Use the upper materials of old pavement and soil foundation. First, remove the stones on the surface of the old pavement or soil foundation, and then dig a small hole every 10~20m ~ 20m to make the bottom elevation of the hole the same as that of the pre-determined lime stabilized soil layer, and mark the bottom of the hole to check the digging depth. Use plough, scarifier, grader or bulldozer with strong teeth to loosen the upper part of old pavement or soil foundation to a predetermined depth.
Use aggregate from the yard. Before collecting aggregate, trees, turf and miscellaneous soil must be removed. Particles exceeding the specified size in aggregate should be crushed or screened to meet the maximum particle size requirements, and aggregate should be collected within a predetermined depth range.
2, construction lofting
When setting out the base, old pavement or soil foundation, line piles should be set every 15 ~ 30m on the straight line, and every 10 ~ 15~30m on the horizontal curve, and indicator piles should also be set on the shoulder edges on both sides of the road.
When leveling subbase, old pavement or soil foundation, it is necessary to mark the design height in the indicator piles set at the edge of cement stabilized layer and on both sides of the road.
3, raw material mixing
When mixing raw materials, it is necessary to apply raw materials such as gravel and lime into the soil and mix them with a Chinese mixer. The mixture should be of the same color, avoiding gray stripes, gray balls and "painted faces", and paying attention to avoid omitting interlayers and seams when mixing.
4, material backfill
Cloth soil. The loose coefficient of soil and the thickness of subgrade base are the main basis for determining the compaction thickness of soil. Construction personnel should master the location and density of soil spreading, so as to improve the efficiency of soil spreading and achieve the ideal construction effect.
Pave according to the calculated thickness. If bulldozers are used for paving, the paving coefficient is generally1.2 ~1.5; If a grader is used for paving, the paving coefficient is generally 1. 1 ~ 1.2, or the accurate paving coefficient can be determined according to the actual situation.
Gravel. First of all, it is necessary to measure the loose paving coefficient of gravel, and then according to the measurement results, gravel is laid on qualified soil materials. The standard of crushed stone meets the design requirements, and the paving width is determined according to the mixing width. The paving thickness should meet the design requirements and be evenly paved.
Prepare ash and horizontal gravel. After acceptance, draw a gray border and a callback width line. First of all, lime should be sieved before use to remove undigested stones. The mesh should be 3 ~ 5cm. After the lime is delivered to the site, it will be piled into triangular ash strips according to the calculated quantity.
After the acceptance of lime, lime should be evenly sprinkled on the gravel within 24 hours by means of deduction and sprinkling. Construction personnel shall maintain the lime loose laying thickness according to the calculation, and deal with the uneven places.
Cloth cement. Usually, cement is laid by manual loading and unloading, and the grid is laid in advance. After the cement is unloaded, the construction personnel will deal with it. In the process of spreading cement, spread the cement evenly in the grid, and scrape it with a scraper after spreading.
5, shaping and rolling
Forming: After mixing raw materials and mixture evenly with mixing machinery and equipment, stabilize the pressure, quickly roll the pavement with crawler machinery and equipment, or gently roll the pavement with a roller.
When the mixture pressure is real-time, the sliding mode cannot be adopted between them, and various exposed or uneven places on the road surface need to be leveled, and corresponding measures should be taken to control them.
In the case of artificial shaping, if the stabilized soil layer is loose, it is necessary to use tractors and road rollers to roll the pavement first to ensure that there are no obvious wheel tracks on the pavement and the dry density meets the design requirements.
Rolling forming: After forming, when the mixture is at the optimum water content 1%, it should be immediately rolled by a three-wheel roller, a heavy tire roller or a vibratory roller with water content above 12t. If the surface water is insufficient, water should be sprayed appropriately.
For the straight line segment, the horizontal curve segment should be rolled from the shoulders on both sides to the center of the road, and from the inner shoulder to the outer shoulder. When rolling, the rear wheel should overlap the wheel width of 1/2, and the rear wheel must exceed the joint of two sections. When the rear wheel is pressed to the full width of the road surface, it shall be rolled once to the required compactness, generally 6 ~ 8 times. Compaction method is the same as subgrade rolling.
During the rolling process, the surface of lime stabilized soil should always be moist. If the surface water evaporates quickly, a small amount of water should be replenished in time. In case of "spring", looseness, peeling, etc. , should be opened in time to mix, or use other methods to meet the quality requirements.
Treatment of joints and turning points: Before the rolling construction is completed, it needs to be leveled again with a grader to make the road arch and superelevation meet the final requirements. In the final leveling construction, it is necessary to scrape off the local high part. For local low-lying parts, it is no longer necessary to make up, and it will be treated when paving the surface. The connection between the two working ends should be overlapped.
After the first stage of mixing and molding, leave 5 ~ 8m without rolling. In the later stage of construction, the uncompressed part of the front end should be remixed with some quicklime and rolled together with the later stage.
6, maintenance work
Generally speaking, the curing time should not be less than 7 days. After the completion of rolling, the cement stabilized mixture should be solidified immediately; The lime-fly ash stabilized mixture shall be cured on the second or third day after rolling. Waterproof film or wet sand should be used for curing. If covered with sand, the thickness should be controlled at 7 ~ 10 cm, and the sand should be kept wet during the whole curing period.
It can also be covered with wet canvas, burlap, straw curtain or other suitable materials. After the maintenance, the covering layer must be removed, and the prime asphalt should be sprayed in time or the next seal coat should be carried out. When the base is not paved with seal coat or surface coat, traffic shall not be opened. In addition, you need to pay attention to the following two points:
The base course can be cured with asphalt emulsion and sprayed twice. The slow-cracking asphalt emulsion with asphalt content of about 35% is sprayed for the first time, so that it can slightly penetrate into the surface layer of the base, and the asphalt emulsion with higher concentration is sprayed for the second time.
The general maintenance period is 7 days. For roads of Grade II and below, if the base course is cement concrete panel and the panel is constructed by small machinery, the concrete surface course can be paved in advance after the base course is completed.
Extended data
action principle
Cement stabilized macadam takes graded macadam as aggregate, fills the gaps of aggregate with a certain amount of cementing material and sufficient mortar volume, and spreads and compacts according to the principle of embedding and squeezing. Its compactness is close to its compactness, and its strength mainly depends on the interlocking principle between crushed stones. At the same time, there is enough mortar volume to fill the gap of aggregate.
Its initial strength is high, and the strength increases with age, and soon forms a plate shape, so it has higher strength, better impermeability and frost resistance. The dosage of water-stabilized cement is generally 3%~6% of the mixture, and the 7-day unconfined compressive strength can reach 1.5~4.0mpa, which is higher than other subgrade materials. After water survives stably, it is not muddy in rain and has a solid surface, so it is an ideal base material for advanced pavement.
According to the Technical Specification for Highway Pavement Base Construction issued by the Ministry of Communications, cement stabilized macadam used in roads belongs to medium-grained soil. Because the water-stabilized macadam contains cement and other cementing materials, it is required that the whole construction process should be completed before the final setting of cement and meet the quality standards at one time, otherwise it will be difficult to repair.
Therefore, it is required to strengthen the construction organization design and plan management, increase the sense of urgency and responsibility of on-site construction personnel, speed up the construction progress, increase the degree of mechanized construction and improve the mechanical efficiency. The construction method of water stabilization is also in line with the development direction of modern large-scale mechanization, so the application of water stabilization in highway engineering will be popularized soon.
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