Scope of Application

This method is applicable to the determination of the content of cohesive soil or impurities in fine aggregates, thereby assessing the cleanliness of the aggregate; the sand equivalent is denoted by SE.

This method is applicable to natural sand, manufactured sand, and stone chips used in asphalt mixtures and cement concrete, provided that the maximum aggregate size does not exceed 4.75 mm (5 mm on a round-hole sand sieve).

Sample Preparation

Pass the sample through a 4.75 mm aperture sieve (5 mm round-hole sieve) to remove the coarse fraction retained on the sieve, ensuring that the sample mass is not less than 150 g. If the sample is excessively dry, moisten it slightly with a small amount of water before sieving. When using a rubber-tipped hammer to break up soil clods and inadvertently entrapping unseparable impurities within the coarse fraction, such impurities shall be washed away, and the recovered fine particles shall be returned to the sample.

Determine the moisture content of the test specimen; during both the moisture-content determination and the sampling tests, the test specimen must not lose any moisture. Since the specimen has been moistened with water, its moisture content shall be determined in accordance with the current method for moisture-content determination, with the result expressed as the average of two determinations and accurate to 0.1%. Test specimens that have undergone moisture-content determination shall not be used for subsequent testing.

Weigh the wet mass of the sample, and based on the determined moisture content w, calculate the wet mass m₁ of the sample equivalent to 120 g of dry sample, accurate to 0.1 g.

SE=120×(100+W)/100

In the formula: W — Moisture content of the aggregate sample, %

m₁—mass of the moist sample in grams, corresponding to a 120 g dry sample.

Chemical reagent preparation ：

Preparation of High-Concentration Calcium Chloride Solution

Prepare the solution by mixing anhydrous calcium chloride (in grams) with distilled water (in milliliters) at a ratio of 1:2. Calcium chloride is exothermic upon dissolution, causing the solution temperature to rise; after allowing the solution to cool to room temperature, filter it through filter paper to remove insoluble impurities, and then store the filtered solution for later use. The resulting solution contains 410 g/L of calcium chloride.

Anhydrous calcium chloride, 111 ± gl, analytical grade, 96% purity.

Glycerol: 480 ± 5 g, analytical grade, 98% purity.

Formaldehyde: 12–13 g, analytical grade, 36% concentration.

Preparation of 1 L of concentrated solution:

① Use a graduated cylinder to measure 272 mL of high-concentration calcium chloride solution.

② Weigh out 484.8 g of glycerol.

③ Weigh out 13.6 g of formaldehyde.

④ Transfer the above three reagents into a 1-L graduated cylinder, and rinse the containers that held the three reagents three times each with small amounts of distilled water, collecting the rinse water in the graduated cylinder each time. Finally, add distilled water to the 1-L mark.

⑤ Pour the prepared 1 L solution into a 2 L graduated cylinder, mix thoroughly, and transfer to a sealed container for storage as the concentrated stock solution for the experiment.

Take 125 ± 1 mL of the concentrated solution for testing and transfer it into a 5-L plastic bucket; then dilute it with distilled water to a final volume of 5 ± 0.005 L.

Test Procedure

Use the flushing tube to draw the flushing solution into the test cylinder until it reaches the 100 mm mark at the bottom (approximately 80 ml of flushing solution is required).

Carefully pour the wet sample, weighing 120 g ± 1 g of dry material, into the upright test cylinder using a funnel.

Repeatedly tap the lower part of the test cylinder with the palm of your hand to remove air bubbles and ensure rapid wetting of the sample, then allow it to stand for 10 minutes.

Allow to stand for 10 minutes. Upon completion, insert the rubber stopper into the test cylinder, then hold the cylinder horizontally with your hand and perform shaking—using only wrist motion, without swinging the entire arm—maintaining an amplitude of 230 ± 25 mm. Shake for 30 ± 1 seconds, completing a total of 90 cycles. Finally, place the cylinder vertically on the test bench and unscrew the rubber stopper.

Insert the rinsing tube into the test cylinder, use the rinsing solution to flush off the aggregate adhering to the cylinder wall, then gradually lower the rinsing tube to the bottom of the cylinder while slowly rotating it. Simultaneously raise the rinsing tube at a uniform and slow rate to bring suspended fine soil particles and impurities from the aggregate surface to the surface of the solution until the solution reaches the 380 mm mark.

Withdraw the flushing tube from the liquid surface so that the liquid level reaches the 380 mm mark, then shut off the flow in the flushing tube and start the stopwatch. Allow the system to stand undisturbed for 20 ± 15 seconds.

7. After allowing the mixture to stand for 20 minutes, use a ruler to measure the height (H₁) from the bottom of the test cylinder to the liquid surface above the flocculent precipitate; if possible, also measure the height (H₂) from the bottom of the test cylinder to the sediment layer, accurate to 1 mm.

8. Slowly lower the weighted piston into the test cylinder until it contacts the sediment, then tighten the sleeve screw. Align the zero mark of the scale with the bottom surface of the piston, read the sediment height H₂ from the top of the sleeve to the nearest 1 mm, and record the temperature inside the test cylinder to the nearest 1°C.

9. Conduct parallel tests on two test specimens according to the above steps.

Result Calculation

1. Sand equivalent value of the specimen: SE = h₂/h₁ × 100

In the formula: SE – Sand Equivalent of the specimen

h₂—height of the aggregate sediment in the test cylinder as measured with a piston

h₁--Total height of flocculent flocs and precipitates in the test cylinder

2. Visual sand equivalent of the specimen: SEV = h′₂/h₁ × 100

In the formula: SEV is the visual sand equivalent of the test specimen.

h₁—Total height of flocculent flocs and precipitates in the test cylinder, in mm

Visual height of the aggregate sediment in the h′₂ test cylinder, in mm

3. Aggregate shall be tested in duplicate in parallel. The sand equivalent (SE) or SEV of the aggregate is the average of the two parallel determinations, with the value obtained by the piston method taken as the final result and reported as an integer.

For specific procedures, refer to the “Fine Aggregate Sand Equivalent Test” section of T0334-94 in the Ministry of Transport’s Industry Standard, “Test Procedures for Aggregates in Highway Engineering,” JTJ0.8-94.

Note: During installation of the counterweight piston, the distance from the bottom of the piston to the bottom of the counterweight shall be maintained at 430 ± 1 mm.

Packing List

Test cylinder, one piece

One rubber clamp tube

One counterweight piston

One flushing pipe

Siphon tube, one

One instruction manual

One certificate of conformity

All other test equipment, instruments, and reagents required for the tests shall be provided by the applicant.