§ 11-125. Crushed stone base course.

(a)

The base material shall consist of a mixture of crushed stone and natural fines, and shall have a percent loss by the Los Angeles Test (AASHTO T 96) not greater than forty-five (45). The material shall contain no more than five (5) percent, by weight, of deleterious. The crushed stone base material shall meet the following gradation requirements:

Total Percent Retained by Weight

Size of Sieve	SB-2	SB-3
1″	0	0
¾″	10—50	40—35
#4	50—75	50—75
#40	70—90	70—90
#200	90—97	90—97

 

(b)

The fraction passing the No. 200 sieve shall not be greater than two-thirds ( 2/3 ) the fraction passing the No. 40 sieve. The fraction passing the No. 40 sieve shall have a LL not greater than 25 and a PI not greater than 6.

(c)

The depth of the crushed stone base course shall be within ½ inch of the required depth shown in Table 1. The average of all depth measurements shall not be less than the required depth shown in Table 1, and any depth in excess of the + ½ inch shall not be used in computing the average depth.

(d)

The base course shall be placed on an approved subgrade and spread uniformly in such a manner that no segregation of coarse and fine particles will occur. Under no circumstance shall the base course be placed on a frozen subgrade.

(e)

The base course shall be constructed in layers not exceeding eight (8) inches of compacted depth at substantially optimum moisture. The contractor must be capable of compacting the material at this depth, otherwise the material be placed and compacted in layers. The density of the compacted material in each layer, as determined by AASHTO T 191 or T 238, shall not be less than ninety-eight (98) percent of the maximum density obtained in the laboratory.

The laboratory density shall be obtained as follows: the sample is prepared by removing the aggregate retained on the three-fourths-inch sieve and adding passing aggregate passing the three-fourths-inch sieve and retained on the No. 4 sieve in an amount equal to that removed. The sample so prepared shall be compacted in five (5) equal layers in a cylindrical mold six (6) inches in diameter and seven (7) inches high. Each layer shall be compacted by fifty-five (55) blows with a ten-pound, two-inch diameter hammer dropped at a height of eighteen (18) inches. Trial sample specimens shall be molded at various moisture contents. The oven dry weight per cubic foot of material at optimum moisture content is termed the maximum density.

(f)

When stringlined, the surface shall be within ½ inch of the typical section shown in Appendix B.

(Ord. No. 91-9, Art. 1, § 4.06, 4-11-91; Ord. No. 99-32, Art. 1, 7-8-99)