312.1 312.3(a)
312.1DESCRIPTION —This work is construction of a dense graded stone, gravel, or slag base course,
uniformly premixed with a predetermined quantity of water. When placed on subgrade, it includes the preparation of subgrade, as specified in Section 210.
312.2MATERIAL —
courses. Acceptable granulated blast -furnace slag, as specified in Section 350.2, meeting the gradation requirements specified in Table A, may be used.
the final compacted mixture meets the specified gradation within limits of the reviewed job -mix formula.
Add sufficient water to the mixture to provide optimum moisture content at the time of compaction. Do not vary this quantity by more than 2 percentage points from the optimum moisture, as determined according to PTM No. 106, Method B.
To maintain specified criteria throughout the progress of work, at least twice daily analyze samples of the completed mixture taken at the plant or after spreading. Unsatisfactory results or changes in the supply source may require a change in the JMF. The supply source may be changed, if allowed . Maintain accuracy of control so at least 90% of test samples fall within the tolerance limits of Table A. Remove and replace material failing to meet this requirement.
TABLE A COMPOSITION OF MIXTURE (Weight Percent Passing Square Openings Based on Laboratory Sieve Tests)
SIEVE SIZE PERCENT PASSING TOLERANCE LIMITS OF THE APPROVED JMF 2 inches 100 3/4-inch 52-100 ± 8% 3/8-inch 36-70 ± 8% No. 4 24-50 ± 6% No. 16 10-30 ± 6% No. 200 0-10 ± 3%
312.3CONSTRUCTION —
Measure the coarse and fine material separately, by either volume or weight, and feed into the mixer 312.3(a) 312.3(g) a metering device, and u niformly distribute in the mix. Use mixing plants equipped with automatic cutoff devices, which stop the feed to the mixer if delivery of any component of the mix stops. P