What is the Best Concrete Mix for Finishing?

4 Best Mixes By Finish Type

Different finishes demand different mix designs. Here’s what works for each application.

• Smooth Trowel Finish (Garages, Basements)

Smooth trowel finishes require a dense paste with minimal bleed water. This allows the trowel to burnish the surface without pulling up excess moisture that causes discolouration and weakness.

Recommended 4,000 PSI mix design:

• Portland cement: 270 kg/m³
• 10mm maximum aggregate
• Water to cement ratio: 0.42-0.45
• 6% to 8% air entrainment (for unheated garages and freeze-thaw exposure; non-air-entrained mixes are often preferred for interior, hard-troweled floors.)

The smaller aggregate size creates a cream-rich surface that responds well to multiple trowel passes. Higher air entrainment improves freeze-thaw resistance in unheated garages and basements.

• Broom Finish (Driveways, Walkways)

Broom finishes need enough paste to hold texture while resisting delamination. The slightly larger aggregate provides durability for vehicle and foot traffic.

Recommended 3,500 to 4,000 PSI mix design:

• 12mm maximum aggregate
• Water to cement ratio: 0.45
• 6% ± 1% air entrainment with spacing factor no greater than 0.20mm

This mix creates durable traction patterns when properly placed, finished, and cured. The moderate water content gives you adequate working time to achieve consistent broom lines across the entire surface.

The specific air void structure is critical for driveways and walkways because these outdoor surfaces face constant exposure to harsh weather. Properly spaced air pockets allow moisture to expand safely during freezing. 

• Exposed Aggregate (Patios)

Exposed aggregate finishes showcase decorative stones without honeycombing or paste residue. This requires a sticky mix that holds aggregate in place during washing.

Recommended 4,500 PSI mix (white or grey cement, depending on desired appearance):

• 10mm decorative aggregate
• Water to cement ratio: 0.38
• Superplasticiser at 8 oz per hundredweight

The low water content and superplasticiser combination provides workability without excess bleed water. This exposes clean, vibrant stones with sharp definition between each piece. Ordering ready-mix concrete with pre-added superplasticiser ensures consistent results across large patio pours.

• Stamped and Decorative

Stamped concrete must resist micro-cracking under the pressure of texture mats. Fibre reinforcement distributes stress across the slab during and after stamping.

Recommended 4,500 PSI fibre reinforced mix:

• 10mm rounded aggregate
• Polypropylene fibres at 0.9 kg/m³
• Water to cement ratio: 0.40

Rounded aggregate prevents fibres from balling during mixing. The result is a uniform, crack-resistant surface that holds intricate stamp patterns for years.

Universal Finishing Mix Formula

Need one mix that handles multiple finish types? This formula delivers 4,200 PSI at 28 days with excellent workability for most applications.

For a 25 square metre slab:

• 9 bags Portland Type I/II cement (94 lb bags)
• 0.19 cubic metres 10mm washed stone
• 0.15 cubic metres fine masonry sand
• 120 litres of water maximum
• 3 oz retarder per 45 kg cement

This universal mix works well for residential garages, patios, walkways, and basement floors. The retarder extends working time in warm weather without compromising final strength. Many residential contractors use this as a reliable general-purpose mix when multiple finish types are required on the same project.

Key Mix Ratios Contractors Demand

Quick reference for the most common finishing applications:

Higher cement content generally improves finishability by increasing surface paste, but excessive cement can increase shrinkage and cracking risk. When in doubt, increase cement by 10% rather than adding water to improve workability.

Takeaway

The right finishing mix eliminates most surface defects before you even pick up a trowel. Match your mix design to your intended finish, maintain proper water-to-cement ratios, and never compromise on aggregate size. These fundamentals separate professional results from callbacks and repairs.

Pro Mix Concrete supplies contractor-grade finishing mixes engineered for smooth trowel, broom, exposed aggregate, and stamped applications. Our ready mix concrete arrives with precise aggregate sizing, optimised cement content, and consistent workability batch after batch.

Poorly designed mixes make finishing harder than it needs to be and often lead to surface defects. Call Pro-Mix Concrete now and see the difference quality concrete makes on your next project.