Basic concrete is made from just four key components: small rocks, sand, Portland cement, and water. The Portland cement acts as the binder that binds the sand and rocks together.

When water is mixed with these materials, a chemical reaction begins, causing the formation of countless microscopic Portland cement crystals. These crystals weave through the sand and rocks, locking them into a solid, cohesive structure.

To further enhance the strength of concrete, various additives can be used. However, before getting into that, let’s unpack the basics of concrete strength.

Concrete Strength Basics

It’s inherent strength comes from a combination of factors:

  • Low water content: This increases the density of concrete, leading to greater strength due to fewer voids within the cured concrete.

  • Minimal air entertainment: Air bubbles within concrete can weaken it so mimising the amount of air mixed into it helps maintain its strength and structural integrity.

  • High-quality aggregates: Well-graded aggregates such as gravel, stone, sand, and/or geosynthetics help fill in gaps between larger particles, creating a denser material.

  • Reinforcements: The addition of reinforcements like steel rebar or mesh provides additional tensile strength helping concrete withstand bending and stretching forces.

While these aspects are foundational for achieving a strong concrete mixture, its strength can be further enhanced with the additives.

Concrete Additives – Which to Choose & Why?

Concrete additives can improve the strength, workability, and durability of concrete. However, it’s crucial to balance these enhancements with other factors like cost and cure time to ensure the concrete meets all the necessary project requirements.

  • Retarder – This is used to slow down the setting time of concrete.

    Choose this if you require more time to mix your concrete, or if you’re working on a large project that requires a continuous pour, a retarder is useful in ensuring that the concrete maintains its consistency and sets at the same rate.

  • Water Reducers – This helps improve the workability of concrete without adding extra water.

    Consider this because reducing the amount of water needed leads to cost savings in large-scale concrete projects as it reduces the amount of cement needed.

  • Shrinkage Reducers – This minimises the shrinkage that occurs when concrete cures and dries.

    Keep this in mind as minimising shrinkage improves the overall durability of concrete, making it less prone to damage and degradation over time. It also improves the aesthetic of the concrete due to fewer cracks and a smoother surface.

  • Air Entrainers – This is useful in stabilising tiny air bubbles within the concrete mixture.

    Keep this in mind if you’d like to increase the workability of concrete to make it easier to mix, place, and finish.

  • Corrosion Inhibitors – This is used in concrete mixtures to limit the corrosion of reinforcing steel (rebar) within a structure.

    This is crucial to help safeguard the steel reinforcement within concrete from rust and degradation, thus extending its lifespan.

  • Alkali-Silica Reactivity (ASR) Inhibitors – This is used to prevent and/or mitigate the effects of alkali-silica reaction.

    Use this to prevent cracks and enhance the durability of concrete to protect its structural integrity and durability.

  • Silica Fume – This is used to enhance the properties of concrete by improving its strength through filling the voids between cement particles.

    Add this to enhance the durability of concrete, improve its workability, and limit permeability to water and chemical ingress.

  • Viscosity & Rheology Modifiers – This increases the viscosity of a concrete mixture.

    Consider this if you’d like to improve the flow of your concrete mix and minimise its bleeding, leading to a uniform and stable concrete surface.

How to Choose the Best Additive?

Deciding on the best concrete additive depends on a range of project-specific factors. It is crucial to…

First, identify specific project requirements such as strength requirements, durability needs, and workability.

Second, understand the range of concrete additives. As highlighted in the section above, there are about eight main additives that you can choose from.

Third, consider your climate. Some additives work better in hotter climates while others in colder climates.

Fourth, assess the mix design and evaluate the application method. What is the water to cement ratio utilised? What is the quality and reactivity of the aggregate?

Fifth, perform a trial mix to evaluate the performance of your chosen additive.

Last but not least…

Consult with Experts

Need help deciding on the best additive for your next project, reach out to SPG Go Green. We will work with you to understand the specific needs of your project and guide you through the additives you can choose from.

From there on, you can select the most appropriate additive for your project. Contact us TODAY!