Why asphalt pavement will appear network cracking, cracking and so on?

In accordance with the "Highway Culvert Pavement Maintenance Technical Specification" on the classification of asphalt pavement damage, combined with the actual damage to the pavement, early damage to asphalt pavement is divided into cracks, surface damage, deformation and water damage categories.

Cracks class - asphalt pavement after the completion and use of the process by the environment and the grass-roots level, the gradual loss of adhesion, thus reducing the tensile capacity of the pavement, resulting in cracks and expansion.

From the asphalt pavement cracks to classify the mechanism, the main form of cracks are: temperature shrinkage cracks, reflection cracks and load cracks three.

1, temperature shrinkage cracks in most parts of China is quite common, the main form of transverse cracks, there are also longitudinal cracks and network cracks. There are two main reasons for temperature shrinkage cracks:- is the low-temperature shrinkage cracks. Asphalt mixture is a very sensitive material to temperature, in the summer when the temperature is high, with good stress relaxation properties, the mixture will not produce excessive internal temperature stress: in winter, the stress relaxation of the mixture is not enough to resist the temperature drop in the stress generated by the growth of the material contraction of the tensile stress generated once more than the tensile strength of the material, the pavement will be cracked, the cracks are mainly manifested as transverse cracks pavement The larger the longitudinal length, the greater the constraints in the contraction process, the more serious the cracking, while the pavement is generally narrower in the transverse direction, the constraints are also smaller, in the contraction process is not easy to crack. Another is the temperature fatigue cracks. Ambient temperature changes not only in the spring, summer, fall, winter seasonal changes, and every day the ambient temperature also repeatedly rise and fall, asphalt pavement temperature stress day after day repeatedly, resulting in temperature fatigue cracks.

2, reflective cracks in composite pavement and semi-rigid grass-roots paving asphalt mixture is more typical in winter, with the lowering of ambient temperatures, concrete slab contraction, there have been cracks become wider, asphalt paving layer and cracks corresponding to the production of tensile stress, not only rigid or semi-rigid grass-roots level of contraction, but also produce the same asphalt surface layer contraction and deformation of the contraction and deformation of the concrete slab shrinkage (expansion) joint displacement is opposite. The displacement of the shrinkage deformation is opposite to that of the concrete slab shrinkage (expansion) joint. Thus exacerbating the strain at the crack, resulting in stress superposition. Similarly, the role of day and night temperature difference loading can also lead to reflection cracks in composite pavements. When the daytime temperature is high, the upper part of the concrete slab than the lower part of the temperature is high, the slab produces concave deformation, and the expansion joints or shrinkage joints corresponding to the asphalt surface layer produces tension; when the night temperature is low, the upper part of the concrete slab temperature is low, the lower part of the temperature is high, the slab produces convex deformation, and the expansion joints or shrinkage joints corresponding to the asphalt surface layer produces compression, day in and day out as the daily temperature cycling, the asphalt surface layer at the joints produces reflection cracks. Uneven subsidence of the roadbed will also cause longitudinal cracks or transverse cracks in the pavement, such as the old road widening or bridge, access to the end of the uneven subsidence caused by the end, etc..

3, load crack is due to the vehicle load effect of cracks. When the tensile stress generated under load is greater than the tensile strength of the pavement material, it will lead to asphalt pavement surface layer or grass-roots cracks. With the increase in the number of load cracks gradually expand, and eventually produce network cracks or cracks and other fatigue damage. The main reason for the occurrence of load cracks is that the structural design of the pavement is unreasonable, the pavement material is unqualified, or there are construction quality defects.

Road cracks are caused by more and more complex reasons, there are from the design, but also from the construction and the material itself, etc. In addition, rain penetration will also lead to cracks in the pavement, due to cloudy days and rain, part of the rain penetrates into the pavement gaps and cracks in the external force, resulting in the reduction of the adhesion between the asphalt and aggregates and the gradual loss of bonding force. Moisture infiltration, in the car wheel dynamic load repeated action, into the pavement gap cracks in the water constantly produce dynamic pressure and vacuum negative pressure suction repeated cycles, water gradually penetrate into the asphalt and aggregate interface, asphalt membrane from the aggregate surface off, asphalt mixture drop material, loose, open into the mesh cracks and constantly expanding. Pavement micro-cracks do not take preventive maintenance measures, cracks will be under the action of the traffic load will grow rapidly, widening, pavement micro-cracks will develop into a network of cracks and block cracks, and even potholes, these damages will seriously affect the pavement driving performance, reduce traffic safety, while the aggravation of the hazards, the maintenance costs doubled, the pavement can be taken by the original pre-maintenance, and the development of cracks to the block or potholes have to be taken to overhaul the pavement. The pavement can be pre-maintained, but when it develops to block cracks or potholes, it has to be overhauled.

How to prevent pavement cracks?

Traditional materials emulsified asphalt or modified emulsified asphalt sprayed on the asphalt pavement, with the prolongation of time, water evaporation, in a similar soluble role, emulsified asphalt to restore the characteristics of asphalt, the formation of a thin layer of asphalt on the surface of the pavement membrane, and has a certain strength to achieve the closure of the road surface to prevent the efficacy of water seepage. Emulsified asphalt or modified emulsified asphalt wrapped around the loose aggregates on the pavement, breaking the emulsion of the new asphalt and the old asphalt on the pavement bonded to each other, so that the loose aggregates bonded.

New ultra-thin micro-sealer (including sand fog sealer) asphalt pavement maintenance agent sprayed on the asphalt pavement, maintenance agent in the role of surface energy, in the asphalt pavement surface spread, at the same time in the principle of similar soluble in the asphalt pavement maintenance agent and the interaction of the old asphalt, new asphalt and the original asphalt between the formation of a continuous whole, and at the same time, in the asphalt pavement maintenance agent, due to the special additives containing a number of At the same time, in the asphalt pavement maintenance agent, due to the special additives contain many unsaturated bonds, there is a strong polarity, can effectively wrap the asphalt, so that asphalt can be easier for the asphalt pavement maintenance agent in the other components of the solubility, thus making the aging asphalt can be activated, restore and update, the old and new asphalt fusion, with the extrusion of the air and the volatilization of some of the light components of the asphalt pavement maintenance agent to form a layer of continuous asphalt on the original asphalt pavement film, thereby closing the road surface to prevent water seepage. After spraying the new road maintenance agent, the loose aggregates on the road effectively wrapped up, in the asphalt pavement maintenance agent with a series of physicochemical action of the old asphalt, forming a thin layer of asphalt on the old asphalt pavement continuous film, before the formation of the strength of the asphalt film, the new asphalt and the original asphalt on the pavement effectively bonded to bond the loose aggregates; at the same time, the road maintenance agent contains a certain amount of functional additives in the functional At the same time, the road maintenance agent contains certain functional additives, in the function of additives, further strengthen the new asphalt and the original asphalt adhesion, making the loose aggregate bonding more solid and stable.