07/08/2025
Slump Test for Fresh Concrete – Complete Notes
📌 1. What is a Slump Test?
The slump test is a simple, quick field method used to measure the consistency or workability of fresh concrete. It assesses how easily the concrete flows and its suitability for placement and compaction.
🎯 2. Purpose – Why is it Performed?
To assess the workability of concrete.
To detect variation in water-cement ratio or mix uniformity.
To verify batch quality before placing concrete.
To ensure compliance with project specifications and consultant approvals.
To determine suitability for pumping and placing in reinforced sections.
📍 3. Where is it Conducted?
At batching plant: To check consistency before dispatch.
At construction site: On every truck prior to pouring.
At critical concrete pours such as:
Base Slabs
Walls and Columns
Suspended Slabs
Foundations and Raft
Tunnel and Infrastructure elements
📅 4. When is it Required?
During trial mixes and mix approvals.
At the start of each major pour.
For each delivery truck or every 50 m³ of concrete (as per project QC plan).
When a change is suspected in:
Mixing method
Temperature
Admixture dosage
🛠️ 5. How is the Slump Test Performed?
Apparatus Required:
Slump Cone (300 mm high, 200 mm bottom dia, 100 mm top dia)
Tamping rod (16 mm diameter, 600 mm length, bullet end)
Flat steel base plate
Ruler or scale (at least 300 mm)
Test Procedure (as per ACI 211 / BS EN 12350-2):
1. Place the slump cone on a flat, moist, rigid surface.
2. Fill concrete in three equal layers.
3. Tamp each layer 25 times using the rod.
4. Strike off excess concrete to level the top.
5. Lift the cone vertically in 5–10 seconds without disturbing.
6. Measure the slump as the difference in height from the top of the cone to the displaced concrete's highest point.
📊 6. Types of Slump and Interpretation:
Slump Type Description
True Slump: Even vertical settlement – indicates cohesive, workable mix
Shear Slump: One side shears off – indicates lack of cohesion
