Plasticizers are a form of chemical concrete admixtures added to concrete during mixing to reduce the amount of water used in the concrete mix by about 15%. Superplasticizers reduce the required water content by 30%.Concrete plasticizers are a form of industrial chemicals. Naturally, if the amount of water used in concrete preparation is less by such a percentage, the concrete mix would be too dry and stiff. This would reduce the workability of the concrete mix during transportation and setting. Additionally, the resultant concrete’s strength would be compromised and would not stand the test of time.
Therefore, to ensure concrete’s workability, strength and help the same concrete remains comfortable at desired levels; even when the water used is less by up to 15%, plasticizers are added to the mix during preparation. Thus, the concrete remains fluid and flows just as smoothly as if it had 100% water content.
How do concrete plasticizers work?
Simply put, concrete plasticizers act as lubricants between the concrete molecules. They reduce the viscosity of the concrete as well as its plasticity. Naturally, cement molecules carry both positive and negative charges on their surface. When the plasticizers are added to the mix, they embed themselves on the cement molecules’ surface. The plasticizers, however, carry negative charges.
They, therefore, transform the surface of the cement molecules to appear entirely negatively charged. This increases the repulsion action between the molecules, thereby increasing the fluidity of the concrete mix. This form of action is known as electrostatic repulsion.
Other plasticizers work through a different form of action; steric hindrance. These are the most recent plasticizers to enter the market. What these plasticizers do is that they hinder some chemical reactions from taking place within the concrete mix.
Concrete is a compound product that results from the chemical reaction between cement, water, and aggregate. When some of the chemical reactions do not take place completely, the concrete forming process isn’t complete, and therefore the mixture remains more fluid and is easier to handle and pour.
Where are concrete plasticizers used?
There are some conditions during construction that necessitate the preparation of concrete using less water content. It is these conditions that require the use of concrete plasticizers. Some of such conditions are discussed below.
Increased concrete strength
During the construction of some structures that need to be very strong such as bridges, dams, and building foundations, engineers may recommend reducing the concrete’s water content to boost its strength. Plasticizers come in handy to ensure such concrete is still workable even with less water.
Increase concrete plasticity
When there is a delay in using already prepared concrete on a construction site, it hardens. However, I would be uneconomical to discard such concrete once the delaying factors have been addressed. Concrete plasticizers are used in such a case to increase the plasticity of the concrete.
Increase water tightness
When added to concrete, plasticizers increase cement water tightness, making it more effective when waterproofing is critical.
Concrete plasticizers enable the preparation of concrete using up to 15% less water content. They increase the fluidity and plasticity of the concrete. Superplasticizers reduce the required water content by up to 30%.