The separation of coarse and fine materials should be avoided in paving. The paving quality directly affects the compactness, road arch, smoothness, uniformity of thickness strength distribution and appearance quality. Therefore, it must be strictly controlled to ensure that the quality of cement stabilized gravel base meets the specification requirements.
3. 1 First of all, we must strictly check the longitudinal elevation and cross-section slope of subbase, and the test indexes and deviations must meet the design and specification requirements. Then sprinkle water to wet the surface of subbase, but there can be no free water.
3.2 Accurately measure, stack and hang the walking steel wire of the paver, and adjust the locking paving thickness according to the designed loose paving thickness and loose paving coefficient. The loose paving coefficient should be based on the data determined by the test section. During the construction, there should be a special person to regularly check the loose laying thickness to ensure that the compaction thickness meets the design requirements.
3.3 When paving the mixture with a paver, there should be no interruption in the middle. When the interruption exceeds the initial setting time for some reason, construction joints shall be set. The walking speed of the paver should be controlled at 1.0m-.5m/min, and the paver should travel at a constant speed. The spiral feeding of paver is even and full. When paving widely, the mixture will segregate within the range of 20cm-40cm at both ends of the paver screw, and artificial oiling should be adopted in time.
3.4 The mixture that exceeds the final setting time for some reason should be abandoned or used for other purposes, and cannot be used on the road. Samples were taken from the paving mixture to make test pieces, and 7-day saturated compressive strength test was conducted to verify whether the strength meets the standard requirements.
4. Roller compacted cement stabilized gravel base is a plastic semi-rigid structure. From mixing with water to rolling, it is completed within the initial setting time of cement, but not later than the final setting time of cement.
Compaction is the formation stage of base strength, so the construction of cement stabilized gravel base should be closely organized and coordinated to ensure the compactness meets the requirements of specifications. Those that fail to be crushed or molded after the final setting time shall be carved from the roots.
4. 1 Rolling must follow the principle of "light first, heavy later, slow to fast", and the overlap of wheel tracks shall not be less than 30cm. The ultra-high section is rolled from low to high, that is, the inner side is separated from the center and the outer side is separated from the center to the side.
4.2 The roller should walk in a straight line, and it is forbidden to brake, stop, start and turn around halfway, and it is forbidden to brake and start again when reversing at a slow and uniform speed.
4.3 At present, sand filling method is generally used for compaction degree detection, and it takes one to two hours to dig a pit, weigh and measure water content. However, the compaction test results must be presented within the initial setting time of cement and not later than the final setting time of cement. Because after the initial setting time of cement, due to pressure compensation, the compaction power is too large, and the effect of improving compaction degree is not obvious; After the final setting time of cement, not only the supplementary pressure is invalid, but also the whole structure of cement stabilized gravel base is destroyed, so it has to be demolished and repaved. Therefore, in the construction site of cement stabilized gravel base, sufficient testing personnel and instruments must be equipped to ensure the smooth testing.
4.4 Advanced paver machinery ensures the longitudinal and transverse slopes and smoothness of the pavement. However, due to the existence of wheel tracks during rolling, the mixture will be loose when the driving wheel backs up, and the rolling process must be supplemented by artificial decoration, and it should be checked with 5m feet at any time.
4.5 In the construction of cement stabilized gravel base, transverse joints are inevitable, and there are strict requirements for the treatment specifications of joints. In addition, according to the practical experience, our treatment method is to fill more mixture in the transverse joints, then roll them horizontally for 2-3 times, then remove the obviously higher part, then roll them horizontally for 1-2 times, and finally roll them longitudinally in sequence. The longitudinal travel of the roller will exceed the transverse joint, and then the roller will be manually removed for L meters after rolling to facilitate the next joint.
5. Healthy inorganic binder
Cracks on the pavement are inevitable, which is recognized by highway industry. There are many reasons for the formation of cracks. Such as longitudinal cracks caused by settlement of high fill subgrade; Segregation of coarse and fine aggregates leads to cracks in the concentrated area of fine aggregates; Because the thickness is too small, it can't resist the transverse cracks caused by load bending and tensile stress; Shrinkage cracks caused by improper maintenance. Strengthening health care can effectively prevent the formation of various cracks and increase strength.
5. 1 After the cement stabilized gravel base is rolled and formed, it shall be wetted by water in time to prevent the cement stabilized gravel base from drying or being washed away. Keep the surface moist and not dry within 48 hours, then spray water continuously for 3 days, and the number of spraying water can be reduced appropriately for the next 4 days, but the surface must be moist. Sprinkle water for at least 7 days, during which all vehicles are prohibited from passing. Sprinklers should move slowly and sprinkle water evenly.
5.2 During running water construction, the cement stabilized gravel base can be maintained by spraying water for 4 days, and then emulsified asphalt is sprayed for maintenance. On the fifth day, asphalt can be laid below. This operation has no influence on the quality of grass-roots units, and can also speed up the progress of the project.
5.3 Cement-stabilized gravel base shall be kept in good health by sprinkling water and wetting with sand, that is, the washed sand shall be sprinkled on the surface of the base according to the thickness of 5- 10cm, and wetted with water for 7 days, which shall be cleaned before asphalt spraying. There is also a film-covered curing method, that is, after rolling is completed, sprinkle water and cover the whole area with film until the curing is over.
Adequate watering for health preservation can make the surface of the base moist, the hydration heat uniform and the hardening speed of cement slow down. Although there are shrinkage cracks, the cracks are thin and long. The lower asphalt has a large gap, which can fully absorb part of the reflection force and will not affect the integrity of the upper asphalt.
In the construction of several roads, we insist on strictly controlling the construction of cement stabilized gravel base from the above four links, and achieved good results. The completion acceptance was rated as an excellent project, and the pavement was not damaged during the defect liability period. It can be seen that if these four links can be strictly controlled, high-quality roads can be built.