Semi-rigid Pavement Research Articles

Application of Iron Tailing Sand in Pavement Base

Iron tailings are solid wastes produced after iron ore is refined. Based on the analysis of the development of road engineering in our country, the application status of iron tailings sand in road engineering in recent years is summarized. The optimal moisture content, maximum dry density and compressive strength of iron tailings cement stable macadam are evaluated by using the compaction test and unconfined compressive test. The results show that UNDER the condition OF a certain amount of cement and the content of iron tailing sand is 10%-20%, iron tailing sand can be used as semi-rigid pavement base material in road engineering construction. Finally, the author puts forward his own views on the future research direction.

Influence of Axle Load and Asphalt Layer Thickness on Dynamic Response of Asphalt Pavement

Based on the test data of vehicle load test on asphalt pavement, the significance of dynamic response index of different asphalt pavement to axle load change of single and double rear axle trucks is analyzed. The changes of horizontal strain at the bottom of asphalt layer, vertical compressive stress at the top of subgrade, and vertical displacement of transition layer and bottom compressive stress before and after laying of middle and upper layers are revealed. The test results show that reducing the thickness of asphalt layer or increasing the vehicle axle load can lead to the more unfavorable stress-strain distribution in asphalt pavement under driving load. The influence of the fluctuation of truck axle load or asphalt layer thickness on the stress-strain distribution in asphalt pavement varies with the type of pavement structure, pavement response index, vehicle driving speed, vehicle type, and the horizon of the measuring point. The transverse strain at the bottom of the asphalt layer is more affected by the axle load and the thickness of the asphalt layer than the longitudinal strain at the bottom of the asphalt layer. The measured value of the dynamic response index of the semirigid asphalt pavement is more affected by the axle load than that of the inverted asphalt pavement. However, the measured value of the dynamic response index of the semi-rigid asphalt pavement is less affected by the thickness of the asphalt layer when the thickness of the asphalt layer changes within a certain range. The tensile strain part of the longitudinal strain at the bottom of the asphalt layer and the compressive strain part of the transverse strain at the bottom of the asphalt layer are greatly affected by the thickness of the asphalt layer. The sensitivity of fatigue life of asphalt pavement of inverted structure to driving speed and axle load is less than that of semirigid structure. The research results can provide reference for the analysis of the asphalt pavement disease mechanism and provide guidance for asphalt pavement structural design and service life analysis.

Rutting Prediction Models in Holistic Concept to Sustainability of Semi-Rigid Pavements

Abstract Authors have long been guided by the following premise in their research, educational, professional and publishing activities. Components of the Integrated Transport Infrastructure (ITI) of Slovakia, including roads, should be designed, built, managed, maintained, recycled (decomposed) at a reasonable price, in reasonable quality, respecting the relevant requirements of users, residents and sustainable development throughout life cycle. Elements of ITI Slovakia, as important landscape ecological elements, should be designed with respect to aesthetic principles considering the cultural and natural wealth of Slovakia. Slovak technical universities have recently been criticized for teaching 50-years-old curriculum. The authors dare to disagree with the statement and, due to their scientific profile, pre-sent their partial outputs of a holistic approach to the sustainability of transport structures with a priority focus on pavement. In the intentions of the above mentioned, it could perhaps be partly convergently concluded that they learn new things in the field of transport construction, but under the old names.

Multiple Reflective Cracks in Semirigid Base Asphalt Pavement under Traffic Load Using XFEM

This paper built a three‐dimensional layered structure model of semirigid base asphalt pavement with single and double transverse reflective cracks based on the Extended Finite Element Method and fatigue fracture theory. The effects of the number of cracks, crack spacing, and crack length on the stress intensity factors (KI, KII, and Keff) under moving vehicle loads were studied. The fracture life of the asphalt pavement structure was calculated based on the Pairs formula. The results demonstrate that reflective cracks in semirigid asphalt pavement are composite cracks of type I and type II under moving vehicle loads, and shear fracture is the main reason for the failure of the base. The damage to the pavement base will be accelerated with the increase in the number of cracks and the length of the cracks. As the distance between the two reflection fractures is closer, the interaction between the cracks has a superimposed enhancement effect on the crack propagation. Compared with the single nonpenetrating crack model, the fatigue life of the nonpenetrating reflective crack in the double crack pavement structure with a crack spacing of 30 cm is reduced by 46.87%. The research on the propagation mechanism of reflective cracks in this paper provides the essential theoretical and numerical basis for the design, construction, working condition evaluation, and maintenance of pavement structures.

Laboratory Investigation of Fiber Bragg Grating Strain Sensors for Semirigid Base Asphalt Pavements

Aiming to evaluate the applicability of Fiber Bragg Grating (FBG) strain sensors for semirigid pavement monitoring, beam and cylinder specimens with three types of FBG strain sensors embedded in two kinds of classic semirigid pavement materials, asphalt mixture (AC-25) and cement-stabilized crushed stones (CSCS), were prepared in the laboratory. Four-point bending tests and uniaxial-compression tests were carried out under different loading frequencies and temperatures to evaluate the working properties of these sensors and then obtain the corresponding real sensitivity coefficients (SCs). The experimental results showed that the synchronism, repeatability, and linearity of all these sensors were prominent. However, the real SC results were significantly different from the recommended and dependent on many factors including temperature, the loading frequencies, the stress state, and the type of embedded material to different degrees. The SCs remained stable when the moduli of the embedded materials were high enough; otherwise, the SCs varied. Two SC prediction models that used the modulus of the embedded material as the only independent variable were developed to deal with the problem of instability. The modulus difference level between the sensors and the embedded material could integrate the factors roughly, except for the stress state. It is recommended that the factors above should be considered when using FBG strain sensors in practice, and it is still necessary to perform laboratory calibration in advance.

Equivalent Resilient Modulus Inversion and Calculation of Different Asphalt Pavement Structures

Based on the modulus inversion theory and the equivalent principle of deflection basin, by analyzing the deflection basin data of each structure layer measured by the FWD, the obtained equivalent resilient moduli of different structural layers in three different structures (a semirigid type Asphalt pavement and two inverted asphalt pavements) were compared. At the same time, the calculated equivalent resilient modulus of the top surface of the structural layer based on the inversion method was used to modify the existing theory formula. The results show that, with the inversion method and the theoretical calculation method, the calculated equivalent resilient modulus of the top surface of the cushion layer has a small error, but the theoretical calculation method overestimates the equivalent resilient modulus of the top surface of the cement stabilized crushed stone layer and the top surface of the graded crushed stone transition layer, especially for the inverted asphalt pavement; by contrast, the corresponding result of the inversion method is closer to the value in actual engineering. While determining the equivalent resilient modulus of the cushion layer, the influence of the thickness of the cement stabilized crushed stone layer needs to be considered, and the inverted asphalt pavement structure should adopt a thicker asphalt layer to reduce the modulus deviation; at the same time, the more the structural layers and the larger the difference in the interlayer modulus ratio, the larger the deviation of equivalent resilient modulus of the top surface of the base layer; for the inverted asphalt pavement and semirigid asphalt pavement, the correction coefficients of the calculation formula of the equivalent resilient modulus of the top surface of cement stabilized gravel layer are 0.35∼0.55 and 0.65∼0.75, respectively. The inversion method can be used to determine the equivalent resilient modulus of each structural layer of the inverted asphalt pavement and semirigid asphalt pavement, and its results can provide a basis for the design of the structure reconstruction of asphalt pavement.

Field evaluation and statistical analysis of the dynamic response of semi-rigid pavement under full-scale moving truck load

Mechanistic-based pavement distress prediction models or transfer functions are often used to assess damage or predict the service life of the pavement structure. The reliability of pavement structure design and performance predictions is highly dependent on the accuracy of the critical responses. The present study provides an experimental and statistical evaluation of the relationship between influencing factors such as traffic speed, vehicle axle load, and seasonal temperature, and the pavement mechanical response. In addition, the level of impact of each influencing factor and their two-way interaction or coupling effect on the pavement critical response was investigated. The results of the experimental investigation and the statistical analysis of the pavement mechanical response were presented, analyzed, and discussed. Besides, by combining the application of the orthogonal array test and multivariate regression analysis, the current study proposes a prediction model to predict the critical stress response at the bottom of the semi-rigid layer.

Estimation of Vehicle Speed from Pavement Stress Responses Using Wireless Sensors

Vehicle speed is a crucial input for mechanistic-based design and maintenance decision making of asphalt pavement. It can be measured using direct methods and indirect methods. Direct methods, such as video camera and inductive loops, have difficultly achieving real-time data processing and have a sophisticated installation process. Indirect methods use the mechanical responses collected by the traditional mechanical sensors to estimate speed. Although effective, these traditional mechanical sensors usually have a low survival rate and require highly sophisticated installation procedures. Recently, a new type of wireless micro-electromechanical sensor (MEMS), SmartRock (Sensor Technology Research Development and Application Laboratory, Hong Kong), has been promising in pavement research to monitor contact stress and acceleration at the particle level. This paper aims to explore the potential and reliability of using the SmartRock in acquiring vehicular speed and to evaluate the effect of loading amplitude and wandering effect (i.e., the loading location relative to the sensor or monitoring-point location) on speed estimation. In this study, SmartRock sensors were embedded in a semirigid pavement, and an accelerated pavement testing (APT) facility was used to apply loadings. Vehicle speed was estimated according to the dynamic stress responses (i.e., stress waves) measured by the SmartRock. In addition, a finite-element model was developed. After being calibrated by SmartRock stress data, this model, combined with SmartRock data, was used to evaluate the effect of load amplitude and wandering on the speed estimation. Findings indicate that SmartRock can reasonably estimate the vehicle speed using both time-domain and frequency-domain methods. The loading amplitude and wandering may have little effect on the speed estimation according to the results of this study, but future work is recommended to verify such findings.

Meso-cracking characteristics of rubberized cement-stabilized aggregate by discrete element method

As a sustainable solution, embedding rubber inclusions in the semi-rigid pavement base course can ensure the consumption of a large amount of waste tire pollution and improve the mechanical properties of cement-treated base materials. The rubber modification has a potential effect on reducing the possibility of pavement reflective cracks caused by base cracking. This paper aims to investigate the meso-cracking characteristics of rubberized cement-stabilized aggregate (RCSA) mixtures and to quantitatively evaluate the influence of rubber inclusion content and particle size through numerical simulation. The rubber particle size of 0.6–4.75 mm was selected. The virtual RCSA samples were prepared by replacing similar-size aggregates with rubber particles based on the reference mixtures without rubber. Five volumetric replacement contents (20%, 40%, 60%, 80% and 100%) of three gradation ranges (0.6–1.18 mm, 1.18–2.36 mm, and 2.36–4.75 mm) were adopted. An indirect diametric tensile (IDT) simulation test was adopted to obtain the investigated performance of IDT strength, static stiffness, toughness and toughness index. The simulation results show that the incorporation of rubber inclusion has a negative effect on the IDT strength of the RCSA sample. However, material extensibility and post-peak toughness are improved and stiffness is reduced with increasing rubber replacement percentage. The optimal rubber content of the investigated mixtures should be controlled within 80% of the corresponding aggregate gradation volume, which is conducive to controlling the reduction of the overall strength and the play of the extensibility. The strength reduction and ductility improvement of modified concrete are positively correlated with the particle size of rubber inclusion. The modified RCSA mixture with a smaller rubber particle size could ensure a higher IDT strength and extensibility. For the investigated sample, the best comprehensive modification effect can be obtained using the finer rubber substitute with a particle size of 0.6–1.18 mm. The rubber inclusion acts similarly to a cavity defect, which will result in fracture preferring to occur adjacent to the rubber aggregate. Ignoring the adverse effect of strength, the practical implication of rubber incorporation is to improve the ductile behaviour of the RCSA mixture and reduce base cracking. The present numerical simulation methods have the potential to investigate the meso-cracking mechanism of RCSA. It also provides a theoretical guidance for the gradation design of rubberized mixtures.

Performance research of fiber-reinforced asphalt rubber as a stress-absorbing membrane interlayer

To delay the expansion of reflective cracks on semi-rigid base asphalt pavements and strengthen the cracking resistance of asphalt rubber stress-absorbing membrane interlayers, the bonding and fracture performances as well as cracking resistance of a fiber-reinforced asphalt rubber stress-absorbing membrane interlayer (FAR-SAMI), rubber asphalt stress-absorbing membrane interlayer (AR-SAMI), and SBS-modified asphalt stress-absorbing membrane interlayer (AS-SAMI) were studied. In addition, the resistance to reflective cracking for FAR-SAMI was evaluated by finite element (FE) analysis. The results show that FAR-SAMI exhibits appropriate bonding performance at 15 and 40 The addition of glass fiber increases the toughness of the composite specimens and the fracture energy of FAR-SAMI increases by 23% compared with AR-SAMI. Furthermore, FAR-SAMI is effective in restraining the development of reflection cracks and prolonging the fatigue life. FE analysis also shows that FAR-SAMI can significantly reduce the stress concentration phenomenon in the crack. Therefore, fiber-reinforced asphalt rubber was found to be suitable as a SAMI to prevent and control reflective cracking.

A BP Neural Network Method for Grade Classification of Loose Damage in Semirigid Pavement Bases

This study aims to address the problem that loose damage of the pavement base course cannot currently be quantitatively identified, and thus the classification and recognition of the extent of looseness mainly rely on empirical judgments. Based on the finite‐difference time‐domain (FDTD) method, a backpropagation (BP) neural network identification method for loose damage of a semirigid base is presented. The FDTD method is used to simulate a semirigid base road model numerically with different degrees of looseness, and the eigenvalue parameters for recognition of the presence and extent of the looseness of the base layer are obtained. Then, a BP neural network identification method is used to classify and identify the loose damage of the base course. The results show that the classification and recognition of simulated electromagnetic waves have an accuracy of over 90%; the classification and recognition of radar data from an actual project have a recognition accuracy of over 80%. The good agreement between the classification and recognition results for the simulated data and measured data verifies the feasibility of the classification and recognition method, which can provide a new method for the use of ground‐penetrating radar to detect loose damage and the extent of looseness in the base.

Adaptability of asphalt pavement structures to deformation of embankment underlain by black cotton soil

Three pavement structures, including fatigue-resistant layer sandwich structure (FRLSS), sandwich asphalt pavement structure (SAPS) and semi-rigid base pavement structure (SRBPS), were designed to investigate their adaptability to the differential deformation of highway embankment on black cotton soil (BCS), which shrink/swell behavior was modeled by the coupled consolidation theory for unsaturated soils. The maximum additional tensile stress in pavement was obtained, and the present serviceability index (PSI) and the international roughness index (IRI) were calculated by the vertical movement, pavement properties and traffic data. The adaptability of those pavement structures to the differential deformation of highway embankment was evaluated by grey relational analytical method using the PSI, IRI and additional tensile stress as the indexes. The results reveal that FRLSS presents the better effect in controlling cracks on the key-layer bottom, while SRBPS presents the better effect in controlling cracks on the pavement surface. The effect in controlling roughness decreases gradually from FRLSS, SAPS to SRBPS in order. The adaptability of FRLSS to the soil movement of highway embankment on BCS is superior to SAPS, which excels SRBPS. Overall, FRLSS should be given priority in designing asphalt pavement underlain by BCS foundation from the perspective of controlling roughness and cracks.

Modeling the international roughness index performance on semi-rigid pavements in single carriageway roads

Pavement deterioration models are a vital feature in any pavement management system since they are capable of predicting the evolution of pavement characteristics. Pavement roughness is measured by most of the highway administrations due to its relation to comfort and safety, generally by means of the International Roughness Index (IRI). The Regional Government of Biscay (Spain) has collected IRI values since 2000 on its road network. Although many models have been developed for flexible pavements, very few have been proposed for semi-rigid pavements. The paper aims to develop IRI prediction models for semi-rigid pavements in single-carriageway roads. Considering the high quantity of available information in the database, deterministic models were selected. Due to the importance of the pavement structure in IRI evolution observed in flexible models, only segments with completely known pavement details were employed, i.e., a section where the complete structure is known: materials and thickness of existing layers above the subgrade. The pavement age, as precise as practical, and the accumulated total traffic and heavy traffic through the section were identified as roughness accelerating factors. Conversely, the materials used in base and subbase layers, their thickness, and the total thickness of bituminous layers were observed as degradation reducing factors. Possible treated base and subbase materials included in the model were soil–cement, gravel-cement, and gravel and slag. The obtained model achieved a determination coefficient (R2) of 0.569. Additionally, the bituminous material of the surface layer was verified as an affecting factor too, which can be introduced to improve the model’s accuracy. Possible surface layer materials included dense (D) and semi-dense (S) asphalt concrete, with a maximum aggregate diameter of 16 and 22 mm, discontinuous mixing (BBTM 11A) and porous asphalt (PA 11). The additional model achieved a higher determination coefficient (0.645) and, hence, a more accurate IRI prediction resulted.

Performance evaluation of semi rigid pavement mix

Semi rigid pavement is a composite pavement, in which porous bituminous mix with 20–30% voids are filled with cementious grout. In recent years performance of semi rigid pavement has drawn attention to researchers. The research problem in this project mainly focus on selection of aggregate gradations and mechanical performance of semi rigid pavement mix. The research contents included 3 adopted gradation and acceptable proportions of cementious grout, Strength properties were carried such as compressive, flexural, indirect tensile strength and performance evaluation by rutting and fatigue for 1 and 28 days with different binder content. The investigations showed that selected ASTM gradation with 4.5% bitumen content has better strength properties and fatigue life. The permanent deformation of ASTM gradation shows slight variation compared to New Zealand gradation. The selected gradations mechanical properties and performance characteristics met standards of semi rigid pavement, so suggested that semi rigid pavement can be an alternative pavement.

Influence of geosynthetic reinforcement on maximum settlements of semi-rigid pavements

The aim of this paper was to improve the understanding of the influence exerted by geosynthetic reinforcement on stress and strain states in typical semi-rigid pavement structures subjected to traffic loading. A comparison of traffic-load-induced settlements of pavements with and without reinforcement is presented. The pavement-subgrade structure was modelled as a two-dimensional three-layer system using the finite element method. The behaviour of such structures was analysed in terms of ground compaction. A model of soil compaction was used to predict pavement deformation under repeated traffic loading. A series of numerical simulations were conducted to investigate the settlements of pavements with and without reflective cracks. It was assumed that reflective cracks propagate from the base layer to the pavement surface. The main attention was focused on the positive effect of the inclusion of reinforcement in pavements on the behaviour of such structures under traffic loading. The influence of such factors as subgrade properties, the magnitude of traffic loading and the presence of cracks in the pavement structure on stress and strain states was investigated. It was confirmed that placing a geosynthetic reinforcement layer inside the bituminous layer leads to a significant reduction in pavement settlements.

Compressive behaviour of rubberized cement-stabilized aggregate mixtures

An investigation was undertaken to study the behaviour of cement-stabilized aggregate mixtures modified with small amounts of rubber under compressive loading with the aim of providing more sustainable and less brittle mixtures for use in semi-rigid pavements. Three rubber replacement levels (15%, 30%, and 45% by same volume of one aggregate fraction that has similar particle gradation) were investigated. The rubber particles have higher surface roughness than the aggregate particles they replace. To understand the behaviour, this study was conducted at both macro- and meso-scale levels utilizing mechanical testing, x-raying the internal structure and monitoring the crack propagation. The results showed a higher reduction in the compressive strength compared to the tensile strength. X-ray images confirmed an interconnected cracking network through/around the rubber particles. This resulted in a delay to crack development, with the velocity of crack propagation declining due to rubber incorporation. As the latter phenomenon is governed by the stress distribution inside the mixture, therefore a rubber distribution quantitative study confirmed a fairly uniform rubber distribution only for low and moderate rubber content, suggesting that the low rubber content can be used to ensure better properties and to overcome the shortcomings of normal cemented pavement mixtures.

Prospects for estimating the pavements structural capacity based on rolling wheel deflection

This article contains the results of the study of elastic deflection of semi-rigid pavement defined by the method of a rolling wheel (RWD) under different axial loads. For the investigations, an exclusive mobile complex was developed, allowing measurements to be made in a motion for various axial loads from 100 to 250 kN. It has been observed that the dynamic method of testing a semi-rigid pavement with a rolling wheel with different load levels allows determining non-linear characteristics of the deformation curve and deformation features of the package of asphalt concrete layers with appropriate loads, that cannot be done with the standard method of estimating the elastic deflection under a load of 100 kN. The results of the study can be used to develop criteria for assessing the strength, reliability, and deformability of semi-rigid pavement. It is possible to determine the likelihood of a joint failure-free operation of a rigid base and non-rigid layer with a resource forecast and the feasibility of its cold recycling.

General applications of the semi-rigid pavement in South East Asia

The Semi Rigid Pavement (SRP) is an alternative solution to overcome the limitations caused by conventional pavements, i.e. Flexible (asphalt concrete) and Rigid (cement concrete) pavements, which consists both the flexibility from asphalt component and the rigidity from cement constituent. The Semi Rigid Pavement has already become more and more popular for years internationally as a surface layer of those pavements under serious conditions such as road junctions, airport aprons, bus depots and heavy loading yards. In this paper, the fundamental properties and general technical requirements of SRP, including its two main components of the porous asphalt concrete and the grouting material, were introduced after a briefing on SRP development history. The advantages and benefits of SRP were deduced and discussed together with the comparisons among the flexible pavement, rigid pavement and SRP. The application/construction procedure of SRP was introduced step by step. The selected typical pavement projects constructed with this SRP system were presented and some studies on special cases when SRP was laid on the top of concrete surface and on the weaker base were also conducted. Lastly, the durability of SRP has been reviewed.

Critical position of fatigue damage within asphalt pavement considering temperature and strain distribution

ABSTRACT The fatigue properties of the asphalt pavement layer are influenced significantly by different strain levels and temperatures. This research investigated the critical fatigue position within the asphalt pavement layer considering the couple effects of strain levels and temperatures. Firstly, field tests were conducted to measure the typical temperature distribution of the asphalt pavement layer. Secondly, laboratory four-point beam fatigue test and dynamic modulus test were applied to evaluate the fatigue life and the dynamic modulus of the asphalt mixture, respectively. Based on the results of field and laboratory tests, the distributions of strain and fatigue damage within the asphalt layer at different temperature conditions were calculated. It was found that the fatigue life of asphalt mixture decreased with the rising strain level but increased with the rising temperature. The critical fatigue position in the flexible pavement changed from 5 to 20 cm when the pavement temperature condition varied from high to medium/low. In terms of the semi-rigid pavement, this position varied between 6 and 12 cm at different temperature conditions. In addition, the fatigue damage within the semi-rigid pavement at high temperature was found to be as noticeable as that at medium/low temperatures. Thus, the fatigue properties of the asphalt layer at higher temperatures need to be carefully evaluated as well.

Identification of asphalt pavement transverse cracking based on vehicle vibration signal analysis

Transverse cracking is a common distress of semi-rigid asphalt pavement in China. Crack detection offers essential information for pavement performance evaluation and maintenance. A vibration-based method is proposed for transverse cracking identification of asphalt pavement. Vibration signals of the running vehicle at the transverse-cracked sections and the adjacent uncracked sections are measured and preliminarily analysed in time domain. Symlet3 wavelet is used for signal denoising. Frequency domain analysis of signals by fast Fourier transform (FFT) and discrete wavelet transform (DWT) shows that the occurrence of the transverse crack leads to a dramatic increase of energy in the sensitive frequency band (10∼20 Hz). Considering the computation efficiency, the dual relative energy (DRE) process by FFT and DWT is proposed for crack detection. In addition, the continuous wavelet time-frequency analysis is utilised to locate the transverse cracking precisely. This approach seems promising for the rapid identification of pavement cracks.