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Concrete additives for precast elements
Concrete additives for precast elements
The precast concrete industry, also known as the prefabricated elements industry , encompasses the sector of civil construction dedicated to the manufacture of structural and non-structural precast concrete elements. In this type of construction, the elements are produced in a factory, off-site, and subsequently transported and assembled at the destination.
Precast elements are widely used in various types of projects, such as commercial, residential, and industrial buildings, bridges, infrastructure structures, and other applications . The precast industry plays an important role in optimizing civil construction, offering efficient, sustainable, and high-quality construction solutions.
What is a concrete additive?
According to NBR 11768/2011, a concrete additive (chemical additive) is a product added to the mass of cementitious material during the concrete preparation process, in a quantity not exceeding 5% of the mass of the cementitious material contained therein, with the objective of modifying its properties in the fresh and/or hardened state.
Additives modify the rheological properties of concrete and/or alter the hydration reactions of cement. They can improve workability, modify viscosity, cohesion, modify water retention, accelerate or retard setting time, control the development of mechanical strength, contribute to the reduction of shrinkage, mitigate the consequences of sulfate attack, alkali-aggregate reaction and reinforcement corrosion, among other characteristics of concrete.
The main additives used in concrete plants aim to guarantee the workability of the concrete during production and transport , as well as to optimize costs. The most commonly used types are listed below.
Polykem™ water-reducing admixtures are multifunctional water-reducing admixtures added to concrete during its preparation . They increase the workability of the concrete and improve control over slump maintenance during transport to the construction site.
PKT™ (Polykem Turbo) water-reducing admixtures promote greater water reduction in ready-mixed concrete. They can act as neutral or retarding admixtures on the setting of concrete.
Superkem™ water-reducing admixtures are superplasticizing admixtures with high water reduction. Added to concrete during its preparation, they significantly increase the workability of the concrete and have no effect on the setting of the concrete.
Hyperkem™ water-reducing admixtures are superplasticizing admixtures with extremely high water reduction . Added to concrete during its preparation, they greatly increase the workability of the concrete and can help control slump and the production of Ultra High Performance Concrete (UHPC). It has no secondary effect on setting. Its chemical composition is primarily based on polycarboxylate ethers.
Hybrid K™ additives are known as Mid Range additives , which promote greater water reduction than usual multifunctional additives, and may have the secondary function of controlling the setting of concrete. They are mainly used in special concretes or in the production of concretes with characteristic strength, fck > 30 MPa.
Hydrakem™ hydration control additives serve to increase workability time and control the initial hydration reactions of cement in concrete transported over long distances, reused returned concrete, or stabilized mortars.
For wet or dry mix sprayed concrete, the Jetkem™ additive Alkali-free concrete is an important factor in the quality and productivity of these concretes for tunnels, slopes, and underground mines.
Depending on the type of construction or structure, achieving initial strength is fundamental for productivity and safety. Durakem™ accelerating additives guarantee greater concrete strength in the first few hours .
Airkem™ air-entraining admixtures are chemical agents developed for use in concrete and lightweight mortar that require controlled and stable air incorporation in both concrete and mortar.
NBR 12653:2018 establishes the specifications and test methods for silica fume used as a mineral addition in concrete . According to the standard, silica fume must be composed mainly of amorphous silicon dioxide (SiO2 ) at a minimum concentration of 85% by mass.
Novakem distributes activated silica powder , activated silica suspension (Silike m) , and colloidal silica (Nanokem ).
Discover other Novakem™ products designed for use in precast concrete.
For more technical information, please contact our team of expert engineers.
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