What Is A Superplasticizer in Concrete?
What Is A Superplasticizer in Concrete?
Superplasticizers, also called high range water reducers, are chemicals used to make high-strength concrete with less water. These additives, which include purified lignosulfonates, carboxylate synthetic polymers, sulfonated synthetic polymers, and synthetic polymers with mixed functionality cementitious materials, are used in small amounts to improve the flow of concrete mixtures and enable the production of self-consolidating concrete and high performance concrete.
Superplasticizers allow for a reduction in water content by 30% or more without negatively impacting the workability of the mixture. The use of superplasticizers in concrete improves the performance of the hardening fresh paste and increases the strength of the concrete as the water to cement ratio decreases.
In recent years, the use of automated slump management systems, like Verifi, has allowed concrete producers to add admixtures during transit to maintain slump until discharge without sacrificing concrete quality.
Types Of Superplasticizers
There are three types of superplasticizers: Sulphonated Melamine-Formaldehyde Condensates (SME), Sulphonated Naphthalene Formaldehyde Condensates (SNF), and Modified Lignosulphonates (MLS). SME is often used in the precast industry because it does not affect the setting of cement.
SNF is a high range water reducer. MLS are water-soluble polyelectrolyte polymers made from the byproducts of wood pulp production using sulfite pulping.
Superplasticizer In Concrete Examples
Superplasticizers are admixtures that are added to concrete to increase its workability and decrease the required water content.
Examples of superplasticizers include Polymelamine Sulfonate, Polynaphthalene Sulfonate (PNS), Polycarboxylate Ether (PCE) based polymers, and Polymer Melamine Sulfonate (PMS). These superplasticizers work by deflocculating, or separating, the cement particles in the mixture.
Advantages Of Superplasticizers
Superplasticizers are an incredibly beneficial form of concrete admixture, designed to improve the performance of a mixture while actually reducing its water content. This is highly advantageous because it can allow for improved structural integrity and strength, with the added bonus of lower water-cement ratios.
Additionally, superplasticizers reduce shrinkage within concrete mixtures, minimizing cracks and shrinkage-related issues. Superplasticizers tends to be especially beneficial for large pours in projects such as dams or other massive structures that require increased workability and durability.
Superplasticizers also increase the workability of concrete at low water-cement ratios making them suitable for use with heavy reinforcement. Additionally they can reduce the permeability of concrete.
Disadvantages Of Superplasticizers
The main disadvantage of using superplasticizers is the rapid slump loss and incompatibility of cement and superplasticizers, resulting in a loss of workability. This can lead to problems such as ineffective mixing, inadequate coverage, poor bonding and adhesion, and insufficient strength.
In addition, improper use of a superplasticizer can also cause excessive segregation and bleeding, leading to a decrease in strength and durability.
Moreover, incorrect selection or dosage of the superplasticizer can increase the water-cement ratio beyond the optimum range resulting in reduced strength due to weakened hydration products.
