Color asphalt concrete mixing and pavement construction technology

3.1 Mixing of blends. The mixing of colored asphalt with regular asphalt is generally similar, but the following points should be emphasized:

Before mixing, the mixing tank of the mixing station, asphalt conveying pipeline, transport vehicles, construction machinery and equipment, etc., should be cleaned thoroughly.

② Raw material properties should be stable to ensure that the production target mix can approach the design mix as closely as possible.

③ Due to the high specific gravity of the color powder, which provides coloring, dispersion, adsorption, stabilization, and thickening effects in the mixture, its environmental impact should be considered during addition. Before production, the amount of color powder per batch of mixture should be calculated based on the target blend ratio, packaged in polyethylene plastic bags, and manually assisted in during the mixing process.

④ The mixing temperature should be maintained between 150℃ and 170℃, with a mixing time 10 seconds longer than that of conventional asphalt mixture, and the particle distribution and color uniformity should be checked promptly after discharging.

3.2 Mixed Material Spreading

Before laying colored asphalt mixture, the quality of the subgrade should be carefully inspected to ensure it is firm, level, and clean. Additionally, the working condition of the spreading and compaction machinery should be checked to avoid stoppages during construction due to inadequate preparation.

3.2.2 To enhance the bonding strength of the interface and reduce water seepage into the pavement structure, the subgrade should be cleaned thoroughly before laying, and emulsified asphalt should be sprayed, with a dosage of 0.3-0.5 kg/m².

3.2.3 When starting the laying process, strictly use spacers to adjust the leveling board to the specified elevation, ensuring the initial laying thickness meets the requirements.

 According to the project timeline, taking into account the production, transportation, spreading, and compaction capabilities of the mixed material, ensure continuous spreading and strictly control the working speed of the paver within the range of 2.0 to 2.5 m/min.

3.2.4 The mixed material should be spread to full width, formed in one continuous pass to ensure uniform color, particle distribution, and appearance, and promptly compacted after spreading.

3.3 Compacted Molding of Blended Material

3.3.1 Compactor Selection: Choose the model, power, and number of compactors based on the project's scale and the complexity of the construction site.

Due to the black rubber tires of tire rollers causing severe contamination and adhesion on colored asphalt surfaces during compaction, they are not suitable for use.

3.3.2 Compaction Method of Rolling Combination: The compaction of colored asphalt mixture is also carried out in three stages: initial compaction, secondary compaction, and final compaction.

Initial temperature should be controlled between 130℃ and 145℃, final temperature should not be less than 70℃, and the rolling process should be carried out according to the principle of "quick follow-up, slow pressure, high frequency, and low amplitude".

Under normal circumstances, the method of roller compaction is determined based on the results of the trial section. The conventional approach is:

① The initial compaction is completed by a heavy roller, which statically presses the road surface once, followed by one pass with light vibration compaction, at which point the initial compaction is finished.

② The primary compaction work is carried out by a light roller, with the number of passes varying according to the site until full compaction is achieved.

③Upon completion of the edge finishing by the light compactor, and when the road temperature drops to 80℃, the final compaction begins. It involves the heavy compactor statically compacting 1-2 passes until the wheel marks are completely eliminated, at which point the rolling process is finished.

3.4 Details to note during the rolling process:

3.4.1 To prevent the sticking phenomenon during the roller compaction process, you can add laundry detergent (0.15kg/m3) to the roller compactor's water tank for appropriate lubrication of the steel wheels, thus avoiding sticking issues with the steel wheel roller.

3.4.2 To ensure civilized construction and prevent damage to curb stones due to excessive edge-pressing by heavy rollers, during the rolling process, the distance between the steel wheels of the heavy roller and the curb stone should not be less than 15 cm. The remaining area will be compacted by a light roller under the guidance of a designated person.

3.4.3 To prevent contamination of the colored asphalt surface, all debris and sand adhering to the roller's steel wheels must be rinsed off with water prior to rolling. The roller equipment must be confirmed clean before proceeding with the compaction. Additionally, traffic can only be opened after the temperature has cooled down to ambient, following the compaction process.