Field Testing of Fresh Concrete

Most decisions about concrete on a paving or structures job are made in the first half hour after a truck arrives. The fresh concrete is sampled and tested for temperature, consistency and air, and strength specimens are made that will be broken weeks later. These are the tests in the ACI Concrete Field Testing Technician certification and in state technician programs, and they are the basis of most concrete acceptance (Taylor et al., 2019¹).

This article gives the sequence and timing. The individual tests are described in their own articles:

• Sampling Freshly Mixed Concrete
• Air Content of Fresh Concrete
• Unit Weight and Yield of Fresh Concrete
• Making and Curing Concrete Test Specimens
• Concrete Batch Tickets and the Water–Cementitious Ratio
• Workability, which covers the slump test

Order and Timing

Fresh concrete changes quickly: it loses slump, its temperature drifts toward the air's, and air can be lost with handling. The sampling practice (AASHTO R 60, ASTM C172) therefore puts time limits on the work (Taylor et al., 2019¹):

1. Sample. Take the portions that make up the composite sample within 15 minutes of each other, then remix them.
2. Start the quick tests. Begin the temperature, slump and air tests within 5 minutes of getting the composite sample.
3. Start the specimens. Begin molding strength specimens within 15 minutes of getting the sample.

A practical order at the truck is temperature first (the thermometer can sit in the sample while other tests run), then slump and air together if two technicians are available, then unit weight (often in the base of the pressure air meter), then the cylinders or beams.

Temperature

Concrete temperature affects slump loss, setting time, strength gain and the risk of cracking. Specifications usually set a range at placement, for example 10 to 32°C (50 to 90°F), with tighter limits for hot or cold weather and for mass concrete.

The temperature test (AASHTO T 309, ASTM C1064) is simple: a calibrated thermometer, accurate to about ±0.5°C (±1°F), is pushed into the concrete so that at least 75 mm (3 inches) of concrete surrounds the sensing tip, left for at least two minutes or until the reading settles, and read in place. It can be run in the wheelbarrow, the sample container, or the placed concrete, and should be finished within 5 minutes of sampling (Taylor et al., 2019¹).

See Heat of Hydration and PCC Curing for why temperature matters after placement.

Slump

The slump test (AASHTO T 119, ASTM C143) is described in Workability. Slipform paving concrete is stiff, often 25 to 50 mm (1 to 2 inches) of slump, while structural concrete placed in forms is usually wetter. Slump is a check on consistency from load to load: a sudden change usually means a change in water, air or materials, and that load deserves a closer look.

Air Content

Entrained air protects concrete against freezing and thawing. Air is measured on every load or at a set frequency with the pressure meter, or with the volumetric meter where the aggregate is porous or lightweight. See Air Content of Fresh Concrete and PCC Durability.

Unit Weight and Yield

The unit weight (density) test is quick and often under-used. It checks the yield (whether the customer is getting the volume ordered), and a change in unit weight is an early sign of a change in air or water. See Unit Weight and Yield of Fresh Concrete.

Strength Specimens

Cylinders (for compressive strength) or beams (for flexural strength) are made from the same sample, left to set undisturbed, and moved to standard curing. How they are handled in the first day matters as much as how they are made. See Making and Curing Concrete Test Specimens, Compressive Strength and Portland Cement Flexural Strength.

The Batch Ticket

Before testing, read the ticket: the mix, the time batched, the water added at the plant and allowed on site, and the drum revolutions. It decides whether the load can be placed at all. See Concrete Batch Tickets and the Water–Cementitious Ratio.

Records

A complete field record for each sample includes the ticket number, the time sampled, the location of the placement, the air temperature, each test result, any water added at the site and by whom, and the specimen identification. Results that miss the specification should be reported to the person with authority to reject the load before it is placed, not after (Western Alliance for Quality Transportation Construction, 2025²).

Standard Test Methods

• AASHTO R 60, ASTM C172: Sampling freshly mixed concrete
• AASHTO T 309, ASTM C1064: Temperature of freshly mixed concrete
• AASHTO T 119, ASTM C143: Slump of hydraulic cement concrete
• AASHTO T 152, ASTM C231: Air content by the pressure method
• AASHTO T 196, ASTM C173: Air content by the volumetric method
• AASHTO T 121, ASTM C138: Density (unit weight), yield and gravimetric air content
• AASHTO R 100, ASTM C31: Making and curing concrete test specimens in the field

@misc{pavint-field-testing-of-fresh-concrete,
  author = {{Pavement Interactive}},
  title = {Field Testing of Fresh Concrete},
  year = {2026},
  publisher = {HeadLight},
  howpublished = {\url{https://pavementinteractive.org/reference-desk/testing/cement-tests/field-testing-of-fresh-concrete/}},
  note = {Accessed [date]}
}