What Is the Slump Test?
The slump test is a simple and widely used field test to measure the consistency and workability of fresh concrete before it sets. The test is standardized as ASTM C143/C143M – Standard Test Method for Slump of Hydraulic-Cement Concrete.
Test Procedure:
Fill a slump cone (300 mm high, 100 mm bottom diameter, 200 mm top diameter) in three equal layers with concrete.
Each layer is tamped 25 times with a steel rod.
After filling, the cone is lifted vertically upwards.
The concrete will “slump” or settle down.
The vertical distance between the height of the cone and the highest point of the slumped concrete is measured as the slump value (in mm or inches).
Purpose:
To indicate the workability and fluidity of the mix.
To check batch-to-batch consistency on site.
Not a direct measure of quality or strength, but poor slumps can indicate problems in water-cement ratio or mix uniformity.
Suitable Slump Values for Various Concrete Elements (Based on ASTM & ACI Recommendations)
| Concrete Application | Recommended Slump |
|---------------------------------------|-----------------------|
| Mass Concrete (e.g., foundations, gravity dams) | 25–50 mm (1–2 in.) |
| Beams and Slabs (with vibration) | 50–100 mm (2–4 in.) |
| Columns, Walls, Footings (light reinforcement) | 75–100 mm (3–4 in.) |
| Columns, Walls (heavy reinforcement, pump placement) | 100–150 mm (4–6 in.) |
| Concrete to be pumped | 100–150 mm (4–6 in.) |
| Slip-formed or pavement concrete | 25–75 mm (1–3 in.) |
| Precast or Architectural Elements | 50–100 mm (2–4 in.) |
| Highly Flowable or Self-Consolidating Concrete (SCC) | Not applicable (use spread test) |
Note:
Actual slump required is determined by project specifications, method of placement, reinforcement congestion, and weather.
Consult project engineer or local code for specific requirements.
Slump Test According to ASTM
The test must be conducted according to ASTM C143/C143M.
Temperature, ambient conditions, and consistent sampling are important for reliable results.
Abnormally high or low slumps should trigger a review of water content, admixtures, or mixing time.
Summary Table
| Element | Recommended Slump (mm) | Recommended Slump (in.) |
|----------------------------|---------------------------|-----------------------------|
| Mass Concrete | 25–50 | 1–2 |
| Beams, Slabs | 50–100 | 2–4 |
| Reinforced Walls/Columns | 75–100 (light reinforcement)
100–150 (heavy/pumped) | 3–4 / 4–6 |
| Pumped Concrete | 100–150 | 4–6 |
| Pavement, Slip-formed | 25–75 | 1–3 |
| Precast/Architectural | 50–100 | 2–4 |
For more technical information, admixtures, or site support in Iran, consult :
Clinic Beton Iran | https://www.clinicbeton.com
RBS-CONTECH International Brand | https://www.rbs-contech.com