Cement stabilized macadam base structure and construction method

Abstract

The cement stabilized macadam base structure and construction method, the base structure is composed of stress compensation type upper base, cement paste connecting layer and stress compensation type lower base, the upper base is composed of upper stress compensation joint and upper base cement stabilized macadam respectively; the upper stress compensation joint is formed by pouring upper base high expansion concrete in the pre-cut joint of the stress compensation type upper base. The construction method of the cement stabilized macadam base structure comprises: 1) stress compensation type lower base construction; 2) lower stress compensation joint construction; 3) cement paste connecting layer construction; 4) stress compensation type upper base construction; 5) the upper stress compensation joint construction; 6) tack coat construction. The cement stabilized macadam base structure and construction method can reduce or eliminate the influence of dry shrinkage and temperature shrinkage on the cement stabilized macadam base, prolong the time of transverse cracks of the cement stabilized macadam base due to fatigue, greatly improve the strength of the cement stabilized macadam base and prolong the service life of the asphalt pavement.

Description

Technical Field

[0001] This invention relates to a cement-stabilized crushed stone base course structure and construction method, and more particularly to a long-life cement-stabilized crushed stone base course structure and construction method suitable for the design and construction of semi-rigid base asphalt pavements. Background Technology

[0002] Cement-stabilized crushed stone base courses are characterized by high strength, good stability, and high stiffness, and are widely used as load-bearing layers in the pavement structure of high-grade highways both domestically and internationally. However, cement-stabilized crushed stone base courses are brittle, have low early strength, and take a long time to develop later strength. When temperature and humidity conditions change, due to their low tensile strength, they are prone to transverse cracks and reflective cracks in the asphalt surface layer, affecting the integrity, continuity, and comfort of the road, and reducing the service life of the pavement. Traditional improvement methods involve setting pre-cut joints at equal intervals in the base course and placing geotextile or fiberglass geogrid on top of the pre-cut joints. However, the pre-cut joints damage the integrity of the base course and are prone to stress concentration at the pre-cut joints. Under long-term loads, the base course along the edges of the pre-cut joints is easily damaged, leading to road distress. Another traditional approach is to improve the mix proportion of the base course by increasing the proportion of coarse aggregate, reducing the cement content, and increasing fiber, etc. This method has some improvement effect, but the degree of improvement is limited and cannot fundamentally solve the impact of drying shrinkage and thermal shrinkage on the base course.

[0003] To overcome the aforementioned deficiencies in the prior art, this invention provides a cement-stabilized crushed stone base course structure and construction method, applicable to the design and construction of semi-rigid base asphalt pavements. The base course structure comprises a stress-compensating upper base course, a cement slurry bonding layer, and a stress-compensating lower base course. The stress-compensating upper base course is composed of an upper stress-compensating joint and several equal-length upper base course cement-stabilized crushed stone sections spaced apart by the upper stress-compensating joint. The upper stress-compensating joint is formed by pouring high-expansion concrete into a pre-cut joint in the stress-compensating upper base course. The stress-compensating lower base course is composed of a lower stress-compensating joint and several equal-length lower base course cement-stabilized crushed stone sections spaced apart by the lower stress-compensating joint. The lower stress-compensating joint is formed by pouring high-expansion concrete into a pre-cut joint in the stress-compensating lower base course. By utilizing the expansion characteristics of high-expansion concrete, longitudinal compressive stress is generated in the base layer between adjacent stress compensation joints. This can reduce or eliminate the impact of drying shrinkage and thermal shrinkage on cement-stabilized crushed stone base layers. Since the temperature difference of asphalt pavement gradually decreases from top to bottom, the corresponding thermal shrinkage caused by the temperature difference also decreases. Therefore, the upper base layer has more stress compensation joints to offset thermal shrinkage than the lower base layer. This arrangement can improve the stress conditions of the upper and lower base layers, prolong and improve the stress conditions of the base layer, extend the time before the cement-stabilized crushed stone base layer develops transverse cracks due to fatigue, and at the same time significantly improve the strength of the cement-stabilized crushed stone base layer, extending the service life of the asphalt pavement. It has considerable economic and social benefits. Summary of the Invention

[0004] The technical problem solved by this invention is that cement-stabilized crushed stone base courses are brittle, have low early strength, and take a long time to develop later strength. When temperature and humidity conditions change, they are prone to transverse cracks due to their low tensile strength, which affects driving comfort and safety as well as the service life of the road.

[0005] To address the aforementioned problems, this invention provides a cement-stabilized crushed stone base structure and construction method, which can reduce or eliminate the impact of drying shrinkage and thermal shrinkage on the cement-stabilized crushed stone base, extend the time before transverse cracks appear due to fatigue, improve the fatigue life of the base, extend the major and medium-scale road repair cycle, and reduce the number of repairs.

[0006] A cement-stabilized crushed stone base course structure, characterized in that the base course structure comprises a stress-compensating upper base course, a cement grout bonding layer, and a stress-compensating lower base course, wherein:

[0007] The stress-compensating upper base layer is composed of upper stress-compensating joints and several equal-length upper base cement-stabilized crushed stone blocks spaced apart by the upper stress-compensating joints.

[0008] The stress compensation joint is formed by pouring high-expansion concrete of the upper base layer into the pre-cut joint of the stress compensation type upper base layer;

[0009] The stress-compensating subbase is composed of a stress-compensating joint and several equal-length cement-stabilized crushed stone subbases spaced apart by the stress-compensating joint.

[0010] The stress compensation joint is formed by pouring high-expansion concrete of the lower base layer into the pre-cut joint of the stress compensation type lower base layer;

[0011] The arrangement order of the base structure is as follows: from top to bottom, the base structure consists of a stress-compensating upper base layer, a cement grout bonding layer, and a stress-compensating lower base layer.

[0012] According to a preferred embodiment of the present invention, the upper stress compensation joint and the lower stress compensation joint are arranged at equal intervals perpendicular to the centerline of the road.

[0013] According to another preferred embodiment of the present invention, the spacing of the lower stress compensation joint is twice that of the upper stress compensation joint, and the lower stress compensation joint of the stress compensation type lower base layer is connected vertically to the upper stress compensation joint of the stress compensation type upper base layer at a distance of one position, with their center lines coinciding and separated by the cement slurry connecting layer.

[0014] According to another preferred embodiment of the present invention, the stress-compensated upper base cement-stabilized crushed stone has a 7-day unconfined compressive strength of 3-10 MPa and a thickness of 15-27 cm.

[0015] According to another preferred embodiment of the present invention, the stress-compensated subbase cement-stabilized crushed stone has a 7-day unconfined compressive strength of 2-5 MPa and a thickness of 15-27 cm.

[0016] According to another preferred embodiment of the present invention, the cement slurry layer is a pure cement slurry with a water-cement ratio of 0.45-0.55.

[0017] According to another preferred embodiment of the present invention, the transverse length of the stress compensation joint is equal to the width of the stress compensation type subbase, the height is the same as the thickness of the stress compensation type subbase, the joint width is 12cm-25cm, the spacing is 40m-90m, the grade is 25MPa-35MPa, and the 90-day self-stress value is 1.5MPa-2.5MPa.

[0018] According to another preferred embodiment of the present invention, the transverse length of the upper stress compensation joint is equal to the width of the stress compensation type upper base layer, the height is the same as the thickness of the stress compensation type upper base layer, the joint width is 22cm-38cm, the spacing is 20m-45m, the grade is 25mpa-35mpa, and the 90-day self-stress value is 2mpa-3mpa.

[0019] According to another preferred embodiment of the present invention, the outer edge of the upper stress compensation joint is 5cm-7cm wider than the outer edge of the corresponding lower stress compensation joint connected thereto.

[0020] According to another aspect of the present invention, a construction method for a cement-stabilized crushed stone base structure is provided, characterized in that the method comprises the following steps:

[0021] 1) Construction of the stress-compensated subbase: Cement-stabilized crushed stone is laid by a paver, compacted by a vibratory roller and a rubber-tired roller, and covered with curing cloth and watered for 7 days.

[0022] 2) Construction of the stress compensation joint: The stress compensation type subbase is cured for 3-5 days, with intervals of 40m-90m; a 12cm-25cm wide cutting joint with the same thickness as the stress compensation type subbase is cut using a concrete cutter; the water-stabilized crushed stone between the two joints is removed, and the vertical surfaces of the two joints are smoothed with No. 10 mortar. Then, the expansion concrete of the subbase is poured and water-cured for 7 days.

[0023] 3) Construction of the cement slurry bonding layer: Cement slurry is sprayed onto the stress-compensated subbase using a sprayer.

[0024] 4) Construction of the stress-compensated upper base course: Cement-stabilized crushed stone is laid on the stress-compensated lower base course using a paver, compacted by a rubber-tired roller in conjunction with a vibratory roller, and cured with tack coat for 7 days.

[0025] 5) Construction of the stress compensation joint: The stress compensation type upper base layer is cured for 3-5 days, with an interval of 20m-45m; a cutting joint with a width of 22cm-38cm and the same thickness as the stress compensation type upper base layer is cut using a concrete cutting machine; the water-stabilized crushed stone between the two joints is removed, and the two vertical surfaces of the joint are leveled with No. 10 mortar, and then the high expansion concrete of the upper base layer is poured and water-cured for 7 days.

[0026] 6) Tack coat construction: Apply a tack coat to the stress compensation joint, and then apply a hot asphalt tack coat to the entire stress compensation type upper base layer.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1) It can reduce or eliminate the impact of drying shrinkage and thermal shrinkage on cement-stabilized crushed stone base courses, reduce reflective cracks caused by drying shrinkage and thermal shrinkage, reduce the damage of water to the road, ensure road quality, and improve driving comfort and safety.

[0029] 2) Improves the stress condition of the base layer and prolongs the time before transverse cracks appear in the cement-stabilized crushed stone base layer due to fatigue, thereby increasing the fatigue life of the base layer and effectively extending the service life of asphalt pavement.

[0030] 3) It effectively reduces and delays the occurrence of road surface defects, thereby extending the major and medium-scale road repair cycle, reducing the number of repairs, increasing the total life cycle of the road surface, saving maintenance costs, and having considerable economic and social benefits. Attached Figure Description

[0031] Figure 1 This is a cross-sectional view of the present invention;

[0032] Figure 2 This is a top view of the present invention;

[0033] The relevant labels in the figure are as follows:

[0034] 1. Stress-compensating upper base course; 2. Stress-compensating lower base course; 3. Subbase course; 4. Asphalt surface course; 5. Prime coat; 6. Upper stress compensation joint; 7. Lower stress compensation joint; 8. No. 10 mortar; 9. Cement grout bonding layer; 10. Upper base course high-expansion concrete; 11. Lower base course high-expansion concrete; 12. Upper base course cement-stabilized crushed stone; 13. Lower base course cement-stabilized crushed stone. Detailed Implementation

[0035] Cement-stabilized crushed stone base courses possess characteristics such as high strength, good stability, and high rigidity, thus they are used as load-bearing layers in high-grade pavements both domestically and internationally. To overcome the drawback of cement-stabilized crushed stone base courses being prone to transverse cracking due to drying shrinkage and thermal shrinkage, this invention provides a cement-stabilized crushed stone base course structure and construction method, applicable to the design and construction of cement-stabilized crushed stone base courses for asphalt pavements. Its features include:

[0036] The aforementioned base structure consists of a stress-compensating upper base layer 1, a cement grout connecting layer 9, and a stress-compensating lower base layer 2.

[0037] The stress-compensating upper base layer 1 is composed of an upper stress-compensating joint 6 and several upper base cement-stabilized crushed stone 12 of equal length spaced apart by the upper stress-compensating joint 6.

[0038] The upper stress compensation joint 6 is formed by pouring high-expansion concrete 10 of the upper base layer into the pre-cut joint of the stress compensation type upper base layer 1;

[0039] The stress-compensating subbase 2 is composed of a stress-compensating joint 7 and several equal-length subbase cement-stabilized crushed stone 13 spaced apart by the stress-compensating joint 7.

[0040] The stress compensation joint 7 is formed by pouring high-expansion concrete 11 of the lower base layer into the pre-cut joint of the stress compensation type lower base layer 2.

[0041] The arrangement order of the aforementioned base structure is as follows:

[0042] The base structure, from top to bottom, consists of stress-compensating upper base layer 1, cement grout bonding layer 9, and stress-compensating lower base layer 2.

[0043] The upper stress compensation joint 6 and the lower stress compensation joint 7 are arranged at equal intervals perpendicular to the road centerline.

[0044] The spacing of the lower stress compensation joint 7 is twice the spacing of the upper stress compensation joint 6. The lower stress compensation joint 7 of the stress compensation type lower base layer 2 is connected vertically to the upper stress compensation joint 6 of the stress compensation type upper base layer 1 at a distance of one position, with their center lines coinciding and separated by the cement slurry connecting layer 9.

[0045] Because the load from vehicles and the temperature load on highways gradually decrease from top to bottom, the stress-compensated upper base course 1 bears a large load from vehicles and the temperature load. Therefore, the stress-compensated upper base course 1 is designed with high strength, with a design 7-day unconfined compressive strength of 3-10 MPa, and preferred strength values ​​of 4 MPa, 5 MPa, 6 MPa, 8 MPa, and 10 MPa. The thickness is 15-27 cm, with preferred thicknesses of 16 cm, 18 cm, 20 cm, 25 cm, and 27 cm.

[0046] Compared with the stress-compensated upper base course 1, the stress-compensated lower base course 2 of the highway bears less vehicle load and temperature load. The design 7-day unconfined compressive strength is 2MPa-5MPa, with the preferred design strengths being 2MPa, 3MPa, and 5MPa. The thickness is 15cm-27cm, with the preferred design thicknesses being 16cm, 18cm, 20cm, 25cm, and 27cm.

[0047] The parameters mentioned above are the optimal parameters selected by the inventor through countless experiments and on-site construction results. They are not subjective guesses, but were obtained through countless comparisons, references and continuous changes.

[0048] The stress-compensating upper base layer 1 and the stress-compensating lower base layer 2 are designed to be continuously stressed, requiring cement grout for connection. A specific water-cement ratio is required for this connection; too low a ratio makes mechanical spreading difficult, while too high a ratio results in insufficient connection strength. Therefore, the designed water-cement ratio is 0.45-0.55, with preferred water-cement ratios of 0.5 and 0.55. Preferred cement grades are 32.5 MPa and 42.5 MPa cement.

[0049] The temperature difference along the highway gradually decreases from top to bottom. In the stress-compensating subbase 2, only minor thermal shrinkage and drying shrinkage are considered. Therefore, the cement-stabilized crushed stone 13 of the subbase between the stress-compensating joints 7 can be made relatively long, resulting in relatively low expansion stress in the joints. The transverse length of the stress-compensating joint 7 is equal to the width of the stress-compensating subbase 2, and its height is the same as its thickness. The width is 12cm-25cm, with preferred widths of 12cm, 15cm, 20cm, 22cm, and 25cm. The spacing is 40m-90m, with preferred spacings of 40m, 50m, 60m, 80m, and 90m. The design strength is 25MPa-35MPa, with preferred strengths of 25MPa and 30MPa. The 90-day self-stress value is 1.5MPa-2.5MPa, with preferred values ​​of 2MPa and 2.5MPa.

[0050] Because the temperature difference of the stress-compensating upper base layer 1 is related to the thickness of the asphalt surface layer 4 and the local climate, the thicker the surface layer and the smaller the temperature difference, the longer the spacing between stress-compensating joints 6 and 7, and vice versa. The upper stress-compensating joint 6 has the same width transversely as the stress-compensating upper base layer 1, and the same height as the thickness of the stress-compensating upper base layer 1. Its width is 22cm-38cm, with preferred widths of 22cm, 26cm, 30cm, and 36cm. The spacing is 20m-45m, with preferred distances of 20m, 25m, 30m, 40m, and 45m. The grade is 25MPa-35MPa, with preferred grades of 30MPa and 35MPa. The 90-day self-stress value of high-expansion concrete is 2MPa-3MPa, with 2.5MPa being preferred.

[0051] The upper base layer 1, which is subjected to greater temperature shrinkage and vehicle load, requires greater compensation stress from the stress compensation joint 6. Therefore, the stress compensation joint 6 is wider than that of the lower base layer 2. The upper stress compensation joint 6, which is designed to be spaced apart, is 5cm-7cm wider at its outer edge than the corresponding lower stress compensation joint 7, with 6cm being the preferred width.

[0052] The inventor would like to reiterate that the specific data and parameters mentioned above are the optimal parameters selected by the inventor through numerous experiments and on-site construction results. They are not subjective conjectures, but were obtained through numerous comparisons, references, and continuous changes. They are indispensable for the technical contribution to this invention and the specific performance optimization of the product.

[0053] Meanwhile, according to another aspect of the present invention, a construction method for a cement-stabilized crushed stone base structure is also provided, characterized in that the method includes the following steps:

[0054] 1) Construction of stress-compensated subbase 2: Cement-stabilized crushed stone 13 of the subbase is laid on the subbase 3 using a paver, compacted by a vibratory roller and a rubber-tired roller, and covered with curing cloth and watered for 7 days.

[0055] 2) Construction of stress compensation joint 7: The stress compensation type subbase 2 is cured for 3-5 days, with an interval of 40m-90m, preferably 60cm; a cutting joint with a width of 12cm-25cm (preferably 20cm) and the same thickness as the stress compensation type subbase 2 is cut with a concrete cutter; the water-stabilized crushed stone between the two joints is removed, the water-stabilized debris in the joint is cleaned, and the vertical surface of the two joints is smoothed with No. 10 mortar 8, cured for 1 day, and then the subbase expansion concrete 11 is poured and water-cured for 7 days.

[0056] 3) Construction of cement slurry bonding layer 9: Apply cement slurry evenly to the stress-compensated subbase 2 using a sprayer.

[0057] 4) Construction of stress-compensated upper base course 1: On the stress-compensated lower base course 2, the cement-stabilized crushed stone 13 of the lower base course is laid with a paver, compacted with a rubber-tired roller and a vibratory roller, and cured with tack coat for 7 days.

[0058] 5) Construction of upper stress compensation joint 6: The stress compensation type upper base layer 1 is cured for 3-5 days, with an interval of 20m-45m, preferably 35cm; use a concrete cutter to cut a cutting joint with a width of 22cm-38cm (preferably 30cm) and the same thickness as the stress compensation type upper base layer, remove the water-stabilized crushed stone between the two joints, and use No. 10 mortar 8 to level the two vertical surfaces of the joint, cure for 1 day, and then pour the high expansion concrete 10 of the upper base layer, and water cure for 7 days.

[0059] 6) Tack coat construction: Apply a tack coat to the upper stress compensation joint 6, and then apply a hot asphalt tack coat to the entire stress compensation type upper base layer 1.

[0060] While exemplary embodiments and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications can be made to these embodiments without departing from the spirit of the invention and the scope of protection defined by the appended claims. For other examples, those skilled in the art should readily understand that the order of process steps can be varied while remaining within the scope of the invention.

[0061] Furthermore, the scope of this invention is not limited to the processes, mechanisms, manufacturing methods, material compositions, means, methods, and steps of the specific embodiments described in the specification. From the disclosure of this invention, those skilled in the art will readily understand that any existing or future processes, mechanisms, manufacturing methods, material compositions, means, methods, or steps that perform substantially the same function or obtain substantially the same results as the corresponding embodiments described in this invention can be applied according to this invention. Therefore, the appended claims are intended to include these processes, mechanisms, manufacturing methods, material compositions, means, methods, or steps within their scope of protection.

Claims

1. A cement-stabilized crushed stone base structure, characterized in that, The aforementioned base structure consists of a stress-compensating upper base layer, a cement grout bonding layer, and a stress-compensating lower base layer, wherein: The stress-compensating upper base layer is composed of upper stress-compensating joints and several equal-length upper base cement-stabilized crushed stone blocks spaced apart by the upper stress-compensating joints. The stress compensation joint is formed by pouring high-expansion concrete of the upper base layer into the pre-cut joint of the stress compensation type upper base layer; The stress-compensating subbase is composed of a stress-compensating joint and several equal-length cement-stabilized crushed stone subbases spaced apart by the stress-compensating joint. The stress compensation joint is formed by pouring high-expansion concrete of the lower base layer into the pre-cut joint of the stress compensation type lower base layer; The arrangement order of the base structure is as follows: from top to bottom, the base structure consists of a stress-compensating upper base layer, a cement grout bonding layer, and a stress-compensating lower base layer; By utilizing the expansion characteristics of high-expansion concrete, longitudinal compressive stress is generated on the base layer between adjacent stress compensation joints, reducing or eliminating the impact of drying shrinkage and thermal shrinkage on cement-stabilized crushed stone base layers.

2. The cement-stabilized crushed stone base structure according to claim 1, characterized in that, The upper stress compensation joint and the lower stress compensation joint are arranged at equal intervals perpendicular to the centerline of the road.

3. The cement-stabilized crushed stone base structure according to claim 1, characterized in that, The spacing of the lower stress compensation joint is twice that of the upper stress compensation joint. The lower stress compensation joint of the stress compensation type lower base layer is connected vertically to the upper stress compensation joint of the stress compensation type upper base layer at a distance of one position, with their center lines coinciding and separated by the cement slurry connecting layer.

4. The cement-stabilized crushed stone base structure according to any one of claims 1-3, characterized in that, The stress-compensated upper base cement-stabilized crushed stone has a 7-day unconfined compressive strength of 3-10 MPa and a thickness of 15-27 cm.

5. The cement-stabilized crushed stone base structure according to any one of claims 1-3, characterized in that, The stress-compensated subbase cement-stabilized crushed stone has a 7-day unconfined compressive strength of 2-5 MPa and a thickness of 15-27 cm.

6. The cement-stabilized crushed stone base structure according to any one of claims 1-3, characterized in that, The cement slurry layer is a pure cement slurry with a water-cement ratio of 0.45-0.

55.

7. The cement-stabilized crushed stone base structure according to any one of claims 1-3, characterized in that, The horizontal length of the stress compensation joint is equal to the width of the stress compensation type subbase, and the height is the same as the thickness of the stress compensation type subbase. The joint width is 12cm-25cm, the spacing is 40m-90m, the grade is 25MPa-35MPa, and the 90-day self-stress value is 1.5MPa-2.5MPa.

8. The cement-stabilized crushed stone base structure according to any one of claims 1-3, characterized in that, The transverse length of the stress compensation joint is equal to the width of the stress compensation type upper base layer, and the height is the same as the thickness of the stress compensation type upper base layer. The joint width is 22cm-38cm, the spacing is 20m-45m, the grade is 25MPa-35MPa, and the 90-day self-stress value is 2MPa-3MPa.

9. The cement-stabilized crushed stone base structure according to any one of claims 1-3, characterized in that, The upper stress compensation joint is 5cm-7cm wider at its outer edge than the corresponding lower stress compensation joint.

10. A construction method for a cement-stabilized crushed stone base structure as described in any one of claims 1-3, characterized in that: The method includes the following steps: 1) Construction of the stress-compensated subbase: Cement-stabilized crushed stone is laid by a paver, compacted by a vibratory roller and a rubber-tired roller, and covered with curing cloth and watered for 7 days; 2) Construction of the stress compensation joint: The stress compensation type subbase is cured for 3-5 days, with intervals of 40m-90m; a 12cm-25cm wide cutting joint with the same thickness as the stress compensation type subbase is cut using a concrete cutter; the water-stabilized crushed stone between the two joints is removed, the vertical surfaces of the two joints are smoothed with No. 10 mortar, and then expansion concrete is poured and water-cured for 7 days; 3) Construction of the cement slurry bonding layer: Cement slurry is sprayed onto the stress-compensated subbase using a sprayer; 4) Construction of the stress-compensating upper base course: Cement-stabilized crushed stone is laid on the stress-compensating lower base course using a paver, compacted by a rubber-tired roller in conjunction with a vibratory roller, and cured with tack coat for 7 days; 5) Construction of the stress compensation joint: The stress compensation type upper base layer is cured for 3-5 days, with an interval of 20m-45m; a cutting joint with a width of 22cm-38cm and the same thickness as the stress compensation type upper base layer is cut using a concrete cutting machine; the water-stabilized crushed stone between the two joints is removed, and the two vertical surfaces of the joint are leveled with No. 10 mortar, and then high expansion concrete is poured and water-cured for 7 days; 6) Tack coat construction: Apply a tack coat to the stress compensation joint, and then apply a hot asphalt tack coat to the entire stress compensation type upper base layer.

Images