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The Four Common Quality Issue Prevention Measures for Asphalt Pavement

Thomas Huang posted this article in June 28, 2020

Poor road surface smoothness? Pavement waves? The pavement is uneven, loose, and there are wheel tracks? Pavement package, washboard? How to prevent the common quality problems of these asphalt mixture pavements? Come take a look with me!
1. Poor road roughness
phenomenon:
The surface of the asphalt mixture is paved, leveled and rolled, and the surface is relatively smooth. When the traffic is open, waves or "dish" pits or "pits" pits appear.
Cause Analysis:
(1) The flatness of the bottom layer is poor, because all types of asphalt mixtures have their certain compaction coefficients. After paving, the surface is flattened. Due to the unevenness of the base, the thickness of the virtual paving is thin and thick. After rolling, If there is less settlement at a thin place, it will be higher, and if there is more settlement at a later place, it will be lower, and the surface flatness will be poor.
(2) Improper paving method. In the equal-thick virtual paving layer, the asphalt mixture is smashed due to the high throwing of iron during paving, or the impact force during transportation and unloading, or people and vehicles are in the virtual paving mixture. Randomly stepping on and rolling, and then flattened, resulting in inconsistency between the virtual and the real, the virtual place is lower, the real place is higher, and the flatness is poor.
(3) The bottom of the material is not cleaned, the asphalt mixture is directly dumped on the bottom layer, the bottom of the material adhered to the base layer is not cleaned, or the leftover material of the day is randomly scattered on the bottom layer to serve as a part of the paving material. However, it has been compacted and condensed, which greatly reduces the compaction coefficient. When the new material is supplemented by flattening and compacting, local high protrusions, pimples, and unevenness are formed.
harm:
(1) Pavement smoothness is the main function of road engineering. If the road is uneven, it will reduce driving speed, increase driving bumps, increase impact, damage vehicle parts, reduce comfort, reduce safety, reduce economic and social benefits.
(2) The more uneven the road surface, the greater the impact of the vehicle and the more severe the damage to the road, which will greatly reduce the investment benefits of road engineering construction.
Prevention:
(1) First, we must solve the problem of flatness of the bottom layer. The bottom layer here refers to the general term. If the asphalt mixture surface layer is divided into three layers, then the bottom layer of the surface layer is the middle layer, the bottom layer of the middle layer is the ground layer, the bottom layer of the ground layer is the base layer of the road, the bottom layer of the base layer is the roadbed, each layer The smoothness of the previous layer is very important. Therefore, it is necessary to strictly control and carefully inspect the pavement layers according to the quality inspection and assessment. In particular, on the basis of ensuring the compactness and vertical and horizontal elevation of each layer, the flatness should be improved to control the standard, and finally the high quality of the flatness of the surface layer can be guaranteed.
(2) The paving of the surface layer should use a paver, and the elevation datum lines of each side should be aligned, and the operator should control the reserved height and stability of the hot plate; when using the paver in a small area or unconditionally, Paving strictly in accordance with the method prescribed in the operating regulations, that is, using the shovel buckle method, the shovel is not allowed to be raised, and the shovel shovel should be overlapped. When preparing the material, apply a hot spade to loosen the bottom part of the material and spread it out, so as to ensure that the virtual and real parts are consistent everywhere. In the flattening process, you can't step on the uncompacted virtual pavement. You must back up and flatten once to survive. If you find any irregularities, you can prepare a special long scraper to make up the flattening.
(3) The asphalt mixture should be unloaded on the iron plate, and cannot be tilted directly on the paving bottom layer. If it is to be unloaded on the base layer, it must be removed. The remaining cold material cannot be directly laid on the base layer as a part of the layer thickness, and should be heated for other purposes.
2. Pavement waves
phenomenon:
The arch is not full, the local high point deviates from the center line, or waves appear longitudinally on the pavement, especially when there are more roadside waves in the side ditch where the near side stones are made, which makes the side stones exposed inconsistently.
Cause Analysis:
The main reason is that the vertical and horizontal cross-section elevation control of each structural layer of the pavement is weak, or the distance between two adjacent control points is too large, and there is a large deviation in the elevation between the two points, forming a control point above or below the two control points Road elevation.
harm:
(1) Affect the appearance quality, the road is not complete.
(2) Waves on the road surface cause bumps in driving, reduce vehicle speed and ride comfort. Pavement waves cause water accumulation.
Prevention:
(1) Both the road bed and the pavement base layer should be checked and controlled by the five-point wireless method.
(2) It is necessary to control the virtual paving thickness of each layer of the asphalt mixture surface layer. Manual paving should adopt the method of laying bricks flat.
(3) In particular, the roadside elevation between the two rainwater outlets should be finely controlled and never lower than the elevation near the downstream rainwater outlet.
3. The road surface is uneven, loose, and there are wheel tracks on the road surface
phenomenon:
(1) Use a paver to pave or manually lay, the longitudinal stubble between the two frames is uneven, there is a height difference, or the phenomenon of loose slag is found at the stubble.
(2) The horizontal stubble of the two pavings is uneven and there is a jump.
 (3) There are wheel marks on the parts where the oil pavement is stubble with the side stones or with other buildings.
Cause Analysis:
(1) The longitudinal stubble is uneven, one is due to the inconsistency of the thickness of the two virtual pavings, resulting in a height difference, and the second is that each of the two frames belongs to each edge, the oil layer is virtual, after rolling, it is not real, and there are loose grooves. .
(2) Whether it is hot or cold jointed horizontal stubble, it is also difficult to connect due to the deviation of the thickness of the virtual paving and the spreading operation of the roller at the paving end.
(3) The stubble part of the oil pavement and side stones or other structures, the roller is not rolled under the edge of the roller, and it has not been tamped with a pier hammer iron, and the oil-deficient part has not been repaired in time, causing the edge to be uneven and loose slag, or Leave a wheel.
harm:
(1) The longitudinal stubble is uneven and loose, and it is easy to be damaged by the impact of the wheel and the erosion of rain and snow.
(2) The horizontal stubble is uneven, there is a jump, and the impact on the road is easy to damage.
(3) The edge part is not true, rain and snow water are easy to infiltrate. After soaking and freezing and thawing in winter and spring, the roadside will increase and deepen the damaged surface. Rain and snow water will easily penetrate into the base and roadbed, which will reduce its strength and stability.
Prevention:
(1) Both vertical and horizontal stubble should strive to make the thickness of the two pavings consistent, if any unevenness or oil increase or loss is found during rolling, it should be replenished or repaired by hand immediately. Cold stubble still needs to be stubble, Brush the oil, smooth it with a hot soldering iron and then compact it.
(2) When the root of the opposite side stone and the structure are stubble, the part that can not be pressed by the rolling wheel should be leveled by a special person. Use a hot pier hammer and a hot soldering iron to tamping and compacting, and at the same time eliminate the wheel marks.
4. Pavement package and washboard
phenomenon:
The surface layer of the asphalt mixture is crowded, and some are formed into lumps, the height of which is as small as 1-3cm and as large as about 10cm. Some form waves and some form washboards.
Cause Analysis:
(1) The content of asphalt mixture itself is too large. Or because the oil transportation distance is too far, the oil content is too large, or the amount of oil in the sticky layer spread on the base layer is too large. When the temperature rises, the oil in the sticky layer floods into the asphalt mixture. . All of the above are to make more "free asphalt" in the asphalt mixture and become a lubricant in the mixture, so that the oil is pushed into the oil bag and waves.
(2) The local combination of the surface layer and the base layer is not good. When the temperature is high, the driving effect will cause the forward direction of the vehicle or the outer side of the curve to push, resulting in a package.
(3) The surface treatment is carried out by layer method, uneven oiling, excessive asphalt content, or semi-legal construction, in the fine aggregate during paving, the local oil content is too large. When the road arch is large or the flatness is poor, the asphalt mixture will accumulate in the lower part in the hot season and form lumps.
(4) Improper treatment of flooding oil, excessive maintenance of minerals, uneven distribution and formation of lumps.
(5) The gradation of asphalt mixture is unreasonable, with more fine aggregates, low squeezing capacity, and poor high temperature stability; or uneven paving during construction, the roller is not rolled according to the operating regulations, or the base is uneven and wavy, and the paving surface is not Equal thickness, all form a washboard.
(6) The soil foundation is uneven, or the surface of the silt-lime soil base is bad, such as dryness and peeling. After paving the road and opening to traffic, it will cause waves.
(7) The water stability of the base is not good, the compaction is insufficient, the strength is uneven, and the pavement is deformed to generate waves.
harm:
(1) Destroy the smoothness of the road surface, reduce the comfort, safety, and damage the vehicle parts.
(2) Due to the unevenness, the impact of the vehicle is increased, and the destruction of the road surface is further exacerbated.
Prevention:
(1) Asphalt mixture should be visually inspected when entering the site. If the oil content is too large, it should not be paved, and the oil deposits should be removed.
(2) For asphalt stone chips added to the old pavement, and the crushed stone of the sticky layer to be poured, the oil consumption should be controlled according to the different thickness of the crushed stone specified in the specification.
(3) The oil piles formed by the asphalt spreader when parking and other reasons should be removed.
(4) Asphalt mixture should use petroleum asphalt with a softening point not lower than 45℃.
(5) The following treatment methods are adopted for pavement package:
1) It is caused by the cause of the grassroots, and the more serious package is treated by digging and repairing the grassroots first, and then making the surface layer.
2) If the temperature is higher, the more severe swells caused by the surface layer should be baked and softened with a heater and then shoveled out.
3) The slight sag has stabilized and can be shoveled directly at high temperature.
(6) The treatment methods for pavement waves are:
 1) If the strength of the base layer is insufficient or the stability is poor, the surface layer should be excavated and reinforced, and then the surface layer should be repaired.
2) If there is an interlayer between the surface layer and the base layer, the surface layer should be cut off to remove the unstable interlayer. After mixing the surface material with appropriate materials, stir-fry and re-lay the surface layer.
3) The surface wave of small area can be filled with bituminous mixture in the valley and leveled. For those with larger ups and downs, eradicate the crest part and resurface.
(7) On the parking sections, traffic lights, small radius bends, and other sections of the parking start driving speed, asphalt mixtures with good thermal stability should be selected. For example, the ground layer should use interruption gradation, large gaps, and inter-particle interlocking ability. Strong bituminous crushed stone: the middle surface layer uses coarse aggregate coarse gradation medium grain type; the surface layer uses continuous gradation, and the amount of stone chips is large.

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