CN114045729B - Anti-segregation crack-reducing construction method for cement stabilized aggregate base layer in low-temperature region - Google Patents
Anti-segregation crack-reducing construction method for cement stabilized aggregate base layer in low-temperature region Download PDFInfo
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- CN114045729B CN114045729B CN202111390310.5A CN202111390310A CN114045729B CN 114045729 B CN114045729 B CN 114045729B CN 202111390310 A CN202111390310 A CN 202111390310A CN 114045729 B CN114045729 B CN 114045729B
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C21/00—Apparatus or processes for surface soil stabilisation for road building or like purposes, e.g. mixing local aggregate with binder
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C19/00—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving
- E01C19/12—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving for distributing granular or liquid materials
- E01C19/18—Devices for distributing road-metals mixed with binders, e.g. cement, bitumen, without consolidating or ironing effect
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C19/00—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving
- E01C19/12—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving for distributing granular or liquid materials
- E01C19/18—Devices for distributing road-metals mixed with binders, e.g. cement, bitumen, without consolidating or ironing effect
- E01C19/185—Devices for distributing road-metals mixed with binders, e.g. cement, bitumen, without consolidating or ironing effect for both depositing and spreading-out or striking-off the deposited mixture
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C19/00—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving
- E01C19/22—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving for consolidating or finishing laid-down unset materials
- E01C19/23—Rollers therefor; Such rollers usable also for compacting soil
- E01C19/28—Vibrated rollers or rollers subjected to impacts, e.g. hammering blows
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C3/00—Foundations for pavings
- E01C3/02—Concrete base for bituminous paving
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C3/00—Foundations for pavings
- E01C3/04—Foundations produced by soil stabilisation
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C7/00—Coherent pavings made in situ
- E01C7/08—Coherent pavings made in situ made of road-metal and binders
- E01C7/18—Coherent pavings made in situ made of road-metal and binders of road-metal and bituminous binders
Abstract
The invention belongs to a construction method for preventing segregation and reducing cracks of a cement stabilized aggregate base layer in a low-temperature region, wherein the grain size ratios of graded gravels in a dense type base layer and a dense type top base layer of a framework in the low-temperature region are as follows: 20-25mm; the top base layer comprises the following components in percentage by weight: graded gravel cement =100, maximum dry density 2.405g/cm 3 The water content is 4.4%, the water immersion after 7 days has no lateral limit strength (MPa) of 5.0, and the thickness of the top base layer is 20cm. The subbase layer comprises the following components in percentage by weight: graded gravel cement = 100; maximum dry density 2.393g/cm 3 The water content is 4.3 percent, the water immersion after 7 days has no lateral limit strength (MPa) of 4.5, and the thickness of the underlayer is 36cm. And sequentially carrying out paving of the subbase layer and the top base layer, auxiliary operation of paving, rolling, health preserving and test detection. The method can ensure that the cement stabilized aggregate base layer in a low-temperature area reduces cracks and meets the requirement of excellent quality, and has the advantages of simplicity, convenience, practicability, low cost, construction period saving, good quality and long service life.
Description
Technical Field
The invention belongs to a construction method for preventing segregation and reducing cracks of a cement stabilized aggregate base layer in a low-temperature area.
Background
The highway pavement of the traditional region is formed by using broken stones with the thickness of 15cm as a subbase layer on the surface of a roadbed (or a cushion layer), arranging a base layer with the thickness of 34cm at the upper end of the subbase layer, and then laying asphalt surface layers with the thickness of 19cm on the upper end of the base layer in total, wherein the subbase layer and the base layer are generally called as the base layer. In order to distinguish the base layer at the upper end of the subbase layer, the subbase layer and the top base layer form the base layer, wherein the base layer plays a role in starting and stopping, and indexes of integrity, strength and compactness of the base layer play a key role in the quality of the highway.
At present, common diseases of asphalt concrete pavements mainly comprise transverse cracks, pits, slurry pumping, pits and cracks, and one of main sources of the diseases is caused by base cracks. The base layer is a semi-rigid structure, and has the advantages of high rigidity, convenient construction, good water stability, good freezing resistance and the like, but has the defects of brittle property and poor deformation resistance, and the phenomena of temperature shrinkage cracks caused by temperature change, shrinkage cracks caused by water content change and the like, particularly the phenomena of temperature shrinkage and shrinkage cracks caused by temperature change and water content change in wide areas such as inner Mongolia, heilongjiang, jilin, gansu and Xinjiang north in China are more serious in low temperature areas (the average temperature per year is-1-10 ℃) below 42 ℃. The initial stage of the crack in the base layer has no obvious influence on the traveling crane, but the crack can cause the downward penetration of surface water, cause the long-term local dampness of the roadbed and influence the integral strength of the supporting base layer, thereby often causing the damage of the asphalt surface layer.
In the aspect of pavement structure combination design, attention to interlayer combination state is insufficient, and interlayer continuity state cannot be guaranteed; the reflection cracks on the pavement are inevitable, and become the root of the occurrence of slurry, pits and other diseases related to the cracks due to the untimely and effective treatment, and the types and the formation reasons of the cracks are as follows:
1) Fatigue cracks, also known as load cracks, are failures that occur as a result of repeated traffic loading. When the wheel acts, the bottom of the semi-rigid base layer generates tensile stress, and when the load is repeatedly acted, particularly a large amount of overrun load is acted, the tensile stress exceeds the tensile strength of the material, so that the bottom of the semi-rigid base layer is firstly cracked and gradually expands to the upper part.
2) Temperature shrinkage cracking, mainly low temperature cracking, refers to the shrinkage of volume caused by the interaction of semi-rigid base materials in the process of cooling. At the moment, tiny cracks are generated at the weak part of the base layer and rapidly develop, and the transverse length of the pavement is far smaller than the longitudinal length, and the lateral constraint force is not large, so the cracks are generally transverse interval cracks.
3) The shrinkage crack refers to a crack generated by volume shrinkage of a semi-rigid material due to capillary action, adsorption action, intermolecular action, carbonization action, and the like, which occur due to the reduction of water.
4) Inadequate base course compaction, strength, or half-fill of the half-cut section, shrinkage or differential settlement leading to cracks.
5) Unreasonable design and irregular construction.
How to construct the base course in the low-temperature area link, the emergence and the influence of reduction crack to the utmost extent, reinforcing structure durability is the problem that needs to solve urgently.
Disclosure of Invention
The invention aims to provide a construction method for preventing segregation and reducing cracks of a cement stabilized aggregate base layer in a low-temperature area, which can prevent segregation and reduce cracks of the cement stabilized aggregate base layer in the low-temperature area to meet the requirement of high quality and has the advantages of simple and practical method, low cost, construction period saving, high quality and long service life.
Therefore, the construction method for preventing segregation and reducing cracks of the cement stabilized granular base layer in the low-temperature area comprises the following steps:
(1) Processing of broken stone raw materials: the crushed stone first crusher adopts a jaw crusher with the model larger than 600 x 900, the second crusher adopts a vertical shaft crusher with the model larger than 175, a vibrating soil sieving screen is arranged between the first crusher and the second crusher to obtain five kinds of aggregates with the grain diameters of 20-25 mm, 10-20 mm, 5-10 mm, 3-5 mm and 0-3 mm, and the five kinds of aggregates are respectively stacked;
(2) The grain size proportion of graded gravel in the dense subbase layer and the top base layer of the framework in the low-temperature region is as follows: 20-25mm;
the top base layer comprises the following components in percentage by weight: graded gravel cement =100:5, maximum dry density 2.405g/cm 3 The water content is 4.4%, the water immersion after 7 days has no lateral limit strength (MPa) of 5.0, and the thickness of the top base layer is 20cm.
The subbase layer comprises the following components in percentage by weight: graded gravel cement =100:4; maximum dry density 2.393g/cm 3 The water content is 4.3 percent, the water immersion after 7 days has no lateral limit strength (MPa) of 4.5, and the thickness of the subbase layer is 36cm;
the cement is ordinary portland cement, slag portland cement and pozzolanic portland cement, the initial setting time is more than 4h, and the final setting time is more than 6h;
(3) The uniformity of the mixture is improved, segregation is reduced, the graded gravel and the cement are placed in a stirring machine, the adding amount of water is 60 percent of the total amount of the added water during the first-stage mixing, the cement, the graded gravel and the water are fully combined, the adding amount of water in the second stage is 40 percent of the total amount of the added water, and the mixture is uniformly mixed by stirring;
(4) The transportation and paving adopt an anti-segregation measure, the periphery of a transportation vehicle is integrally and fixedly wrapped by a cotton quilt, the top surface of the transportation vehicle is covered by tarpaulin, and the rear bucket part of the transportation vehicle is provided with a discharge baffle;
(5) Paving a base layer, wherein the water content of the base layer material is 5.9-6.4% during paving so as to compensate the water loss in the paving and rolling processes;
(a) Firstly, paving an underlayer, wherein the thickness of the underlayer is 36cm, adopting two single-layer spraying cement slurry pavements, namely using an anti-segregation middle and large paver Power-DT1900 to realize a first-layer paving layer with the full thickness of 18cm and the full width of 12.35m, spraying a layer of cement slurry on the upper end surface of the first-layer paving layer, controlling the net amount of cement per square meter to be 0.4-0.5 kg, using an anti-segregation middle and large paver Power-DT1900 to realize a second-layer paving layer with the full thickness of 18cm and the full width of 12.35m to form the underlayer, or adopting 2 pavers to pave the full-width stepped first-layer paving layer, uniformly spreading the cement slurry on the surface of an operation surface, and then using 2 pavers to pave the full-width stepped second-layer paving layer;
then sequentially carrying out auxiliary operation, rolling, health preserving and test detection of paving the subbase layer;
(b) Spraying cement slurry, namely spraying a layer of cement slurry on the upper end face of the subbase layer after the health maintenance and test detection are qualified, wherein the net dosage of the cement per square meter is controlled to be 0.4-0.5 kg, so that the subbase layer and the top base layer form a whole, and the load transfer is facilitated;
(c) Then, paving a top base layer, wherein the thickness of the top base layer is 20cm, adopting one-time full-thickness forming paving, and realizing 20cm full thickness and 12.35m full width one-time paving forming by using an anti-segregation middle and large paver Power-DT1900 at one time or adopting 2 pavers to pave in a full-width stepped manner; and then sequentially carrying out auxiliary operation, rolling, health preserving and test detection on the paving of the subbase layer.
As a preferred technical scheme of the invention: the full-width stepped paving with 2 pavers is as follows: the distance between the front and the back of the two pavers is 5-10 m, the paving lap width is 10-15 cm, the front paver adopts a left side steel wire rope and a right side aluminum gold wire to advance as a guide, the rear paver uses a base layer which is paved and not rolled on the left side as a reference surface and a right side steel wire rope to advance as a guide, the paving thickness of the two pavers is consistent, the loose paving coefficient is consistent, the road arch cross slope is consistent, the flatness is consistent, the vibration frequency is consistent, and the longitudinal joint is level and dense.
As a preferred technical scheme of the invention: in the auxiliary operation of the paving, a specially-assigned person is arranged to eliminate the segregation phenomenon of the coarse and fine aggregates during the paving, timely shovel off the accumulated or segregated part of the coarse and fine aggregates and fill the accumulated or segregated part with a newly-mixed mixture;
when various machines are ready and more than 4 vehicles are stored on site, the paving operation is started; the method comprises the following steps that a person in front of a paver commands a skip car to unload materials, so that the situation that aggregate materials fall outside the paver is avoided as much as possible, if the aggregate materials fall outside, the aggregate materials below a crawler belt of the paver are removed in time, the skip car unloads 1/3 of the materials firstly, then the skip car gradually lifts along with the paving and unloading materials, the excess materials are unloaded, it is ensured that a part of the remaining mixture materials in a receiving hopper do not expose a scraping plate, the skip car timely receives the materials after leaving so that the remaining mixture materials and the mixture materials of the next car are paved, and meanwhile, the number of the skip buckets needs to be reduced as much as possible; when the base layer is paved, the two sides of the screw of the paver are manually assisted to transfer materials, so that the mixture is paved and formed at one time;
constructors check the evenness and the flatness of the paving elevation, the width, the cross slope, the joint, the thickness and the pavement, find problems, manually and timely repair paving defects, timely remove local coarse material pits and coarse material belts, change and fill uniform mixture to find potential unevenness or paving leaks, and manually rake loose and fill qualified material leveling if necessary.
As a preferred technical scheme of the invention: the rolling is to immediately perform the rolling on a paved base layer once paving is finished, or ensure that the construction of paving in front and then performing the rolling is finished, and the interval time is less than 5 minutes;
(a) Firstly, weakly vibrating for 1 time when an HD130 double-steel-wheel road roller moves forward and retreats under static pressure, and rolling for 1.2-1.5 km/h, and then kneading for 1 time by an YL37 rubber-wheel road roller after ensuring the flatness, wherein the rolling speed is 2.0-2.5 km/h;
(b) Then a Yz36 single steel wheel road roller is used for strong vibration for 1 time and a YL37 rubber wheel road roller is used for kneading and pressing for 1 time, the rolling speed is 2.0-2.5 km/h to form a combined cycle strong vibration rolling, and the combined cycle strong vibration rolling is carried out for 3 times to ensure the compactness;
(c) Weak vibration for 1 time by using a Yz36 single steel wheel road roller and kneading for 1 time by using an YL37 rubber wheel road roller, wherein the rolling speed is 2.0-2.5 km/h to form combined circulation weak vibration rolling, and the combined circulation weak vibration rolling is carried out for 2 times to strengthen the compaction degree;
(d) And (3) carrying out static pressure for 2 times by using an HD130 double-steel-wheel road roller, wherein the rolling speed is 2.0-2.5 km/h, and the surface is compacted by static pressure.
As a preferred technical scheme of the invention: the curing is to immediately perform the curing of the rolled base layer once the rolling is finished or ensure the construction of performing the curing immediately after the rolling is finished in the front, and the interval time is less than 5 minutes; after the rolling of the rolling base layer is finished, spraying water on the surface of the rolling base layer by a sprinkler with the water spraying amount of 8-10 liters/m 2 And then spreading a health preserving film on the surface of the rolling base layer, covering the health preserving film with geotextile, pressing the environment-friendly sand bags at intervals on the geotextile, stacking and burying natural gravels in the geotextile and the film on the two sides of the rolling base layer, completing the sealing and fixing of the health preserving film and the periphery of the geotextile, and removing the health preserving film and the geotextile in a health preserving period of 5-7 days.
As a preferred technical scheme of the invention: the test detection is as follows: and (4) carrying out compactness detection on the health-preserving base layer, and processing the points which are not qualified in detection until the points are qualified.
As a preferred technical scheme of the invention: the ratio of 0.6mm grains or less in the graded gravel is less than 15%.
As a preferred technical scheme of the invention: the ratio of fine aggregate with the particle size of 5mm and below to coarse aggregate with the particle size of 5mm in the graded gravel is 7.
As a preferred technical scheme of the invention: the measure for reducing segregation or preventing segregation is a discharging partAn inclination 30 is arranged between the material bearing part and the material bearing part 0 ～60 0 The material guide plate.
As a preferred technical scheme of the invention: a permeable layer and a lower sealing layer are sequentially arranged between the upper end face of the base layer and the asphalt surface layer, the permeable layer is made of PC-2 spraying type cation emulsified asphalt, and the lower sealing layer is made of modified asphalt macadam to improve the reflection crack resistance of the pavement.
The above method achieves the object of the present invention.
Compared with the prior art, the invention has the following advantages and positive effects:
(1) The method can ensure that the cement stabilized aggregate base layer in a low-temperature area reduces cracks and meets the requirement of excellent quality, and has the advantages of simplicity, convenience, practicability, low cost, construction period saving, good quality and long service life.
In order to improve the crack resistance of the cement stabilized macadam material, the invention adopts a vibration molding framework structure and low-dosage cement stabilized macadam according to the mix proportion design. As the main bearing layer of the pavement structure, the pavement base layer has enough strength and rigidity, has the characteristics of good slab property, strong cement stabilization aggregate qualitative property and the like, forms a framework which is mutually embedded and extruded by continuous graded coarse aggregate, and fills gaps of the framework by cement and fine materials to form an inorganic binder with a framework embedded and extruded compact structure. The framework compact structure adopts a vibration forming design method, has the characteristics of high strength, low cement dosage and the like, and can better solve the contradiction between the strength and the crack resistance. The method can effectively reduce the crack generation of the cement stabilization granular material base layer in a low-temperature area, avoids the situation that the crack in one hundred meters on the surface of the cement stabilization gravel base layer is longitudinally generated by using a traditional method, realizes no crack in one thousand meters, and ensures that the cement stabilization gravel base layer reaches the quality high-quality standard.
(2) The construction process is mature and simple, is convenient for field construction operation, can save 15 percent of cement materials, saves construction period by paving, saves maintenance cost by 2.5 yuan per square meter, saves 1.6 yuan per square meter by the health maintenance process, saves construction cost by 25 percent in total, shortens the construction period by 10 percent and has better economic benefit.
(3) The invention greatly reinforces the base course, increases the weight guide area of the base course and greatly prolongs the service life of the highway. The comparison test shows that the service life of two adjacent roads in the connected section is prolonged by 3-5 times compared with the prior art, and the phenomena of loss, pavement cracking, collapse and hollowing do not exist.
Detailed Description
The present invention will be further described with reference to specific embodiments for the purpose of facilitating an understanding of technical means, characteristics of creation, objectives and functions realized by the present invention, but the following embodiments are only preferred embodiments of the present invention, and are not intended to be exhaustive. Other embodiments obtained by persons skilled in the art without making creative efforts based on the embodiments in the implementation belong to the protection scope of the invention. The experimental methods in the following examples are conventional methods unless otherwise specified, and materials, devices, equipments, reagents and the like used in the following examples are commercially available unless otherwise specified.
Example 1: a construction method for preventing segregation and reducing cracks of a cement stabilized aggregate base layer in a low-temperature area takes a project from the city of Mongolian to the first-stage project of an alloplastic ancient platform road and a project from Suzhou high-speed Sunit right flag to the chemical project (Mongolian boundary) section road as an example, and comprises the following steps:
(1) Processing of broken stone raw materials: the crushed stone is crushed by a jaw crusher with the size of more than 600 x 900 for the first crusher, a vertical shaft crusher with the size of more than 175 for the second crusher, a vibrating soil sieving screen is arranged between the first crusher and the second crusher to obtain five kinds of aggregates with the particle sizes of 20-25 mm, 10-20 mm, 5-10 mm, 3-5 mm and 0-3 mm, and the five kinds of aggregates are stacked respectively.
The graded gravel selects 2.5km stock ground graded gravel, and the test tests show that all technical indexes meet the design and specification requirements, and the test results are shown in a table 1-1.
TABLE 1-1 grading gravel quality technical indexes
(2) The grain size proportion of graded gravel in the dense subbase layer and the top base layer of the framework in the low-temperature region is as follows: 20-25mm; namely, the graded grits in the bottom base layer and the top base layer have the same grain size ratio.
The top base layer comprises the following components in percentage by weight: graded gravel cement =100:5, maximum dry density 2.405g/cm 3 The water content is 4.4%, the water immersion after 7 days has no lateral limit strength (MPa) of 5.0, and the thickness of the top base layer is 20cm.
The subbase layer comprises the following components in percentage by weight: graded gravel cement =100:4; maximum dry density 2.393g/cm 3 The water content is 4.3 percent, the water immersion after 7 days has no lateral limit strength (MPa) 4.5, and the thickness of the underlayer is 36cm.
The ratio of 0.6mm grains or less in the graded gravel is less than 15%. The ratio of fine aggregate of 5mm and below 5mm particles to coarse aggregate of 5mm or above in the graded gravel is 7.
The cement is P.S.A 32.5 cement, the initial setting time is more than 4h, and the final setting time is more than 6h.
(3) The uniformity of the mixture is improved, segregation is reduced, the graded gravel and the cement are placed in a stirring machine, the adding amount of water is 60 percent of the total amount of the added water during the first-stage mixing, the cement, the graded gravel and the water are fully combined, the adding amount of water in the second stage is 40 percent of the total amount of the added water, and the mixture is uniformly mixed by stirring;
(4) The transportation and paving adopt anti-segregation measures, the periphery of a transportation vehicle is integrally and fixedly wrapped by a cotton quilt, the top surface of the transportation vehicle is covered by tarpaulin, and the rear bucket part of the transportation vehicle is provided with a discharge baffle plate for preventing segregation;
preventing segregation, i.e. avoiding the material from falling freely during transport, so that an inclination 30 should be provided between the discharge part and the receiving part of the graded gravel during transport 0 ～60 0 The material guide plate.
(5) Paving a base layer, wherein the water content of the base layer material is 5.9-6.4% during paving so as to compensate the water loss in the paving and rolling processes; the water content can be reached when the mixture is mixed and stirred.
(a) Firstly, paving an underlayer, wherein the thickness of the underlayer is 36cm, adopting two single-layer spraying cement slurry pavements, namely using an anti-segregation middle and large paver Power-DT1900 to realize a first-layer paving layer with the full thickness of 18cm and the full width of 12.35m, spraying a layer of cement slurry on the upper end surface of the first-layer paving layer, controlling the net dosage of cement per square meter to be 0.4-0.5 kg, and then using an anti-segregation middle and large paver Power-DT1900 to realize a second-layer paving layer with the full thickness of 18cm and the full width of 12.35m to form the underlayer;
or 2 spreading machines are adopted to spread a first layer of paving layer in a full-width stepped manner, cement slurry is uniformly spread on the surface of an operation surface (comprising a side butt joint surface and a bottom butt joint surface), then 2 spreading machines are used to spread a second layer of paving layer in a full-width stepped manner, the distance between the front and the back of the two spreading machines is 5-10 m, the paving lap joint width is 10-15 cm, the front spreading machine adopts a left-side steel wire rope and a right-side aluminum gold wire to advance as guidance, the back spreading machine adopts a base layer which is spread out on the left side and is not rolled as a reference surface and a right-side steel wire rope to advance as guidance, the two spreading machines are guaranteed to have consistent paving thickness, the loose paving coefficients are consistent, the road arch and the cross slope are consistent, the flatness is consistent, the vibration frequency is consistent, and the longitudinal joint is smooth and compact.
Then sequentially carrying out auxiliary operation, rolling, curing and test detection on the paving of the subbase layer; namely:
in the auxiliary operation of the paving, a specially-assigned person is arranged to eliminate the segregation phenomenon of the coarse and fine aggregates during the paving, timely shovel off the accumulated or segregated part of the coarse and fine aggregates and fill the accumulated or segregated part with a newly-mixed mixture; when various machines are ready and more than 4 vehicles are stored on site, the paving operation is started; the method comprises the following steps that a worker in front of a paver commands a skip car to unload materials, so that aggregate is prevented from falling outside the paver as much as possible, if the aggregate falls outside, the aggregate below a crawler belt of the paver is removed in time, the skip car unloads about 1/3 of the aggregate firstly, then the skip car gradually lifts up along with the paving and unloading materials, the excess materials are unloaded, it is ensured that a part of the remaining mixture in a receiving hopper does not expose a scraping plate, the skip car is timely collected after leaving so that the remaining mixture and the next mixture are paved, and meanwhile, the collection hopper is reduced as much as possible; when a base layer is paved, the two sides of a screw conveyor of the paver are manually assisted to transfer materials, so that the mixture is paved and molded at one time; constructors check the evenness and the flatness of the paving elevation, the width, the cross slope, the joint, the thickness and the pavement, find problems, manually and timely repair paving defects, timely remove local coarse material pits and coarse material belts, change and fill uniform mixture to find potential unevenness or paving leaks, and manually rake loose and fill qualified material leveling if necessary.
The rolling is to immediately perform the rolling on the paved base layer once the paving is finished, or ensure that the paving in front is finished and the rolling is performed immediately after the paving is finished, and the interval time is less than 5 minutes. Firstly, weakly vibrating for 1 time when an HD130 double-steel-wheel road roller moves forward and retreats under static pressure, and rolling for 1.2-1.5 km/h, and then kneading for 1 time by an YL37 rubber-wheel road roller after ensuring the flatness, wherein the rolling speed is 2.0-2.5 km/h; then a Yz36 single steel wheel road roller is used for strong vibration for 1 time and a YL37 rubber wheel road roller is used for kneading and pressing for 1 time, the rolling speed is 2.0-2.5 km/h to form a combined cycle strong vibration rolling, and the combined cycle strong vibration rolling is carried out for 3 times to ensure the compactness; then, a Yz36 single steel wheel road roller is used for weak vibration for 1 time, an YL37 rubber wheel road roller is used for kneading and pressing for 1 time, the rolling speed is 2.0-2.5 km/h to form combined circulation weak vibration rolling, the combined circulation weak vibration rolling is carried out for 2 times, and the compaction degree is enhanced; finally, carrying out static pressure for 2 times by using an HD130 double-steel-wheel road roller, wherein the rolling speed is 2.0-2.5 km/h, and carrying out static pressure surface rolling.
Curing is to immediately perform curing on the rolling subbase layer or ensure the construction of curing immediately after the rolling is finished in front, wherein the interval time is less than 5 minutes; after the rolling of the subbase layer is finished, spraying 8-10L/m of water onto the surface of the subbase layer by a sprinkler 2 And then, paving a health preserving film on the surface of the rolled base layer, covering geotextile on the health preserving film, pressing an environment-friendly sand bag at intervals on the geotextile, stacking natural gravel on the geotextile and the geotextile on the two sides of the rolled base layer, sealing and fixing the periphery of the health preserving film and the geotextile, and removing the health preserving film and the geotextile after 5-7 days of a health preserving period.
The test detection is as follows: and (4) carrying out compaction degree detection on the cured subbase layer, and processing the points which are not qualified until the points are qualified.
After the test detection and the treatment of the subbase layer are qualified, the construction of the top base layer is carried out;
(b) Spraying cement paste, namely spraying a layer of cement paste on the upper end face of the subbase layer after the health maintenance and test detection is qualified, wherein the spraying amount is controlled to be 0.4-0.5 kg per square meter of cement, so that the subbase layer and the top base layer form a whole, and the load transfer is facilitated;
(c) And then paving a top base layer, wherein the thickness of the top base layer is 20cm, adopting one-time full-thickness forming paving, and the one-time full-thickness forming paving is realized by using an anti-segregation middle and large paver Power-DT1900 at one time, wherein the full width of the top base layer is 12.35m, or adopting 2 pavers to realize full-width stepped paving.
And then sequentially carrying out auxiliary operation, rolling, health preserving and test detection of the paving of the top base layer. The auxiliary operation, rolling, health preserving and test detection of the top base layer are the same as those of the bottom base layer, so that the description is omitted.
When the construction of the asphalt surface layer at the upper end of the base layer is carried out, a permeable layer and a lower sealing layer are sequentially arranged between the upper end surface of the base layer and the asphalt surface layer, the permeable layer adopts PC-2 spraying type cation emulsified asphalt, and the lower sealing layer adopts modified asphalt macadam to improve the reflection crack resistance of the pavement.
And (3) performing performance test on the cement stabilized aggregate base layer in the low-temperature area formed in the steps, wherein the test method adopts a conventional test method in the technical field, and the obtained test results are shown in tables 1-3.
Tables 1-3 summary of compaction test results for cement stabilized macadam mixtures
Tests show that when the cement content in the cement stabilized macadam mixture is lower than 4%, the maximum dry density index is reduced.
The invention is applied to the project from Mandu La map to the first-stage project of the alloplastic ancient platform highway and the project from Su Zhang high-speed Sunit right flag to the highway of the chemical engineering section (Mongolian Ji boundary), thereby greatly reducing the cracks of the base course. The invention realizes the good effect of no crack in kilometers for the first time, the core sample is compact and complete, the plate property is good, the unconfined compressive strength of the cement-stabilized gravel base layer for 7 days is not less than 4.5MPa, the compactness (surface vibration compactor method) is not less than 98%, the performance indexes of the water-stabilized road surface meet the specification and design requirements, and the service life of the road surface is prolonged.
And the cracks with the length of more than 10cm in hundreds of meters of the base layer are 30-40 in the traditional ingredient side, and the defects of loose core sample, incompleteness and the like exist.
The present invention forms skeleton with continuous graded coarse aggregate, and cement and fine material are used to fill the gap in skeleton to form inorganic combined material with dense skeleton structure. The framework compact structure adopts a vibration molding design method, the aggregate freely moves and is compacted in the molding process, the friction resistance in the mixture and the binding power of the binding material and the aggregate are main strength bodies, the composite material has the characteristics of better dry shrinkage resistance, low cement dosage and the like, and the contradiction between the strength and the crack resistance can be better solved.
The above-mentioned embodiments only express 1 implementation manner of the present invention, and the description thereof is more specific and detailed, but not to be construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (7)
1. The construction method for preventing segregation and reducing cracks of the cement stabilized aggregate base layer in the low-temperature area is characterized by comprising the following steps of:
(1) Processing of broken stone raw materials: the crushed stone first crusher adopts a jaw crusher with the model larger than 600 x 900, the second crusher adopts a vertical shaft crusher with the model larger than 175, a vibrating soil sieving screen is arranged between the first crusher and the second crusher to obtain five kinds of aggregates with the grain diameters of 20-25 mm, 10-20 mm, 5-10 mm, 3-5 mm and 0-3 mm, and the five kinds of aggregates are respectively stacked;
(2) The grain size proportion of graded gravel in the dense subbase layer and the top base layer of the framework in the low-temperature region is as follows: 20-25mm;
the top base layer comprises the following components in percentage by weight: graded gravel cement =100:5, maximum dry density 2.405g/cm 3 The water content is 4.4%, the water immersion unconfined strength (MPa) is 5.0 in 7 days, and the thickness of the top base layer is 20cm;
the subbase layer comprises the following components in percentage by weight: graded gravel cement =100:4; maximum dry density 2.393g/cm 3 The water content is 4.3 percent, the water immersion after 7 days has no lateral limit strength (MPa) of 4.5, and the thickness of the subbase layer is 36cm;
the cement is ordinary portland cement, slag portland cement and pozzolanic portland cement, the initial setting time is more than 4h, and the final setting time is more than 6h;
(3) The uniformity of the mixture is improved, the segregation is reduced, the graded gravel and the cement are placed in a stirring machine, the adding amount of water is 60 percent of the total amount of the added water during the first-stage mixing, the cement, the graded gravel and the water are fully combined, the adding amount of the water in the second stage is 40 percent of the total amount of the added water, and the mixture is uniformly mixed by mixing;
(4) The transportation and paving adopt anti-segregation measures, the periphery of a transportation vehicle is integrally and fixedly wrapped by cotton quilts, the top surface of the transportation vehicle is covered by tarpaulin, and the rear bucket part of the transportation vehicle is provided with a discharging baffle plate;
(5) Paving a base layer, wherein the water content of the base material is 5.9-6.4% during paving so as to compensate the water loss in the paving and rolling processes;
(a) Firstly, paving an underlayer, wherein the thickness of the underlayer is 36cm, adopting two single-layer spraying cement slurry pavements, namely using an anti-segregation middle and large paver Power-DT1900 to realize a first-layer paving layer with the full thickness of 18cm and the full width of 12.35m, spraying a layer of cement slurry on the upper end surface of the first-layer paving layer, controlling the net amount of cement per square meter to be 0.4-0.5 kg, using an anti-segregation middle and large paver Power-DT1900 to realize a second-layer paving layer with the full thickness of 18cm and the full width of 12.35m to form the underlayer, or adopting 2 pavers to pave the full-width stepped first-layer paving layer, uniformly spreading the cement slurry on the surface of an operation surface, and then using 2 pavers to pave the full-width stepped second-layer paving layer;
then sequentially carrying out auxiliary operation, rolling, curing and test detection on the paving of the subbase layer;
(b) Spraying cement slurry, namely spraying a layer of cement slurry on the upper end face of the subbase layer after the health maintenance and test detection are qualified, wherein the net dosage of the cement per square meter is controlled to be 0.4-0.5 kg, so that the subbase layer and the top base layer form a whole, and the load transfer is facilitated;
(c) Then, paving a top base layer, wherein the thickness of the top base layer is 20cm, adopting one-time full-thickness forming paving, and realizing 20cm full thickness and 12.35m full width one-time paving forming by using an anti-segregation middle and large paver Power-DT1900 at one time or adopting 2 pavers to pave in a full-width stepped manner;
then sequentially carrying out auxiliary operation, rolling, health preserving and test detection of paving the subbase layer; the full-width stepped paving with 2 pavers is as follows: the distance between the front and the back of the two pavers is 5-10 m, the paving lap width is 10-15 cm, the front paver adopts a left steel wire rope and a right aluminum gold wire as guide to advance, the rear paver adopts a base layer paved on the left side and not rolled as a reference surface and a right steel wire rope as guide to advance, the paving thicknesses of the two pavers are consistent, the paving coefficients are consistent, the road arch cross slope is consistent, the flatness is consistent, the vibration frequency is consistent, and the longitudinal joint is smooth and compact; in the auxiliary operation of paving, a specially-assigned person is arranged to eliminate the segregation phenomenon of the coarse and fine aggregates during paving, timely remove the accumulated or segregated part of the coarse and fine aggregates and fill the part with a newly-mixed mixture; when various machines are ready and more than 4 vehicles are stored on site, the paving operation is started; the method comprises the following steps that a person in front of a paver commands a skip car to unload materials, so that aggregate is prevented from falling outside the paver as much as possible, if the aggregate falls outside, the aggregate below a crawler belt of the paver is removed in time, the skip car unloads 1/3 of the materials firstly, then the skip car gradually lifts up along with the paving and unloading materials, the excess materials are unloaded, a part of the rest of the mixture in a receiving hopper is ensured not to expose a scraping plate, the skip car is timely collected after leaving, so that the rest of the mixture and the next mixture are paved, and meanwhile, the collection hopper is reduced as much as possible; when the base layer is paved, the two sides of the screw of the paver are manually assisted to transfer materials, so that the mixture is paved and formed at one time; the constructor checks the paving height, width, cross slope, seam, thickness, paving uniformity and flatness, finds problems, manually repairs paving defects in time, removes partial coarse material pits and coarse material belts in time, replaces and fills uniform mixture to find potential unevenness or paving leaks, and manually rakes loose and completes qualified material leveling if the paving defects exist; the rolling is to immediately perform the rolling on a paved base layer once paving is finished, or ensure that the construction of paving in front and then performing the rolling is finished, and the interval time is less than 5 minutes;
(a) Firstly, weakly vibrating for 1 time when an HD130 double-steel-wheel road roller moves forward and retreats under static pressure, and rolling for 1.2-1.5 km/h, and then kneading for 1 time by an YL37 rubber-wheel road roller after ensuring the flatness, wherein the rolling speed is 2.0-2.5 km/h;
(b) Then a Yz36 single steel wheel road roller is used for strong vibration for 1 time and a YL37 rubber wheel road roller is used for kneading and pressing for 1 time, the rolling speed is 2.0-2.5 km/h to form a combined cycle strong vibration rolling, and the combined cycle strong vibration rolling is carried out for 3 times to ensure the compactness;
(c) Weak vibration for 1 time by using a Yz36 single steel wheel road roller and kneading for 1 time by using an YL37 rubber wheel road roller, wherein the rolling speed is 2.0-2.5 km/h to form combined circulation weak vibration rolling, and the combined circulation weak vibration rolling is carried out for 2 times to strengthen the compaction degree;
(d) And (3) carrying out static pressure for 2 times by using an HD130 double-steel-wheel road roller, wherein the rolling speed is 2.0-2.5 km/h, and the surface is compacted by static pressure.
2. The construction method for preventing segregation and reducing cracks of the cement stabilized granule base layer in the low-temperature region as claimed in claim 1, wherein: the curing is to immediately perform the curing of the rolled base layer once the rolling is finished or ensure the construction of performing the curing immediately after the rolling is finished in the front, and the interval time is less than 5 minutes; after the rolling of the base layer is finished, spraying water on the surface of the base layer by a sprinkler, wherein the water spraying amount is 8-10 liters/m 2 Then, paving a health preserving film on the surface of the rolling base layer, covering geotextile on the health preserving film, pressing environment-friendly sand bags at intervals on the geotextile, stacking natural gravels on the geotextile and the film on the two sides of the rolling base layer, completing the sealing and fixing of the health preserving film and the geotextile, wherein the health preserving period is 5-7 days, and tearing off the health preserving film and the geotextile from each otherFilms and geotextiles.
3. The method for constructing a cement stabilized granular base layer for preventing segregation and reducing cracks in a low temperature area according to claim 1, wherein the method comprises the following steps: the test detection is as follows: and (4) carrying out compactness detection on the health-preserving base layer, and processing the points which are not qualified in detection until the points are qualified.
4. The method for constructing a cement stabilized granular base layer for preventing segregation and reducing cracks in a low temperature area according to claim 1, wherein the method comprises the following steps: the ratio of 0.6mm grains or less in the graded gravel is less than 15%.
5. The method for constructing a cement stabilized granular base layer for preventing segregation and reducing cracks in a low temperature area according to claim 1, wherein the method comprises the following steps: the ratio of fine aggregates with 5mm and below grains and coarse aggregates with 5mm above grains in the graded gravel is 7.
6. The method for constructing a cement stabilized granular base layer for preventing segregation and reducing cracks in a low temperature area according to claim 1, wherein the method comprises the following steps: the measure for reducing segregation or preventing segregation is that an incline 30 is arranged between the discharging part and the material bearing part 0 ～60 0 The material guide plate.
7. The method for constructing a cement stabilized granular base layer for preventing segregation and reducing cracks in a low temperature area according to claim 1, wherein the method comprises the following steps: a permeable layer and a lower sealing layer are sequentially arranged between the upper end face of the base layer and the asphalt surface layer, the permeable layer is made of PC-2 spraying type cation emulsified asphalt, and the lower sealing layer is made of modified asphalt macadam to improve the anti-reflection crack capability of the pavement.
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