CN104674627A - Joint construction method for preventing reflection cracks generated during spreading of asphalt on old concrete pavement - Google Patents

Abstract

The invention relates to a joint construction method for preventing asphalt reflection cracks on the old cement pavement. Firstly, the deflection difference between the plates is measured for the old concrete panels that need joint reinforcement. Cut strip-shaped grooves at equal intervals across the joints, and then use the impact drill to vertically drill the ends of the strip-shaped grooves; according to the depth of the hole, the length of the groove and the width of the joint between the plates, bend the steel bar to complete the forming of the horseshoe bar ; After the horseshoe-shaped steel bars are implanted in the strip grooves and the vertical holes at the ends, epoxy resin planting glue is poured into the drilled holes after the holes are cleared; Form a protective layer of planting bars; lay several layers of protective covers on the upper layers of the two old concrete panels from bottom to top. The invention has the advantages of preventing the occurrence and development of reflective cracks by reducing the relative vertical displacement on both sides of the old slab seam, thereby reducing or preventing the occurrence of reflective cracks in the asphalt surface layer added to the old cement road surface.

Description

A Joint Construction Method for Preventing Asphalt Reflective Cracks Overlaid on Old Cement Pavement

technical field

The invention relates to the technical field of road and traffic engineering, in particular to a joint construction method for preventing asphalt reflection cracks on old cement pavement.

Background technique

Cement concrete has good deformation resistance and water stability. In the 1880s and 1890s, a large number of cement concrete pavements were built in various places. At present, the cement concrete pavement in many areas or urban roads in our country is facing maintenance and renovation, and the old cement pavement reconstruction technical solution is to add asphalt overlay on the old cement pavement.

Due to the structural characteristics of the asphalt overlay on the old cement pavement, after a period of use, the asphalt overlay overlay is prone to cracks under the action of vehicle load and temperature. The cause of the reflective cracks in the overlay asphalt surface is the horizontal displacement of the old cement slab and the relative vertical displacement on both sides of the slab seam. The reason for the vertical displacement on both sides of the plate seam is the driving load. For the cement concrete pavement with voids at the bottom of the slab, at the joints of the old concrete slabs on the lower floor, the concrete slabs can hardly follow the deformation of the base layer, and the concrete slabs cannot work together. Under the action of traffic load, considerable additional stress will be generated at the joints of concrete surface slabs, which will put the structure in an unfavorable stress state. Under the repeated action of the traffic load, the overlay layer is subjected to repeated stresses of two kinds. Therefore, as time goes by, reflection cracks will appear on the upper and lower surfaces of the overlay layer corresponding to the crack positions, and expand along the thickness direction of the structure, finally forming a through Reflective cracks throughout the overlay. For the overlay pavement with no void and good interlayer contact conditions, the impact of traffic load on the generation of reflective cracks is not obvious, but it has a great impact on the expansion of reflective cracks in the overlay. Horizontal displacement is caused by changes in ambient temperature and humidity. Seasonal temperature changes cause the shrinkage and expansion of the cement board, and day and night temperature and humidity changes will cause the deformation of the cement board, which will cause the horizontal displacement of the cement board joints, so that the overlay layer will be in contact with the old cement concrete pavement. Stress concentration occurs at the place, which induces reflection cracks at the bottom of the overlay layer. Subsequently, under the repeated action of the traffic load, the cracks gradually penetrated the entire overlay layer along the thickness direction. The magnitude of the horizontal displacement is related to the size of the plate, the larger the plate, the greater the horizontal displacement. As far as the asphalt structure of the old cement pavement is concerned, the vertical displacement should be the main reason for the generation and development of reflection cracks in the asphalt surface layer of most cement pavements. Therefore, using appropriate methods to minimize the vertical relative displacement between plates is the main means to delay the occurrence of reflective cracks.

The existing technical measures to prevent reflection cracks mainly focus on the design of the overlay structure, including: (1) increasing the thickness of the asphalt overlay; (2) adding geogrid or geotextile as a waterproof layer; (3) using For the bonding and interlocking effect of the reinforced material, add mesh reinforcing ribs; (4) Add a stress-absorbing layer, such as setting an open-graded large-size asphalt macadam stress-absorbing layer. Schemes (1) and (4) can affect the position and shape of reflective cracks by increasing the thickness of the overlay layer, but they cannot effectively slow down the crack propagation speed and prevent the occurrence and development of reflective cracks. At the same time, the method of increasing the thickness of the asphalt overlay layer is limited by the elevation of the pavement on the one hand, and will increase the cost of the pavement on the other hand. In addition, in the case of high temperature in summer, the high-temperature creep of the asphalt mixture is easy to produce ruts, and it loses the old cement. The advantages of the strong base and thin surface produced by using concrete slabs as the base. Schemes (2) and (3) have limited effects on load-type reflective cracks, but the construction technology is relatively complicated, and it is not conducive to the interlayer shear resistance of the overlay composite structure.

The purpose of setting joints between cement concrete pavement slabs is to eliminate the temperature stress caused by temperature changes and prevent pavement damage caused by temperature changes. Especially when the wheel load passes through the joint between plates, the greater the relative vertical displacement on both sides of the joint, the more obvious the stress concentration of the old cement plate, and the more serious the reflection crack disease.

The repeated action of traffic load is an important cause of reflection cracks in the old cement pavement asphalt overlay structure. Numerical calculation and analysis results show that during the process of vehicle load, the deflection difference of the two sides of the original cement pavement joint is too large, resulting in asphalt The stress on the bottom surface of the asphalt layer is too large and cracks, and then the cracks spread to the surface of the overlay layer to form cracks on the road surface. For this failure mode of the asphalt overlay layer, the design should focus on the deflection difference and average deflection of the original cement pavement In terms of control. Under the condition of different overlay layer thicknesses, the shear stress at the bottom joint of the overlay layer has basically the same variation law as the deflection difference changes. That is, the deflection difference is small, and as the deflection difference increases, the shear stress of the surface layer increases rapidly; when the deflection difference increases to a certain extent, the shear stress shows a slow increasing trend. This change law shows that when the asphalt layer is added, If the load transfer at the joints of the original cement pavement is very good, the cracking life of the reflective cracks of the asphalt overlay mainly depends on the decay rate of the load transfer capacity at the joints of the original cement pavement; if the deflection difference is at a high level, then the asphalt overlay The shear stress is at a high level continuously from the beginning of the overlay, and the rate of reflection cracks will be faster. At this time, the cracking life of the overlay mainly depends on the thickness of the overlay. However, it is uneconomical to delay the occurrence of shear-type reflective cracks by increasing the thickness of the overlay. Therefore, strictly controlling the deflection difference at the joints of the original cement pavement before laying the asphalt layer is the most effective measure to delay the occurrence of reflective cracks.

Contents of the invention

The technical problem to be solved by the present invention is to provide a joint construction method for preventing asphalt reflection cracks on the old cement pavement, so as to control the deflection difference at the joints of the original cement pavement, prevent and slow down the reflection of the old cement pavement overlaying asphalt overlay The appearance of cracks.

In order to solve the above-mentioned technical problems, the technical solution of the present invention is: a joint construction method for preventing old cement pavement overlaying asphalt reflection cracks, characterized in that, the steps are:

a) Deflection pretreatment of old concrete panels: measure the deflection difference between the two old concrete panels that need joint reinforcement, and select the old concrete panels whose deflection difference exceeds 0.04mm;

b) Reinforcement pretreatment: Carry out rebar pretreatment for the old concrete panels whose measured deflection difference is above 0.04mm, and cut out equal intervals across the joints of the additional stress concentration area of the vehicle load at the joint of the two old concrete panels The strip-shaped grooves, and each strip-shaped groove is defined as the planting bar; the end of the strip-shaped groove is vertically drilled, and the hole extends to the inside of the base layer at the lower end of the old cement concrete panel, forming a vertical direction drilling;

c) Cleaning: Use a blower to blow the strip grooves and drilled holes to clean the grooves and holes;

d) Forming of horseshoe-shaped steel bar: According to the depth of the hole, the length of the groove and the width of the joint between the plates, bend the two ends of the threaded steel bar into a horseshoe shape to complete the forming of the horseshoe-shaped steel bar;

e) Rebar planting: vertically implant horseshoe-shaped steel bars along the direction of the strip groove, and insert the bent parts at both ends of the horseshoe-shaped steel bars into the drilled holes;

f) Glue filling: pour epoxy resin planting glue into the drilled hole until it reaches 2/3 of the hole depth;

g) Production of reinforcement protection layer: mix cement gravel and pour it into the strip groove and seal the drill holes, finally form the protection layer of reinforcement and maintain it;

h) Subsequent asphalt overlay structure: Lay emulsified asphalt oil layer, asphalt gravel fiber seal layer, coarse-grained asphalt concrete layer, and emulsified asphalt sticky layer oil layer on the upper layer of the two old concrete panels in sequence from bottom to top , Medium-grain asphalt concrete layer, emulsified asphalt sticky layer, asphalt mastic macadam layer.

Preferably, in the step a, for the old concrete panels whose measured deflection difference exceeds 0.06mm, grouting is performed before step b; the grouting material is cement mortar with compressive strength ≥ 15Mpa, and the gradation composition of cement mortar is It is: cement: water = 1.0:5, then based on the total mass of cement mortar, add 0.001wt% of aluminum powder and 0.01wt% of early strength agent.

Preferably, in the step b, the cutting direction of the strip-shaped groove is parallel to the driving direction of the vehicle on the old concrete panel, its longitudinal length is 1/25 of the long side of the old concrete panel, the width matches the diameter of the horseshoe-shaped steel bar, and the depth It is 1/3-1/4 of the thickness of the old concrete panel, the distance between adjacent strip grooves is 100-120cm, and the distance between the outermost strip groove and the edge of the old concrete panel is 30-45cm.

Preferably, in the step b, the diameter of the drilled hole is 4-6mm larger than that of the horseshoe tendon, and the drilled hole extends 4-6cm into the base layer at the lower end of the old cement concrete panel.

Preferably, in the step d, the horseshoe-shaped steel bar is a threaded steel bar with a diameter of 20-35mm, the total length of the horseshoe-shaped steel bar L bar=L bar+2*H plate+2*5cm+L seam, wherein, the L bar is a strip groove The H plate is the thickness of the old concrete panel, the L joint is the width of the plate gap between the two old concrete panels, and the depth of the horseshoe-shaped steel bar implanted in the base layer at the bottom of the old concrete panel is 3-5cm.

Preferably, in the step g, the thickness of the asphalt macadam fiber seal layer is 0.8cm, the thickness of the coarse-grained asphalt concrete layer is 8cm, the thickness of the medium-grained asphalt concrete layer is 5cm, and the thickness of the high-viscosity asphalt mastic macadam layer is It is 4cm; The label adopted in the coarse-grained asphalt concrete protective layer is AC-25C, the label adopted in the medium-grained asphalt concrete protective layer is AC-16C, and the label adopted in the high-viscosity asphalt mastic macadam layer is SMA-13.

The advantage of the present invention is that: by implanting horseshoe-shaped threaded steel bars between the joints of two old concrete road slabs, it can be closely bonded with the old concrete road slabs to form a "bolt-lock" effect. On the one hand, it can control the old On the other hand, it can effectively inhibit the cracks between the slabs from spreading to the upper asphalt overlay layer, reduce the relative vertical displacement on both sides of the old slab slab joints, prevent the occurrence and development of reflective cracks, and then reduce or prevent Overlay asphalt surfacing reflects the appearance of cracks.

On the old cement pavement, asphalt macadam fiber seal layer, coarse-grained asphalt concrete, medium-grained asphalt concrete protective layer, high-viscosity asphalt mastic macadam surface layer and modified emulsified asphalt bonding layer are added. The waterproof, interlayer cohesion and deflection performance of the joints between the old cement pavement slabs, so as to prevent the reflective cracks of the asphalt pavement on the old cement pavement.

In this method, the deflection difference of the old concrete road slab is measured before the reinforcement is planted, and the old concrete road slab with a measured value of 0.04-0.06mm is planted with reinforcement, and the old concrete road slab with a measured value exceeding 0.06mm The slab grouting treatment is carried out before the bars are planted. Through the above treatment, the strength of the old concrete road slab to be planted with bars is ensured, and the bar planting is effectively carried out.

The length, width and spacing of strip grooves, the diameter and length of horseshoe-shaped steel bars, the thickness of asphalt macadam fiber seal, etc., should be reasonably designed to ensure maximum prevention and slowdown of asphalt cover on old cement pavement Surface reflection cracks appear.

Fill the gap between the vertical drilling hole wall, the groove wall and the horseshoe-shaped steel bar with epoxy resin consolidation glue and cement gravel protective layer. The cover protects and strengthens the structure of the horseshoe rebar.

Description of drawings

Fig. 1 is the schematic diagram of the planar layout position of the planting bar of the joint construction method for preventing old cement pavement overlaying asphalt reflection cracks of the present invention.

Fig. 2 is a schematic diagram of the joint structure layout of the joint construction method for preventing asphalt reflection cracks on the old cement pavement overlay of the present invention.

Detailed ways

Example 1

In this embodiment, first, the deflection pretreatment of the old concrete panels is carried out, and the deflection difference between the two old concrete panels that need joint reinforcement is measured, and the old concrete with a deflection difference exceeding 0.04-0.06mm is selected. panel.

For old concrete panels with a deflection difference between 0.04-0.06mm, the joint construction method of paving asphalt reflective cracks on the surface is realized through the following steps:

The first step, the pretreatment of planting reinforcement: in the joint of the two old concrete panels 8, the additional stress concentration area of the vehicle load acts on the joint and cuts out strip grooves 13 at equal intervals across the joint, and the strip grooves 13 are the planting Rib position, use impact drill to carry out vertical drilling to the end of strip groove 13 again, and this hole extends to be positioned at the inside of base 9 at the lower end of old concrete panel 8 all the time, forms the drilling of vertical direction.

The structure of the strip groove 13 is specifically shown in schematic diagram 1. The cutting direction of the strip groove is parallel to the direction of the vehicle on the old concrete panel, and the length of the strip groove 13 is 1/25 of the long side of the old concrete panel plate , the width of the strip groove 13 matches the diameter of the horseshoe steel bar, and the depth of the strip groove 13 is 1/3-1/4 of the thickness of the old concrete panel,

The finite element analysis and experimental results show that the most unfavorable position of the traffic load on the old concrete slab is close to the edge of the slab, which is 1/10 of the slab span. In terms of quantity, the denser the planting bars, the more obvious the weakening of the board will be. Too many planting bars will waste materials and time-consuming, but the protective effect is not ideal. Therefore, in the present invention, the distance between two adjacent strip-shaped grooves 13 is controlled at 100-120cm, and the distance between the outermost strip-shaped groove 13 and the edge of the old concrete panel 8 is 30-45cm.

In the above steps, when molding the strip groove 13 and the end hole 11, the damage to the two old concrete panels 8 should be minimized to avoid cracking of the panels and ensure the integrity of the panels. The bottom should be flattened, and the side should be trimmed close to vertical. The diameter of the drill bit of the impact drill is 4mm-6mm larger than that of the horseshoe-shaped steel bar 12, and the depth of the drilled hole is >4cm thicker than that of the old concrete panel after slotting. The thickness of the old concrete panel is 4-6cm after slotting,

The second step, cleaning: use a blower to blow the strip grooves and drilled holes to clean the grooves and holes;

The third step, forming the horseshoe-shaped steel bar: according to the depth of the hole, the length of the groove and the width of the joint between the plates, bend the two ends of the threaded steel bar into a horseshoe shape to complete the forming of the horseshoe-shaped steel bar;

The concrete structure of horseshoe-shaped steel bar 12 is as shown in schematic diagram 2, and it adopts the threaded steel bar of diameter 20-35mm, and horseshoe-shaped steel bar total length L bar=L bar+2*H board+2*5cm+L seam, and wherein, L bar is bar shape The length of the groove, the H plate is the thickness of the old concrete panel, the L joint is the width of the plate gap between the two old concrete panels, and the depth of the horseshoe-shaped steel bar implanted in the bottom base of the old concrete panel is 3-5cm.

The fourth step, planting bars: vertically implant horseshoe-shaped steel bars along the direction of the strip groove, and insert the bent parts at both ends of the horseshoe-shaped steel bars into the drilled holes;

The fifth step, glue filling: pour epoxy resin planting glue into the drilled hole until the 2/3 position of the hole depth; after inserting the planting bar, it should be ensured that the glue fills the gap between the hole wall and the steel bar to ensure good waterproof performance.

The sixth step is to make the reinforcement protective layer: mix cement macadam and pour it into the strip groove 13 and seal the drill holes, finally form the reinforcement protection layer and maintain it; in this step, the cement macadam used for pouring What concrete adopts is the cement of label C20-C40.

The seventh step is the subsequent asphalt overlay structure: the specific distribution is shown in the schematic diagram 2. On the upper layer of the two old concrete panels 8, the emulsified asphalt permeable oil layer 7 and the asphalt macadam fiber seal layer are laid sequentially from bottom to top. 6. Coarse-grained asphalt concrete layer 5. Emulsified asphalt sticky oil layer 4. Medium-grained asphalt concrete layer 3. Emulsified asphalt sticky layer 2. High-viscosity asphalt mastic macadam layer 1. Among them, among the more critical protective layers: the thickness of the asphalt macadam fiber seal layer is 0.8cm, the thickness of the coarse-grained asphalt concrete layer is 8cm, the thickness of the medium-grained asphalt concrete layer is 5cm, and the high-viscosity asphalt mastic macadam layer The thickness is 4cm.

In this step, the label used in the coarse-grained asphalt concrete protective layer 5 is AC-25C, the label adopted in the medium-grained asphalt concrete protective layer 3 is AC-16C, and the high-viscosity asphalt mastic macadam concrete surface layer 1 The designation used in is SMA-13.

Example 2

In this embodiment, the deflection difference between the two old concrete panels requiring joint reinforcement is measured, and the old concrete panels whose measured value of the deflection difference exceeds 0.06 mm are selected.

For the old concrete panels whose deflection difference exceeds 0.06mm, when performing joint treatment of overlaying asphalt reflective cracks, it is necessary to pre-treat the old concrete panels before planting bars on the basis of Example 1. The slab grouting treatment is carried out on the concrete slab, so that the deflection difference between the slabs is less than the allowable value of the deflection difference, which is convenient to meet the requirements of the design standard and ensure the effectiveness and success rate of the subsequent reinforcement. The grouting material is cement mortar with compressive strength ≥ 15Mpa. The gradation composition of cement mortar is: cement: water = 1.0:5, based on the total mass of cement mortar, add 0.001wt% of aluminum powder and 0.01wt% of early strength agent . If the admixture is added, the water shall be in accordance with the product requirements and may refer to the "Technical Specifications for the Application of Concrete Admixtures" GB50119-2013.

The principle of the method of the present invention is: the stiffness of the implanted bar (the implanted bar is the horseshoe-shaped steel bar 6) is greater than the stiffness of the cement concrete, and a small vertical displacement difference is generated at the joint of the old concrete panel 5, that is, the measuring plate If the deflection difference between plates exceeds a certain limit (>0.04mm), the implanted ribs can transmit bending moment and shear force at the joints between plates, improve the coordination ability between plates, and help reduce deformation and additional The implanted tendons connect the front and rear adjacent plates together in the driving direction, so that stress redistribution and coordinated deformation are carried out between the implanted tendons and the plates of the old concrete panel 5, and the performance of the asphalt overlay structure on the old cement pavement is improved. Overall shear and overall tensile strength.

The horseshoe-shaped steel bar 12 can be closely bonded with the old concrete panel 8 to form a "bolt lock" effect, which can control the width of the crack at the cement-concrete joint, effectively inhibit the cracks between the panels from spreading to the upper asphalt overlay, and prevent the overlay Reflective cracks form on the surface.

If the deflection difference between the boards exceeds 0.06mm, the old board should be grouted to adjust the deflection difference between the boards to less than 0.06mm to reduce the additional stress caused by the void at the bottom of the board.

The basic principles and main features of the present invention and the advantages of the present invention have been shown and described above. Those skilled in the industry should understand that the present invention is not limited by the above-mentioned embodiments. What are described in the above-mentioned embodiments and the description only illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have Variations and improvements are possible, which fall within the scope of the claimed invention. The protection scope of the present invention is defined by the appended claims and their equivalents.

Claims (6)

1. A joint construction method for preventing old cement pavement from overlaying asphalt reflection cracks, characterized in that, the steps are: Deflection pretreatment of old concrete panels: measure the deflection difference between the two old concrete panels that need joint reinforcement, and select the old concrete panels whose deflection difference exceeds 0.04mm; Reinforcement pretreatment: For the old concrete panels whose deflection difference is more than 0.04mm, carry out pretreatment for planting bars, and cut strip grooves at equal intervals across the joints in the area where the additional stress concentration of the vehicle load acts on the joints of the two old concrete panels, and Define each strip-shaped groove as the planting bar part; Carry out vertical drilling on the end of the strip groove, and the hole has been extended to the inside of the base layer at the lower end of the old cement concrete panel to form a vertical drilling; Cleaning: Use a blower to blow the strip grooves and drilled holes to clean the grooves and holes; Forming of horseshoe-shaped steel bar: According to the depth of the hole, the length of the groove and the width of the joint between the plates, the two ends of the threaded steel bar are bent into a horseshoe shape to complete the forming of the horseshoe-shaped steel bar; Rebar planting: vertically implant horseshoe-shaped steel bars along the direction of the strip groove, and insert the bent parts at both ends of the horseshoe-shaped steel bars into the drilled holes; Glue filling: pour epoxy resin planting glue into the drilled hole until it reaches 2/3 of the hole depth; Production of reinforcement protection layer: mix cement gravel and pour it into the strip groove and seal the drill holes, finally form the reinforcement protection layer and maintain it; Subsequent asphalt overlay structure: Lay emulsified asphalt penetration layer oil layer, asphalt gravel fiber seal layer, coarse-grained asphalt concrete layer, emulsified asphalt adhesive layer oil layer, medium Granular asphalt concrete layer, emulsified asphalt sticky layer, asphalt mastic macadam layer. 2. The joint construction method for preventing old cement pavement overlaying asphalt reflection cracks according to claim 1, characterized in that: in the step a, for the old concrete panel whose measured value of deflection difference exceeds 0.06mm, in the step of Board grouting treatment before b; the grouting material is cement mortar with compressive strength ≥ 15Mpa, the gradation composition of cement mortar is: cement: water = 1.0:5, and then based on the total mass of cement mortar, add aluminum powder 0.001wt% , early strength agent 0.01wt%. 3. The joint construction method of preventing old cement pavement overlaying asphalt reflection cracks according to claim 1, is characterized in that: in the described step b, the cutting direction of the strip groove is parallel to the direction of vehicle running on the old concrete panel direction, its longitudinal length is 1/25 of the long side of the old concrete panel, its width matches the diameter of the horseshoe steel bar, its depth is 1/3-1/4 of the thickness of the old concrete panel, and the spacing between adjacent strip grooves 100-120cm, and the outermost strip groove is 30-45cm away from the edge of the old concrete panel. 4. the joint construction method of preventing old cement pavement overlaying asphalt reflection cracks according to claim 1, is characterized in that: in the described step b, the diameter of the borehole is 4-6mm larger than the horseshoe tendon diameter, and the borehole extends Insert 4-6cm into the lower base of the old cement concrete panel. 5. the seam construction method of prevention old cement pavement overlay asphalt reflection crack according to claim 1, it is characterized in that: in described step d, horseshoe-shaped steel bar is the threaded steel bar of diameter 20-35mm, horseshoe-shaped steel bar total length L bar =L bar+2*H board+2*5cm+L seam, wherein, L bar is the length of the strip groove, H board is the thickness of the old concrete panel, L joint is the width of the board seam between two old concrete panels, The horseshoe-shaped steel bars are implanted into the base layer at the bottom of the old concrete panel to a depth of 3-5cm. 6. The joint construction method of preventing old cement pavement overlaying asphalt reflection cracks according to claim 1, is characterized in that: In the described step g, the thickness of the asphalt macadam fiber seal layer is 0.8cm, and the coarse-grained asphalt concrete The thickness of the layer is 8cm, the thickness of the medium-grained asphalt concrete layer is 5cm, and the thickness of the high-viscosity asphalt mastic macadam layer is 4cm; the label used for the coarse-grained asphalt concrete protective layer is AC-25C, medium-grained asphalt concrete The code used in the protective layer is AC-16C, and the code used in the high-viscosity bituminous mastic macadam layer is SMA-13.