Causes and prevention measures of the hottest asph

2022-08-12
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In recent years, with the continuous development of the automotive industry, the driving speed of vehicles is faster and faster, and vehicles have higher and higher requirements for road driving conditions. However, due to various cracks in the asphalt concrete pavement, No. 4. The installation of samples only destroys the continuity and smoothness of the pavement, affects the driving comfort of vehicles, and is also easy to cause harmful substances such as water to enter, affecting the service life of the road. Therefore, the prevention and treatment of cracks in asphalt concrete pavement is the key to ensure the driving quality and prolong the service life of the road

2 crack types of asphalt concrete pavement

13. Multiple protection functions: experimental force overload protection; Overcurrent and overvoltage protection; Safety protection when the sample breaks; Operation prompt wizard protection; After the experiment, automatic protection, etc. Generally speaking, cracks in asphalt concrete pavement, which is also the reason why Tesla, the most technologically advanced in the research and development of new energy vehicles, has not used graphene batteries in one product, can be divided into two types: one is load type cracks, which are mainly caused by driving loads. Under the action of vehicle load, tensile stress is generated at the bottom of the semi-rigid base. If the tensile stress is greater than the tensile strength of the base material, the bottom of the base will crack quickly until the asphalt surface is affected; The other is non load crack, low temperature shrinkage crack and temperature fatigue crack, which are mainly temperature cracks; Cracks caused by improper construction technology or the use of unqualified materials. The two types of cracks are shown in the forms of transverse cracks, longitudinal cracks, cracks and reflection cracks respectively

3 cause analysis and preventive measures of crack forms

3.1 transverse cracks

3.1.1 manifestation

cracks are basically perpendicular to the center line of the road, with different line widths. Some of the joint lengths run through the whole pavement, and some of the pavement cracks

3.1.2 causes

(1) the asphalt quality does not meet the local construction climate requirements or does not meet the relevant technical standards, resulting in the temperature shrinkage or temperature fatigue stress of the asphalt concrete surface is greater than the tensile strength of the asphalt concrete, resulting in transverse cracks

(2) improper treatment of construction joints, the joints are not tight, resulting in poor combination of different parts, resulting in transverse cracks

(3) pavement shrinkage cracks caused by comprehensive factors such as cement dosage and construction quality of semi-rigid base are shown in the form of transverse cracks

(4) the backfill parts of bridges, culverts and other structures are not constructed as required, or are not handled properly, resulting in uneven settlement, resulting in transverse cracks in the pavement

3.1.3 preventive measures

(1) in accordance with the relevant requirements of the technical code for construction of highway asphalt pavement, select the asphalt types that meet the requirements in combination with the climatic conditions and road grades in the region, so as to reduce or eliminate the temperature shrinkage cracks of the asphalt surface. The asphalt used in the construction should be tested by the relevant test and detection institutions in the region to verify whether it meets the relevant technical standards

(2) reasonably organize the construction. The paving operation shall be as continuous as possible, and cold joints shall be avoided as far as possible. If it cannot be avoided, the edge of the compacted paving belt shall be cut neatly according to the requirements, the floating material shall be removed, and the new hot mixture shall be applied to the joint part to preheat and soften the cold material part, the application material shall be removed, the bonding asphalt of 0.3 ~ 0.6kg/m shall be applied to the joint wall, and then the new asphalt mixture shall be paved

(3) fully compact the transverse joint. When rolling, the roller first extends the steel wheel into the newly paved part for about 15cm on the road width with the transverse joint compacted, and then moves 15 ~ 20cm to the new paving layer every time, until the roller completely enters the new paving layer, and then turns to the longitudinal rolling

(4) the cement used for semi-rigid base should be produced in rotary kiln with stable quality. The cement dosage should meet the design and construction requirements, and the cement and other mixtures should be fully mixed to make it uniform. Road cement should be tested by relevant departments at the required frequency

(5) gravel and other materials with good water permeability and material quality shall be selected for the backfill of bridges and culverts, and shall be filled and fully rolled as required; For sections with serious settlement, soft soil foundation treatment should be carried out first, and the construction should be reasonably organized to reduce the uneven settlement of backfill parts

3.2 longitudinal cracks

3.2.1 manifestation

the crack trend is basically parallel to the route trend, and more and more technical barriers have been broken, with different crack lengths and widths

3.2.2 causes

(1) unqualified materials are used in subgrade filling, and the subgrade water absorption and expansion cause pavement cracking

(2) the longitudinal widening is not constructed according to the requirements, or the rolling does not meet the requirements, resulting in the settlement of the widened part and longitudinal cracks

(3) the slope of subgrade slope is less than the design value, and the compactness of subgrade slope is insufficient to produce landslide

(4) the side ditch is too deep, which increases the actual filling height, resulting in landslide and pavement cracking

(5) the cold joints at the joint of the front and rear paving of the surface course were not treated according to the relevant requirements, and the combination was not tight and separated from each other, resulting in longitudinal cracks

3.2.3 preventive measures

(1) fill the subgrade with qualified materials or treat the filler before filling

(2) for the widened or half filled and half excavated sections of the old road, the loose soil of the slope shall be removed first for the subgrade filling, and the bench

step treatment shall be carried out step by step according to the requirements of the filling thickness, and full compaction shall be carried out

(3) the subgrade construction shall be filled in layers, the slope shall be fully compacted, and the heavy compaction standard shall be adopted; Correct grading, slow down the slope in high fill sections and reduce the depth of side ditches

(4) full width paving shall be adopted for the construction of surface course as far as possible. If the conditions for full width paving are not available, two pavers can be used to pave closely in front and behind, so as to avoid the second half paving after the front mixture has cooled as far as possible, so as to ensure the hot connection of the mixture; When paving in sections, the construction joints of the upper and lower layers should be staggered for at least 15era. If cold joints occur, cold joint treatment shall be carried out according to measures 2 and 3 in

3.1.3

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