1. Influencing factors of smoothness of cement stabilized macadam base

Material factors?

(1) Segregation of mixture: When the particle size of stable mixture is larger or there are more coarse aggregates, the segregation is generally larger; When the water content is small, the segregation is also serious when the mixture is dry. When the car is picking up and unloading, the segregation near the rear and on both sides is large. When the paver is paving, the segregated aggregates on both sides of the car are distributed on both sides of the hopper of the paver, so that the paving materials are segregated. Segregated mixture directly affects the compaction coefficient, making it uneven, thus affecting the smoothness of the base.

(2) Water content of the mixture: The water content of the mixture does not reach the optimal water content, so the cement stabilized macadam mixture is required to be rolled and formed at the optimal water content, but it cannot be guaranteed to reach the optimal water content in the actual construction process, which has a certain impact on the smoothness of the base.

When the water content is high, it will affect the best compaction effect and easily cause waves, springs, movement and rutting. When the water content is low, it is not easy to form rolling, and the surface is loose, so the integrity and smoothness cannot be guaranteed. 2. Equipment and operation of construction machinery

2. Construction machinery is also an important factor affecting its flatness. Incompatible construction machinery or improper operation will affect its flatness.

1) Paver: In order to improve the smoothness of the road surface and the uniformity of the mixture, it is required to use a paver for paving construction. But if you don't know much about the performance of the paver or the operator is not skilled enough and the operation is unreasonable, the best paving effect will not be achieved. Paver stops halfway or the speed is uneven, which will affect the flatness. When the paver paves the last section and paves the next section, if the joint is uneven, the flatness before and after will be discontinuous; In the process of paving, the driving speed is unstable and uneven, and the initial compaction degree of the fast and slow paving sections is different. After the final compaction, slight waves may be formed, which may affect the smoothness of the base. The reasons that cause the paver to stop halfway or the uneven driving speed are discontinuous feeding, intermittent discharging, receiving or damage of the paver.

(2) Rolling: Rolling is the direct reason that affects the flatness. If the rolling process is unreasonable, the smoothness of the base will be poor. The influence of roller rolling on flatness is mainly manifested in the following aspects. ① The rolling process is unreasonable. During construction, it is not rolled according to the principle of "light before heavy, static before vibration", and it is directly placed on a heavy roller, which causes the paving base mixture to move and form a lump or wave shape, which is difficult to eliminate; Too many vibratory rollers are used, and the vibration distribution is uneven, or only vibratory rollers are used for rolling, and static rollers are not used for final pressing, resulting in tiny waves or obvious wheel tracks on the base surface.

② The rolling process is unreasonable. The roller operator is not skilled, does not overlap the width of L/2 wheel, or does not roll in the direction of the route and is skewed, resulting in some overvoltage and some undervoltage, which artificially causes uneven surface; The rolling section is not long enough, and it is often reversed or turned around without manual treatment, which is easy to produce pushing and turning wheel tracks at the place of reversing and turning around; The long-term stop of the roller in the newly pressurized or unpressurized area will make the stop concave.

③ Improper control of rolling time. After paving by paver, the roller can't keep up with the rolling operation, and the water content during rolling is lower than the optimal water content, and the surface part is not easy to be compacted, resulting in peeling or loosening of the surface; When the water content is too high, the mixture is not easy to compact, resulting in wheel tracks or ruts on the surface.

3. Construction techniques and methods

(1) elevation control: one of the common methods to control the elevation and smoothness of paver in cement stabilized macadam base construction is to hang steel wires. The principle of hanging wire method is to provide a datum plane parallel to the top surface of paving with steel wire, so that the top surface of paving base is parallel to the steel wire. In the process of construction, for various reasons, it is difficult to provide accurate reference points by messenger wire, thus affecting the smoothness of the base.

(1) The tension stress of steel wire is insufficient or the distance between hanging points is too large, which causes the steel wire to sag between two hanging points. Due to the limited tensile capacity and dead weight of steel wire, the straightness of steel wire can only be guaranteed if the spacing between lifting points matches the tension of steel wire. If it is not handled properly, the middle of the steel wire hanging point will sag, and the paved base surface will fluctuate, which will affect the flatness.

(2) The elevation measurement of steel wire lifting point is inaccurate. The hanging steel wire nail is not firm, and there is a certain downward pressure on the steel wire when the steel wire is tensioned.