Term: Superplasticizer
– Working Mechanism:
– Superplasticizers are additives used in concrete to reduce water content.
– Different classes of superplasticizers include lignosulfonates, sulfonated synthetic polymers, and polycarboxylates-ether.
– The addition of superplasticizers improves flow characteristics and decreases water-to-cement ratio without affecting workability.
– Superplasticizers enhance concrete strength and durability by reducing porosity.
– Incompatibilities between cement and superplasticizers can occur due to unclear working mechanisms.
– Types of Superplasticizers:
– Traditional plasticizers are lignosulphonates.
– Synthetic polymers like sulfonated naphthalene formaldehyde condensate and polycarboxylates ethers are also used.
– Polycarboxylate superplasticizers stabilize colloidal suspensions through steric interactions.
– Superplasticizers function as dispersants to prevent particle segregation in fresh concrete.
– Melaminesulfonate and naphthalenesulfonate act by electrostatic interactions, while polycarboxylate-ether sorb and disperse cement particles.
– Applications and Benefits:
– Superplasticizers enable the production of self-consolidating concrete and high-performance concrete.
– They greatly improve fluidity and rheology of fresh concrete.
– Lower water-to-cement ratios lead to better resistance to compression in hardened concrete.
– Superplasticizers added in transit through automated systems maintain concrete slump until discharge.
– Admixtures in transit ensure fresh concrete quality is preserved.
– Related Concepts:
– Superplasticizers are linked to particle aggregation and peptization processes.
– Understanding rheology and surfactant properties is essential in using superplasticizers.
– Plasticizers, polycarboxylates, and suspension chemistry are closely related.
– Rheology studies help in optimizing superplasticizer performance.
– Special cements and admixtures play a role in enhancing concrete properties.
– References:
– Various studies have been conducted on superplasticizers and their impact on concrete.
– Research highlights the importance of superplasticizers for durable high-performance concrete.
– In-transit concrete management systems have been developed to improve concrete quality.
– Books and articles provide in-depth knowledge on superplasticizers and their applications.
– Cement-superplasticizer interactions and models are subjects of ongoing research.
Superplasticizers (SPs), also known as high range water reducers, are additives used for making high-strength concrete or to place self-compacting concrete. Plasticizers are chemical compounds enabling the production of concrete with approximately 15% less water content. Superplasticizers allow reduction in water content by 30% or more. These additives are employed at the level of a few weight percent. Plasticizers and superplasticizers also retard the setting and hardening of concrete.
According to their dispersing functionality and action mode, one distinguishes two classes of superplasticizers:
- Ionic interactions (electrostatic repulsion): lignosulfonates (first generation of ancient water reducers), sulfonated synthetic polymers (naphthalene, or melamine, formaldehyde condensates) (second generation), and;
- Steric effects: Polycarboxylates-ether (PCE) synthetic polymers bearing lateral chains (third generation).
Superplasticizers are used when well-dispersed cement particle suspensions are required to improve the flow characteristics (rheology) of concrete. Their addition allows to decrease the water-to-cement ratio of concrete or mortar without negatively affecting the workability of the mixture. It enables the production of self-consolidating concrete and high-performance concrete. The water–cement ratio is the main factor determining the concrete strength and its durability. Superplasticizers greatly improve the fluidity and the rheology of fresh concrete. The concrete strength increases when the water-to-cement ratio decreases because avoiding to add water in excess only for maintaining a better workability of fresh concrete results in a lower porosity of the hardened concrete, and so to a better resistance to compression.
The addition of SP in the truck during transit is a fairly modern development within the industry. Admixtures added in transit through automated slump management system, allow to maintain fresh concrete slump until discharge without reducing concrete quality.