Superplasticizers (SP’s), also known as high range water reducers, are additives used in making high strength concrete. Plasticizers are chemical compounds that enable the production of concrete with ca. 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 retard the curing of concrete.
SPs are used where well-dispersed particle suspension is required to improve the flow characteristics (rheology) of suspensions such as in concrete applications. Their addition to concrete or mortar allows the reduction of the water to cement ratio without negatively affecting the workability of the mixture, and enables the production of self-consolidating concrete and high performance concrete. They greatly improve the performance of the hardening fresh paste. The strength of concrete increases when the water to cement ratio decreases.
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 systems, such as Verifi, allows concrete producers to maintain slump until discharge without reducing concrete quality.
Traditional plasticizers are lignosulphonates as their sodium salt. Superplasticizers are synthetic polymers. Compounds used as superplasticizers include sulfonated naphthalene formaldehyde condensate, sulfonated melamine formaldehyde condensate, acetone formaldehyde condensate and polycarboxylate ethers. Cross-linked melamine- or naphthalene-sulfonates, referred to as PMS (polymelamine sulfonate) and PNS (polynaphthalene sulfonate), respectively, are illustrative. They are prepared by crosslinking of the sulfonated monomers using formaldehyde or by sulfonating the corresponding crosslinked polymer.
Idealized structure of naphthalenesulfonate/formaldehyde polymer used as a superplasticizer.
Polycarboxylate displacement on a multi-phase suspension.
The polymers that serve as plasticizers exhibit surfactant properties. They are often ionomers. They function as dispersants to minimize particle segregation (gravel, coarse and fine sands). The negatively charged polymer backbone adsorbs on the positively charged colloidal particles. However, their working mechanisms lack a full understanding, revealing in certain cases cement-superplasticizer incompatibilities.
Polycarboxylate Superplasticizer DK
Our Superplasticizers are the specifically designed polycarboxylate superplasticizer which exhibits excellent dispersion performance while maintaining good retention effects due to our cutting-edge processing technique; it has a wide range of applications as used in the industrial fields of normal concrete, pumping concrete, as well as self-compacting with high strength & durable concrete projects.
Traditional ones including high speed railways, highways, (air)ports, (hydro)power plants in forms of pre-cast concrete, reinforced concrete and pre-stressed concrete; Excellent performance in dispersion and good slump retention; Good compatibility with various concrete material components; Low application dosage and contraction rate; No corrosion effects; Environmentally friendly.
Mechanism of action
It was commonly thought that plasticizers work by embedding themselves between the chains of polymers, spacing them apart (increasing the “free volume” or swelling them and thus significantly lowering the glass transition temperature for the plastic and making it softer; however it was later shown that the free volume explanation could not account for all of the effects of plasticization. The classical picture on the mobility of polymer chain is more complex in the presence of plasticizer than that drawn by Fox&Flory for simple polymer chain. The molecules of plasticizer take control over mobility of the chain, and polymer chain does not show an increase of the free volume around polymer ends; in the case that the plasticizer/ water creates hydrogen bonds with hydrophilic parts of polymer, the associated free volume can be decreased. For plastics such as PVC, the more plasticizer added, the lower their cold flex temperature will be. Plastic items containing plasticizers can exhibit improved flexibility and durability. Plasticizers can become available for exposure due to migration and abrasion of the plastic since they are not bound to the polymer matrix. The “new car smell” is often attributed to plasticizers or their degradation products. However, multiple studies on the makeup of the smell do not find phthalates in appreciable amounts, likely due to their extremely low volatility and vapor pressure.
The effect of plasticizers on elastic modulus is dependent on both temperature and plasticizer concentration. Below a certain concentration, referred to as the crossover concentration, a plasticizer can increase the modulus of a material. The material’s glass transition temperature will decrease however, at all concentrations. In addition to a crossover concentration a crossover temperature exists. Below the crossover temperature the plasticizer will also increase the modulus.
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