Part 4 covers the mechanical strength of aggregate: aggregate crushing value (ACV), aggregate impact value (AIV), ten percent fines value, and abrasion resistance (Los Angeles / Deval). These hardness/toughness indices matter most for pavement, wearing-surface and high-strength concrete — weak aggregate caps concrete strength and abrades out of pavements regardless of the paste.
Key Requirements
•Aggregate crushing value (ACV) / ten percent fines value — resistance to crushing under load
•Aggregate impact value (AIV) — resistance to sudden shock (pavement aggregate)
•Abrasion resistance (Los Angeles abrasion / Deval) — wear resistance for pavements/wearing surfaces
•Judge against IS 383 / IRC limits for the application (stricter for pavement & high-grade concrete)
✓For pavement-quality and high-strength concrete, weak aggregate — not the paste — often governs: a soft aggregate cannot make a strong, abrasion-resistant concrete.
✓ACV/AIV/LA limits are stricter for pavement and high-grade work; using ordinary-limit aggregate there is a hidden non-compliance.
Common Mistakes
⚠Ignoring aggregate strength/abrasion for pavement or high-grade concrete.
⚠Applying ordinary-concrete limits to pavement/wearing-surface aggregate.
⚠Assuming a strong paste compensates for weak aggregate (it does not).