Colored asphalt concrete mixing and paving techniques
3.1 Mixing of Blends. The mixing of colored asphalt with regular asphalt is generally similar, but the following points should be emphasized:
Prior to mixing, the mixing tank of the mixing station, asphalt conveying pipes, transport vehicles, construction machinery, and equipment should be thoroughly cleaned.
② Raw material properties should be stable to ensure that the production target mix ratio can approach the design mix ratio 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 must be considered during addition. Before production, the amount of color powder per batch of mixture should be calculated based on the target proportion, packed in polyethylene plastic bags, and manually assisted in the mixing process.
④ Mix temperature should be controlled between 150℃ to 170℃, with a mixing time 10 seconds longer than that of standard matrix asphalt mixtures. After discharge, promptly check for uniformity of the granular material and color.
3.2 Mixed Material Spreading
3.2.1 Prior to laying colored asphalt mix, carefully inspect the subgrade quality to ensure it is firm, level, and clean. Additionally, check the working condition of the spreading and compaction machinery to avoid work 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.
At the beginning of the laying process, strictly follow the loose laying elevation and use blocks to properly elevate the smoothing plate, ensuring the initial laying thickness meets the requirements.
Based on the project timeline, considering 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 in full width, forming a single, uninterrupted layer to maintain consistent color, even particle distribution, and aesthetics. After spreading, it should be compacted promptly.
3.3 Compacted Molding of Blended Material
3.3.1 Compaction Equipment Selection: Select the model, power, and number of rollers based on the scale of the project and the complexity of the construction site.
Due to the black rubber tires of tire compactors causing severe contamination and sticking on colored asphalt surfaces during compaction, they are not to be used.
3.3.2 Compaction Method of Rolling Combination: The compaction of colored asphalt mixture is also divided into three stages: initial compaction, secondary compaction, and final compaction.
Initial pressing temperature should be maintained between 130℃ and 145℃, final pressing temperature should not be less than 70℃, and the rolling process should be carried out according to the principle of "close follow-up, slow pressing, high frequency, and low amplitude".
Generally, under normal circumstances, the rolling combination method is determined based on the results of the test section after laying. The conventional practice is:
① The initial compaction is completed by passing a heavy roller over the road surface once statically, followed by one pass with light vibration compaction; the initial compaction is then finished.
② The primary compaction work is performed by a light roller, with the number of passes determined on-site until full compaction is achieved.
③Upon completion of the edge finishing by the light roller, and when the road temperature drops to 80°C, the final compaction begins. It is carried out by a heavy roller with 1-2 passes of static compaction until all wheel marks are eliminated, at which point the rolling 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) for grain to the roller's water tank to provide appropriate lubrication for the steel wheels, thus avoiding sticking in 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, it is necessary to rinse off debris and sand adhering to the steel wheels of the roller with water before compaction. The roller equipment must be confirmed clean before compaction is permitted. Additionally, traffic may only be opened after the temperature has cooled to normal after compaction is completed.
