Concrete additives — also called admixtures — are ingredients added to the mix to change how it performs. Some make it set faster. Some slow it down. Others improve durability, workability, or crack resistance. Knowing which ones apply to your project can save you time, money, and headaches on pour day.

Fiber Reinforcement

Synthetic or steel fibers are blended into the mix to reduce plastic shrinkage cracking — the fine surface cracks that appear as concrete cures. Fiber doesn't replace rebar for structural strength, but it's excellent for slabs, driveways, and flatwork where surface cracking is a concern.

• Best for: driveways, patios, garage floors, sidewalks
• Benefit: reduces surface cracking during cure
• Does not replace: structural rebar or wire mesh

Accelerators

Accelerators speed up the hydration process, causing concrete to set and gain strength faster. They're commonly used in cold weather (below 50°F) when normal concrete would set too slowly, or when a project needs to be back in service quickly.

• Best for: cold weather pours, fast-turnaround projects
• Common type: calcium chloride (non-structural) or non-chloride accelerators (for reinforced concrete)
• Note: calcium chloride can corrode rebar — use non-chloride types in reinforced pours

Retarders

Retarders slow the set time, giving you a longer working window. They're essential in hot weather (above 90°F) when concrete can set too quickly, and for large pours where placement takes time.

• Best for: hot weather pours, large slabs, long placement windows
• Benefit: prevents cold joints and premature stiffening
• Common in: summer pours in the Charlotte area

Water Reducers and Plasticizers

These admixtures improve workability without adding water — which would weaken the mix. A mid-range water reducer makes concrete easier to place and finish while maintaining strength. High-range water reducers (superplasticizers) are used in high-strength commercial mixes.

Air Entrainment

Air-entrained concrete contains microscopic air bubbles that improve freeze-thaw resistance. It's standard in northern climates but less common in the Charlotte area. If your project will be exposed to deicing salts (like a driveway near a road), ask about air entrainment.

How to Order Additives

When you call UNO Concrete, just tell us your project type, pour date, and any concerns (cracking, hot weather, fast turnaround). We'll recommend the right admixture package and include it in your mix at the plant. There's no need to source additives separately.