Ready-Mix Concrete Acceptance Criteria

IS 4926:2003 · IS 4926 — Ready-Mixed Concrete & IS 456 Cl. 16.1 — Acceptance Criteria

Complete acceptance criteria for ready-mixed concrete at site. Covers delivery ticket verification, slump testing, transit time limits, cube casting frequency, and strength acceptance rules per IS 4926 and IS 456.

IS 4926 →

22 items shown

Delivery Checks

Verify before unloading each transit mixer at site

Check	Requirement	Tolerance	If Failed
Delivery ticket / challan	Must accompany every transit mixer and state: batch time, grade, mix design reference, slump ordered, volume, batch plant address	No tolerance — mandatory document	Do not accept concrete without a valid delivery ticket
Grade ordered vs delivered	Grade on ticket must match site order (e.g., M30, M40)	No tolerance — exact match required	Reject the load; do not use higher or lower grade as substitute without engineer's approval
Volume delivered	Actual volume must match ordered quantity within tolerance	±3% by volume	Record shortage; raise claim with RMC supplier
Batch time vs arrival time	Note exact time of batching (from ticket) and arrival at site	Transit time ≤ 2 hours from batching	Reject if transit time exceeds 2 hours; concrete may have started initial set
Drum revolution counter	Total drum revolutions from batching to discharge must not exceed 300	Max 300 revolutions total	Reject concrete — over-mixing causes segregation and loss of workability
Seal / lock on water tank	Water tank on transit mixer must be sealed to prevent unauthorised water addition	Seal must be intact	If seal is broken, reject the load — water may have been added in transit (retempering)

Slump & Workability Tests

Slump test per IS 1199 — at point of discharge before placing

Check	Requirement	Tolerance	If Failed
Slump test for ordered slump ≤ 75 mm	Measured slump must be within ±25 mm of ordered value	±25 mm	Reject if outside tolerance; record and report to supplier
Slump test for ordered slump 75–100 mm	Measured slump must be within ±25 mm of ordered value	±25 mm	Reject if outside tolerance
Slump test for ordered slump > 100 mm	Measured slump must be within ±25 mm of ordered value	±25 mm	Reject if outside tolerance
Slump testing frequency	Test every transit mixer load at site	—	No test = no acceptance — insist on testing every load
Visual check for segregation	Concrete must appear uniform with no separation of paste and aggregate	No visible segregation or bleeding	Reject load; segregated concrete cannot be re-mixed
Shear slump or collapse slump	Slump cone must give a true slump (not shear or collapse)	If shear slump occurs, re-test with fresh sample	Repeated shear slump indicates poor mix design — reject and report

Strength Acceptance (IS 456 Cl. 16.1)

Cube strength acceptance based on 28-day compressive strength results

Check	Requirement	Tolerance	If Failed
Cube casting frequency	Minimum 1 sample per 25 m³ or part thereof	1 sample = 3 cubes (150 mm)	If frequency not maintained, quality records are considered incomplete
Individual test result (3-cube average)	≥ fck − 3 MPa	No individual result shall fall below this	Investigate — may require core testing of structure (IS 456 Cl. 17.4)
Mean of 3 consecutive results (M20 and above)	≥ fck + 0.825σ or ≥ fck + 4 MPa, whichever is higher	σ = standard deviation from 30+ results; use assumed σ if < 30 results	Non-compliant — review mix design, increase cement content, or change supplier
Mean of 3 consecutive results (below M20)	≥ fck + 4 MPa	—	Mix design to be revised by supplier
Core test (if cubes fail)	Core strength ≥ 0.85 × fck	Average of 3 cores ≥ 0.85 × fck; no individual core < 0.75 × fck	If cores also fail, structural assessment required — may need strengthening or demolition

Temperature & Time Limits

Transport and placing temperature requirements for RMC

Check	Requirement	Tolerance	If Failed
Concrete temperature at discharge	Measure with stem thermometer at point of discharge	5°C to 40°C (normal range); preferred ≤ 30°C in hot weather	Reject if outside 5–40°C range
Transit time — normal weather	≤ 2 hours from time of adding water to cement	No extension without retarder	Reject concrete exceeding 2 hours transit
Transit time — hot weather (> 35°C)	≤ 1 hour recommended; max 1.5 hours with retarder	Use retarding admixture per IS 9103	Reject if workability is lost even within time limit
Placing time after discharge	Place within 30 minutes of discharge from transit mixer	No holding in chutes or pumps beyond 30 min	Discard concrete that has been standing for > 30 min after discharge
Retempering with water	Not permitted under any circumstances	Zero tolerance	Reject immediately — water addition alters w/c ratio and destroys mix design

Notes

• Retempering (adding water at site to increase slump) is strictly prohibited by IS 4926. Only addition of superplasticiser by trained RMC technician is permitted for slump recovery.

• Pump line losses: expect 25–50 mm slump loss through the pipeline. Order slump 25 mm higher than required at point of placing when using a boom pump.

• Rejection protocol: rejected loads must be documented with ticket number, reason, time, and photographed. Notify RMC supplier immediately and confirm in writing.

• For structural concrete, insist on RMC plants certified under IS 4926 with current BIS licence. Uncertified plants may not follow proper batching and QC procedures.

• Cube moulds must be oiled and kept on a level vibration-free surface. Cubes should be covered with wet cloth within 30 minutes of casting.

• Maintain a concrete register at site recording: date, structural element, grade, ticket number, supplier, transit mixer number, slump, temperature, cube IDs, and acceptance/rejection status.

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