Kerb concrete mix is typically a low-slump, dry-stack, or semi-dry concrete designed for stability, high compaction, and fast setting, often ranging from 17.5MPa to 40MPa strength. It is used for bedding and backing kerbs, requiring good compaction to prevent movement. 

Typical Kerb Mix Components & Ratios:

• Mix Ratio: A common site-mixed ratio for bedding is 1:4 (cement to builders mix/aggregate) or a 1:2:4 (cement:sand:aggregate) mix, prepared as a semi-dry mix.
• Slump: Low slump is essential, especially for machine-laid (extruded) kerbing.
• Strength: Typically 17.5 MPa to 40 MPa.
• Aggregate: Usually 10mm or 20mm chip, depending on the required finish and strength. 

Key Application Details:

• Bedding: Kerbs are laid on a 100mm thick bed of compacted semi-dry concrete.
• Haunching: Concrete should be brought up the back of the kerb (haunching) to provide lateral support and prevent overturning.

Temperature: Do not install in temperatures below 3 degrees celsius on a falling thermometer or 1 degree celsius on a rising thermometer.