To determine the percentage of undesirable particles in the fine aggregate fraction used in the design of Portland cement concrete mixes. This method is also applicable to determine the relative proportions of harmful fine dust or clay-like materials in soil.
Tools and Materials
The sand equilibration test kit includes the following:
- graduated plastic cylinder
- rubber stopper
- irrigation hose
- Weighted leg assembly and siphon assembly
- 78-liter (1 gallon) bottle
- About 57 mm (2. in) in diameter and 85 ± 5 ml. four measuring tins with a capacity of
- stop the clock
- Mechanical Sand Equivalent Shaker
- stock calcium chloride solution
- 75-mm (No. 4) Sieve
- fine aggregate
- Prepare fine aggregates prior to testing by using a 4.75-mm (US Standard No. 4) sieve, oven-dried and passing room temperature conditions. Approximately 1500 grams divided by quarter. Wet each sample slightly to prevent loss of fines, and mix each sample thoroughly. Place each of the four samples in a closed compartment.
- Siphon 101.6 ± 54 mm (4 ± 0.1 in) of a working calcium chloride solution into a plastic cylinder. Pour one of the prepared samples into a plastic cylinder using a funnel to avoid spillage. Tap the bottom of the cylinder sharply with your hand to release any air bubbles. Let the ingredients stand for about 10 minutes.
- Place the stopper on the cylinder and shake it vigorously by hand to loosen the contents. Place the cylinder in the mechanical sand-equivalent shaker, set the timer, and let the machine run for 45 seconds. Remove the cylinder from the mechanical shaker, remove the stopper, and set it upright on the table.
- Insert the irrigator tube into the cylinder and wash off the contents from the bottom surface. Force the irrigator through the material to the bottom of the cylinder by applying a gentle stabbing and twisting action, while the working solution flows through the tip of the irrigator. This action causes fine particles to flow into suspension over the size of coarse sand. Continue this irrigation process until the cylinder is filled to the 381 mm (15 in) mark.
- Slowly raise the irrigator without turning off the flow so that the liquid level remains at about 381 mm (15 in) when irrigating. Control the flow and adjust the final level to 381 mm (15 in) just before the irrigation is completely withdrawn.
- The effluent is supplied through a siphon assembly into a 3.78-liter (1 gallon) bottle of calcium chloride solution placed on a shelf approximately 1 m (3 ft ± 1 in) from the work surface. Now let the cylinder stand for 20 minutes without moving it. Begin timing immediately after withdrawing the irrigator tube. At the end of 20 min of sedimentation, read and record the top of the soil suspension. it is referred to as soil reading, If no clear demarcation line is drawn at the end of the 20-minute period, let the cylinder stand until a soil reading is obtained.
- Quickly read and record the level of the top of the soil suspension and the total suspension time. If the total sedimentation time exceeds 30 min, run the test again on other prepared samples of the same material. Read and record only the soil column height of the sample requiring the shortest sedimentation period.
- After taking the clay readings, place the weighted foot assembly into the cylinder and slowly lower it until it comes to the top of the sand. Be careful not to hit the cylinder mouth with the weighted foot assembly. Tip the assembly toward the graduation on the cylinder until the indicator touches the inside wall of the cylinder. Subtract 25.4 cm (10 in) from the level indicated by the extreme top edge of the indicator and record it as sand reading, Never pressurize the assembly.
Report the result as a percentage, always equal to sand (From) to the next higher whole number (don’t use any decimals). If more than one SE test is performed, for each test sample take the average of each whole number value to the next higher whole number. Use 2.5 mm (0.1 in) as the smallest unit for the reading, and always use a higher graduation if the reading falls between one-tenth of an inch. Calculate the sand equivalent to the nearest 0.1% using the following formula:
From,Sand Reading/Soil Reading)*100%
The SE value of the cleaner aggregate will be higher. Specifications generally demand a minimum SE on the order of 25 to 35%.