To start, the porous nature of concrete is one of the main reasons they are prone to degradation. As a consequence of this porosity, some aggressive chemicals found in water (e.g., chloride ions) may penetrate the concrete. This therefore affects the microstructure of the concrete, leading to a reduction in its overall durability.
To avoid such situations, there is an increasing interest in innovative and sustainable approaches that can inherently reduce the permeability of Concrete improving the durability of the concrete at various scales.
What Are Concrete Admixtures?
There are additives added during concrete mixing to enhance specific properties of the fresh or hardened concrete, such as workability, setting time, durability, or early and final strength. Could be natural or manufactured.
They are of two main types: Chemical and Mineral Admixtures.
Mineral admixtures make mixtures more economical by replacing certain percentages of cement weight, reducing permeability, increasing strength, and influencing other concrete properties.
Mineral admixtures affect the nature of the hardened concrete through hydraulic or pozzolanic activity. Includes natural pozzolans, fly ash, Slag, and silica fume.
Chemical admixtures reduce the cost of construction, modify the properties of hardened concrete, and ensure quality of concrete during mixing/transporting/placing/curing.
These Products are sold in ready-to-use form and are applied to concrete either in the factory or on-site. Stay with us to discover more about concrete Admixtures.
Chemical admixtures are used to improve the quality of concrete during mixing, transporting, placement, and curing.
They fall into the following categories:
• Water reducers
• Air entraining
• Specialty admixtures: which include corrosion inhibitors, shrinkage control, alkali-silica reactivity inhibitors, and coloring.
Will discuss today the most used types of concrete admixtures in today's applications.
1. Water Reducing Admixtures
They are used to minimize the water demand in a concrete mix while maintaining workability and by reducing the water required, they enhance the strength and durability properties of concrete. They are also called plasticizers and these are classified into three types; normal plasticizers, mid-range plasticizers, and super plasticizers according to water reduction percentage.
Superplasticizers are needed in areas such as the need for high strength, pumpability, self-consolidating properties of concrete, low permeability, low water absorption, and low shrinkage properties of concrete.
Uniguard offers a range of water-reducing & high-range water-reducing admixtures with different technologies such as lignosulphonates, Formaldehyde derivatives, and 3rd generation polycarboxylate in system 118.
2. Retarding Admixtures
Retarding admixtures slows down the rate of hydration of cement in its initial stage and increases the initial setting time of concrete. used in high-temperature zones where concrete will set quickly, minimize the transport delay problems by delaying the setting time, and help eliminate cold joints in concrete.
Uniguard offers retarding admixtures as Admix RD in addition to retarding admixtures which act as well as water-reducing admixtures as Admix RD Plus.
3. Accelerating Admixtures
reduces the initial setting time of concrete. They speed up the process of the initial stage of hardening of concrete improving the strength of concrete in its early stage by increasing the rate of hydration, and useful in a variety of conditions including early removal of formwork, shorter curing times, emergency repair work, construction in low-temperature zones, and so on.
Uniguard offers Type C Accelerators and Type E Water-reducing and accelerating admixtures as per ASTM C494 in System 119.
4. Bonding Admixtures
For bonding old and fresh concrete surfaces. In general, if fresh concrete is poured over a hardened concrete surface, there is a chance of failure of the fresh concrete surface due to a weak bond with the old surface. Bonding admixtures are added to cement or mortar grout that is placed on the concrete surface just before placing fresh concrete to strengthen the bond. These admixtures will significantly improve adhesion and cohesion as well as the tensile, compressive, flexural, and mechanical properties of cement-based mixtures.
System 123 shows acrylics, and butadiene-styrene copolymers bonding admixtures uniguard offers.
Concrete admixtures Role in the Future of Concrete Technology
Admixtures are an important component of modern concrete technology. They provide a cost-effective way to improve the properties of concrete and extend the lifespan of concrete structures.
Engineers can build concrete structures that are strong, durable, and resistant to the effects of weather and time by employing the right admixtures in precise doses. Admixtures will play an increasingly essential part in the future of concrete technology as demand for sustainable and eco-friendly construction develops.