Pavement sample

Scanning electron microscope observation of the microsurfacing pavement confirmed the presence of the polymer honeycomb structure [22]. Here, a sample of the freshly applied pavement sample was treated with OSO4 and the asphalt was extracted with MEK (methyl ethyl ketone) solvent The treatment with OSO4 makes the SBR polymer insoluble to the organic solvent and also improves the contrast for the scanning electron microscope, SEM, observation. 

Repeated Load Triaxial Tests for Permanent Strain Evaluation. In accordance with the procedure in the VESYS IIM Users Manual, the same sample used in the creep tests was also used to measure permanent strain, an important indicator of the rutting potential of a pavement. Repetitive loads of the haversine type were applied to the specimen at a magnitude equal to the applied vertical stress used in the creep tests. The load duration was 0.1 sec followed by a rest period of 0.9 sec. 

According to this experimental work, the waste rubber reinforcement can obviously improved characters of asphaltic samples. As stability, creep tests indicated that reinforcement by waste rubber reduced their permanent deformation significantly, it means that waste rubber provides a strong eomposite for designing mixes to avert both pavement rutting and low temperature cracking in order to prolong road life. 

The dynamic stabilities of the mixtures with the plastic sample-5 and 6, from domestic wastes, were moderate values, which are within the range recommended for heavy traffic road pavements. 

ASTM C136A, 1994. Field Sampling and Laboratory Testing Procedures Rejuvaseal Pavement Sealer. 

Both alternative sampling methods have the advantages that there is certainty of the location of the material in the pavement, there is minimal risk of segregation and there is no interruption to paving operations. The disadvantages are that there is a possibility of affecting the finished surface and it requires more labour. 

Sampling by coring has the advantage that there is certainty of the location of the material been sampled. However, it requires a core-cutting machine, it affects the pavement surface in case of insufficient restoration and cutting operation affects to some extent the aggregate grading (particularly of coarse mixtures). 

The load equivalency factors were derived from terminal serviceability factor (pj values equal to 2.0, 2.5 or 3.0 and pavement structural number (SN) values equal to 2, 3, 4, 5 or 6. The lower p value represents a pavement with serious structural distress where maintenance is unavoidable. The upper value of 3.0 represents a pavement with structural distresses needing maintenance, if high level of service is to be provided. The SN values represent different pavement structures. A sample of the equivalency factors derived from flexible pavements, for pt = 2.5 and SN = 5, for the three types of axles (single, tandem and triaxial), is given in Table 12.3. All equivalency factors for flexible pavements can be found in tabular form in the AASHTO pavement design guide (AASHTO 1993). 

The thickness determination of a flexible pavement with asphalt concrete layers over untreated aggregate base/sub-base is obtained using the appropriate nomograph. A sample of those nomographs, for 15.5°C MAAT and for 300 mm thickness of base/sub-base, is given in Figure 13.3. 

The determination of the thickness of a full-depth asphalt concrete pavement is carried out from a similar to a flexible pavement with unbound layer nomographs. A sample of the nomographs used for 15.5°C MAAT is shown in Figure 13.4. 

Sampling of RA should be representative and may be carried out from existing pavement to be recycled, from a lorry load (hauling trucks) of RA or from stockpiles. 

FIGURE 3.2 Calculated dependences of the relative durability W of cyclic loaded rubber-bitumen binder samples on the sizes of the rubber particles introduced into the bitumen. Curve 1 - at an average mechanical stress in the pavement a = 2.5 MPa. 

This work allowed to expand the knowledge in this topic and is expected to have made a useful contribution to other similar situations. Evaluating WBV in urban bus drivers with both ISO standards, allowed a more complete assessment of working conditions. It was clear that the WBV exposures in this sample of urban bus drivers, do not exceed the recommended limit values. The seats are also doing its role reducing the transmission of the WBV to the drivers in all the cases. The constant adoption of preventive measurements is recommended, as well as the preoccupation about pavements improvement. In the future, this research may be consolidated starting from the limitations identified. 

Variable slip technique is used to measure the friction coefficient between tire and pavement. The test equipment consists of an automotive vehicle. Each test wheel contains a variable brake system. The resulting resistive force caused by friction between the tire and the pavement surface is sampled and recalculated to slip friction numbers. Frictional properties of pavement surface as a function of speed are measured by a d5mamic friction tester. A disk spins with its plane parallel to the test surface. The rubber sliders come into contact with the pavement, and torque is monitored when rotational velocity reduces, due to friction. A graph of friction vs. speed is plotted. 

Fig. 12-14 SEM photographs of microsuifacing pavement taken under the wheel path Texas State Highway 84 near Waco, paved in 1998, and samples taken in 2001.

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