HomeMy WebLinkAboutCT 00-06; BRESSI RANCH; LABORATORY BULK DENSITY TEST RESULTS; 2004-09-15C-r 00
Leighton and Associates, Inc.
A LEIGHTON GROUP COMPANY
September 15, 2004
Project No. 971009-019
To: Lennar Communities
1525 Faraday Avenue, Suite 300
Carlsbad, California 92008
Attention: Mr. Jim Urbina
Subject: Laboratory Bulk Density Test Results of the Asphalt Concrete Cores Obtained
along Cottage Drive and a portion of Paradise Road, Planning Area PA-7, Bressi
Ranch, Carlsbad, California
References: Carlsbad, City of, 1996, Standards for Design and Construction of Public Works
Improvements in the City of Carlsbad, California, Project No. 05332-12-01, dated
April 20, 1993, revised December 10, 1996
Caltrans, 1992, Standard Specifications, July 1992
This letter presents the results of the laboratory bulk density tests performed on the asphalt
concrete (AC) cores obtained along Cottage Drive and a portion of Paradise Road within Bressi
Ranch Planning Area PA-7 located in Carlsbad, California. The coring of the streets was
performed on August 31, 2004 due to prior nuclear gauge field density testing that indicated the
AC might have been compacted to less than the minimum required 95 percent relative
compaction per the City of Carlsbad specifications.
A total of 15 random cores were obtained along the roadway alignments. Bulk density tests of
the AC cores were performed in accordance with Caltrans test Method CT-308. The results of
the laboratory tests are presented in Table 1.
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971009-019
Table 1
Laboratory AC Bulk Density Test Results
Sample
Number
Core Location Core Thickness
(inches)
Bulk Density
(pcf)
Relative
Compaction
C-i Cottage Sta. 1+37 (right side) 2-1/2 144.0 97
C-2 Cottage Sta. 1+60 (right side) 3 146.6 98
C-3 Cottage Sta. 3+50 (right side) 1-7/8 153.9 100
C-4 Cottage Sta. 4+23 (left side) 3-1/8 148.9 99
C-S Cottage Sta. 4+85 (right side) 2 147.2 99
P-i Paradise Sta. 10+05 (right side) 2-3/4 146.5 98
P-2 Paradise Sta. 9+10 (left side) 2-1/2 144.8 97
P-3 Paradise Sta. 8+85 (left side) 2-3/4 148.0 99
P-4 Paradise Sta. 8+25 (right side) 2-3/4 149.8 100
P-5 Paradise Sta. 7+30 (left side) 2-3/4 147.2 97
P-6 Paradise Sta. 7+05 (right side) 1-7/8 144.2 97
P-7 Paradise Sta. 6+30 (right side) 2-3/8 144.1 97
P-8 Paradise Sta. 5+30 (center) 2-1/2 143.8 96
P-9B Paradise Sta. 5+10 (left side) 3 151.4 100
P-10 Paradise Sta. 3+05 (right side) 1-7/8 145.2 97
As indicated in Table 1, the bulk densities of the AC Cores indicated the cores met the minimum
95 percent relative compaction required by the City of Carlsbad. Although the relative
compactions obtained by the nuclear gauge indicated densities less than the required 95 percent
relative compaction Leighton, 2004), the bulk density test results of the AC cores are considered
to be more accurate. Therefore, from a geotechnical standpoint, it appears that the AC base
course has been placed and compacted to a minimum relative compaction of 95 percent (in
accordance with the Hveem method) as required by the City of Carlsbad.
It appears that the relatively low density test results obtained by the nuclear gauge may have
been caused by a number of reasons. They include: 1) the depth that the nuclear gauge
determines the density of the tested material (the nuclear gauge reads to a depth of 2.5- to 3-
inches and since the aggregate base material densities on are on the order of 130 psf or less and
the AC density is in the high 140's, the actual AC densities will be higher than what the gauge
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971009-019
reads); and 2) void spaces(or irregularities) on the upper and lower surfaces of the AC (the void
spaces will greatly affect the nuclear gauge density values but not the core densities due to the
bulk density testing method that includes coating the surface of the core with paraffin which
effectively eliminates the surface voids). The variations of the core bulk densities (including the
results that are higher than the reported Hveem density of the AC samples) are likely due to
variations in the amount of aggregate in each core (areas containing more aggregate will have
higher bulk densities due to the higher specific gravity of the aggregate).
If you have any questions regarding this letter, please do not hesitate to contact this office. We
appreciate this opportunity to be of service.
Respectfully submitted
LEIGHTON AND ASSOCIATES, INC.
W, - Ran4LQ 1 . Wagner, CE 1612
Director of Geology
Distribution: (4) Addressee
(2) City of Carlsbad, Public Works Department, Attention: Mr. Casey Arndt
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