Does Concrete Have to Be Placed Within 90 Minutes?
No universal current ASTM C94 rule requires every ready-mixed concrete load to be discharged within 90 minutes. Since the 2021 edition, the applicable time limit is established for the project by the purchaser and producer or communicated by the producer.
What happened to the 90-minute concrete rule?
ASTM C94/C94M used to include a default requirement to complete discharge within 1-1/2 hours after mixing began. The 2021 revision replaced that default with a time limit established between the purchaser and concrete producer. If the purchaser does not select a limit, the producer communicates its limit and records it on the delivery ticket.
This change does not make delivery time irrelevant. It means a load should be evaluated against the applicable project limit and fresh-concrete requirements rather than rejected solely because a universal stopwatch passed 90 minutes.
What determines the concrete discharge limit?
| Condition | Why it matters | What to verify |
|---|---|---|
| Mixture | Different mixtures and admixtures retain workability and set at different rates. | The ordered mixture and producer delivery plan |
| Temperature and weather | Concrete temperature and ambient conditions affect slump retention and setting. | Weather plan and any specified temperature limits |
| Travel and site access | Long hauls, traffic, staging, and pumping affect the time available for discharge. | Expected route, access, truck spacing, and placement rate |
| Project specification | A project can establish its own time, revolution, testing, or acceptance requirements. | The contract documents and delivery ticket |
What should homeowners check on the delivery ticket?
Ticket fields vary with the producer and project, but the record can identify the batch time, ordered mixture, quantity, and applicable discharge limit. It may also document permitted water or admixture adjustments. Retaining the tickets creates a better project record than relying on memory after the pour.
A ticket does not prove that placement, consolidation, finishing, joints, or curing were correct. Read it alongside the written scope and the jobsite water guidance.
How should delivery delays be managed?
The contractor and producer should plan the mixture, truck spacing, crew, equipment, access, and weather response before placement. Approved water-reducing, workability-retaining, set-retarding, or hydration-controlling admixtures may be used when appropriate to the mixture and project.
Do not infer acceptance from appearance alone or assume that adding water is automatically prohibited. Any adjustment should remain within the ordered mixture limits, follow the producer and project requirements, and be documented. The responsible project party should decide whether delayed concrete remains acceptable.
What should the written scope say about concrete delivery?
- The ordered mixture and applicable project specification
- The discharge time or revolution limit and who establishes it
- Expected truck spacing, placement rate, access, and pumping plan
- Weather limits and permitted producer-authorized adjustments
- Delivery-ticket retention, testing, acceptance, and rejection responsibility
- The response to traffic, equipment failure, or other placement delays
Technical sources and limitations
- ACI Concrete Q&A: 90-Minute Rule for Ready Mixed Concrete
- NRMCA 2026 Guide to Improving Specifications for Ready Mixed Concrete
- NRMCA CIP 31: Ordering Ready Mixed Concrete
ASTM C94 establishes ready-mixed concrete requirements, but the contract documents, producer, purchaser, and responsible project professionals establish the applicable delivery and acceptance limits.