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Slump Test Calculator

More slump is not better — 40 mm separates a pumpable mix from a bleeding one.

Also known as concrete slump · slump cone test · slump test procedure

Quick answer

With the default inputs: Target slump 120 mm · Maximum aggregate size 20 mm · Air entrainment Non air-entrained etc.Water demand 200 kg/m³

Use your own dimensions ↓

Inputs

Result

Water demand
200kg/m³
EN 206 slump classS3 (flowing, 100-150)
Base water (75-100 mm)190kg/m³
Slump correction5%
Water demand200kg/m³
Water per extra 25 mm6.0kg/m³
Binder at w/b 0.50401kg/m³
PumpabilitySuitable for pumping
How this is worked out

Slump measures softness, not quality. A wetter mix is not a better mix — it is simply more water, and more water means less strength. Every extra 25 mm of slump needs about 3% more water, roughly 6 kg/m³, which either costs 12 kg more cement at constant w/b or drops the strength; each 0.01 of w/b is worth about 1.5 to 2 MPa at 28 days. Adding water on site to make the mix work therefore trades strength for feel: 20 kg into an 8 m³ truck moves w/b from 0.50 to 0.51 and loses 2 MPa, one whole grade. The proper fix is a superplasticiser, which cuts water 10 to 20% at the same slump and raises strength instead. The pumping window is narrow: below 100 mm the line resists and blocks, above 200 mm the aggregate segregates and bleeding causes more blockages, not fewer. Between 120 and 180 mm is the stable range, and air entrainment or fly ash widens it further.

Next up: Concrete Volume Calculator · Concrete Mix Design Calculator

Formula

Base waterACI 211.1 Table 6.3.3 by maximum size: 207 at 10 mm, 190 at 20 mm, 166 at 40 mm
Slump correctionw = wbase × [1 + 0.03(slump − 75)/25]
Sand correctionabout ±2% per 0.1 of fineness modulus (empirical)
Air entrainmentair-entrained mixes use ×0.89 (ACI Table 6.3.3 air column)
Slump classEN 206 / GB/T 14902: S1 10-40, S2 50-90, S3 100-150, S4 160-210, S5 ≥220 mm
120 mm target slump, 20 mm aggregate, non air-entrained, fm 2.6: base water 190 kg/m³, a 5% slump correction, 200 kg/m³ actual, EN 206 class S3, suitable for pumping, and about 400 kg/m³ of binder at a 0.50 water-binder ratio.

Basis

FAQ

What slump is acceptable?
It depends on use and code. EN 206 has five classes: S1 at 10 to 40 mm for foundations and mass pours, S2 at 50 to 90 mm for ordinary beams and slabs, S3 at 100 to 150 mm for congested reinforcement or pumping, S4 at 160 to 210 mm for high-rise pumping and S5 above 220 mm for self-compacting. GB/T 14902 uses the same S1-S5 classes, and pumped work in practice sits at S3-S4, that is 120 to 180 mm. What matters most is consistency: scatter beyond 30 mm points to batching or moisture control problems.
Why is adding water on site not allowed?
Because it raises the water-binder ratio directly and strength falls with it — about 1.5 to 2 MPa per 0.01 of w/b. Twenty kilograms into an 8 m³ truck takes w/b from 0.50 to 0.51 and loses roughly 2 MPa, turning C30 into something that may fail as C28. Adding water also improves slump without improving cohesion, so the mix bleeds, segregates and blocks the pump more readily. The right move is a superplasticiser slurry at the same mix proportions, or reject the load.
How does spread differ from slump?
Slump measures vertical deformation, spread measures lateral flow, which is what matters in highly fluid mixes. Ordinary concrete at 100 mm slump spreads to about 350 mm; beyond 220 mm slump the cone test itself stops discriminating because the mix collapses as a mass, so spread takes over — typically 550 to 650 mm for SF1 and 660 to 750 mm for SF2. Self-compacting concrete also needs T500 (2 to 5 seconds) and a V-funnel time.
What slump does pumping need?
100 to 200 mm is stable, with 120 to 180 mm the sweet spot. Below 100 mm line resistance grows and blocks appear at bends and vertical runs; above 200 mm the aggregate settles, paste rises, mortar runs ahead at bends and the aggregate arches — which blocks more often, not less. So “wetter pumps better” is backwards. What actually matters is cohesion and water retention, which fly ash, slag or a viscosity modifier improve far better than water ever will.

What to calculate next

These jobs are done back to back on site — follow the steps to work through the whole sequence.

Concrete: strength to workabilityStep 3 of 4

  1. 1Water Cement Ratio Calculator
  2. 2Concrete Mix Design Calculator
  3. 3Slump Test Calculator
  4. 4Concrete Strength Acceptance Calculator

Cite this page

Use this format in reports, method statements or coursework. The link is permanent.

Building Calculator. Slump Test Calculator. 2026-10-25. https://jianzhujisuan.com/en/slump-test

Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.