Concrete Additives: Building Construction

What Concrete Additives Are Necessary for Building Construction Projects?

To meet technical requirements, concrete used for building construction often requires additives to enhance its natural properties. Products added to concrete when it is mixed, sometimes called additives but more commonly known as admixtures, can serve various purposes.

Concrete Building Construction Considerations

Construction projects require materials with sufficient compressive and flexural strength to support weight, provide a skeletal structure, and serve as foundation. Nonstructural materials also have strength and durability requirements that allow them to endure temperature shifts, chemical exposure, abrasion, and other impacts over time.

Depending on the building construction projects, engineers and contractors may find specific cement types work better than others. Ordinary Portland Cement (OPC) is the building block of concrete and is widely used for most concrete applications. It is also used to develop other types of cement, such as Portland Pozzolana Cement (PPC), which is ideal for concrete regularly exposed to water, sewage, or otherwise subject to frequent chemical interactions. These types of cement are frequently mixed with chemical, mineral, or fiber additives to enhance the natural properties of concrete.

Additives for Strength

There are multiple additives for strength that engineers and contractors should consider when planning building construction projects, including:

• Accelerating additives: Accelerating additives speed up concrete’s setting time and can help lock in the strength gains concrete develops early on.
• Corrosion inhibitors: These additives are primarily used to reduce the amount of corrosion and subsequent expense of maintenance on structures reinforced with steel or other embedded metals. Additionally, they can speed up strength development during the construction process.
• Water-reducing additives: These additives can help engineers and contractors develop concrete of a specific strength by reducing the water-cement ratio, which increases strength.
• Superplasticizers: Superplasticizers drastically reduce the water demand of concrete and can help develop high-strength material. Moreover, superplasticizers are excellent at creating concrete with high workability.

Additionally, some fiber additives, such as carbon nanofibers, and mineral ones, such as ground granulated blast furnace slag mineral additives, can aid in strength development.

Additives for Durability

Several chemical additive types help improve concrete’s durability to weather, chemicals, abrasions, and other factors:

• Air-entrainment additives: These effectively reduce concrete’s vulnerability to repeated seasonal freeze-thaw cycles. They are also effective in improving concrete workability and durability.
• Shrinkage-reducing additives: These compounds help reduce short- and long-term shrinkage, increasing concrete’s resistance to cracking. It should be noted that some shrinkage additives may hinder strength development.
• Set-retarding additives: These delay how quickly the concrete starts the setting process, allowing workers more time to complete construction. They also help concrete develop resistance to cracking.

These, along with corrosion inhibitors, can be especially effective in mitigating the risk of shrinkage, cracking, corrosion, spalling, delamination, or scaling. Water-reducing additives also reduce the risk of efflorescence.

Additives for Job-Site Requirements

Chemical and other additives should also be carefully selected to meet the onsite requirements of the job. Particular consideration should be paid to job-site weather conditions, curing and water requirements, and the distance between the concrete plant and the site. In certain cases, an additive may be necessary to address job-site requirements that may undercut the required strength, durability, or workability of the concrete. In these cases, engineers and contractors may need to utilize two or more additives to develop concrete that meets the building construction project’s technical requirements.