Concrete Slump Test (ASTM C143/C143M / EN 12350-2): Procedure, Values and What They Mean

The concrete slump test measures the consistency of fresh concrete as the distance a molded sample subsides after a 305 mm (12 in.) cone is lifted, under ASTM C143/C143M-26b in the US and EN 12350-2:2019 in Europe. The slump test, also called the slump cone test or Abrams cone test, gives the first number a producer reads after an admixture, a mineral addition or a fiber goes into a batch. A water reducer, a slag cement and a steel fiber each move that number, so the slump is the first field check of every one of the concrete additives in a mix.

ASTM C143/C143M-26b treats slumps from 15 to 230 mm (1/2 to 9 in.) as meaningful: below that range concrete may not be adequately plastic, above it not adequately cohesive. Inside the range, admixtures rather than water move the slump, since NRMCA CIP 26 puts the water route at about 5 L/m³ (1 gal/yd³) for each 25 mm (1 in.).

European specifications order concrete by class, from S1 at 10 to 40 mm (0.4 to 1.6 in.) to S4 at 160 to 210 mm (6.3 to 8.3 in.), and UK designated concretes default to S3 (BRMCA 2020). At equal water, a normal-range water reducer adds 60 to 100 mm (2.4 to 3.9 in.) of slump (CAA ATS 1) and a superplasticizer more than 120 mm (4.7 in.) (CAA ATS 2). Between 50 and 80 mm, two operators testing the same concrete can differ by up to the reproducibility limit of 25 mm (1.0 in.) set in EN 12350-2:2019, so a single reading is judged against a tolerance window rather than a single number.

Each value is traced to its source: standards and codes to their issuing body, product values to the data sheet named with them, prices to the dated source beside them (methodology and fact-checking).

The table below sums up the concrete slump test in eight attributes.

What Is the Concrete Slump Test?#

The concrete slump test is the field and laboratory check of consistency, which ACI CT-25 defines as the degree to which a freshly mixed concrete ... resists deformation, read as the subsidence in mm (in.) of a cone-molded sample. ASTM C172/C172M-25, active since 2025-10-10, governs the sampling, and the same composite sample serves the other fresh concrete tests run on a delivery, from air content to strength specimens, as set out under fresh concrete tests.

Time limits frame the test from the moment of sampling. The AASHTO R 60 field procedure requires a sample of at least 0.03 m³ (1 ft³) and 1.5 times the volume the tests need, with every increment of the composite sample taken within 15 minutes, and the slump test started within 5 minutes of obtaining the sample. In the UK, BRMCA (2020) lists 8.5 L (2.2 gal) of concrete for a slump test.

What slump measures and what it does not#

Slump measures consistency only: ASTM C143/C143M-26b Note 2 states that in the laboratory slump generally increases with water content and is inversely related to strength, but that in the field the relation is not clear or consistent. A high field slump therefore says nothing reliable about the strength a batch reaches, and cylinders or cubes answer that question.

Consistency is one part of a wider property. ACI CT-25 defines workability as the property of freshly mixed concrete that determines the ease with which it can be mixed, placed, consolidated and finished to a homogenous condition. Slump is one measure of that property, alongside the Vebe (EN 12350-3), degree of compactability (EN 12350-4) and flow table (EN 12350-5) tests, and the levers that move it are compared under concrete workability.

Where the slump test applies: aggregate size and slump range#

The slump test applies to plastic, cohesive concrete with coarse aggregate up to 37.5 mm (1-1/2 in.) and slumps of 15 to 230 mm (1/2 to 9 in.) under ASTM C143/C143M-26b. Particles above 37.5 mm are removed by the large-aggregate procedure of ASTM C172 before the test, and the method does not apply to non-plastic and non-cohesive concrete. Below 15 mm (1/2 in.) the concrete may not be adequately plastic, and above about 230 mm (9 in.) it may not be adequately cohesive (Note 3). EN 12350-2:2019 sets a narrower window: the test is sensitive between 10 and 210 mm (0.4 and 8.3 in.), unsuitable where the slump keeps changing 1 minute after the cone is withdrawn, and not suitable for a maximum aggregate size above 40 mm (1.6 in.). Self-compacting concrete lies beyond both windows and is measured by its spread, not by its drop.

Which Standards Govern the Slump Test?#

Three test methods and one class system govern the slump test: ASTM C143/C143M-26b and its AASHTO counterpart T 119-23 in the US, EN 12350-2:2019 in Europe, and the EN 206 consistence classes that turn a reading into a specified class. The US and European methods share the cone, the three layers and the 25 rod strokes per layer. They differ in lift time, reading point, resolution and valid range, and the table below compares the two methods item by item.

Admixture classes behind these tests: ASTM C494 chemical admixtures types.

ASTM C143/C143M-26b and AASHTO T 119#

ASTM C143/C143M-26b, "Standard Test Method for Slump of Concrete", is the active US edition, last updated on 2026-08-06. The current title is shorter than that of ASTM C143/C143M-20, which read "Standard Test Method for Slump of Hydraulic-Cement Concrete".

Subcommittee C09.60 of ASTM Committee C09 maintains the method, which sits in Book of Standards volume 04.02. The ASTM C143/C143M-26b catalogue record lists an edition run from C143-78 through the 2000, 2003, 2005, 2008, 2009, 2010, 2012, 2015 and 2020 editions to three editions in 2026 (-26, -26a and -26b). AASHTO T 119-23 is the AASHTO counterpart, and field technicians run it to the WAQTC field operating procedure, reprinted in the Alaska DOT testing manual of 2026, which supplies the step values on this page.

EN 12350-2:2019 and what changed from the 2009 edition#

EN 12350-2:2019 superseded EN 12350-2:2009 under CEN/TC 104, with national adoption due by December 2019. The four changes of the 2019 edition are listed below.

• Editorial revision of the whole text.
• Common apparatus moved to EN 12350-1, the part that also covers sampling.
• A slump retention procedure added to the method.
• An option to report the result as the specified class or target.

EN 12350-2 is part 2 of a 12-part series: part 1 sampling and common apparatus, part 3 Vebe, part 4 degree of compactability, part 5 flow table, part 6 density, part 7 air content by the pressure method, and parts 8 to 12 for self-compacting concrete (slump flow, V-funnel, L-box, sieve segregation and J-ring). The European admixture standard sets its slump rules for superplasticizers in EN 934-2:2009+A1:2012 Table 3.2, covered under EN 934-2 admixture requirements.

How Is a Concrete Slump Test Performed?#

A slump test fills a 305 mm (12 in.) cone in three layers of 25 rod strokes each, lifts it in 5 ± 2 s and finishes within 2-1/2 minutes of the start of filling (AASHTO T 119 procedure). EN 12350-2:2019 allows a lift of 2 to 5 s and 150 s from the start of filling to the removal of the cone.

Apparatus: the Abrams cone, tamping rod and base#

The Abrams cone is an open frustum with a 203 mm (8 in.) base, a 102 mm (4 in.) top and a height of 305 mm (12 in.) (ACI CT-25). The tamping rod is 16 mm (5/8 in.) in diameter and 400 to 600 mm (16 to 24 in.) long with a hemispherical tip (AASHTO T 119 procedure). After the lift, the rod laid across the inverted mold marks the original height for the reading.

Slump test procedure step by step#

Seven steps make up a slump test to ASTM C143/C143M-26b and the AASHTO T 119 procedure.

1. Start the test within 5 minutes of obtaining the sample.
2. Fill the cone to about 67 mm (2-5/8 in.) and rod this first layer 25 times.
3. Fill the cone to about 155 mm (6-1/8 in.) and rod the second layer 25 times, each stroke penetrating about 25 mm (1 in.) into the layer below.
4. Overfill the cone with the third layer and rod it 25 times, again about 25 mm (1 in.) into the layer below.
5. Lift the cone 300 mm (12 in.) in 5 ± 2 s with no lateral or torsional motion.
6. Measure the slump to the nearest 5 mm (1/4 in.) from the bottom of the rod to the displaced original center of the top of the specimen.
7. Complete the whole operation, from the start of filling to the removal of the mold, within 2-1/2 minutes.

Measuring and reporting the slump#

The two methods read different points: the US procedure measures to the displaced original center of the specimen top, to the nearest 5 mm (1/4 in.), and EN 12350-2:2019 to its highest point, to the nearest 10 mm (0.4 in.). In the US procedure the distance runs from the top of the mold, taken as the bottom of the rod laid across it. EN 12350-2:2019 defines the slump as the difference between the cone height and the highest point of the slumped specimen. Since the 2019 edition, the European result may also be reported as the specified class or target.

What Are Normal Slump Values and Classes?#

The right slump is the one the specification sets: European specifications order concrete by slump class, from S1 at 10 to 40 mm (0.4 to 1.6 in.) to S4 at 160 to 210 mm (6.3 to 8.3 in.). US project specifications state a target slump instead, and ASTM C94/C94M-26c, the US ready-mix specification maintained by Subcommittee C09.40, holds delivered concrete to a tolerance around it.

The class or target follows the placement, and the published slumps by placement further down show how far apart placements sit, from about 40 mm (1.5 in.) on low-cracking bridge decks to 225 mm (9 in.) in mass concrete with a high-range water reducer.

EN slump classes S1 to S5#

Four EN 206 slump classes carry ranges as used in BS 8500-1 (Concrete Society): S1 10 to 40 mm, S2 50 to 90 mm, S3 100 to 150 mm and S4 160 to 210 mm, with S5 above S4. The table below compares each class range with the spot-sample limit that BRMCA (2020, Table B.1) applies to concrete from the initial discharge.

The slump test itself is valid for 10 to 210 mm (EN 12350-2:2019).

Standard designated concretes in the UK are supplied at S3 by default (BRMCA 2020). The current EN 206 edition, EN 206-1:2026 (CEN approval 2026-01-19), places its consistence classes in clause 5.2.1. The class values of that clause are not reproduced here: the 2026 clause text has not been checked against the ranges above, and exposure classes and the other rules of the standard are covered under EN 206 concrete specification.

Slump tolerance on delivered concrete#

A target slump carries a tolerance of ±30 mm (1.2 in.) up to 40 mm, ±40 mm (1.6 in.) at 50 to 90 mm and ±50 mm (2.0 in.) from 100 mm (Concrete Society, BS 8500-1 basis). The tolerance applies to a spot sample taken from the initial discharge. Specifying by class works differently: the class range sets the intended consistence and BRMCA (2020, Table B.1) sets the wider spot-sample limits shown in the class table, for example 80 to 170 mm (3.1 to 6.7 in.) for an S3 concrete.

US tolerances on delivered slump sit in ASTM C94/C94M-26c, active since 2026-08-12, and in the project specification. The C94 tolerance values, hold time and jobsite-water clauses are not reproduced here: they have been checked only against an earlier edition of the specification, not against the active one.

Slump chart for concrete by placement#

Published slumps by placement range from about 50 mm (2 in.) for mass concrete without a high-range water reducer to 175 to 225 mm (7 to 9 in.) with one (PCA EB547). The table below compares published slumps by placement, each with its named source.

Published values from named sources, not limits.

The LC-HPC window comes from the Kansas low-cracking bridge-deck program, which pairs it with a w/c of 0.43 to 0.45 and discourages high-range water reducers (HPC Bridge Views No. 55, 2009). For slipform paving, the CP Tech Center (April 2017) names two alternatives: the Box test, a vibrated 0.03 m³ (1 ft³) form inspected for voids and edge slump, and the V-Kelly test, a 13.6 kg (30 lb) Kelly ball with a vibrator.

How Do Admixtures, Mineral Additions and Fibers Change the Slump?#

At equal water, a normal-range water reducer adds 60 to 100 mm (2.4 to 3.9 in.) of slump (CAA ATS 1) and a superplasticizer more than 120 mm (4.7 in.) (CAA ATS 2). Mineral additions and fibers move slump in both directions: slag cement lowers the water needed for a given slump, while metakaolin and steel fibers lower the slump itself. Water reducers, superplasticizers and workability-retaining products belong to the 12 groups of concrete admixtures in ACI PRC-212.3-16.

The table below compares each additive's effect on slump with its value, basis and source type.

Doses convert to batch quantities with the admixture dosage calculator.

Dispersing admixtures: slump gain at equal water#

EN 934-2:2009+A1:2012 Table 3.2 requires a superplasticizer to raise slump by at least 120 mm (4.7 in.) from an initial (30 ± 10) mm ((1.2 ± 0.4) in.) at equal water-cement ratio. The flow-table alternative is an increase of at least 160 mm (6.3 in.) from (350 ± 20) mm ((13.8 ± 0.8) in.). In both cases the consistence 30 minutes after addition must not fall below the initial consistence of the control mix, and the same table sets 28-day strength at no less than 90 % of the control and air content at no more than 2 percentage points above it.

ACI PRC-212.3-16 Table 1.2 describes high-range water reducers (ASTM C494 Type F or G) as reducing water content by at least 12 to 40 percent and as increasing slump, decreasing placing time and increasing flowability. NRMCA CIP 26 states that using a water reducer or superplasticizer to raise slump usually will not significantly alter concrete properties, provided segregation is avoided.

Slag, metakaolin and steel fibers#

Slag cement, metakaolin and steel fibers each shift slump by a published amount, listed below with the source of each value.

• Slag cement lowers water demand by up to 5 % for a given slump (Slag Cement Association, Info Sheet 2); grades and replacement levels are covered under slag cement (GGBS).
• Metakaolin lowers slump by about 30 % at a 15 % metakaolin content (Brooks et al. 2000, reviewed in ADOT SPR-780, 2025); reactivity and replacement levels are covered under metakaolin in concrete.
• Steel fibers lower consistence by about one class, a slump 25 to 45 mm (1.0 to 1.8 in.) lower, at 20 to 40 kg/m³ (34 to 67 lb/yd³) of concrete, a manufacturer statement in the ArcelorMittal WireSolutions FAQ; types and dosage are covered under steel fibers for concrete.

None of the three values is a standard requirement, and a trial batch with the actual materials shows the slump a given mix reaches.

Slump retention over time#

Slump loss is the amount by which slump changes during a period after an initial slump test (ACI CT-25). BRMCA (2020) notes that fresh concrete may lose up to 25 % of its workability in the first hour after batching. Haul time, temperature and slump loss are managed with water reducers, workability-retaining and retarding admixtures instead of jobsite water, a central part of planning concrete workability for ready-mix deliveries.

Two European standards address retention directly. EN 934-2:2009+A1:2012 Table 3.2 requires a superplasticized mix to hold, 30 minutes after addition, a consistence not below the initial consistence of the control, and EN 12350-2:2019 added a slump retention procedure to the test method itself.

ACI PRC-212.3-16 Table 1.2 describes workability-retaining admixtures as giving slump retention in combination with a normal-, mid- or high-range water reducer, with no effect on initial slump, set time or strength gain. US specifications list them as ASTM C494 Type S workability-retaining admixtures (NRMCA 2PE004-26, March 2026).

How Do You Read a Slump Test Result?#

A slump result counts only when the specimen subsides as a true slump; a specimen that shears off or falls away is discarded (AASHTO T 119 procedure). A valid result is then compared with the class limits or the target tolerance, and the gap between two results is judged against the precision of the method.

True slump versus shear slump#

A shear slump is a decided falling away or shearing off of a portion of the specimen, and the US procedure disregards it and runs a new test on another portion of the sample. Two consecutive shear results mean the concrete itself lacks the plasticity and cohesiveness the test needs. EN 12350-2:2019 likewise reports only a true slump. A mix that cannot hold together in the cone has a cohesion problem, and segregation and its mix fixes are covered under bleeding and segregation in concrete.

Precision: how far two slump results can differ#

EN 12350-2:2019 gives a repeatability limit r of 16 mm (0.6 in.) and a reproducibility limit R of 25 mm (1.0 in.) for single slump results between 50 and 80 mm. The repeatability limit applies to two results from one operator on the same concrete, the reproducibility limit to results from different operators, and the standard deviations behind them are 5.8 mm and 9.0 mm. For the mean of duplicate tests the limits fall to r 11 mm (0.4 in.) and R 22 mm (0.9 in.). The values come from a UK experiment of 1987 with 16 operators, ordinary portland cement and Thames Valley aggregates, so they describe concrete in that slump band.

Worked example, calculated from the EN 12350-2:2019 precision and the Concrete Society tolerance: a target of 70 mm (2.8 in.) carries the ±40 mm (1.6 in.) tolerance, so the acceptance window runs from 30 to 110 mm (1.2 to 4.3 in.) and is 80 mm (3.1 in.) wide. The reproducibility limit R of 25 mm (1.0 in.) is 31 % of that window (25 / 80 = 0.31), and the repeatability limit r of 16 mm (0.6 in.) is 20 % (16 / 80 = 0.20). A reading within 25 mm (1.0 in.) of either edge of the window therefore sits inside the scatter expected between two testers.

What Goes Wrong in Slump Testing on Site?#

Six errors spoil slump results on site, and five of them break a timing, handling or range limit that the test method itself sets. The six errors and their fixes are listed below.

1. Start the test within 5 minutes of obtaining the sample; the AASHTO R 60 procedure sets that limit for slump and air.
2. Lift the cone 300 mm (12 in.) in 5 ± 2 s with no lateral or torsional motion, never fast, slow or twisted.
3. Remove aggregate above 37.5 mm (1-1/2 in.) with the large-aggregate procedure of ASTM C172 before filling the cone.
4. Discard readings outside 15 to 230 mm (1/2 to 9 in.) as a measure of consistency (ASTM C143/C143M-26b Note 3).
5. Raise slump with an admixture, not with water: NRMCA CIP 26 puts the water route at about 5 L/m³ (1 gal/yd³) for each 25 mm (1 in.), and jobsite water rules are covered under admixtures in ready-mix concrete.
6. Test strength with cylinders or cubes, not with the cone; ASTM C143/C143M-26b Note 2 finds the field relation between slump and strength not clear or consistent.

Automated slump systems move part of the check into the truck: NRMCA notes that ASTM C94 recognizes systems that estimate slump in the mixer and add water or admixtures, with records.

Which Other Tests Run Alongside the Slump Test?#

The slump test shares its sample with other fresh concrete checks, and five related tests cover what the cone cannot see. The five tests are listed below.

• Sampling under ASTM C172/C172M-25 comes first, with every increment of the composite sample taken within 15 minutes; the order of testing is set out with the other fresh concrete tests.
• Air content testing chooses its consolidation by slump: rodding above 75 mm (3 in.), rodding or vibration at 25 to 75 mm (1 to 3 in.) and vibration below 25 mm (1 in.) (AASHTO procedure); the methods are compared under air content tests.
• Slump flow replaces the drop with a spread for self-compacting concrete under ASTM C1611/C1611M-21 and EN 12350-8; the spread and its companion tests are covered under SCC fresh tests (slump flow, J-ring, L-box, V-funnel).
• Setting time under ASTM C403/C403M-23 applies to concrete with a slump greater than zero; set and admixture effects are covered under setting time of concrete.
• Vebe (EN 12350-3), degree of compactability (EN 12350-4) and flow table (EN 12350-5) measure consistence by other means and complete the picture of concrete workability.

Concrete slump test FAQs#

Six questions about the concrete slump test are answered below.

What does a concrete slump test measure?#

A concrete slump test measures consistency, the degree to which fresh concrete resists deformation, as the subsidence in mm (in.) of a cone-molded sample (ACI CT-25). It does not measure strength: ASTM C143/C143M-26b Note 2 finds the field relation between slump and strength not clear or consistent.

What is a good slump for concrete?#

A good slump is the class or target the specification sets for the placement; UK designated concretes default to S3, 100 to 150 mm (3.9 to 5.9 in.) (BRMCA 2020). That target comes out of concrete mix design, and the methods that set it are covered under concrete mix design.

How many types of slump test are there?#

Three standardized slump methods are in use: ASTM C143/C143M-26b (with AASHTO T 119-23), EN 12350-2:2019 and, for self-compacting mixes, the slump-flow test (ASTM C1611/C1611M-21, EN 12350-8). In the first two, only a true slump counts as a result.

What are the dimensions of a slump cone?#

A slump cone has a 203 mm (8 in.) base, a 102 mm (4 in.) top and a 305 mm (12 in.) height (ACI CT-25). The tamping rod is 16 mm (5/8 in.) in diameter and 400 to 600 mm (16 to 24 in.) long (AASHTO T 119 procedure).

Does a higher slump mean weaker concrete?#

Not necessarily: in the laboratory slump rises with water content and strength falls, but ASTM C143/C143M-26b Note 2 says the field relation is not clear or consistent. An admixture raises slump without adding water, by 60 to 100 mm (2.4 to 3.9 in.) for a normal-range water reducer (CAA ATS 1).

Does the slump cone work on very fluid mixes?#

No: above about 230 mm (9 in.) concrete may not be cohesive enough for a valid slump (ASTM C143/C143M-26b), so flowing and self-compacting mixes are measured by slump flow. The spread test covers self-compacting concrete (SCC) with coarse aggregate up to 25 mm (1 in.) (ASTM C1611/C1611M-21).