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QC acceptance

Acceptance criteria.

The numbers that decide whether a delivery is accepted or rejected — fresh-concrete tolerances, strength acceptance, discharge window, mass-concrete temperature.

IS 516:2021 + IS 456:2000

Four numbers decide each load.

The rules of acceptance are defined by IS 516:2021 (testing) and IS 456:2000 (compliance). Kalokhe RMC works to tighter internal limits than the standards require, so every dispatched load starts with margin on its side.

01 Workability slump · flow
02 Discharge window batching → truck → chute
03 Temperature ≤ 32 °C standard · ≤ 26 °C mass
04 Strength 7 d & 28 d cubes
Spec sheet

The four numbers, side by side.

Slump tolerance
± 25 mm
OR ± 1/3 of specified slump — whichever is lower. Examples: 60 mm → ±20 mm; 100 mm → ±25 mm; 150 mm → ±25 mm.
Flow (SCC)
± 80 mm
For a 600 mm specified flow, the acceptable range is 520 – 680 mm. Run the J-ring test in parallel for aggregate blocking.
Discharge window
≤ 180 min
From batching to start of discharge per IS 516:2021. Reduce in hot weather; extend only when retarder design and tests allow.
Mass concrete
≤ 26 °C
Pour temperature cap for mass concrete (≤ 32 °C for normal members, ≥ 5 °C minimum). Reduce via chilled water / GGBS blends.
Tolerances

Acceptable ranges at a glance.

How the four limits translate into minimum and maximum bound values.

Lower bar 75 mm slump = 100 ± 25 mm. Flow bounds 520 – 680 mm. Discharge 0 – 180 min. Normal delivery temperature 5 – 32 °C. Mass-concrete ≤ 26 °C.

IS 456:2000

Compressive-strength acceptance.

Group result · ≥ 4 samples Mean and individual
  • Mean of 4 consecutive samples ≥ fck + 0.825 σ (σ from ≥ 30 prior samples)
  • OR Mean ≥ fck + 3 MPa if σ is not established
  • AND every individual sample ≥ fck − 3 MPa (or 0.85 fck when fck < 20)
Individual result · < 4 samples Single sample rule
  • Each sample ≥ fck + 4 MPa
  • For fck < 20 MPa: sample ≥ fck + 0.825 σ
  • Average of two cubes from the same sample constitutes one test result
Reject

Four grounds for rejection.

Any one of these conditions means the load is rejected at site — Kalokhe RMC replaces rejected trucks at no charge.

Time exceeded Discharge window > 180 min From batching to start of discharge — IS 516:2021 limit, tighter in hot weather.
Temperature exceeded > 32 °C normal · > 26 °C mass Out of tolerance at delivery — heat is one of the largest strength-killers on a hot pour.
Segregation Visible aggregate separation Coarse piles to one side, paste runs free, the mix has lost homogeneity — placement will create rock pockets.
Workability outside ±tolerance Slump · flow outside limits Outside ±25 mm / 1/3 of specified slump, or ±80 mm flow. Retempering on site is not permitted.
Pre-pour

Pre-acceptance checklist.

Before acceptance At the chute.
  • Challan matches order — grade, slump, admixture spec.
  • Truck within batching-to-discharge window.
  • Slump test passes tolerance; record value.
  • Concrete temperature within limit.
  • Visual check — no segregation, bleeding, or foreign matter.
  • Cubes cast per sampling frequency.
Records to keep Documentation.
  • Delivery challan — signed at site.
  • Slump and temperature record card.
  • Cube-casting register — date, location, grade, sample ID.
  • 7-day and 28-day cube test reports.
  • Rejection reports if any — with photographs.
  • Site engineer signature on every record.

Questions about an acceptance decision?

Our QC team is on call during every pour to read results live and assist with rejection or rework decisions.

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