Learn the essential steps for conducting a concrete slump test as per Philippine standards. This guide covers equipment, procedures, slump types, and tips to ensure accurate consistency and workability measurements for construction projects.
To improve and ensure accuracy, let’s align this explanation with the Philippine Standards for Concrete Slump Testing as outlined by the Philippine National Standards (PNS) and international standards such as ASTM C143/C143M. This is commonly followed in the construction industry to meet both local and international standards.
Philippine Standard for Concrete Slump Test (PNS ASTM C143/C143M):
The slump test in the Philippines
The same principles as ASTM C143/C143M, ensuring consistency in testing practices across regions. Here’s the detailed, standardized procedure as per Philippine standards:
Required Equipment:
1. Slump Cone (Abrams Cone): A metal cone with the following specifications:
Height: 300 mm (30 cm)
Bottom Diameter: 200 mm (20 cm)
Top Diameter: 100 mm (10 cm)
2. Tamping Rod: A steel rod with a diameter of 16 mm (5/8 inch) and a length of 600 mm (24 inches), rounded at the end to prevent concrete damage.
3. Measuring Scale: A ruler or scale to measure the slump in millimeters or centimeters.
4. Non-absorbent Base Plate: A solid, smooth, non-absorbent surface to place the cone on, ensuring consistent results.
Step-by-Step Procedure for the Slump Test:
The test should be conducted within five minutes of obtaining the concrete sample to maintain consistency and accuracy.
Step 1: Prepare the Slump Cone
Place the cone on the base plate in an upright position, ensuring it’s stable.
The interior of the cone should be dampened, but there should be no excess water.
Step 2: Fill the Cone in Three Layers
1. First Layer: Fill the cone with fresh concrete to one-third of its height (approximately 10 cm).
Compaction: Insert the tamping rod vertically, and rod the concrete 25 times. Ensure the rod penetrates the layer but does not touch the base plate.
2. Second Layer: Add concrete until the cone is two-thirds full (approximately 20 cm).
Compaction: Again, rod this layer 25 times, ensuring the rod penetrates slightly into the previous layer to compact the concrete properly and remove air pockets.
3. Third Layer: Fill the cone until it is level with the top.
Compaction: Rod the top layer 25 times, ensuring compaction while not disrupting the lower layers.
Step 3: Level the Concrete
After filling and compacting each layer, scrape off excess concrete at the top of the cone to make it level with the cone’s edge.
Step 4: Lift the Cone Vertically
Carefully lift the cone vertically in 5 to 10 seconds without any lateral or rotational movement. This ensures the concrete is undisturbed and allows it to slump naturally.
Any hesitation or jerky movement can affect the accuracy of the slump measurement.
Step 5: Measure the Slump
1. Position the Cone: Place the empty cone next to the slumped concrete sample.
2. Measure the Slump: Using the measuring scale, measure the distance from the top of the cone to the highest point of the slumped concrete. Record this as the slump value.
Slump Classification (Philippine Standards):
The measured slump indicates the workability and suitability of the concrete mix:
1. 0-25 mm (0-1 inch): Very low slump, very stiff mix, suitable for road construction or heavy foundations.
2. 25-75 mm (1-3 inches): Low slump, ideal for foundations with light reinforcement and roads.
3. 75-125 mm (3-5 inches): Medium slump, commonly used for standard beams, columns, and walls with moderate reinforcement.
4. 125-150 mm (5-6 inches): High slump, highly workable, suitable for structures with dense reinforcement such as beams and columns.
5. Greater than 150 mm (6 inches): Considered a collapse slump, generally indicates too much water or admixture, making the mix unsuitable for structural purposes.
Types of Slump and Their Implications:
1. True Slump: The concrete retains its shape and settles uniformly. This is typically desirable for structural integrity and indicates a balanced mix.
2. Shear Slump: The concrete slumps more to one side, indicating a potential inconsistency or low cohesion in the mix. It may require remixing or adjustment.
3. Collapse Slump: The concrete fully collapses, showing excessive water content or insufficient binding. This mix may be too fluid for construction use and needs adjustment.
Importance of the Slump Test:
The slump test helps verify that the concrete mix will be workable and appropriate for its intended structural application, as per Philippine construction standards:
High Slump: Easier placement and flow, suitable for dense reinforcement, but might compromise strength if excessively high.
Low Slump: Stiffer and harder to work with, usually used in structural elements needing high durability and strength.
Additional Philippine Standard Guidelines:
Temperature Control: Test the concrete in shaded conditions to minimize temperature impacts on workability.
Time Frame: The slump test should be completed within 5 minutes of sampling.
Sampling Frequency: On-site slump tests should be conducted regularly during the concrete pouring process to ensure mix consistency.
By following these detailed steps and adhering to Philippine standards, construction teams can ensure that the concrete used is both workable and strong enough for the specific project requirements.
