Keywords

1 Introduction

Ultra-thin cover is a common technical measure in the preventive maintenance technology of old cement concrete pavement [1]. The so-called preventive maintenance is a cost–benefit maintenance strategy for existing pavement under the condition of good pavement condition. Preventive maintenance is carried out before obvious damage to the pavement. The benefit cost ratio of the pavement with preventive maintenance is 6−10 times that of the pavement with any maintenance measures.But from the national scope, the highway and national provincial highway have just entered a new stage from construction mainly to construction and maintenance. The traditional road maintenance consciousness is still the mainstream, and is still the “correct maintenance” of “road not bad (repair)”. It has not yet entered the preventive maintenance stage. Prevent and delay the pavement diseases occur, however, focus on maintenance, the preventive maintenance technology can continue to keep the pavement performance, prolong DaZhong**u maintenance cycle, reduce the cost of the whole life cycle economic investment, prolong the service life of road surface integral, and the comparison, from the total life cycle cost accounting preventive maintenance money less than corrective maintenance maintenance [1, 2].

At present, the preventive maintenance measures for the old cement concrete pavement at home and abroad are to directly overlay the asphalt surface cover, make full use of the stiffness and strength of the cement pavement, improve the driving comfort, but the reflection cracks and interlayer bonding problems, and the noise reduction of the protection board are still urgent problems to be solved [2, 3].

According to the present situation of and the demand, consider the caking property of rubber asphalt mixture, flexibility, crack resistance, at the same time, considering the economic costs and the status quo of traffic paving layer, function orientation and durability problems, this paper tested after evaluation of pavement and so good, and poor board edge deflection of old cement concrete pavement, A preventive maintenance structure with noise reduction and anti-skid type of ultra-thin rubber asphalt overlay for old cement concrete pavement is proposed, which can effectively reduce the impact load of driving load on the old cement concrete pavement panel, improve the driving comfort, and extend the service life of the old cement pavement and the whole pavement after paving. From top to bottom, it is as follows: 3.0 cm optimized ARAC-10 rubber-asphalt concrete ultra-thin cladding, rubber-asphalt adhesive layer, old cement concrete surface layer, noise reduction and anti-slip type ultra-thin rubber-asphalt cladding preventive curing structure schematic diagram is shown in Fig. 1.

Fig. 1
A diagram. The layers are labeled 1, 2, and 3 from top to bottom. The bottom layer is blank, the middle layer is a thick line, and the top layer has cross patterns.

Noise reduction anti slip type ultra thin rubber asphalt cover preventive maintenance structure diagram

Full size image

2 Raw Materials and Experimental Study

2.1 Rubber Asphalt

In this paper, the experimental study shows that the matrix asphalt is No. 70 Grade A road petroleum asphalt from Maoming, with rubber powder (30−80 mesh).And the stirring and shearing processing technology was adopted, the processing temperature was (175−185) ℃, the stirring time was 1 h, and the shearing time was 30 min. Rubber asphalt was prepared indoors. The performance test results of rubber asphalt were shown in Table 1, in which the content of rubber powder in rubber asphalt was 21% (i.e. the quality of rubber powder: asphalt quality = 21:100).

Table 1 Test results of main performance indexes of rubber asphalt
Full size table

2.2 Aggregate and Packing

In this paper, the coarse aggregate is 1# (6−11), 2# (3−6) mm limestone gravel, fine aggregate is 3#(0−3) mm limestone rock debris, the filler is limestone mineral powder. The screening test results of aggregate and packing used in this test are shown in Table 2. below.

Table 2 Test results of aggregate and packing screening
Full size table

2.3 Optimized Ore Grading Design of ARAC-10 Rubberized Asphalt Mixture

Considering the characteristics of rubber asphalt slurry, the structure of multi-gravel small skeleton ore is adopted. The aggregate dosage range of 4.75−9.5 mm is 60−65%, the aggregate dosage range of 2.3−4.75 mm is 15−20%, and the aggregate dosage range of 0.075−2.36 mm is 20−25%. The key screen pass rate of 9.5 mm is 85−90%, 4.75 mm passes 35−40%, 2.36 mm passes 23 − 28%, 0.075 mm passes 4−6%, resulting in the formation of dense and stable skeleton structure between aggregates, so as to improve its high temperature, fatigue, deformation and cracking resistance.

According to the screening test results of aggregates and fillers, combined with existing engineering practice and field practice experience, ARAC-10 rubber-asphalt mixture ore grading design is selected and determined, as shown in Fig. 2.The water stability test results and high temperature stability test results of rubberized asphalt mixture are shown in Table 3.The optimized ARAC-10 rubber asphalt mixture has excellent performance, water stability and high temperature stability far exceed the technical requirements of the specification, and has good high and low temperature, fatigue resistance, deformation resistance, cracking resistance, and noise absorption. The function is very suitable for hot and humid high temperature areas.

Fig. 2
An ore grading curve. It plots percentage by percentage versus mesh size in millimeter. It gives values for synthesis and match, grading limit, graded lower limit, and values in the grading. The lines are similar with an increasing trend.

Ore grading curve

Full size image
Table 3 Water stability and dynamic stability performance test results
Full size table

3 Study on Mechanical Response of Ultrathin Overlay Structure on Old Cement Concrete Pavement

3.1 Construction of Finite Element Calculation Model of Ultra-Thin Overlay on Old Cement Concrete Pavement

In order to grasp the mechanical properties of the ultra-thin overlay structure of cement concrete pavement, this paper uses the finite element analysis software to build the overlay structure finite element model with overlay thickness of 3, 4, 5, 6 cm, as shown in Fig. 3.Because the numerical model of asphalt pavement structure is symmetrical and the stress state of the structure is axisymmetric, the axisymmetric model is used to calculate the stress characteristics of the pavement structure.The numerical model is calculated by using a single garden load pattern, the uniform pressure is 0.7 MPa, the equivalent garden diameter is 30.4 cm, and the thickness and elastic modulus of each structural layer of the old cement concrete pavement are selected as shown in Table 4.The numerical simulation model is shown in Fig. 3 [4, 5]. The numerical simulation model uses a four-node quadrilateral element, the length of the element is divided according to the principle of dense on the top and sparse on the bottom. The boundary conditions of the model are set as follows: the bottom surface of a certain depth of the subgrade is a fixed surface, the left and right surfaces parallel to the Y axis have no displacement in the X direction, and the structural layers of the pavement are completely continuous contact [5, 6].

Fig. 3
A model diagram of an ultra thin overlay structure for cement concrete pavement. A load x acts in the downward direction on the top left corner.

Numerical simulation model diagram

Full size image
Table 4 Parameters of ultrathin overlay structure model for old cement concrete pavement
Full size table

3.2 Finite Element Calculation Analysis of Ultra-thin Overlay on Old Cement Concrete Pavement

In this paper, only considering the traffic load, the finite element analysis software is used to simulate the changes of horizontal compressive stress at the bottom of asphalt layer, shear stress and shear strain in the depth direction with the thickness of asphalt layer under different overlay thickness (3, 4, 5, 6 cm), the calculation results are shown in Figs. 4, 5 and 6.

Fig. 4
A graph plots horizontal stress under asphalt layer versus transverse distance of pavement. It gives values for 3, 4, 5, and 6 centimeters. The lines start between negative 0.60 and negative 0.50 and gradually increase to (0, 0.5), (1, 0.01), (1.5, 0.02) and (1.5, 2), approximately.

Variation law of horizontal compressive stress distribution at asphalt layer bottom with asphalt layer thickness

Full size image
Fig. 5
A graph plots shear stress versus depth of road surface. It gives values for 3, 4, 5, and 6 centimeters. The lines start at (0, 0.10), gradually increase and then drop down.

Variation of shear stress distribution in depth direction of structural layer with asphalt layer thickness

Full size image
Fig. 6
A graph plots shearing strain versus depth of road surface M. It gives values for 3, 4, 5, and 6 centimeters. The lines start at (0, 2.00 E negative 04), then increase and drop down, and remain stable from 0.05 to 0.25.

Variation of shear strain distribution in depth direction of structural layer with asphalt layer thickness

Full size image

The results show that when the thickness of asphalt layer increases from 2 to 5 cm, the mechanical response index of ultra-thin overlay structure on old cement concrete pavement does not change obviously, and the horizontal compressive stress, shear stress and shear strain at the bottom of asphalt layer change greatly.

The relationship between the change of mechanical response index and the change of asphalt layer thickness in the ultra-thin overlay structure layer of old cement concrete pavement is shown in Fig. 7. The road surface displacement and the shear strain in the structure layer are positively correlated with the change of layer thickness, that is, with the increase of asphalt layer thickness, the peak value of road surface displacement and shear strain in the structure layer increases. The other indexes are negatively correlated with the change of layer thickness, but the change range of each index is not large. Considering the economic applicability and construction workability, it is recommended that the thickness of 3 cm should be used for the overlay of old cement concrete pavement.

Fig. 7
A graph plots rangeability versus thickness of asphalt surface in centimeter. It gives 8 different values. The lines start at (0, 3) and scatter up and down. Amplitude of thickness increase rises to (6, 1). Horizontal strain at surface bottom goes below to (6, negative 0.2).

Correlation between variation amplitude of mechanical response index in structural layer and increase amplitude of asphalt layer thickness

Full size image

4 Study on Application of Ultrathin Overlay Structure on Old Cement Concrete Pavement

A section of the old cement concrete pavement has excellent road conditions, basically no broken plates and no obvious dislocation. Therefore, it is considered to protect the force of the existing cement plate, reduce the direct impact of heavy load traffic on the cement plate, prolong the service life, etc. At the same time, considering the economic cost input and the current road conditions, the function orientation and durability of the overlay layer, etc., the section adopts 3.0 cm optimized ARAC-10 rubber asphalt concrete ultra-thin overlay for transformation during preventive maintenance. The comparison diagram of the test section of the old cement concrete pavement overlaid with ultra-thin rubber asphalt overlay before and after paving is shown in Fig. 8. After 3 years of follow-up investigation, it is found that the road condition of the test section of the overlay is good, and there is no obvious disease on the road surface. The overall change of the road condition and the tracking survey test data is not large. The tracking survey test data of the old cement concrete pavement overlaid with ultra-thin rubber asphalt overlay are shown in Table 5.

Fig. 8
Two photos of the before and after construction of concrete pavement on road. On the left, cement concrete pavement is laid by a road roller. The workers stand beside the vehicle. The right photo is of a road with a car and a bike at a distance.

Comparison diagram of old cement concrete pavement with ultra - thin overlay test section before and after construction

Full size image
Table 5 Parameters of ultrathin overlay structure model for old cement concrete pavement
Full size table

After the old cement concrete pavement is paved with 3cmARAC-10 rubber asphalt concrete ultra-thin overlay, the pavement condition is good, which effectively solves the noise and anti-skid problems of the cement pavement, improves the driving comfort, and reduces the driving load on the old cement pavement panel. The load effect, especially the impact vibration load, effectively solves the problem of increased plate breakage and performance attenuation in the later period, thereby prolonging the service life of the cement concrete panel. Compared with ordinary asphalt overlay, rubber asphalt ultra-thin overlay can slow down the expansion rate of reflection cracks and prolong the service life of old cement concrete pavement and pavement structure after overlay.

5 Conclusion and Suggestion

  1. (1)

    Aiming at the old cement concrete pavement with good road conditions such as no void, broken plate and poor deflection of plate edge after detection and evaluation, considering the adhesion, flexibility and crack resistance of rubber asphalt mixture, economic cost investment and current road conditions, functional orientation and durability of overlay, this paper proposes a noise reduction and anti-sliding type ultra-thin rubber asphalt overlay preventive maintenance structure for old cement concrete pavement, which can effectively reduce the impact load of driving load on the old cement concrete pavement panel, improve driving comfort, and prolong the service life of old cement pavement and the whole pavement after overlay.

  2. (2)

    The experimental results of water stability and high temperature stability of rubber asphalt mixture show that the ARAC-10 rubber asphalt mixture proposed in this paper has good high and low temperature, fatigue resistance, deformation resistance, cracking resistance and noise absorption function, which is very suitable for hot and humid high temperature areas.

  3. (3)

    In this paper, through the finite element simulation analysis, it is known that the surface displacement and the internal shear strain of the structural layer of the old cement concrete pavement overlay ultra-thin overlay structure are positively correlated with the change of layer thickness, and the remaining indicators are negatively correlated with the change of layer thickness, but the change range of each index is not large. Comprehensively considering the economic applicability and construction workability, it is recommended that the thickness of 3 cm should be adopted for the ultra-thin overlay of the old cement concrete pavement.

  4. (4)

    After paving 3 cmARAC-10 rubber asphalt concrete ultra-thin overlay on the old cement concrete pavement, the pavement condition is good, which effectively solves the noise and anti-sliding problems of the cement pavement, improves the driving comfort, and reduces the load of the driving load on the old cement pavement panel, especially the impact vibration load. Compared with ordinary asphalt overlay, rubber asphalt ultra-thin overlay can slow down the expansion rate of reflection cracks and prolong the service life of old cement pavement and the whole pavement structure after overlay.