El plan de manejo

This research was divided into three phases. The phase I testing was used to determine the number of freeze-thaw cycles that will cause the equivalent damage to

AASHTO T283 specimens for different methods of compaction and specimen sizes. A phase II sensitivity study considered the effects of moisture conditioning and test temperature on dynamic modulus testing. Phase II testing of mixes for moisture damage used the results of Phase I for the AASHTO T283 testing on 150mm specimens and the results of Phase I and Phase II for dynamic modulus and AASHTO T283 testing. In the following sections, the mixture and laboratory testing experimental plans are outlined.

3.1.1 Phase I Testing – Sensitivity Study

The experimental plan considered different mix types, aggregate sources, laboratory test systems, conditioning approaches, and test specimen size. The experimental plan included two integrated plans: one for the mixes and one for the planned laboratory tests. A sensitivity study considering the effects of specimen size and compaction method was

performed on a limited number of mixes to determine the amount of conditioning that should be done on larger Superpave compacted specimens. Table 3.1 below outlines the executed sensitivity experimental plan.

Table 3.1 Sensitivity Experimental Plan for Mix and Aggregate Types

≤ 3,000,000 >3,000,000

Limestone - M50 Dundee Gravel - M21 St. Johns

Limestone - BL96 Howell Limestone - I-196 Grand Rapids

Gravel - M21 Owosso Slag/Gabbro - I-75 Clarkston

PHASE 1 MOISTURE

Traffic Level (ESAL)

25.0 or 19.0 Limestone - M59 Brighton

12.5 or 9.5 NMAS (mm)

Table 3.2 outlines the laboratory test plan that was executed for the sensitivity study. As previously mentioned, this plan partially duplicates the work done and reported in NCHRP 444 (Epps et al. 2000). Twenty specimens per project per compaction method/diameter size were produced. This resulted in a total of 420 specimens tested for the sensitivity study. Superpave designed mixes were used in the study, but the method of compaction to achieve 7.0% air voids varied because the Superpave gyratory compacted and Marshall hammer were used to compacted specimens. It was also necessary to determine the conditioning time necessary to produce the same tensile strength ratios in larger specimens, 150mm diameter, undergoing Superpave compaction compared with 100mm Marshall compacted specimens. The standard conditioning of specimens was the same as outlined by AASHTO T283 for 150mm specimens. The 150mm specimens for Phase I testing were also used for the results for the AASHTO T283 testing for Phase II.

Table 3.2 Sensitivity Experimental Plan for Effect of Compaction Method and Conditioning Period on Performance

Unconditioned Conditioned Conditioning

Period 100mm

Marshall Superpave 100mm Superpave 150mm Marshall 100mm Superpave 100mm Superpave 150mm AASHTO T283, Standard Conditioning Time XXXXX1 _{XXXXX XXXXX XXXXX XXXXX XXXXX} AASHTO T283, 2 Times Standard Conditioning Time

N/A2 _{N/A N/A XXXXX XXXXX XXXXX}

AASHTO T283, 3 Times Standard Conditioning Time

N/A N/A N/A XXXXX XXXXX XXXXX

1_{One X represents a specimen tested per job;} 2_{Not applicable.}

3.1.2 Phase II Testing – Sensitivity Study

A sensitivity study using the simple performance test was accomplished, which considered additional factors such as test temperature and conditioning, before the expanded experimental plan was undertaken. The projects selected for the sensitivity study were based on the results of the Phase I testing. The projects chosen were based on a good and poor performing HMA mixture in the AASHTO T283 testing. The gabbro/slag, I-75 Clarkston was the good performing mixture and a limestone mixture, I-196 Grand Rapids, was the poor performing mixture. The test temperatures for intermediate and high dynamic modulus and flow number are stipulated by an effective test temperature (Teff) in NCHRP Report 465

(Witczak et al. 2002). Four conditioning cycles were considered: control group, vacuum saturation plus freeze-thaw cycling, vacuum saturation only, vacuum saturation plus freeze- thaw cycling with dynamic creep testing performed on specimens submerged under water.

3.1.3 Phase II Testing

The Phase II experimental plan considered different mix types, aggregate sources, and laboratory test systems. The experimental plan included two integrated plans: one for the mixes and one for the planned laboratory tests. A sensitivity study that considered the effects of specimen size and compaction method was accomplished in the Phase I testing to determine the amount of conditioning that should be performed on larger Superpave

compacted specimens. Table 3.3 below outlines the final expanded experimental plan.

Table 3.3 Expanded Experimental Plan for Phase II Projects

≤ 3,000,000 >3,000,000

Limestone - M50 Dundee Limestone - M59 Brighton

Limestone - M36 Pinckney Limestone - Michigan Ave. Detroit

Gravel - M45 Grand Rapids Limestone - Vandyke Detroit

Gravel - M21 St. Johns Limestone - US23 Hartland

Limestone - M84 Saginaw Gravel - I-75 Levering Road

Limestone - BL96 Howell Limestone - I-196 Grand Rapids

Gravel - M21 Owosso Slag/Gabbro - I-75 Clarkston

Gravel - M66 Battle Creek Gravel - M53 Detroit

Limestone - M50 Dundee Limestone - Michigan Ave. Detroit

Limestone - US12 MIS Gabbro I-75 Toledo (in MI)

SMA N/A Gabbro - I-94 SMA Ann Arbor

PHASE 2 MOISTURE

NMAS (mm)

25.0 or 19.0

Traffic Level (ESAL's)

12.5 or 9.5

Table 3.4 below shows the laboratory testing experimental plan. The test temperature and moisture conditioning of the specimens was determined in the Phase I sensitivity study for the Phase II experimental plan. A proposed method of determining moisture susceptibility will be compared to the current method of determining moisture susceptibility from which conclusions and recommendations will be drawn upon.

Table 3.4 Laboratory Experimental Plan for Phase II

Unconditioned Conditioned

Test System for _Sensitiv

ity S

tudy Dynamic Complex _{Modulus Testing}

followed by Flow Number Testing followed

by Dynamic Complex Modulus Testing

XXX XXX

AASHTO T283 XXXXX XXXXX

Test System for Phase II Testing Dynamic Complex _{Modulus Testing} XXX XXX