Page 4 - ICJ Feb Openaccess 2026

POINT OF VIEW

REVOLUTIONIZING READY-MIX

CONCRETE: THE END OF THE

90 MINUTE RULE N. SUBRAMANIAN*

1. INTRODUCTION 3. THE DEMISE OF THE 90-MINUTE RULE
[3]
Traditionally, read-mix concrete (RMC) must be delivered within The 2020 edition of ASTM C94/C94M was the last to require
90 Minutes of mixing to ensure its quality and structural integrity. completion of discharge within 90 minutes after the start of
The transportation method that is chosen will depend on mixing. This requirement was replaced with the alternative of a
factors like location, project size, and environmental conditions. time limit established between the purchaser and the concrete
For general deliveries, truck mixers are the standard option. producer.
However, if you need to make adjustments on-site, volumetric [4]
mixers are a great choice. Effective transportation is crucial Below is the revised clause in ASTM C94/C94M-2021 :
as it helps minimize delays, reduces waste, and complies with Section 12.9: Discharge of the concrete shall be completed
appropriate standards for concrete quality. Proper planning within time limit as established in 6.1.10. This limitation may
and selecting the right equipment are essential to prevent
be waived by the purchaser if the concrete is of such slump or
mishandling and to ensure efficient delivery. slump flow after the specified time limit has been reached that it
The 90-Minute (1-1/2 hour ) rule is a time limit for delivering can be placed, without the addition of water to the batch.
RMC from the time it’s mixed to when it’s poured. The American The April 2021 revision to ASTM C94/C94M states in section
[4]
Society for Testing and Materials (ASTM) introduced the rule in 6.1.10 that the “Purchaser shall state a time limit from the start
the 1930s . Extending discharge times can provide significant of mixing defined in 12.3 or 12.5 to when the concrete discharge
[1]
economic and sustainable benefits.
must be completed. If no time limit is stated by purchaser,
manufacuturer prior to delivery. The time limit to complete
2. NECESSITY FOR THE 90 MINUTE-RULE discharge shall be stated on the delivery ticket.”

Establishing the time limit for delivering RMC is important It may be of interest to note that the ASTM C94/C94M [2,3] had
to produce good quality of concrete. There may be some always included an option for the purchaser to waive discharge
environments or concrete mixes where 90 Minutes-old limits for time and revolutions if the slump is satisfactory and
concrete may not be workable or suitable without some special water addition has not exceeded the quantity established by the
procedures or excessive addition of water. Whatever be the time concrete mixture design. This option has not changed with the
limit, the concrete quality must be acceptable to clients and revision to discharge limits; however, it has often been ignored,
[2]
meet their requirements. This rule by ASTM C94/C94M ensures resulting in the rejection of acceptable concrete based solely on
that the concrete remains workable and doesn’t set before it can exceeding the 90 Minutes time limit.
be poured, avoiding long delays in concrete placement.
This time limit is related to the quality of concrete. For example, 4. RETHINKING THE 90 MINUTE RULE: IS IT
mixtures designed for a low slump for slip-form construction STILL NECESSARY?
are generally not acceptable. at 90 minutes in hot weather
conditions without special precautions. Delivery time for RMC can vary significantly depending on
distance, placement methods, and ambient conditions. The
Those following this rule rejected the concrete that hadn’t been previous default limit of 90 minutes may not be suitable for
poured within 90 minutes of adding water to the mix. However, every mixture or scenario. Advances in admixture technology
the 90-Minute limit may be extended to 120 minutes if no water now allow for extended delivery times–well beyond 90 minutes–
is added after 90 minutes and the concrete temperature is less which can be particularly beneficial in remote regions or
than 90°F. metropolitan areas where heavy traffic delays concrete delivery.

THE INDIAN CONCRETE JOURNAL | FEBRUARY 2026 7
* Corresponding author: N. Subramanian, Email: drnsmani@gmail.com