Thermal and Flood Resiliency Evaluation of Rigid Pavement Using Various Pavement Characteristics

Abstract

Temperature variations have a significant impact on the performance and durability of rigid (concrete) pavement. As concrete is subjected to daily and seasonal temperature changes, it experiences thermal expansion and contraction. These movements, if not properly managed, can lead to cracking, joint deterioration, and loss of structural integrity. The pavement system is adversely affected by intense heat and significant flooding. This study aims to analyze the impact of several parameters on the performance of rigid pavement under typical, thermal, and flooding situations. This study investigates the properties of concrete and the dimensional design of rigid pavement with FEACONS IV software to assess their impact on the performance of concrete pavement during thermal and flooding conditions. The main conclusions of this study derived from the FEACONS IV analysis are as follows. Rigid pavement can enhance load-carrying capacity due to a lower elastic modulus, adequate flexural strength, and aggregates with a lower coefficient of thermal expansion. Increased thickness of concrete slabs and shorter slab lengths assist in minimizing load- and temperature-induced stresses. The increase in the subgrade modulus reaction value during flooding conditions improves pavement strength. However, in higher thermal conditions, a higher subgrade reaction modulus can increase the stress induced by temperature and load. Rigid pavement using porous limestone aggregate exhibits a reduced elastic modulus and coefficient of thermal expansion, suggesting higher resilience compared to rigid pavement composed of river gravel or granite. The findings suggest that higher thermal conditions will cause pavement damage. Agencies need to account for higher temperatures while designing and maintaining pavement. Flooding saturates the concrete pavement and subgrade layer, adversely affecting its performance over time.

1. Introduction

Pavement systems, including rigid and flexible pavements, are subject to thermal and flooding hazards. Pavement applications are crucial for the sustainability of economic growth and community activities, as they cannot readily tolerate a decline in pavement performance without incurring additional costs. Damage to pavement infrastructure due to such hazards jeopardizes safety, mobility, and functionality, leading to negative economic and societal consequences. Pavements are continuously subjected to thermal effects, including solar radiation, variations in ambient temperature, and seasonal weather changes. These conditions generate thermal gradients among the pavement layers, resulting in differential expansion or contraction. Repeated thermal cycles over time lead to warping, cracking, and fatigue, potentially undermining pavement functional and structural strength. Flooding can adversely affect pavements by causing actual damage or decreasing their performance over time. Flooding hazards adversely impact individuals and the economy [1].

Numerous studies have demonstrated that rigid pavement exhibits greater resilience than asphalt pavements under thermal and flooding conditions. Asphalt pavements exhibited a greater rise in the International Roughness Index (IRI) compared to concrete pavements during the flooding caused by Hurricane Katrina in 2005 [2]. During this hurricane event, other studies observed a slight reduction in the Effective Structural Number (SNeff) and subgrade resilience modulus (Mr) of concrete pavements in comparison to asphalt pavements [3]. A study on the 2011 flood event in Queensland, Australia, determined that high-strength rigid pavements exhibited greater resilience to flood damage compared to asphalt pavements [4].

Rigid pavement performance is influenced by numerous elements, including design suitability, traffic load, climatic conditions, material properties, and building techniques. Material properties and climatic conditions, including a material’s coefficient of thermal expansion, saturation condition, drying shrinkage, elastic modulus, and modulus of rupture of concrete, are critical parameters in pavement design. Several pavement characteristics, including cross-section, design lifespan, and serviceability, are partially contingent upon these parameters. The bearing capacity of rigid pavement largely relies on slab thickness and slab flexural strength. Pavement performance is enhanced with an increase in slab thickness and the flexural strength of concrete [5].

Temperature is a crucial environmental factor that affects the performance of rigid pavement. The variation in temperature in concrete slabs is a critical component in the design of rigid pavement. Rigid pavement frequently experiences a broad spectrum of thermal effects during its operational lifespan, resulting in various deformations of the slabs. Thermal effects, including temperature variations in concrete, induce horizontal and vertical displacements in a pavement slab. These displacements influence the shear and moment resistance at joints, which convey stresses between adjacent slabs. Temperature differentials cause the upper and lower sections of a concrete slab to compress or expand, resulting in pavement deformation. The combination of lifted corners and high wheel loading leads to up-and-down cracks at the corners. This may result in a loss of support within the slab core or at the slab borders, leading to increased stress in the concrete pavement. Temperature differentials can produce thermal stress, leading to early cracking of pavement [6]. Fatigue damage from heavy wheel loading is significantly greater when there is a large temperature differential compared to a concrete slab with no temperature differential. Temperature gradients between the upper and lower surfaces of a concrete slab may result in fatigue damage [7].

Pavement inundation may result in floods, leading to soil erosion, decreased pavement strength, and lower load-bearing capability of the pavement. Seasonal variations in moisture content significantly influence pavement performance by altering soil behavior in the subgrade layers. Moisture content has been demonstrated to impact soil stresses, hence affecting the pavement material’s resilient modulus. A reduction in the soil material modulus may occur due to a higher moisture content [8,9,10]. The traffic load induces maximum deformation in a saturated subgrade layer due to the increasing loss of soil stiffness resulting from an increased water table [11]. Air-dried concrete samples are widely recognized to exhibit 15% to 20% greater compressive strength compared to saturated samples. Nonetheless, the decrease in the flexural strength and splitting tensile strength of concrete resulting from water saturation is recognized to be significantly smaller and not clearly characterized [12]. In contrast to the strength of concrete, which typically declines when saturated, the concrete elastic modulus usually increases under saturation conditions [13,14]. With an increase in the elastic modulus, the maximum stress caused by load also escalates [5]. Given that load-induced stresses in concrete slabs typically rise with a higher elastic modulus, it is anticipated that stresses in rigid pavement will escalate during flooding situations.

This study investigates the properties of concrete and the dimensional design of rigid pavement with FEACONS IV software to assess their impact on the performance of rigid pavement during thermal and flooding conditions. The first objective of this study is to evaluate the characteristics of concrete that influence stress distribution, cracking potential, and overall rigid pavement performance, involving the coefficient of thermal expansion, flexural strength, and elastic modulus. The second objective is to assess the impact stress and deflection of the dimensional design of rigid pavement, including the slab length and thickness, on its performance. The third objective is to examine the impact of temperature differentials in concrete slabs on the performance of rigid pavement, as higher temperature differentials increase curling stress and joint movements, hence lowering pavement durability. The last objective of this study is to assess the impact of moisture conditions during flooding events on rigid pavement performance, encompassing the concrete slab and subgrade materials, as flooding events deteriorate subgrade and concrete slab characteristics, resulting in increased deflections and pavement failure.

2. Research Methodology

FEACONS IV software (Finite Element Analysis of Concrete Slabs version IV) is utilized for conducting stress analysis. FEACONS software was established through collaborative research between the Florida Department of Transportation (FDOT) and the University of Florida. The FEACONS software program is an analytical model utilized for the assessment of rigid (concrete) pavement behavior. This program enables effective and reliable analysis of rigid pavement under applied loads, considering weather conditions such as thermal effects and saturated concrete. It can represent a rigid base or subbase layer as a separate layer, or it can consider both layers as a singular liquid foundation with a specific effective subgrade modulus. FEACONS IV software can assess the response of rigid pavement systems to a variety of concentrated and distributed loads. The analysis may examine the following factors: the weight of the concrete slab, the effects of joints, the impacts of edges, the nonlinear response characteristics of the subgrade, and the variations in temperature effects between the top and bottom of the slabs.

The software generated the mesh constraints with a maximum of 40 x-divisions and 16 y-divisions. In addition, the software generated a maximum of 641 elements and 730 nodes. The findings from FEACONS IV may not be entirely relevant to situations that substantially deviate from its intended scope. The accuracy and reliability of FEACONS IV are significantly influenced by the quality and quantity of the input data. If the data used are incomplete, the results may be compromised. A jointed rigid pavement was simulated in FEACONS IV software, as illustrated in Figure 1. The analysis of the rigid pavement response often requires assessing deflections and stresses on a slab, which are mostly affected by two adjacent slabs; thus, modeling rigid pavement as a three-slab system is frequently sufficient. Utilizing a more complex model, for example, a five- or nine-slab system, is unnecessary as it would complicate and prolong the analytical process.

The FEACONS finite element model employed for the analysis of the rigid pavement incorporates several fundamental assumptions to simplify the intricate behavior of materials and structures. The concrete layer and subgrade are considered to function as linear elastic, isotropic, and homogeneous materials, disregarding nonlinear phenomena such as cracking, plasticity, or creep. The slab geometry is conceptualized as entirely flat with consistent thickness. Traffic loads are assumed to be static and evenly distributed, disregarding dynamic effects and inconsistent pressure distributions.

Figure 2 presents an illustration of the finite element model mesh for the stress evaluation of the rigid pavement subjected to traffic loads as a single axle wheel. This study used 29 x-divisions and 14 y-divisions for a three-slab system. The element number is 406, and the node number is 480. The equation used to determine the wheel contact area utilized in FEACONS IV is as follows:

WCA = LT/PT,

(1)

where

WCA is the contact area for each tire in a single axle (cm²).

LT represents the load applied on each tire (N).

PT represents the pressure produced by a tire (Pa).

This study used a load of 50 KN and a pressure of 0.7 MPa. The determined contact area from each wheel in this study was 700 cm² (28 cm × 25 cm), utilized in FEACONS IV for finite element mesh. Figure 3 illustrates the dimensions of the contact area between the concrete slab surface and the tires. To evaluate the impact of specific pavement input parameters, a range of input parameters were used. The input parameters utilized in FEACONS IV were categorized into two types, i.e., fixed inputs and varied inputs, as illustrated in

Table 1. Input parameter types: fixed and variable [15,16].

Fixed Parameters	Fixed Value	Varied Parameters	Range Value
Slab Thickness [cm]	30	Slab Thickness [cm]	20–50
CTE * [×10−6/°C]	9	Temperature Differentials ∆T [°C]	0–22
E ** [GPa]	28	CTE * [×10−6/°C]	5.4–12.6
Uniform Load [MPa]	0.7	E ** [GPa]	21–48
Slab Dimensions [m*m]	3.7 × 4.8	K Value *** [MPa/m]	11–110
K Value *** [MPa/m]	110	Slab Dimensions [m*m]	3.7 × 4.3–3.7 × 6.7
Poisson’s Ratio	0.2

* Coefficient of thermal expansion, ** concrete elastic modulus, *** subgrade reaction modulus.

. A sensitivity analysis was performed to assess the impact of varied parameters. The findings indicated that slab thickness and temperature differentials were the most important factors, with slab thickness markedly diminishing stress and deflection, whereas greater temperature differentials amplified thermal stresses. The subgrade reaction modulus was crucial in limiting deflections, while slab length and the concrete elastic modulus exhibited moderate to high sensitivity, influencing the stress distribution and stiffness. The coefficient of thermal expansion exerted a minor influence, particularly affecting thermal-related responses. This study primarily utilized numerical modeling to assess the performance of rigid pavement, recognizing the lack of experimental data as a limitation. To address this limitation, the numerical model was based on well-established methodologies. Additionally, a sensitivity analysis was undertaken to analyze the influence of input parameters and ensure the robustness of the results. Despite this limitation, this study yields important insights into the relative effects of concrete properties, dimensional design, temperature differentials, and moisture conditions on pavement performance, hence providing practical suggestions for design and maintenance techniques. The ranges of the varied inputs were selected according to FDOT guidelines [15,16].

According to research conducted by Tia et al. [5,17,18], there are three main types of aggregates utilized in the production of rigid pavement in Florida state, United States. The aggregates include Calera limestone, a dense limestone located in Calera, Alabama; Brooksville limestone, a porous limestone located in Brooksville, Florida; and river gravel obtained from Alabama state.

Table 2. Properties of concrete using different aggregate types [17,18].

Pavement Designs	Aggregate Type	CTE *** [1/°C]	MR ** [MPa]	E * [GPa]	Unit Weight [kg/m³]
Used by FDOT #	Brooksville limestone	10.25	4.5	32.9	2322
	Calera limestone	10.8	4.5	34.3	2434
	River gravel	13	4.5	30.4	2402

* Elastic modulus of concrete, ** modulus of rupture, *** coefficient of thermal expansion, # Florida Department of Transportation.

presents the typical parameters of concrete utilizing these aggregates, including coefficients of thermal expansion, the elastic modulus, and unit weights of concrete corresponding to a flexural strength of 4.5 MPa. The parameters were utilized as inputs for analysis via FEACONS to assess concrete produced from these types of aggregates under thermal and flood conditions.

3. Results and Discussion

3.1. Temperature Differential Effects on Rigid Pavement Performance

Certain properties of concrete, such as the coefficient of thermal expansion and elastic modulus, influence the performance of rigid pavement in thermal effects. The dimensional design of rigid pavement also influences its performance under thermal effects. The dimensional parameters encompass slab thickness and length. Fatigue damage from wheel loading is significantly greater when there is a substantial temperature differential compared to a concrete slab with no temperature differential. The structural response of rigid pavement to traffic loads is influenced by thermal effects, including the temperature differential within the concrete slab. An investigation of the critical stress was performed with FEACONS IV software to determine the various pavement parameters’ influences on the maximum stress endured by rigid pavement under temperature differentials.

Concrete with a high elastic modulus is inappropriate for pavement applications as it heightens the risk of cracking. Consequently, high-strength concrete with a low modulus is preferable. Figure 4 illustrates the highest stresses related to temperature differentials and the elastic modulus of rigid pavement. This figure illustrates comparable stress results for the proposed elastic modulus values when the input ΔT is set to 0 °C. Furthermore, the study results indicate that the stress for all proposed values of E escalates as ΔT rises. A greater elastic modulus value results in increased stress under conditions of increased ΔT.

The coefficient of thermal expansion causes the degradation of rigid pavement and induces stress due to environmental temperature variations. Increased CTE correlates with an increased propensity for curling, hence exacerbating pavement distress during its design lifespan, irrespective of consistent conditions. Figure 5 illustrates the highest stress results related to temperature differentials and the thermal coefficient expansion (CTE) for the concrete slab. The computed maximum stress for the concrete slab, as shown in the figure, exhibits nearly identical values (1.26 MPa) across all CTE values when the input temperature differential (ΔT) is 0 °C. Similar to the study of the elastic modulus, the results indicate that the maximum stress for every value of CTE escalates as ΔT rises. A greater CTE value results in increased stress under increased ΔT conditions.

The concrete slab’s thickness is a critical design parameter that affects the occurrence of cracks, including transverse cracking. Certain studies examining the impact of slab thickness on pavement performance indicated that thicker concrete slabs resulted in a reduction in pumping, spalling, transverse cracking, corner deflections, and faulting [19,20]. Figure 6 illustrates the highest stress results related to temperature differentials and slab thickness. It exhibits varying stresses corresponding to different slab thicknesses. The analysis results indicate that the stresses for every slab thickness value increase as ΔT rises. The results indicate that increased slab thickness yields reduced stress levels.

Thermal effects might influence the dimensional design of rigid pavement regarding slab length. Figure 7 illustrates the highest stress results related to temperature differentials and slab length. It demonstrates nearly identical stresses (1.24 MPa) for every slab length value in the case of temperature differentials of 0 °C. The results indicate that the stresses on all slab lengths escalate with an increase in ∆T. It also indicates that an increased slab length results in higher stress levels.

The impact of subgrade properties on rigid pavement under differential temperatures was also assessed. Although the temperature differential directly affects the concrete slab, it also influences the subgrade layer under it. Figure 8 illustrates the highest stress results related to temperature differentials and the subgrade reaction modulus. An increase in the subgrade reaction modulus results in a reduction in stress when the input value of ΔT is 0 °C. Conversely, applying the maximum input value of ΔT at 22 °C yields distinct results. An increase in the subgrade reaction modulus results in higher stress. Every subgrade reaction modulus value yields comparable stress results when ΔT is between 5 °C and 6 °C. It is generally understood that elevated temperature differentials and a high subgrade reaction modulus lead to increased stress. In the absence of a temperature differential, slab curling does not occur, resulting in complete contact between the slab and the subgrade. Utilizing an elevated subgrade modulus, which indicates a more rigid subgrade layer, enhances the slab’s load distribution ability. Temperature differentials in the slab can induce slab curling, resulting in incomplete contact with the subgrade.

3.2. Flooding Effects on Rigid Pavement Performance

Flooding can adversely affect pavements by washout or inundation, diminishing their performances over time. Pavement inundation causes the subgrade layers and concrete slab to remain saturated, resulting in a decrease in strength. The potential impacts of the relevant variables influenced by flooding were investigated utilizing FEACONS IV software.

Figure 9 illustrates the highest stresses as an effect of the subgrade reaction modulus and slab thickness. The results indicate that the concrete slab stress diminishes as the subgrade reaction modulus escalates. Furthermore, an increased slab thickness results in reduced stress.

In the analysis of the elastic modulus, assuming constant temperature conditions, the results depicted in Figure 10 indicate that for all values of the concrete’s elastic modulus, the maximum stress reduces as the subgrade reaction modulus increases. Furthermore, the results indicate that a greater elastic modulus corresponds to an increased stress level. Significant results are obtained due to temperature differentials. When utilizing input values of ∆T at 11 °C and 22 °C, the results indicate that stress escalates with an increase in the subgrade reaction modulus.

Longer slabs may exhibit more curling and warping due to the moisture content and temperature differentials. A shorter slab length is often selected for rigid pavement as it mitigates certain pavement distresses. Figure 11 illustrates the highest stresses as a result of the subgrade reaction modulus values and slab length values. The analysis shows that in the absence of temperature differentials, the stress across all slab lengths diminishes as the subgrade modulus escalates. When utilizing input values of ∆T of 11 °C and 22 °C, the results indicate that stress escalates with an increase in the subgrade modulus.

3.3. Thermal Impacts on the Performance of Rigid Pavement Utilizing Different Types of Aggregates

Several research studies examined concrete composed of various aggregates. An analysis was conducted to assess the impact of temperature differentials on concrete composed of the following aggregates: Calera limestone, Brooksville limestone, and river gravel. This study presents the highest value stress and stress–strength ratio, as illustrated in Figure 12. The results indicate consistent stress across all three aggregate types in the case of ΔT 0 °C. Nevertheless, the results indicate that stress increases with an increase in ΔT. The results indicate that at a ΔT of 22 °C, concrete composed of Brooksville limestone exhibits the lowest stress, whereas river gravel concrete has the highest stress. The stress–strength ratio indicates that Brooksville limestone exhibits the lowest ratio, succeeded by Calera limestone and, subsequently, river gravel.

FEACONS IV, similar to any numerical modeling tool, depends on assumptions and varied input parameters, which might have intrinsic variability or uncertainty. The results of this study, determined by FEACONS IV, are influenced by uncertainties resulting from variations in the input parameters and model assumptions. The sensitivity analysis indicated that slab thickness, temperature differentials, and the subgrade reaction modulus are the most critical parameters, with ±10% variations resulting in substantial alterations in expected stresses.

4. Conclusions

This study investigates the properties of concrete and the dimensional design of rigid pavement with FEACONS IV software to assess their impact on the performance of concrete pavement during thermal and flooding conditions. The conclusions drawn from the FEACONS IV analysis are as follows:

• Utilizing concrete with a lower elastic modulus, sufficient flexural strength, and aggregates possessing a decreased coefficient of thermal expansion can enhance the load-bearing capability of rigid pavement in thermal and flooding conditions.
• Utilizing thicker concrete slabs helps mitigate load- and temperature-induced stresses in rigid pavement during weather conditions.
• The use of an increased subgrade reaction modulus in rigid pavement during flooding situations enhances pavement strength. Nevertheless, at higher temperature differentials, a high subgrade reaction modulus might exacerbate temperature-induced and load stresses.
• Concretes using porous limestone aggregate exhibit a lower coefficient of thermal expansion and a lower elastic modulus, demonstrating potentially superior performance compared to those made with river gravel.

Consequently, for future research, we recommend optimizing concrete mixtures in response to higher thermal and flooding conditions, examining the influence of the thickness of the concrete slab on the long-term sustainability of pavements, and investigating methods to attain a balanced subgrade reaction modulus.