How to choose the right chippings grade for your concrete mix

Choosing an aggregate grade is a balance between workability, strength and cost. The right size depends on what you are building, the reinforcement spacing and the finish you need. Here is a practical guide for common jobs.

What aggregate size should I use for structural concrete?

For most reinforced concrete — columns, beams and suspended slabs — 14mm to 20mm chippings are the usual choice. The aggregate should be no larger than about a quarter of the smallest section and should clear the reinforcement comfortably. For mass concrete with wide sections, 25mm aggregate is economical.

When should I use quarry dust instead of chippings?

Quarry dust is a fine aggregate. It is used in blockmaking, screeds and as a fill or blinding layer, and it can partly replace sand in some mixes. It is not a substitute for coarse chippings in structural concrete, where you need the larger angular particles for strength.

How does aggregate grade affect strength and cost?

Larger aggregate needs less cement paste for the same volume, so it can be more economical for mass pours. Smaller chippings give a finer finish and suit congested reinforcement but use more paste. Matching the grade to the job avoids both weak concrete and wasted cement. All rates shown on this site are indicative — confirm by quote.