Pavement Stress Research Articles

Evaluation of the Moisture Dependence of Concrete Coefficient of Thermal Expansion and Its Impacts on Thermal Deformations and Stresses of Concrete Pavements

The coefficient of thermal expansion (CTE) is one of the material properties of concrete that has the largest impact on rigid pavement performance. Concrete CTE is typically measured in the laboratory, under saturated conditions, or estimated on the basis of the mix constituents, past experience, or both. Whichever method is used, the mechanistic-empirical design of concrete pavements traditionally assumes a constant value for this material property. This assumption has important consequences in relation to predicting thermal deformations and stresses since the CTE of concrete actually changes with the concrete’s internal moisture conditions. The experimental data presented in this study show that this assumption, together with the way CTE is measured in the laboratory, leads to systematic underestimates of thermal deformations and stresses in concrete pavements. The experimental data come from six concrete overlays of asphalt pavements that were instrumented with thermocouples, relative humidity sensors, and vibrating wire strain gauges to measure the expansion/contraction and bending of the slabs because of temperature and moisture-related actions. The apparent CTE of the overlay slabs reached values up to 65% larger than the CTE measured in the laboratory under saturated conditions. Using finite element method modeling, it was determined that thermal stresses were up to 70% larger than predicted using the saturated CTE.

Experimental and numerical analysis of the critical heating strategy for hydronic heated snow melting airfield runway

Hydronic heated technology is an efficient and controllable method for airfield-runway snow removal. The heating strategy plays an important role in the application process. Nowadays, the users only consider the snow melting performance of pavement to determine the heating strategy, however the thermal stress of pavement is another considerable but missing aspect for the design of hydronic heated snow melting pavement. This paper investigated the thermal strain distribution of hydronic pavement through the digital-image-correlation and fiber Bragg grating strain sensors in a full-scale field experimental system. Thereafter, the thermal stress field of hydronic heated pavement was analyzed by a two-dimensional numerical model which contains the pavement temperature, thermal strain, and thermal stress distribution. Model validation results indicated that pavement temperature and thermal strain distribution between the experiment and the model were in good agreement. Numerical results showed that the remarkable compressive stress was observed near the hydronic pipe, and the maximum tensile stress appeared in the midpoint between two pipes at the depth of the pipes. The maximum thermal stress of pavement increased with fluid temperature but decreased with air temperature. The comparison results between the maximum thermal stress and mechanical strength of pavement show that the critical heating temperature increased with air temperature. The critical fluid temperature °C = 73 °C + 1.17 × ambient air temperature °C. The obtained results could ensure the security of hydronic heated snow-melting airfield-runway.

Effect of pavement and water deficit on biomass allocation and whole-tree transpiration in two contrasting urban tree species

Aiming to explore the species-specific responses of biomass allocation and whole-tree transpiration in urban trees to pavement and drought, a field manipulation experiment grew saplings of two common greening trees, ash (Fraxinus chinensis Roxb.) and ginkgo (Ginkgo biloba L.). Pavement slightly increased leaf area and leaf biomass in ginkgo under sufficient water supply. When water deficit occurs, the height, basal diameter, and biomass in ash reduced and more biomass was allocated to roots, pavement aggravated the reduction of stem biomass in ash. Pavement slightly increased soil evaporation and total evapotranspiration, irrespective of whether the water supply was sufficient or not. However, whole-tree transpiration and stem sap flow increased under pavement when the water supply was sufficient for ginkgo but not so for ash. The down-regulation of water use generated by an insufficient water supply was aggravated and retarded by pavement for ginkgo and ash, respectively. Ash grows faster and can maintain its transpiration better under pavement and drought stress, making it the preferred tree for planting on paved land in urban areas.

Fracture performance of a PCM-Rich concrete pavement under thermal stresses

ABSTRACT Curling stresses in rigid pavements are the result of temperature gradient through the thickness of the concrete slab. These stresses have a periodic nature, and the induced cyclic flexural curling stresses lead to the cracking of the concrete slab. In a previous research by the authors, a phase change material (PCM)-rich concrete overlay was proposed as an effective method to control this failure mechanism. A PCM-rich concrete overlay is a concrete surface layer that contains a relatively high percentage of PCM. In the previous study, a phenomenological approach was employed, and it was demonstrated that the incorporation of PCM improves the curling fatigue performance of the concrete slab. Using fracture mechanics, this paper builds upon the findings of the previous study, and it serves as a mechanistic verification of the conclusions of the previous work. A modified Paris’ Law was adopted to calculate the cumulative fatigue-fracture damage of the concrete slab due to cyclic thermally-induced curling stresses. The findings of this research demonstrated that the PCM-modified concrete slab undergoes a curling-induced fracture process that is less severe than the slab without the PCM. The impact of this reduction was quantified in terms of an improved fatigue-fracture performance of the pavement.

Experimental investigation on dynamic response of asphalt pavement using SmartRock sensor under vibrating compaction loading

Although compaction is one of the most critical steps during the construction of asphalt pavements, effective real-time technologies to detect the compactness of the asphalt mixture non-destructively are still rare. Currently, most methodologies in practice are experience-based, and few studies have provided insight into the particle interaction characteristics and quantitative response during the vibration compaction of asphalt pavements. Accordingly, both field and laboratory tests are conducted in this study to investigate the response of an asphalt mixture quantitatively under a vibrating compaction load at the meso-scale. First, a field test program is designed, and sensors (e.g., SmartRock and acceleration sensors) are used to measure the dynamic response of an asphalt pavement and the vibrating drum during vibrating compaction. The quantitative analysis reveals that the first three rolling impacts exert a significant and dominant compact effect on the asphalt mixture. Subsequently, a linear relationship between the acceleration of the vibrating drum and the vertical stress in the asphalt pavement is demonstrated. Furthermore, the SmartRock sensor is also employed in the laboratory test to detect the internal dynamic response under gyratory compaction, and the relationship between the compaction degree and the vertical stress in the asphalt mixture is established. Finally, three assessment methods for asphalt mixture compactness are proposed as characterization of the compactness by the acceleration of a vibrating drum, intermediate variables such as the stress of the mixture under a gyratory compaction, or acceleration and stress of the pavement. Comparison of the results illustrates that the dynamic response inside the mixture during the compaction can directly reflect the compaction degree of the asphalt mixture, and the compaction degree and the peak acceleration of the vibrating drum exhibit a strong linear correlation during the vibration rolling process.

A Study on the Friction Dynamic Response of Asphalt Pavement Considering the Unevenness

In order to quantitatively analyse the influence of pavement unevenness on the stress of asphalt pavement, a tire-road coupling model with stable rolling was established. Sinusoidal wave is used to describe the pavement unevenness, and based on the established tire-road coupling model, different conditions of axle load and base elastic modulus are used to analyse the influence of unevenness on the dynamic response of asphalt pavement. The results show that the influence of unevenness on vertical stress of asphalt pavement increases with the increase of axial load. As the elastic modulus of base increases, the vertical stress of asphalt layer will decrease, while the vertical stress of base layer increases. But the influence of unevenness on dynamic response of asphalt pavement cannot be eliminated. Therefore, the unevenness should be taken into account in the simulation of real road surface.

Design and maintenance of airport aprons: recommendations from thermomechanical analysis

In this study, general recommendations for apron design are made by analysing the thermomechanical behaviour of concrete pavements under the effects of aircraft traffic and the environment. This analysis provides designers with data for decision-making on dimensioning to minimise maintenance costs throughout the pavement lifecycle. Pavement thermal differentials and stresses were compared for five Brazilian regions, as represented by the capitals Brasilia, Manaus, Porto Alegre, Sao Paulo, and Teresina, considering the ambient temperature, solar radiation and typically-used coarse aggregate for each region. Parametric analyses for the pavement thermal differentials and stresses were also carried out. Thermal simulations were performed using a numerical model and ANSYS®/Multiphysic (Version 15.0) software, and structural simulations were performed using EverFE (Version 2.23) software. The resulting recommendations for the effective management of airport design provide clear guidance for the definition of metrics for managing apron pavement lifecycles.

Evaluation and reduction of temperature stresses in concrete pavement by using phase changing material

Due to an increase in the population, the need for good and efficient transportation becomes essential to provide better facilities to the people. Nowadays, concrete pavements are more adopted in highway construction. The concrete pavement is more efficient because of its higher strength, durability, and reliability, but concrete pavements are largely affected due to temperature stresses. This study investigates the potential use of phase changing material (PCM) for the reduction of temperature stresses in concrete pavements. To inspect compressive strength and temperature differential of concrete mixes at different substitution levels of PCM. An indoor heat simulator with temperature sensors was used to measure the temperature differential of concrete mixes. The temperature differential is a major factor for generating curling in concrete pavement. Results recommend that increment in PCM content reduces the temperature stresses in concrete pavement.

Ways to Minimize Volume (Weight) and Increase the Bearing Capacity of Rigid Pavement

The objective of research is finding of a possibility economy of rigid pavement weight and volume of material. The subject of the research is a mathematical model of rigid pavement in the form of a multilayer structure on an elastic foundation. The method of a research consists in modeling the behavior of rigid pavement in the form of a set of equations. These equations reflect the change in the stress-strain state of such structures. The system of equations takes into account the geometric nonlinearity of the work of materials and makes it possible to investigate the influence of various parameters on the values of stresses and displacements. Critical force coefficient and stress of shells are calculated by Bubnov-Galerkin. The formation way of the elastic foundation allows modeling the spreading layers with various characteristics. Use of two-layer model allows considering of a surface course and base course of road pavement designing (for example concrete and crushed stone). The graphs show the patterns of change of the stress of rigid pavement when changing the characteristics. The form of rigid pavement allowing to maintain big loadings is exposed to improvement. Findings shows the possibility of optimizing the geometric parameters of the design and achieving the savings in weight and volume of the consumable material.

Concrete pavements subjected to hail showers: A semi-analytical thermoelastic multiscale analysis

Climate changes result in an increase of extreme weather events. Concrete pavements e.g.may be subjected more frequently to hail showers, following significant solar heating of their top surface. This scenario is studied by means of multiscale thermoelastic analysis. The semi-analytical solution of the heat conduction problem provides access to the temperature fields inside the pavement plates. The thermal expansion coefficient, the modulus of elasticity, and Poisson’s ratio of concrete are homogenized based on the Mori-Tanaka scheme. The thermoelastic analysis of pavement plates, resting on an elastic Winkler foundation, is based on the Kirchhoff hypothesis and a Vlasov-type of structural analysis. This delivers macroscopic stress states of the concrete. Finally, top-down scale transition is used to compute the average stresses, experienced by the three concrete constituents: cement paste, fine aggregates, and coarse aggregates, and by the interfacial transition zones (ITZs), covering the aggregates. This mode of analysis is applied to a realistic pavement plate. It is found that the stresses in concrete pavements subjected to temperature changes are governed by self-equilibrated thermal stresses resulting from nonstationary heat conduction. In case of a sudden hail shower, these stresses are likely to reach the tensile strength of concrete. Cracking starts at the ITZs, representing the weakest link of the microstructure. From quantitative thermoelastic analysis it is concluded that hail showers represent a serious threat for the integrity of the top layer of concrete pavements and, thus, for the long-term durability of such pavements.

Experimental study on thermophysical properties of HMA during compaction

ABSTRACT The thermal parameters are key parameters for evaluating the temperature field and temperature stress of asphalt pavement. However, due to the restriction of tradition test method, the thermal parameters of asphalt and asphalt mixtures measured by various researchers are quite different. Therefore, it is particularly important to introduce a simple and standard test method for thermal parameters of asphalt mixtures. This research proposed a novel test method to precisely determine the thermal parameters of asphalt mixture during compaction temperature, the effects of different air voids on the thermal diffusivity and parameters were evaluated. Differential scanning calorimetry (DSC) was used to measure the heat flow curves of asphalt and asphalt mixture, and the calculated and measured specific heat values of the mixture were obtained. Then the corresponding thermal conductivity was calculated from the conversion relationship between thermal parameters. The results indicated that the thermal conductivity converted from the calculated value of specific heat is close to previous studies, but the thermal parameters of the temperature field during the compaction process can be obtained accurately and conveniently. This research provides a new method for the thermal properties evaluation of asphalt and asphalt mixture .

Towards fast modelling of the tire-pavement contact

Actual technologies of materials and heavier vehicles generated new conditions of bituminous pavement degradation. The surface layers, now thinner and subjected to intense traffic are more often damaged by rutting and cracks (so called ‘Top Down Cracking’). Both degradation types are closely linked to the pressure generated by tire-pavement contact. In this article, the tire-pavement contact problem is placed in the term of contact and not of adhesion gum areas—aggregate. A model is developed to simulate the surface pavement stresses and compared with experimental tests at different inflation pressures and different loads. The model requires exact geometry of tire and equivalent Young’s modulus. For this, an optical method based on photogrammetry method provides relief displacement field. Estimation of Equivalent Young’s Modulus is also proposed as a function of the inflation pressure from press load tests. Comparison is finally performed between the measured footprint of the tire and the result of the semi-analytical computation and the structural effect of the tire on the stresses distribution are demonstrated.

Optimization of Structure Parameters of Airfield Jointed Concrete Pavements under Temperature Gradient and Aircraft Loads

Daily changing temperature causes significant thermal stress in concrete pavement. Tensile stress obtained can exceed flexural tensile strength when the concrete slabs are subjected to large temperature gradient and traffic loads, resulting in pavement damages. In this paper, maximum tensile stresses in concrete slabs with different slab sizes, thicknesses, and length to width (L/W) ratios were investigated by using the finite element (FE) method. The important parameters in the design of concrete pavement are the flexural tensile strength and the fatigue limit. By analyzing the comparison results between the maximum tensile stress and the fatigue limit, the optimum slab size and the critical thickness were determined. The results indicate that the maximum tensile stress obtained is higher for larger slab size with thin thickness. Furthermore, to reduce cutting work and the amount of dowel bars, the optimum slab sizes of the regional airport concrete pavement are recommended as 4 m × 4 m to 6 m × 6 m. The critical thicknesses of 4 m × 4 m slab and 6 m × 6 m slab are determined as 28.2 cm and 34.7 cm, respectively, based on the most unfavorable coupling between positive and negative temperature gradients and the Boeing 737–800 aircraft load. Moreover, the maximum tensile stress increases as the L/W ratio increases. When the slab length is less than 6 m, it is better to use square slab in airport jointed concrete pavement (JCP).

Critical response analysis of steel deck pavement based on viscoelastic finite element model

ABSTRACT Orthotropic steel deck (OSD) bridges have gained increasing popularity around the world and the steel deck pavement is essential to extend the service life of the bridge. To optimise the design method for OSD pavements, this study evaluated the critical response of this type of pavement using the viscoelastic finite element (FE) model. Firstly, the FE model was elaborated and comprehensively complemented with field strain measurements to simulate the OSD pavement response. Secondly, the critical responses including critical strain, shear stress and deflection of the OSD pavement under various loading and pavement conditions were predicted via the proposed model. It was found that in FE model, a moving load better simulated the field truck loading than a pulse one, while quasi-static and dynamic analysis algorithms provided nearly identical response predictions. The positions of critical horizontal strains were temperature-dependent. Critical strains and deflections dropped with the load motion speed and rose with temperature, while the critical shear stresses exhibited the opposite trend. Moreover, the investigated three types of critical responses were found to be similarly influenced by the layer thickness variation but showed different patterns under varying bonding conditions.

Analysis of temperature gradient in concrete pavement

The paper presents the results of experimental research that is the continuation of the research conducted as a part of a Ph.D. dissertation. The experimental research consisted in measuring the temperature at various depths inside a concrete slab, including its surface, and measuring the air temperature. The temperature distribution was measured on a concrete slab with dimensions similar to real road slab dimensions. The aim of the research was to determine the temperature gradient in the concrete slab in Polish climatic conditions and to verify the available analytical methods. Keywords: temperature gradient, concrete pavement, thermal stress in concrete pavement.

Dynamic Response Analysis of Rutting Resistance Performance of High Modulus Asphalt Concrete Pavement

In order to systematically study the rutting resistance performance of High-Modulus Asphalt Concrete (HMAC) pavements, a finite element method model of HMAC pavement was established using ABAQUS software. Based on the viscoelasticity theory of asphalt, the stress and deformation distribution characteristics of HMAC pavement were studied and compared to conventional asphalt pavement under moving loads. Then, the pavement temperature field model was established to study the temperature variation and the thermal stress in HMAC pavement. Finally, under the condition of continuous temperature variation, the creep behavior and permanent deformation of HMAC pavement were investigated. The results showed that under the action of moving loads, the strain and displacement generated in HMAC pavement were lower than those in conventional asphalt pavement. The upper surface layer was most obviously affected by outside air temperature, resulting in maximum thermal stress. Lastly, under the condition of continuous temperature change, HMAC pavement could greatly reduce the deformation of asphalt material in each surface layer compared to conventional asphalt pavement.

A mechanistic approach to predict built-in temperature in concrete pavements

The built-in temperature difference (BITD), defined as the temperature difference between the top and bottom of a slab at the final setting time, is an important parameter for analysing curling stress and slab deformation in concrete pavements. However, the available methods for estimating this parameter are very limited. A method to predict the BITD in a concrete pavement was therefore developed. To do this, a numerical model was developed to predict the temperature distribution in a concrete slab at early age using a transient one-dimensional finite-difference method. A mathematical equation for predicting concrete final setting time presented in the literature was used and incorporated in the numerical model to predict the BITD. The results of the numerical model showed good agreement with field data. Using the proposed model, the effects of climatic conditions, placement time, pavement thickness and concrete mix proportion on the BITD were also evaluated. The results showed that climatic conditions, placement time and concrete mix proportion have substantial effects on the BITD, whereas pavement thickness has only a slight effect. The proposed model can be used to predict the BITD in concrete slabs for given concrete mix design, placement time, pavement thickness and environmental conditions.

Modelling the effect of plastic sheet curing on early age temperature development in concrete pavement

ABSTRACTPrediction of the temperature development at an early age is a good starting point to assess the development of the restrained thermal stress and thermal cracking in rigid pavements. This paper presents a numerical early age concrete pavement temperature prediction model. It enables to evaluate the effect of various paving conditions, such as paving time, curing method, air temperature, wind speed, and the concrete placement temperature, on the early age concrete pavement performance. A critical review of current heat flux models at the pavement surface covered with a plastic sheet is presented. An extension of existing models to quantify the effect of the plastic sheet curing method is introduced, based on the energy balance method. The numerical implementation procedure for the proposed temperature prediction model is solved by the finite difference method. The temperature prediction model was verified with field measured data of two test sections. The predicted temperature shows a satisfying match with field measured data. Lastly, the effect of plastic sheet curing and its duration on the development of the pavement temperature was analysed by the proposed theoretical model.

Application of a PCM-rich concrete overlay to control thermal induced curling stresses in concrete pavements

This study aims to evaluate the application of a Phase Change Material (PCM) rich concrete overlay to reduce curling stresses in concrete pavements. Curling stresses are the results of temperature gradient in pavements, and are comparable to the stresses that are induced by traffic loads. The weather conditions, which have a cyclic nature, are the source of curling stresses, and they cause cyclic tensile and compressive stresses in pavements. This phenomenon causes fatigue damage in concrete pavements and reduces their service life. The PCMs have a high latent heat of fusion and can increase the thermal inertia of concrete. When PCM is used in a concrete overlay, it tends to moderate the temperature gradient in the slab, and thus mitigate the curling stresses. The efficiency of the proposed PCM-rich overlay was evaluated under the real climatic conditions of three different cities in the US. The findings of this research demonstrated that the cumulative fatigue Damage Index (DI) resulted from repetitive curling stresses can be up to 22% in a concrete slab with the service life of 35 years. However, using a 7.6 cm bonded concrete overlay with 25 vol% PCM can moderate the curling stresses so much that the effect of curling induced fatigue damage would be virtually negligible.

Monitoring the structural capacity of airfield pavement with built-in sensors and modulus back-calculation algorithm

The degree of deterioration in the structural capacity of a pavement is an important indicator of its performance. Conventional falling weight deflectometer, which assesses pavement capacity based on the deflection bowl data under impact loads and is the prevalent method in practice, only characterize the overall bearing capacity of pavement. It does not possess sufficient accuracy in measuring the modulus of pavement structural layer. In this paper, a smart pavement schema was proposed where built-in sensors are incorporated to monitor pavement stress and strain responses under aircraft loads. Theoretical relationship between pavement mechanical responses of a two-layered elastic system subjected to service load is established, which is used for back calculating the modulus of asphalt layer. To demonstrate the concept, sensors are deployed along a taxiway in Beijing Capital International Airport, Beijing, China. The measured mechanical responses by the sensors were incorporated to back-calculate the modulus of asphalt layer, which are then verified through dynamic modulus experiments. The results show that back-calculated modulus by incorporating sensor data is repeatable and can be applied for real-time evaluation of pavement performance without affecting the traffic. Extension of the model and analysis to multi-layered elastic system are discussed.