repulsion and steric hindrance both. Literally, carboxylate groups with negative charge are responsible for adsorption to cement particle and electrostatic repulsion. The other part of PCE structure is side chains based on polyethylene glycol, which is responsible for steric hindrance and preventing re-agglomeration of cement particles. Polycarboxylate-based superplasticizer increases initial resistance. Many important properties of concrete are influenced by the ratio (weight) of water to cementitious materials used in the mix. By reducing the amount of water. The cement paste will have a higher density, which will result in a higher paste quality. Increasing the quality of paste increases compressive and bending strength, lower permeability, increases resistance to environmental factors, improves particle adhesion, reduces volume change after drying, and reduces concrete cracking.
