Diseases of cement concrete pavement and maintenance technology?

Cement concrete pavement has both advantages and its own disadvantages when compared with traditional asphalt roads. Specifically, cement concrete pavement has strong durability, stable internal structure, high mechanical strength, but poor deformation resistance. Therefore, for cement concrete pavement, the disease treatment and maintenance work after the completion of construction is particularly important. In recent years, China's cement concrete highway construction has developed rapidly, how to improve its bearing capacity, resistance to external erosion damage and improve the comfort of the public has become the most concerned about the hot issues.

I, the causes of cement pavement disease

1, the lack of perfect construction technology. For the aggregate of cement pavement, reasonable grading is very important, otherwise it is easy to cause the compactness is not high. Gradation of unreasonable in the later use of the process will cause serious consequences, such as rapid changes in temperature to bring the thermal expansion and contraction of the cavity, and then bring the stress on the surrounding environment, making the pavement easy to crack; and rainy period of moisture is easy to go deep into the ground and accumulated in the panel and the holes between the grass-roots level is difficult to discharge, bring the problem of poor drainage, in addition, when pedestrians, vehicles traveling on the cement surface is bound to impose a certain amount of pavement load resulting in the generation of stress, and the cement surface will not be able to be used. In addition, when pedestrians, vehicles traveling on the cement surface will certainly impose a certain load on the pavement resulting in the generation of stress, which will inevitably lead to the erosion and destruction of the roadbed structure over time.

2, the grass-roots level of processing non-standardized. Grass-roots level is crucial for cement pavement. Because of the need to limit the deformation of cement concrete pavement, it is necessary to use rigid and semi-rigid materials to its design. Most of the subgrade is designed to be semi-rigid, and semi-rigidity, due to its own performance drawbacks, tends to bring about stress fatigue i.e., cracking of the panels after prolonged application of stresses. This has a serious impact on its service life.

3, unreasonable application. In real life, the unreasonable application of cement concrete pavement can be seen everywhere. The most common is no more than overloading, overweight phenomenon. Prolonged traffic overload will make it difficult for the support strength of the cement pavement to overcome the role of contraction stress, resulting in uneven sinking of the slab, difficult to return to the consequences. In this way, the whole pavement will be very easy to break, dislocation and slippage phenomenon, and eventually collapse, the performance is difficult to recover.

Two, cement pavement maintenance measures

1, joint technology. Cement concrete pavement is the weakest part of the concrete slab for the intersection parts, the use of appropriate filler to fill and timely replacement of aging filler is very necessary, if not, will inevitably be due to the pavement moisture and corrosive substances invade the ground and cause corrosion of the foundation. Selection of filler should be carried out in accordance with the following principles: first of all, the filler should have a good bonding capacity with the cement concrete slab, so as to ensure that when the slab due to temperature changes and expansion, tightening, filler and concrete slabs between the solid combination, will not crack; in addition, the selected materials should have good heat resistance and good embeddedness, so as to ensure that when the filler is in high temperature conditions, no melting and flow of the filler. Under the high temperature conditions, does not melt and flow, resulting in the embedding of gravel impurities; good elasticity and toughness, making the low-temperature environment, will not occur brittle fracture; in addition, but also corrosion-resistant, aging-resistant performance, so as to be able to in the harsh and complex environments, with a long service life; Finally, the price should be moderate to ensure that the economic benefits of the construction effect and the harmonization. Highway construction departments usually use pine board as the traditional jointing materials, which is mainly from the economic level of consideration. However, due to the pine board has easy to absorb moisture, low reuse rate, easy to corrosion and other shortcomings, the use of the effect is not very satisfactory.

2, the external treatment technology of cracks. Commonly used grouting materials are mainly alkenes, epoxy resin, polyurethane and asphalt and other polymers. Among them, polyurethane is widely used in repairing pavement cracks with good vibration resistance type and fatigue resistance. In addition, compared with other materials, polyurethane has a high degree of activity and polarity, low temperature resistance is also very good, due to the polyurethane has a very high degree of adhesion to cement concrete, so there will be almost no side effects in the curing, there is no adhesive layer defects.

3. Repair broken slabs. Slightly broken plate, no need to use "plate replacement method" treatment, generally use "five-in-one" repair broken plate, "five-in-one" repair method in the actual construction of the use of DCG reinforcing road base leveling pavement method", "grouting technology at the bottom of the board", "crack treatment technology", "wrong platform, pothole, chipping edge filling technology", "filling technology", "the bottom of the board", "the bottom of the board", "the bottom of the board", "the bottom of the board", "the bottom of the board". technology", "crack treatment technology", "misalignment, pothole and chipping edge filling technology", "joint waterproofing technology" and other five fast and efficient mature technologies (referred to as "5-in-1"), to quickly, comprehensively and thoroughly treat various diseases of roadbed pavement, so that it can be an alternative to replacing the plate and restoring in-situ The road surface is complete and smooth, restoring the normal function of the diseased road surface.

Generally, the "five-in-one" in-situ treatment has five construction procedures: first of all, the implementation of ① reinforcement of the subsoil, ② lifting and adjusting the plane plate, ③ filling the bottom of the plate dehollowing; the purpose of the above steps is to reinforce the subsoil, eliminating the direct root cause of the concrete panel crushing, so that the panel to restore stability and smoothness; and at the same time, to improve the soil's hydraulics performance. On the one hand, to reduce the outside water into the roadbed, on the other hand, the soil will be divided and surrounded by slurry veins, changing "free water" into "constrained water", so as to prevent water damage to the subsoil immersion; and then for the crushing of concrete panels, and then the implementation of ④ cracks, pits, pockmarks, Then for the broken concrete panel, then implement ④ repair of cracks, potholes, pockmarks, chipped edges, misalignment, etc., ⑤ waterproofing of shrinkage joints embedded joints.

This from the subsoil to the concrete panel of a variety of diseases are comprehensively dealt with, treating the symptoms and treating the root of the "five-in-one" in-situ treatment technology, to a large extent, to avoid the shortcomings of the "replacement method".

4, the outside of the empty plate treatment technology. The phenomenon of dehollowing widely exists in the cracks of the pavement, broken situation. Sometimes even if part of the pavement does not look broken and cracked phenomenon, but in fact, the situation has occurred. This is a very hidden disease, because it is not easy to detect, so the harm is very great. If you do not deal with the phenomenon of hollowing out, even if we pave the pavement to more than 2.0cm, cracks may still arise again.

5, pressure slurry method for maintenance. Pressure slurry method is mainly to deal with the less serious pavement. This method by applying pressure, the cement mortar injection pressure to the bottom of the cement pavement, not only can make the bottom plate of the cavity can be filled, but also can promote the discharge of liquefied mortar, to make the grass-roots level and reinforcement layer of the effective combination of the effect of connection.

6, the repair method of severe broken plate. Has been cut into more than three pieces by multiple cracks, there is a serious settlement phenomenon and affects the normal traffic of the broken version is known as serious broken board, for this case, can only be used to replace the board. This requires breaking the whole broken plate and pouring cement concrete. The thickness of the replacement plate is generally greater than 240mm, basically close to the thickness of the original plate.

①Concrete practice. The concrete construction can be carried out according to the following process: field investigation of broken plate → line cutting → chiseling broken plate, remove broken pieces → batching, mixing → pouring → vibration → plastering → pulling → maintenance → open to traffic

② construction requirements. After breaking the broken plate, the side of the panel coated with asphalt, set up transmission reinforcement; the use of strength standards for the C35 concrete, and in strict accordance with the ratio to design the construction rules; mixing process should pay attention to grasp the appropriate ratio, especially to the water-cement ratio under strict control, to ensure that the concrete work; vibration time should be strictly in accordance with the provisions of the implementation of the vibration of the slurry to ensure that the water; the use of artificial smoothing method; the road surface smoothing 2h After smoothing, the surface to achieve sufficient hardness, until the finger pressure no traces can be produced to start maintenance. Maintenance method is to use the method of spraying maintenance liquid or sprinkling maintenance method. During the maintenance period, traffic should be minimized to ensure that a high quality of maintenance.

Summary

The damage of cement concrete pavement panels is the result of stress fatigue under repetitive loads after water penetration. The presence of a large number of defects inside the panel is an internal inducing factor, and water plays a contributing role in the appearance of cracks and the generation of fracture in the panel. Therefore, isolation of cement concrete pavement from water is a fundamental measure to prevent damage. For this reason, effective measures to take to the cracks out of the strengthening, maintenance, in order to effectively extend the life of cement concrete pavement at low cost.

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