To obtain concrete with high strength and extended setting time while reducing the cost of its production, it is necessary to use liquefying / plasticizing admixtures. The second generation of these substances are aqueous solutions of sodium salts of naphthalene sulfonic acids (NSF) formaldehyde polycondensates, and one of such products offered by PCC Rokita is Superplastyfikator BG40 FF.
The product is a 40% aqueous solution with a very low concentration of free sulphates and chlorides, and its undoubted advantage is the very low concentration of free formaldehyde (maximum 50 ppm). It is characterized by very good miscibility with other lignosulphonates plasticizers or melamine-formaldehyde condensates and is recommended mainly in the construction industry as a base for liquefying and plasticizing admixtures. It is a surfactant composed of a hydrophobic organic chain and a hydrophilic sulfone group.
The mechanism of action is mainly based on the principle of electrostatic repulsion. After adsorbing the product onto cement grains, a layer of anonymous charges (sulfone groups) forms on them, the mutual repulsion of which breaks down the cement grain agglomerates and releases the water trapped in them. The fluidity of the concrete mix increases, thus facilitating pumping. The second advantage is the extended formation time of cement hydration products (delay in setting time of the concrete mix), because the cement grains are far apart from each other.
By using Superplastyfikator BG40 FF you can produce airtight concrete, i.e. resistant to aggressive substances and frost, as well as resistant to abrasion, as well as with increased strengths, without compromising the consistency of the mix. Reducing the water / cement ratio by reducing the amount of water by up to 25% (without compromising the rheological properties of the concrete mix), we can get concrete with a late strength of up to 30% higher compared to concrete without the addition of a superplasticizer. At the same time, early strengths also increase, so faster demoulding of concrete elements is feasible.
Superplastyfikator BG40 FF can also be used in the production of drywall. Also in this application, it reduces the amount of water used in the process without compromising the liquefaction of the gypsum mixture (and the setting time and adhesion of the gypsum layer to paper), while reducing production costs by reducing the drying time of the board.
The economic justification for using Superplastyfikator BG40 FF in the production of concrete is the possibility of reducing the amount of cement used while maintaining a constant w / c ratio. The fluidity of the concrete mix is maintained, and the reduction in heat of hydration (caused by a reduction in the amount of cement) reduces the shrinking that occurs during the setting of the concrete. The low chloride concentration means that the product does not contribute to corrosion of steel reinforcements in concrete structures. Superplastyfikator BG40 FF does not introduce large amounts of air into the concrete mix, which can potentially lead to deterioration of frost resistance. In addition, it allows concrete to be made at an air temperature of up to -5 ° C without inhibiting cement hydration.
The use of even small amounts of Superplastyfikator BG40 FF (dosage from 0.5% to 3% per mass of cement) allows you to produce cheap and environmentally friendly concrete, which at the same time is characterized by very good strength and rheological properties. It is mainly recommended for the production of ready-mixed concrete, precast concrete, cement mortars and gypsum products, among others drywall.