Test for Clay Lumps and Friable Particles

Purpose

Clay and friable particles may be present in the form of lumps in natural aggregates. If they are near the surface, these lumps can cause pitting under the influence of traffic. Specifications frequently limit these particles to a maximum of 1%.

Equipment and Materials

• 称重装置精确为0.1％
• Flat pans for spreading the test specimens in a thin layer
• Sieves as called for in the Testing Procedure
• 干燥烘箱能够保持110°±5°C（230°±9°F）的自由循环空气温度
• Required amount of Test samples

测试程序

1. 试验样品应根据ASTM指定制备：C 117，并在110°±5°C（230°±9°F）下干燥后，应包括以下数量：细骨料应包括保留在a上的粒子1.18毫米（No.16）筛和重至少为25克。粗料大小和每个样本的最小量如下：

Size of Particles Making Up Test Sample	Minimum Weight of Test Sample in Grams
4.75 to 9.5 mm (No. 4 to 3/8 inch sieves)	1000
9.5 to 19.0 mm (3/8 to .3/4inch sieves)	2000
19.0 to 37.5 mm (3/4 to 1.5 inch sieves)	3000
Retained on 37.5 mm (1.5 inch sieve)	5000

where the test sample consists of both fine and coarse aggregates, the material is separated on a 4.75-mm (No. 4) sieve. The fine and coarse fractions are then handled as above.

2. The weighed specimens are spread in a thin layer on the bottom of a container and covered with distilled water for about 24 hours.
3. Roll and squeeze the individual particles between the thumb and forefinger. Try to break down the particles but only with the thumb and forefinger. Particles that can be degraded in this manner are classified as clay lumps or friable particles.
4. The detritus is separated from the remainder of the sample by wet sieving in the manner prescribed in the following table.

Size of Particles Making Up Test Sample	Size of Sieve for Removing Residue Particles
Fine Aggregate	850 μm (No. 20)
4.75 to 9.5 mm (No. 4 to 3/8 inch)	2.36毫米（8号）
9.5 to 19.0 mm (3/8 to 3/4 inch)	4.75 mm (No. 4)
19.0 to 37.5 mm (3/4 to 1.5 inches)	4.75 mm (No. 4)
Over 37.5 mm (1.5 inches)	4.75 mm (No. 4)

Agitate the sieve during the wet sieving operation to assure removal of all undersized particles.

5. Remove the retained particles and dry to a constant weight in the oven at a temperature of 110°±5°C (230°±9°F). Allow the aggregates to cool and weigh to nearest 0.1%.

Calculations

P = [(W − R)/W] × 100

P = % of clay lumps and friable particles

W =测试样品的重量

R = weight of particles retained on the designated sieve in wet sieving

粗骨料,Pshall be based upon the weighted average of the clay lumps and friable particles in each sieve size fraction. Any coarse aggregate fraction that is less than 5% of the total gradation shall not be tested separately. That coarse aggregate fraction shall be assumed to contain the same percent of clay lumps and friable particles as that found in the next larger or smaller coarse aggregate fraction.