Professional Concrete Workability & Compliance Tester 2026
Slump test per BS EN 12350-2 measures concrete workability indicating consistency suitable for placement method and reinforcement congestion. S1-S4 classes define slump ranges with specified tolerances ensuring batch compliance throughout delivery window. True slump indicates uniform deformation while shear/collapse slumps signal segregation requiring immediate mix rejection preventing structural quality compromise.
Consistence tolerance varies by class: S1 permits 0-60mm range, S2 30-110mm, S3 80-170mm, S4 140-230mm reflecting production variability inherent ready-mix operations. Target slump specifications apply ±30mm ≤40mm, ±40mm 50-90mm, ±50mm ≥100mm providing flexibility matching site placement requirements while maintaining quality control standards.
Standard slump cone dimensions 300mm height, 100mm top diameter, 200mm base filled three equal layers compacted 25 strokes each layer using 16mm diameter 600mm tamping rod. Cone lifted vertically 5-7 seconds measuring subsidence nearest 5mm from original 300mm height. Base plate ensures level non-absorbent surface preventing moisture absorption affecting measurement accuracy.
Three-layer compaction simulates full batch consolidation eliminating air voids representative placed concrete. Rod diameter and stroke count standardized ensuring repeatable results across operators sites maintaining compliance verification consistency throughout construction operations critical path activities.
S1 (10-40mm) suits dry hard mixes roads pavements requiring high compaction energy. S2 (50-90mm) standard reinforced concrete foundations beams columns normal vibration. S3 (100-150mm) pumped concrete congested reinforcement medium pumping pressures. S4 (160-210mm) high workability self-compacting concrete complex formwork eliminating vibration requirements.
Test validity limited 10-210mm range outside producing unreliable indications. Slump <10mm indicates very low workability suitable slip-form paving. Slump >210mm risks segregation collapse invalidating structural concrete applications requiring batch rejection quality control intervention.
| Class | Slump Range (mm) | Max Deviation |
|---|---|---|
| S1 | 10-40 | 0-60 |
| S2 | 50-90 | 30-110 |
| S3 | 100-150 | 80-170 |
| S4 | 160-210 | 140-230 |
| Target Slump | Tolerance | Typical Use |
|---|---|---|
| ≤40mm | ±30mm | Roads/Pavements |
| 50-90mm | ±40mm | Reinforced Concrete |
| ≥100mm | ±50mm | Pumped/SCC |
UK/Europe standard defining procedure, tolerances, equipment specifications ensuring consistent workability assessment.
Standard dimensions 100/200mm diameters filled three layers 25 strokes each ensuring representative compaction.
True slump uniform deformation acceptable, collapse indicates segregation requiring batch rejection immediately.
50-90mm typical reinforced concrete normal vibration foundations beams columns most applications.
Test reliable only within range, extremes produce unreliable indications unsuitable structural concrete.
Maximum delivery/placement time typical ready-mix maintaining workability compliance throughout operations.
S2 class 50-90mm permits 30-110mm maximum deviation ensuring batch acceptance despite production variability. This range accommodates normal ready-mix tolerances maintaining structural quality throughout delivery placement window critical path construction activities.
True slump shows uniform top subsidence acceptable workability while collapse indicates segregation excessive water requiring batch rejection. Shear slump intermediate condition usually retest confirming true slump preventing structural quality compromise.
Pumped concrete typically specifies S3 100-150mm ensuring flow through pipes without blockage while preventing segregation. Higher S4 occasionally used long-distance pumping maintaining workability throughout delivery maintaining quality vertical rise applications.
Three equal layers compacted 25 strokes each using 16mm diameter 600mm tamping rod simulates full batch consolidation. Each layer represents one-third volume ensuring air void elimination representative placed concrete performance accurately.
Slump >210mm produces collapse unreliable measurement indicating segregation risk unsuitable structural applications. Batch rejection required preventing porous weak concrete compromising long-term durability loadbearing capacity essential quality control.
Low slump <10mm indicates stiff mix high aggregate content low water-cement ratio suitable pavements roads. Insufficient admixture dosage aggregate moisture absorption also reduces slump requiring water adjustment maintaining specified workability class.
First truck each class change subsequent every 50m³ or two-hour period ensures consistency throughout production. Spot samples initial discharge verify compliance before placement preventing quality variations compromising structural integrity safety.
Higher temperatures accelerate setting reduce workability requiring admixture dosage increase maintaining specified slump. Cold weather extends workability permitting longer placement times essential large pours maintaining consistency throughout operations.
For testing equipment, visit Controls Group | ELE International | For standards, check The Concrete Centre