CN107386039B

CN107386039B - Method for modifying old cement concrete pavement

Info

Publication number: CN107386039B
Application number: CN201610325409.XA
Authority: CN
Inventors: 虞鸿昌
Original assignee: Shanghai Changfu Municipal Engineering Co ltd
Current assignee: Shanghai Changfu Municipal Engineering Co ltd
Priority date: 2016-05-17
Filing date: 2016-05-17
Publication date: 2021-03-02
Anticipated expiration: 2036-05-17
Also published as: CN107386039A

Abstract

The present invention relates to a method for modifying old cement concrete pavement, and is characterized by that several methods are used for modifying old cement concrete pavement, and the most commonly used method is to spread asphalt mixture covering layer on the pavement, and the biggest defect of said method is that the reflection crack is very easily appeared on the joint position of correspondent old pavement slab. In order to overcome the defects of the method for modifying the old cement concrete pavement, the invention aims to solve the technical problem of providing a method for modifying the old cement concrete pavement to overcome the reflection cracks generated by additionally laying an asphalt layer. The reconstruction method for solving the technical problems comprises the following steps: an asphalt layer is paved on the old cement concrete pavement under a proper temperature environment, then the paved asphalt is modified, and then the thickness of the paved layer is controlled in the paving process.

Description

Method for modifying old cement concrete pavement

[ technical field ] A method for producing a semiconductor device

The invention relates to a method for reconstructing an old cement concrete pavement, which comprises the steps of low-temperature paving of an asphalt overlay, thickness selection of the overlay and modification treatment of asphalt.

[ background of the invention ]

Several methods are available for the overhaul and reconstruction of the old cement concrete pavement, but the most common method is to additionally lay an asphalt mixture overlay on the pavement, and the method is simple and convenient, can effectively improve the service performance of the old cement concrete pavement, has short construction period and relatively low manufacturing cost, and has little influence on traffic and environment; the reinforced and repaired pavement relates to a composite structure form of rigid and flexible pavements, and the composite pavement structure has the most outstanding advantages that the lower layer of the composite pavement structure is provided with a high-strength cement concrete pavement slab as a base layer, so that the composite pavement structure can bear larger vehicle load, the asphalt overlay layer on the upper layer can also obviously improve the use quality of the pavement, reduce noise and raised dust, prevent rutting and enhance the comfort and safety of driving; the defect is that the difference of material performance of the upper surface layer and the lower surface layer of the pavement is large, the old cement concrete pavement slab is greatly influenced by temperature change, cracks and seams exist on the old concrete pavement slab, the phenomena of slab staggering, void and the like are accompanied, under the combined action of load stress and temperature stress, the asphalt finish coat corresponds to the seams of the old pavement slab, the positions of the cracks are easy to generate reflection cracks, once the cracks penetrate through the surface layer, the asphalt finish coat is grouted, water is damaged, the asphalt finish coat is further cracked, and the service performance and the service life of the asphalt finish coat are greatly shortened.

[ summary of the invention ]

In order to overcome the defects of the method for modifying the old cement concrete pavement, the invention aims to solve the technical problem of providing a method for modifying the old cement concrete pavement to overcome the reflection cracks generated by additionally laying an asphalt layer.

The reconstruction method for solving the technical problems comprises the following steps: an asphalt layer is paved on the old cement concrete pavement under a proper temperature environment, then the paved asphalt is modified, and then the thickness of the paved layer is controlled in the paving process.

The asphalt layer must be laid on the old cement concrete road surface at a natural temperature of 5-10 deg.C, preferably in late autumn or early winter. The thermal expansion value and the shrinkage value of the cement concrete have certain difference depending on the types, the contents, the age of the concrete and other factors, and the thermal expansion value and the shrinkage value of the common strength C30 concrete are extended or shortened by 11.59 x 10-6 mm in the length direction through a test material, namely 0.01159 mm/DEG C.m. When the temperature of the cement concrete slab with the length of 100 meters is increased or reduced by 1 ℃, the length is extended or shortened by 1mm, and when the temperature is about 4 ℃, the mass of water molecules is minimum, and at the moment, the mass of the concrete slab tends to be in a smaller state. The joint of the old cement concrete pavement can not bear the tensile stress, and the tensile stress is mainly caused by the reduction of the length of the plate due to the reduction of the temperature. Through tests and measurement, the asphalt layer is paved at the natural temperature of more than 5 ℃ and less than 10 ℃ so that the shrinkage value of each 6m of the old cement concrete pavement caused by the temperature is less than or equal to 0.36 mm.

As a further improvement of the old cement concrete pavement modification method, the common asphalt material is modified, a proper amount of plastic particles and banana powder are added into the ac25 common asphalt mixture, so that the common asphalt pavement has trace elasticity and extensibility, and the extensibility of the added layer is more than or equal to 0.36mm when the temperature of the added layer is less than or equal to 4 ℃ within the length of 6 meters.

As another improvement of the old cement concrete pavement reconstruction method, the thickness of the asphalt overlay is determined to be 12 cm. When an asphalt layer is additionally laid on an old cement concrete pavement, the thickness of the additionally laid layer needs to be controlled. The spreading speed of the reflection cracks is greatly related to the thickness of the asphalt overlay, generally, the thicker the overlay, the better the effect of preventing or delaying the reflection cracks is, the longer the time for the cracks to spread to the road surface is, but the overlay cannot be thickened in an unlimited way, so that the pavement is not feasible in economy, and the service performance of the pavement is influenced because rutting is easily generated due to the over-thick overlay. The following three tables are formed through a test on the relation between the thickness of the asphalt pavement and the load stress of the train and a test on the influence of the thickness of the asphalt pavement on the deflection of a plate joint:

TABLE 1 Top stress values of asphalt overlay

Unit Pa

Thickness of asphalt overlay	4	6	8	10	12	14	16
								σx	357877	291967	245952	211429	184479	162942	145483
σy	459542	385479	331541	28135	251245	219252	191447
								σz	207427	147619	108504	82283	64678	53023	45527
σ1	196503	119621	99537	73230	54709	42026	33391
								σ2	205403	149689	132349	126497	116501	104583	92297
σ3	722940	558454	454111	382121	329193	288609	256768
								σe	579710	425809	339360	286003	249397	222016	200521
τmax	307891	211501	155695	122012	101253	88424	80626

TABLE 2 asphalt overlay bottom stress values

Unit Pa

Thickness of asphalt overlay	4	6	8	10	12	14	16
								σx	424347	405639	393627	383936	374647	365057	355039
σy	876283	836854	801510	768840	737800	708240	680217
								σz	308432	304670	302690	300270	296495	291185	284529
σ1	179082	86226	187796	185171	79682	172435	164272
								σ2	310680	307708	306671	305193	302240	297578	291390
σ3	1119290	1052960	1003360	962682	927019	894469	864123
								σe	881804	812828	763103	724990	694220	668309	645745
τmax	410521	373467	349521	333019	320661	310631	301919

TABLE 3 influence of the thickness of the asphalt overlay on the deflection of the slab joints

Thickness of asphalt overlay	4	6	8	10	12	14	16
								Load side deflection value U1	1.21907	1.20211	1.18203	1.16041	1.13759	1.11504	1.09192
Unloaded deflection value U2	1.37695	1.3383	1.30412	1.30412	1.24146	1.21173	1.18279
								Difference in deflection
ΔU＝U2-U1	0.15788	0.13619	0.12209	0.12209	0.10387	0.09669	0.09087

Through analysis, the calculation results show that the maximum principal stress sigma 1, the equivalent stress sigma e and the maximum shear stress tau max of the asphalt overlay layer are in a decreasing trend along with the increase of the thickness of the overlay layer, when the thickness of the overlay layer is increased from 4cm to 10cm, the stress in the asphalt overlay layer is rapidly reduced, and the maximum principal stress sigma 1, the equivalent stress sigma e and the maximum shear stress at the top of the overlay layer are all reduced obviously. This demonstrates that increasing the thickness of the asphalt overlay has a significant effect on reducing the stresses within the overlay. In addition, the deflection of the overlay at the slab joint and the deflection difference of the two sides of the slab joint are changed along with the thickness of the asphalt overlay.

When the thickness of the overlay is increased from 4cm to 16cm, the deflection value and the deflection difference of the two sides of the asphalt overlay slab seam are gradually reduced. The deflection of the road surface on the loaded side is reduced by 10.44%, the deflection of the road surface on the unloaded side is reduced by 14.11%, and the deflection difference on the two sides is reduced by 42.5%. When the thickness of the asphalt overlaying layer is increased, the shear stress and the deformation of the asphalt overlaying layer at the joint can be reduced, the possibility of occurrence of reflection cracks is reduced, and the thickness of the overlaying layer in the aspects of cracking resistance and economy is comprehensively considered to be 12 cm.

[ embodiment ] A method for producing a semiconductor device

The concrete implementation mode of the method for modifying the old cement concrete pavement mainly comprises the following four steps: the method comprises the steps of conducting disease treatment on an old cement concrete pavement before an asphalt layer is paved, selecting proper natural temperature, conducting modification treatment on asphalt, and controlling the paving thickness.

The method for reconstructing the old cement concrete pavement needs to carry out disease treatment before the asphalt layer is additionally paved, and ensures the stability of the old pavement slab through panel treatment, crack and joint reinforcement, so that the pavement with the paved layer has a good and stable working state. For the broken plates which are seriously broken and have cracks and blocks because of the very serious peeling of the sunk broken panel and the cracks, and the broken plates which are staggered and start to move, the treatment measures of excavating the old plates to construct new plates are adopted for the crossed cracks penetrating through the whole plates. For the joint with deflection difference of more than 0.06 between two side plates of the joint, a reinforcing measure is taken, in order to restore the load transmission force of adjacent plates and reduce the deflection difference, full-depth cutting is carried out within the range of 30cm-50cm respectively according to the deflection difference of two sides of the joint, the cut old plate is removed, the base layer is visually observed, and if the old plate is loose, the old plate is removed together. And cutting seams and cleaning the seams with the deflection difference of the plates at the two sides of the seams smaller than 0.06mm, and pouring by using hot asphalt mixture. And for the plate with the actual single point deflection value exceeding 0.4mm and serious void, the plate needs to be removed according to crushing and newly built, and for the plate with the actual single point deflection value between 0.2mm and 0.4mm, plate bottom grouting treatment is adopted. And (4) the plate after grouting is finished is forbidden to pass by vehicles until the mortar strength reaches 5Mpa, and the traffic is not opened. After the grouting is finished for 3 days, the rebound deflection values of the four corners of the grouting plate are measured again, and if the bay deflection value is within the grouting range, the plate needs to be drilled again for pressure compensation. And finally, the horizontal displacement of the old cement pavement is controlled by arranging the middle interlayer, and the Hh-3 polyester glass fiber composite cloth is preferentially selected as the interlayer, so that the high-strength concrete composite pavement has high tensile strength, and the shearing damage generated on the interface of the polyester glass fiber composite cloth and the asphalt overlay layer can be eliminated.

One of the important steps implemented by the method for modifying the old cement concrete pavement is that an asphalt layer is additionally paved on the old cement concrete pavement, preferably in late autumn or early winter, and the asphalt layer is required to be paved at the natural temperature of more than 5 ℃ and less than 10 ℃.

According to the method for modifying the old cement concrete pavement, disclosed by the invention, the common asphalt is subjected to modification treatment, and particularly, a proper amount of plastic particles and banana powder are added into an ac25 common asphalt mixture, so that the common asphalt has trace elasticity and extensibility, and the extensibility of the added layer is more than or equal to 0.36mm within 6 meters. When plastic particles and banana powder are added into an ac25 common asphalt mixture, the quantity needs to be controlled, the ductility can be ensured, and the rigidity of a layering is not influenced.

The spreading layer is spread by 12cm and divided into two layers, the bottom layer is 8cm, and the surface layer is 4 cm. The modified asphalt is additionally paved on the bottom layer, so that the spreading degree of the additionally paved bottom layer is more than or equal to 0.36mm within 6 meters, the additionally paved bottom layer has a leveling reinforcing function and a stress absorbing function, and the problem of reflection cracks caused by temperature is solved.

Claims

1. A method for modifying an old cement concrete pavement comprises the following steps: the asphalt overlay is subjected to low-temperature paving, thickness control and asphalt modification treatment, so that the shrinkage value of each 6m length of the old cement concrete pavement caused by temperature is less than or equal to 0.36mm, and the spread of the overlay within 6m length is greater than or equal to 0.36 mm;

the low-temperature paving of the asphalt overlaying layer is to select the asphalt overlaying layer to be paved at the natural temperature of more than 5 ℃ and less than 10 ℃ so that the shrinkage value of each 6m of the old cement concrete pavement caused by the temperature is less than or equal to 0.36 mm;

the thickness control is that the additional layer is paved by 12cm, and the additional layer is divided into two layers, wherein the bottom layer is 8cm, and the surface layer is 4 cm;

the asphalt modification treatment is to add plastic particles and rubber powder into an ac25 common asphalt mixture to ensure that the spreading degree of the added layer is more than or equal to 0.36mm within 6 meters in length and at the temperature of less than or equal to 4 ℃.