Before paving asphalt commercial concrete pavement, the diseases of the original old cement commercial concrete pavement must be seriously and thoroughly treated, and only in this way can the reconstructed pavement achieve good expected results.

1. 1 potting

The joints of old cement commercial concrete pavement should be cleaned by high-pressure air machine and manually, and the joints should be filled with modified asphalt, which can effectively prevent pavement water from infiltrating into the base and ensure sufficient strength and stability of the base. When in use, it is best to heat the asphalt to a certain temperature with a commercial concrete pavement caulking machine, and inject the asphalt into the joint through the glue injection nozzle of the commercial concrete pavement caulking machine. Modified asphalt has good thermal stability at high temperature, is not easy to age and become brittle at low temperature, is safe and economical, does not pollute the environment, and can better meet the needs of joint filling.

1.2 joint undercut and corner folding treatment

For the damaged pavement with large depth and width, at least the depth of 10cm should be cut off, and then the cement commercial concrete should be poured again. If the damaged surface is shallow and narrow, it should be chiseled to a depth of 5cm, and then filled with asphalt commercial concrete for compaction.

1.3 Reduce the relative displacement of adjacent plates.

If there is relative displacement between the hollow slab and the adjacent slab, grouting under the old pavement will make the slab in a stable state. The treatment method is as follows: use a rock drill to drill holes in the unstable commercial concrete slab, and drill 5 holes, each in the middle and four corners of the slab 1 (the cavity slab drills holes in the cavity). The hole diameter is 5cm, and the hole depth is so deep that the drill bit touches the soil layer below the basement. Cement mortar is used for grouting. The perfusion pressure is generally 0.05~0.25MPa. Grouting should be carried out in the hole first, and other holes should be observed at the same time, that is, plugging should be carried out. Pay attention to traffic after sealing the hole, and develop traffic after 3 days of health preservation.

1.4 Treatment of Severe Broken Plate

Slightly broken panels cannot be replaced. Those boards that sink, ooze, lose balance and are seriously damaged must be replaced, and the base must be repaired at the same time. During construction, the original broken commercial concrete is chiseled and cleaned, and then the cement commercial concrete is poured to fill it. The cutting width is determined according to the field conditions. When the original cement commercial concrete plate is seriously damaged, the original plate should be chiseled away as a whole. If the plate is partially damaged, it can also be cut with a cutting machine, keeping the intact part, chiseling off the damaged part, and then pouring cement commercial concrete again.

1.5 Other forms of damage

Such as peeling, bare, peeling, pockmarked surface, etc. On the surface, because they only affect the driving comfort of the original pavement, when the old commercial concrete pavement is used as the base, these failure forms have little influence on the bearing capacity and driving comfort of the whole pavement, so they are not given special treatment.

2, measures to prevent reflection cracks

Reflective crack refers to the crack in the corresponding position of asphalt overlay due to the constant change of environment (mainly temperature and humidity) and the repeated action of wheel load. The mechanical mechanism of reflection cracks is generally considered to be caused by the vertical and horizontal displacement of joints and cracks in the lower pavement. Vertical displacement is the vertical relative displacement caused by multiple rounds of loads on the pavement on both sides of joints and cracks; Horizontal displacement is the horizontal displacement caused by the expansion and contraction of the panel due to the change of temperature and humidity. According to the research, it is found that the level change caused by temperature change is the main reason for the emission crack. The horizontal displacement of the lower pavement slab makes the asphalt overlay produce greater tensile stress at the joints and cracks. However, commercial asphalt concrete should not be deformed at low temperature. When the tensile stress exceeds the tensile strength of commercial asphalt concrete, it will crack. Under the comprehensive action of temperature, humidity stress and multi-wheel load, cracks develop continuously and are finally reflected on the overlay surface.

At present, the most commonly used measures to prevent reflection cracks in China are sticking SBS modified asphalt felt, laying glass fiber mesh, laying geotextile and improving the performance of asphalt mixture.

2. Construction method of1SBS modified asphalt felt (anti-cracking paste)

Anti-crack adhesive is a new waterproof material made of polymer modified asphalt, glass fiber woven fabric or chemical fiber non-woven fabric. It has the characteristics of high tensile strength, high elongation, no deformation at high temperature, no cracking at low temperature, strong adhesion and convenient construction.

During construction, cut the linoleum into strips with a width of 0.5m, remove the dust and sundries within 0.3m of the joint and both sides of the joint with a compressed air machine, and pour the joint materials into the joint. Put the linoleum on the joint, with the film facing down on both sides of the joint. Bake the bottom of one end with a flamethrower until the film melts. Step on the linoleum to make it firmly stick to the old road surface. At the intersection of vertical and horizontal and the lap joint of linoleum (the lap joint width is 0. 1.25m), the linoleum is pressed after baking with a flamethrower, so that the upper and lower layers are bonded with the commercial concrete slab to form a whole.

2.2 glass fiber mesh construction method

Glass fiber mesh is a kind of square mesh glass fiber with a side length of 2cm, which is located between the upper and lower layers of asphalt commercial concrete. Cut it into strips with a width of 1m and spread it over the joint. 0.5m on both sides of the joint. Before laying, mark the position of joints (cracks) in advance, and spray bonding asphalt at a speed of 0.6kg/m on the clean and dry road surface. When laying, the glass fiber net should be flat and tight, and there should be no wrinkles. When paving asphalt commercial concrete, transport vehicles and pavers should try not to turn or turn around, so as to avoid the surge of glass fiber mesh and affect the construction quality.

2.3 Geotextile Construction Method

Geotextiles, also known as non-woven fabrics, spray sticky asphalt on old roads. When the asphalt temperature is 150~ 170℃, the asphalt dosage is 1.0~ 1.2kg/m2, and the spraying range of viscous asphalt is 0.05~0. 10m wider than that of geotextile. At the initial end, fix geotextile with gaskets and cement nails, then tighten it, insert the support rod into the geotextile roll, then lift the geotextile roll and spread it about 5~ 10m. One end of the geotextile roll is aligned with the edge of the road, then the geotextile is tensioned, then put down, spread on sticky asphalt and compacted. Edge-to-edge connection of two adjacent volumes of geotextile should be longitudinally overlapped, and geotextile should be saturated with asphalt. Geotextile construction temperature should be greater than 65438 00℃. After the geotextile is paved, the paving of asphalt commercial concrete should be started immediately, and the amount of geotextile paving should be as much as that of asphalt commercial concrete pavement every day. In order to avoid longitudinal construction joints, full pavement width construction should be adopted. Non-construction vehicles are strictly prohibited from driving on the geotextile, and asphalt commercial concrete transport vehicles are not allowed to turn, turn around or brake suddenly on the geotextile, and can only move forward or backward on the geotextile to ensure the construction quality.

2.4 Improve the performance of asphalt overlay mixture

Try to choose asphalt materials with good thermal stability and strong low-temperature crack resistance. SBS, SBS is the most widely used modifier at present. SBS modified asphalt not only has good thermal stability and low temperature crack resistance, but also can increase the adhesion between asphalt and stone, especially has good elasticity (deformability). In addition, the gradation, acidity and alkalinity, angularity, firmness, mud content and flat particles of mineral aggregate should be strictly controlled through experiments. In order to improve the water stability of the mixture, cement or hydrated lime powder can be used as filler instead of mineral powder, so as to better improve the performance of asphalt mixture.