How Long Can Concrete Stay in the Truck Before It Goes Bad?

How long can concrete stay in the truck before the load is no good? There is no single answer that fits every pour. The clock that matters is printed on your delivery ticket, and the concrete itself has the final say.

Is There a Set Time Limit for Concrete in the Truck?

There is no one universal number. For many years the industry benchmark was 90 minutes, measured from when water first meets the cement and aggregate to the end of discharge. A testing-lab review of the 2021 ASTM C94 changes reports that the standard removed that fixed default.

Since the April 2021 edition, the purchaser states the time limit when ordering. If the purchaser states none, the manufacturer sets one and tells the purchaser before delivery. Either way, the agreed limit is printed on the delivery ticket, and 90 minutes can still be chosen.

The same review notes the aim was not to lengthen or shorten the limit, only to drop the single default. The limit can be waived only if the concrete is still of such slump that it can be placed without adding water. Older descriptions of the rule also mention a cap on drum revolutions. Some state transportation specs still use 90 minutes for truck mixers, which is why the benchmark remains common.

How Delivery Timing Shapes Your Pour Schedule

Timing matters because the discharge clock runs per truck, not for the whole job. Spacing your loads to your crew’s placement speed keeps each truck from waiting past its limit. Our concrete truck calculator turns a volume into a load count and a schedule.

Take the tool’s default of 25 cubic yards with 10 percent waste, placed in 10 cubic yard trucks at 10 cubic yards per hour:

1. Add the waste. 25 x 1.10 = 27.5 cubic yards to deliver.
2. Count the trucks. 27.5 / 10 = 2.75, which rounds up to 3 trucks; the last load carries 27.5 – 20 = 7.5 cubic yards.
3. Space the loads. At 10 cubic yards per hour and 10 per truck, the loads arrive about 1 hour apart, for 2 hours 45 minutes of placement.

The discharge limit, commonly 90 minutes, runs for each load from when its water is added. So a slow crew, not just a long haul, can push a load toward its limit. If you are weighing delivery against mixing bags by hand, see ready-mix vs bagged concrete.

What Makes Concrete Go Off Inside the Drum?

Concrete goes off because cement reacts with water and slowly stiffens, a process called setting. One testing-lab review states that a typical mix of cement, fine and coarse aggregate and water starts to set between 60 and 120 minutes at 40 to 95 degrees F. The exact time depends on the cement, the water-cement ratio and the temperature.

Heat speeds everything up. NRMCA’s hot-weather guidance says higher temperatures accelerate slump loss and make concrete set quicker. A high concrete temperature also raises water demand, which can push up the water-cement ratio and lower strength.

Cold does the opposite. NRMCA’s cold-weather guidance gives a rule of thumb: a drop of 20 degrees F in concrete temperature roughly doubles the setting time. A longer set is not a free pass, so the slump still needs a check before the load is placed.

Can the Crew Add Water to a Stiffening Load?

Sometimes, within strict limits. NRMCA calls adding water to the mixed load on site retempering, and it is allowed only if the specified maximum slump or water-cement ratio is not exceeded. The added water must be measured and recorded on the delivery ticket.

That water can be trim water held back at the plant, or extra water the purchaser requests. Water beyond the design mix lowers strength and raises cracking risk. So if the purchaser asks for it, the purchaser takes responsibility for the result. A common field rule is about 1 gallon of water per cubic yard for each 1 inch of added slump.

Two more limits apply. No water is added once more than about a quarter of a cubic yard has been discharged, and the drum turns 30 more times at mixing speed after water goes in. Adding water in the drum is not the same as wetting the slab after the pour; for that, see curing new concrete.

How Admixtures Buy Time on a Long Haul

Admixtures, not extra water, are the planned way to manage a long trip. NRMCA lists water reducers, mid-range and high-range water reducers, set retarders and extended-set-control admixtures as tools to slow slump loss and control setting time.

These help most on long hauls and in high heat, where a load might otherwise stiffen before it reaches the forms. NRMCA names extended-set-control admixtures for long-haul deliveries and very high temperatures. The supplier adds them to the mix design, so the slump holds without breaking the water-cement ratio.

Ask about admixtures when you order, not when the truck is already stiff. NRMCA also advises scheduling deliveries to avoid delays, so trucks can discharge promptly once they arrive.

What to Ask Before and During Delivery

Ask about the discharge limit and the water plan before the first truck rolls. A short list keeps each load inside its limit and the concrete on spec.

• The ticket limit. Ask what discharge time limit is printed on the delivery ticket.
• Trim water. Ask how much water, if any, was held back at the plant.
• Authority. Agree who on site may request a water addition.
• Records. Have the slump checked on arrival and any added water recorded.
• Admixtures. Ask the supplier about admixtures for a long or hot-weather haul.

You can line up the loads and the paperwork with our concrete volume and ordering calculators.

FAQs About Concrete Delivery Time

Sources and Further Reading

The timing here comes from published standards and industry guidance, not from the calculator, which states no time limit. Read the discharge time on your delivery ticket and have the slump checked, because the right limit is the one on your order. Reviewed for accuracy by Prof. Dr. Khalil Mudassar, PhD. Last updated 2026-10-20.