Portland Cement Concrete Pavement Research Articles

Performance of AC overlays using geogrids on PCC contraction joints

It is widely known that vertical displacements and strains occur on the joints and these cause defects on the asphalt concrete (AC) overlays on existing Portland cement concrete (PCC) pavements. Various approaches were introduced to minimize these defects. In this study, the effect of joint support formed using the geogrid material with grout mortar on the vertical displacement of PCC and the strain at the bottom of the AC layer. Produced layers were exposed to 1,186,000 Equivalent Single Axle Load (ESAL) in an APT (Accelerated Pavement Test) facility and the results were monitored. According to the obtained results, the use of AC overlay reduces vertical displacement in the PCC by 75%. When geogrid reinforced AC overlay was used, an additional reduction in displacement by 41.2% was achieved. Geogrid reinforcement reduced strain values formed at the bottom of the AC layer from 29.5% to 92.5%. The use of geogrid at joints instead of increasing the thickness of the AC layer from 50 to 80 mm resulted a more significant reduction in both strain and displacement. Besides, the usage of a geogrid interlayer instead of increasing the thickness of the AC layer also provided a significant cost reduction of 57.9% in overall cost.

Surface rehabilitation of Portland cement concrete (PCC) pavements using single or double surface dressings with soft bitumen, conventional or modified emulsions

Surface dressings are a sustainable maintenance alternative for pavements with surface distresses, due to the low amount of resources involved. This paper aims to analyze the viability of using twelve different surface dressing solutions, including three binders (conventional and modified emulsions, and a soft 160/220 bitumen) and a covering with diluted emulsion, for surface treatment of Portland cement concrete (PCC) pavements. Several test methods were used to evaluate the macrotexture, skid resistance, adhesion, and resistance to wearing on a large scale prototype. In general, single surface dressings increased further the macrotexture of the concrete pavement surface. The skid resistance of single and double surface dressings was similar. The best surface dressing in the pull-off test was that with the 160/220 bitumen. The conventional and modified emulsions presented similar mechanical adhesion in the Vialit plate test. Concerning the prototype wearing test, the best result was obtained for the double surface dressing with bitumen covered with diluted emulsion. Based on this work’s results, the surface dressings are a potential surface rehabilitation alternative for concrete pavements.

Accelerated construction of urban intersections with Portland Cement Concrete Pavement (PCCP)

The frequent maintenance required on asphalt concrete (AC) pavement sections has made reconstruction with portland cement concrete pavement (PCCP) a feasible alternative. However, many constructability issues need to be addressed in order to realize the full potential of this alternative. Accelerated paving encompasses three classes of activities: methods to accelerate the rate of strength gain, methods to minimize the construction time, and traffic control strategies to minimize user delay. In this paper a case study will be presented in which an AC intersection was reconstructed with portland cement concrete pavement. The entire reconstruction of the intersection, including demolition of the AC pavement and its replacement with PCCP, took place over a period of three days, starting on Thursday evening and opening the intersection to the traffic on Sunday afternoon. This paper documents this effort in order to provide practitioners additional options for rapid reconstruction of urban intersections and includes documentation of the construction process, traffic management strategies, and an analysis of the costs. The results of this investigation can be used to educate pavement construction professionals and the academic community on the use of PCCP for accelerated reconstruction of major urban intersections with minimal user and traffic disruption, using innovative construction techniques and traffic management optimization principles. This investigation produced valuable information to demonstrate that concrete pavements can be constructed efficiently and quickly.

Spatiotemporal distribution characteristics of runoff-pollutants from three types of urban pavements

Pavement runoff is recognized as a primary source of non-point pollution in the urban area. It is difficult to treat the runoff-pollutants from different pavements because of complex distribution characteristics and influencing factors. This study presents the results of an experimental investigation aimed at determining the impact of three types of urban pavements, i.e., portland cement concrete pavements (PCC), dense asphalt concrete pavements (DAC) and permeable asphalt concrete pavements (PAC) on the rainfall-runoff process, concentration levels, and spatiotemporal distribution characteristics of typical runoff-pollutants. Runoff samples from the three types of urban pavements were collected and analyzed at different time-intervals beginning from runoff formation. The results indicated that PAC could better intercept and retain runoff-pollutants than DAC and PCC. In addition to the types of pavements, road-traffic characteristics and the surrounding environment significantly impacted the event mean concentrations of the selected rainfall events. Concentrations of suspended solids and heavy metals were higher at intersections and crosswalks, while those of organic pollutants were high in commercial areas. Besides, three parameters were proposed to characterize the first-flush effect intensity for runoff-pollutants. These findings help better understand the spatiotemporal distribution characteristics of runoff-pollutants from different types of urban pavements, which could also help strategically select measures to treat pavement runoff pollution.

Enhanced photocatalytic decomposition of NO on portland cement concrete pavement using nano-TiO2 suspension

Photocatalyst titanium dioxide (TiO2) has been widely applied on asphalt and concrete pavements to mitigate the air pollution caused by traffic exhaust. In general, most of the TiO2 used in previous studies was pure anatase, which only exhibited excellent photocatalytic activity under ultraviolet (UV) light. Thus, N-doping method was selected to improve the photocatalytic activity, especially under visible light. Additionally, the TiO2 suspension was commonly used on the pavements comparing with other application methods. However, the Nano-TiO2 particles with great surface area-to-volume ratio and surface energy have a strong tendency to agglomerate in the suspension, which has significantly negative effects on the photocatalytic activity. Thus, the objective of this study was to enhance the photocatalytic performance of mortar specimens containing TiO2 by preparing optimum N-doped TiO2 and suspensions using both single-factor and orthogonal experimental design. Methylene blue (MB) decomposition results indicated that the optimum N-doped TiO2 was prepared with 1% N-dosage at 700 °C for 5 h. X-ray diffractometer (XRD) pattern results implied that the phase transformation from anatase to rutile occurred around 700–800 °C and anatase transferred to rutile completely at 900 °C. Absorbance results showed that the optimum suspension was prepared with following conditions: ultrasonic power 100 W, ultrasonic time 120 min, silica sol concentration 0.5%, and sodium hexametaphosphate (SHMP) dosage of 0.3%. Lastly, NO decomposition test was conducted to investigate the effects of TiO2 implementation methods and environmental factors on the photocatalytic performance of mortar specimens. The NO decomposition results showed that the optimum suspension could significantly improve the photocatalytic performance of specimens. Meanwhile, the NO decomposition percentage decreased with the increasing flow rate and NO concentration.

Mitigation possibilities of concrete pavement degradation

Monolithic as well as precast Portland Cement Concrete pavement have shown a gradual increase in quantity and severity of defects and failures in recent years. Especially, the radical increase in the auto-destructive deterioration of the concrete structure, which is most often described as the expansion reaction, is alarming. The consequences may lead to extreme reduction of the lifetime of concrete on loaded or unloaded surface courses. The main causes are due to the combined effect of environmental effects (climate, chemical pollution), drainage of roads and the behaviour of the existing cement binders, provided that we do not reflect the modification of pavement structure layers. Only the impact of climate effects can be effectively reduced on the existing roads. The paper presents a summary of results obtained from the current portfolio of secondary concrete protection products. The testing was performed in terms of resistance to water infiltration and durability against the common effects of freeze/thaw and salt. The results show a dependence or independence according to the material basis when exposed to secondary protection products. Oils, silicate emulsions and a group with other material bases, so called other products, behave quite differently.

Strength analysis of concrete pavement deformation due to Alkali Silica Reaction (ASR)

Alkali Silica Reaction (ASR) is a chemical reaction that negatively affects concrete pavements strengths and integrity. ASR impedes concrete pavements' performance due to the formation of cracks and ultimate deformation if not properly controlled. Concrete pavements are gaining more relevance due to their ability to be constructed on soils with low bearing capacity and support high traffic loadings, thus increasing the need for studies on how ASR in the concrete pavements can be mitigated. This study employed compressive and flexural strength tests to determine the strength properties and deformation of concrete pavements due to ASR when partially replaced with CBA at varying percentages. Static structural modelling of the concrete as a multiphase material in which aggregates, cracks and gel formations are considered as embedded inclusions in the cement paste is then carried out. The results are then compared with relevant standards and findings of other researchers. The study's findings reveal that all the concrete cube samples passed the recommended compressive strength for rigid pavement, which range from 35 - 40 N/mm2 at 28th day. The concrete cube samples also passed the target strength of 48.25 N/mm2 obtained from the mix design. The effect of ASR resulted in lower compressive and flexural strengths observed at 180th and 240th days with lower CBA addition, while samples containing higher CBA contents had increasing compressive strength. The static structural modelling results reveal that the maximum deformation was obtained for the concrete cubes admixed with 0% CBA with 47.045 mm while the least deformation was obtained at 30% CBA replacement with deformation value of 5.542 mm on application of a 900 KN force. Therefore, the study posits that CBA addition will help reduce Portland Cement Concrete Pavement deformation due to ASR in relation to traffic loadings. Cite as: Adanikin A, Falade F, Olutaiwo A. Strength analysis of concrete pavement deformation due to Alkali Silica Reaction (ASR). Alg. J. Eng. Tech. 2020; 3: 020-027. http://dx.doi.org/10.5281/zenodo.4400227 References Hajighasemali S, Ramezanianpour A, Kashefizadeh M. The effect of alkali–silica reaction on strength and ductility analyses of RC beams. Magazine of concrete research. 2014;66(15):751-760. Grimal E, Sellier A, Multon S, Le Pape Y, Bourdarot E. Concrete modelling for expertise of structures affected by alkali aggregate reaction. Cement and Concrete Research. 2010 ;40(4):502-507. Monette LJ, Gardner NJ, Grattan-Bellew PE. Residual strength of reinforced concrete beams damaged by alkali-silica reaction—Examination of damage rating index method. Materials Journal. 2002 ;99(1):42-50. Huaquan YA, Zhen LI, Meijuan RA, Xiaomei SH. Study on Influence of Aggregate Combination and Inhibition Material ofAlkali-silica Reaction in Fully-Graded Concrete. Materials Science. 2020;26(3):363-372. Malhotra VM, Mehta PK. 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Smaoui N, Berube MA, Fournier B, Bissonnette B, Durand B. Effects of alkali addition on the mechanical properties and durability of concrete. Cement and concrete research. 2005;35(2):203-12. Ankit K. Kisku N. Effect of silica fume and fly ash as partial replacement of cement on strength of concrete. International Journal of Innovative Research in Science, Engineering and Technology. 2016;5(10), 18618 – 18624. Subbaramaiah G, Sudarsana HR, Vaishali GG. Effect of addition and partial replacement of cement by wood waste ash on strength properties of structural grade concrete. International Journal of Innovative Science, Engineering & Technology. 2015; 2(9): 736-743 Olutaiwo AO, Yekini OS, Ezegbunem II. Utilizing Cow Bone Ash (CBA) as partial replacement for cement in highway rigid pavement construction. SSRG International Journal of Civil Engineering. 2018; 5(2): 13-19. Adanikin A, Falade F, Olutaiwo AO, Faleye ET. Ajayi AJ. Investigation of the effect of Alkali-Silica Reaction (ASR) on Properties of Concrete Pavement Admixed with Cow Bone Ash (CBA) by Electrical Resistivity Method. IOP Conf. Series: Materials Science and Engineering. 2019, 640(1): 1-9 Kadyali LR. Lal NB. Principles and practices of highway engineering including expressways and airport engineering. (Khanna Publishers, New Delhi). 2014. Marzouk H. Langdon S. The effect of alkali aggregate reactivity on the mechanical properties of high and normal strength concrete. Cement and Concrete Composites. 2003;25: 549–556. Giaccio G, Zerbino R, Ponce JM, Batic OR. Mechanical behavior of concretes damaged by alkali-silica reaction. Cement and Concrete Research. 2008;38(7):993-1004.

The Chemical-Mineralogical Characterization of Recycled Concrete Aggregates from Different Sources and Their Potential Reactions in Asphalt Mixtures.

The incorporation of a recycled concrete aggregate (RCA) as a replacement of natural aggregates (NA) in road construction has been the subject of recent research. This tendency promotes sustainability, but its use depends mainly on the final product’s properties, such as chemical stability. This study evaluates the physical and chemical properties of RCAs from two different sources in comparison with the performance of NA. One RCA was obtained from the demolition of a building (recycled concrete aggregate of a building—RCAB) and another RCA from the rehabilitation of a Portland cement concrete pavement (recycled concrete aggregate from a pavement—RCAP). Characterization techniques such as X-ray fluorescence (XRF), X-ray diffraction (XRD), UV spectroscopy, and atomic absorption spectrometry were used to evaluate the RCAs’ coarse fractions for chemical potential effects on asphalt mixtures. NA was replaced with RCA at 15%, 30%, and 45% for each size of the coarse fractions (retained 19.0, 12.5, 9.5, and 4.75 sieves in mm). The mineralogical characterization results indicated the presence of quartz (SiO2) and calcite (CaCO3) as the most significant constituents of the aggregates. XFR showed that RCAs have lower levels of CaO and Al2O3 concerning NA. Potential reactions in asphalt mixtures by nitration, sulfonation, amination of organic compounds, and reactions by alkaline activation in the aggregates were discarded due to the minimum concentration of components such as NO2, (–SO3H), (–SO2Cl), and (Na) in the aggregates. Finally, this research concludes that studied RCAs might be used as replacements of coarse aggregate in asphalt mixtures since chemical properties do not affect the overall chemical stability of the asphalt mixture.

Improving the ice-melting capacity of traditional deicers

Deicers with low freezing point depression and rapid ice-melting capacity are ideal for winter maintenance of pavements located in snow-prone regions. The current study aims 1) to improve the ice-melting capacity of traditional rock-salt deicer at very low temperatures (0 °C, −10 °C, −20 °C, and −30 °C) by employing bio-based non-toxic corn-derived polyols, 2) to evaluate the skid resistance of the pavements when the polyol-modified deicing solutions are applied on the pavement surface, and 3) to determine the viscosity of the polyol-modified deicing solutions. The deicers investigated herein are prepared by adding three corn-derived polyols (sorbitol, mannitol, and maltitol) to the traditional deicing solution (23.3% wt. salt brine deicer) in varying weight concentrations (5%, 10%, 15%, and 27.7%). The ice-melting capacity of the deicing solutions is evaluated by conducting ice-melting tests at different low temperatures using an in-house built ice-melting test setup. The viscosity of the deicing solutions, the skid resistance of the pavement surfaces, and dissolved oxygen values are then evaluated corresponding to the deicer combinations that resulted in high ice melting capacity. For temperatures up to −20 °C, the increase in the concentration of corn-derived polyols led to an increase in the ice melting capacity of the deicing solutions. Among the investigated additives, the mannitol and salt brine combination (27.7% wt. mannitol + 23.3% wt. salt brine) resulted in two times more ice melting at −20 °C when compared to the 23.3% wt. salt brine alone. The viscosity of the reference deicing solutions increased by up to 23.3% after the addition of optimal amounts polyols (27.7% wt. sorbitol or maltitol or mannitol) in the deicing solutions. The skid resistance tests revealed that the application of the polyol-based deicing solution on the pavements led to up to 33% reduction in the skid resistance of the Portland cement concrete pavement when compared to the skid resistance of dry pavement surface. Moreover, the polyol-modified deicers exhibited up to 64% higher viscosity and resulted in up to 33% consumption of dissolved oxygen in river water when compared to the salt brine deicer.

Non-destructive ultrasonic evaluation of construction variability effect on concrete pavement performance

It is commonly recognized that non-uniformity of as-constructed Portland Cement Concrete (PCC) pavement may negatively affect long-term pavement performance. Conventional wisdom states that PCC thickness deficiency is the most important factor causing premature pavement failures. To address it, transportation agencies often impose strict penalties for not meeting the designed slab thickness requirements, thus contractors build slightly thicker slabs to avoid fines. However, other aspects of construction variability on pavement performance are mostly ignored by studies because conventional methods for construction uniformity assessment fail to provide sufficient information to quantify their effect. This study utilized a non-destructive ultrasonic test to evaluate in-situ pavement construction variability. To investigate the correlation between construction variability and surface distresses, a combination of non-destructive ultrasonic thickness measurements and visual distress surveys were performed in highways prior to rehabilitation. PCC slab thicknesses and shear wave velocities were computed from recorded ultrasound signals. An in-depth statistical analysis was performed to investigate possible relations between thickness or shear wave velocity and distresses using various pavement performance parameters. The main results of this analysis illustrate the importance of material quality and uniformity control during construction, since alterations in material properties significantly influence the presence of distresses. Shear wave velocity variations significantly correlate to cracked and broken slab panels in two sections, and, more importantly, to any type of distress in all tested pavement sections.

Influence of recycled concrete aggregates from different sources in hot mix asphalt design

The waste generated by the construction industry generally has an undesired negative impact on both human and animal life as well as the environment. Among these wastes, recycled concrete aggregate (RCA), due to its good residual physical, mechanical, mineralogical, and chemical properties, has attracted promising potential for re-use and incorporation in the construction of new infrastructural elements. These infrastructure applications include construction of sidewalks, curb and gutters, subbase/base layers, and/or as a partial replacement of natural aggregates (NA) in the production of hot mix asphalt (HMA) mixtures. In this laboratory study, experimental research work was conducted to evaluate the influence of RCA on the mechanical properties and performance of RCA modified HMA mixtures against a control HMA mixture without any RCA. RCAs were obtained from two different concrete sources, namely: (a) one from the demolition of a building (RCAB), and (b) another one from the rehabilitation of a Portland cement concrete pavement (RCAP). Both NA and RCA were characterized taking into account physical and mechanical properties. HMA mixtures were produced using the Marshall mix-design method by replacing 0.0% (control), 15%, 30%, and 45%, respectively, of the coarse NA fraction with RCA. Thereafter, laboratory testing (i.e., Scanning Electron Microscopy [SEM], resilient modulus, indirect tensile strength, etc.) including material property characterization and performance evaluation were conducted on HMA samples. Overall, the laboratory test results showed that the RCA modified mixtures exhibited a similar behavior to conventional HMA mixtures, but with greater environmental benefits and potential cost savings through the recycling and reuse of waste concrete aggregates. However, it was observed that the laboratory performance of RCA modified mixtures is strongly dependent on the RCA source and dosage, with RCAP exhibiting superior performance over RCAB. HMA mixtures produced with RCA provided higher optimum asphalt-binder content (OAC) than that of mixes with NA.

Mitigating reflective cracking in composite pavements through the use of a ductile concrete interlayer

Reflective cracking of composite pavements refers to the phenomenon that cracks propagate from a deteriorated Portland cement concrete (PCC) slab to the newly constructed hot mix asphalt (HMA) overlay at locations where there are joints and cracks in the underlying PCC pavements. It is one of the predominant failure modes of composite pavements, often resulting in premature failure and limited service life of HMA overlays. To improve the resistance of composite pavements to reflective cracking, in this study, a new ductile concrete interlayer made of Engineered cementitious composite (ECC) was proposed and experimentally evaluated. ECC is a type of high-performance fiber-reinforced cementitious composites that features high tensile ductility, high fracture resistance, and high deformation capacity. It is expected that by constructing a thin ECC interlayer between exisiting PCC pavement and HMA overlay, reflective cracking can be prevented or significantly delayed. In the current paper, small lab-scale sandwich-type composite pavement specimens with and without ECC interlayers were constructed and tested under fatigue loadings that simulates repeated traffic loadings. The experimental result indicated that the ECC interlayer successfully suppressed reflective cracking and altered the failure mode of the composite pavement. As a result, specimens with ECC interlayers exhibited significantly (30 to 47 times) higher fatigue life as compared to the control specimens without interlayers. This result demonstrated that ECC interlayer is effective in reflective cracking mitigation.

Structural Characterization of Fractured Portland Cement Concrete Pavements in Pennsylvania from Falling Weight Deflectometer Data

Hot mix asphalt (HMA) overlays on fractured Portland cement concrete (PCC) is a common rehabilitation alternative used for PCC pavements in Pennsylvania. Several fracture techniques including rubblization, crack and seat (C&S), and break and seat (B&S) have been used for decades to minimize reflective cracking by reducing the effective slab length and, with it, expansion/contraction movement. The design of this type of overlay requires knowledge of the structural capacity of the fractured PCC layer. The AASHTO 93 and Pavement ME design methods are used by the Pennsylvania Department of Transportation (DOT). These methods and the Pennsylvania DOT documentation recommend certain values to characterize the structural capacity of the fractured PCC. However, the guidance envisaged the selection of these values provided by these design methods and the Pennsylvania DOT documentation is limited. The objective of this study is to determine realistic Pennsylvania-specific elastic modulus (EPCC) values and layer coefficients (LC) to characterize the in situ behavior of fractured PCC layer for jointed reinforced concrete pavements (JRCP) and jointed plain concrete pavements (JPCP). To obtain these structural properties, 11 different rehabilitation projects located in Pennsylvania were analyzed using falling weight deflectometer (FWD) data, backcalculation programs, and statistical methods. Based on this analysis, the recommended values of EPCC and LC for C&S overlay design are 360 ksi (kips per square inch) and 0.32, respectively. In the case of B&S overlay design, these values correspond to 400 ksi and 0.34, respectively. The variability of the slab fracturing process and the reduction of the structural capacity caused by fracturing were also analyzed in this investigation.

Applications of asphalt concrete overlay on Portland cement concrete pavement

Being one of the most common method to restore the structural and functional capabilities for distressed Portland cement concrete pavement, the practice of asphalt concrete overlay dates to the mid-20th century and even earlier. Workmanships and techniques adopted for the application had been widely researched. In view of the increasing demand for pavement rehabilitation, this work summarizes the following: firstly, the basic procedures for asphalt concrete overlay construction by considering about 100 papers published since 1950 to till date. Secondly, the overlay thickness design methods including the thickness deficiency-based approach and thickness analytical-based approach. Thirdly, the advantages and disadvantages of various kinds of interlayers adopted in engineering fields. Fourthly, the possible factors that would affect the propagation of reflection cracks, such as traffic volume, overlay binder type, base condition, etc. Fifthly, the possible construction alternatives in terms of construction period and traffic closure. Overall, by employing analytical-based methods, this review brings to light that additional overlay thickness can reduce the fatigue stress, thermal stress, and traffic loading stress at the bottom of the overlay, resulting in overall smaller stress level. Moreover, additional overlay thickness also contributes to the decrease in daily reflection crack length according to Paris’ law. Further, this review stresses the indispensable role for pre-overlay treatment and recommends careful investigations during overlay construction.

Analytic pavement modelling with a fragmented layer

ABSTRACT Layered elastic theory is a familiar and commonly accepted framework for modelling and analysis of pavement systems. In actuality however, the suitability of the theory is challenged whenever the system includes a fragmented layer – which violates the inherent layer continuity assumption. This paper addressed the modelling challenge in these situations by introducing a fragmented layer into the accepted framework. A new formulation was proposed, based on the hypothesis that the thickness of the fragmented layer can be incorporated as part of its governing parameters. Doing so allowed for treating the fragmented layer as a new kind of interface. Subsequently, the work focused on formulation development and clear step-by-step presentation of new derived expressions applicable to the case of a stratified half-space containing a fragmented layer. Several synthetic cases were generated and interrogated to verify the correctness of underlying equations and to demonstrate capabilities. Based on this interrogation the proposed formulation is deemed rich of prospective utility, especially for modelling pavements surfaced with concrete paving blocks, pavement systems that contain cracked-and-seated (or rubblised) Portland cement concrete, and aged or rehabilitated pavement systems that contain fatigued (multi-fractured) asphalt concrete layers.

Impact of base type on performance of rigid pavement: a case study

ABSTRACT Base layer stiffness, durability, permeability, and constructability are all significant factors that influence the performance of a concrete pavement system. The interaction between a concrete pavement and the underlying base layer(s) affects the response, including the distribution of stress, strain and deflection, of the pavement system to traffic loads and environmental conditions. Subbase stiffness is also a significant influence on crack initiation in the PCC slabs. To verify these findings, a field investigation experiment was conducted on Interstate 90 in New York to compare the performance of two Portland Cement Concrete (PCC) sections, one with the NY Standard pavement design using Portland Cement Concrete on top of Cement Treated Permeable Base (CTPB), and the other with an alternate design using PCC on top of Dense Graded Aggregated Base (DGAB). Data collected from the two sections were compared, in particular the deflections due to temperature fluctuations and responses to Falling Weight Deflectometer (FWD) testing. The subgrade moisture content for both sections was similar. The DGAB sections provided equal if not better support for the PCC pavement which would result in longer-lasting pavement sections with lower construction and ownership costs than more expensive CTPB.

Automatic Crack Detection on Road Pavements Using Encoder-Decoder Architecture.

Automatic crack detection from images is an important task that is adopted to ensure road safety and durability for Portland cement concrete (PCC) and asphalt concrete (AC) pavement. Pavement failure depends on a number of causes including water intrusion, stress from heavy loads, and all the climate effects. Generally, cracks are the first distress that arises on road surfaces and proper monitoring and maintenance to prevent cracks from spreading or forming is important. Conventional algorithms to identify cracks on road pavements are extremely time-consuming and high cost. Many cracks show complicated topological structures, oil stains, poor continuity, and low contrast, which are difficult for defining crack features. Therefore, the automated crack detection algorithm is a key tool to improve the results. Inspired by the development of deep learning in computer vision and object detection, the proposed algorithm considers an encoder-decoder architecture with hierarchical feature learning and dilated convolution, named U-Hierarchical Dilated Network (U-HDN), to perform crack detection in an end-to-end method. Crack characteristics with multiple context information are automatically able to learn and perform end-to-end crack detection. Then, a multi-dilation module embedded in an encoder-decoder architecture is proposed. The crack features of multiple context sizes can be integrated into the multi-dilation module by dilation convolution with different dilatation rates, which can obtain much more cracks information. Finally, the hierarchical feature learning module is designed to obtain a multi-scale features from the high to low- level convolutional layers, which are integrated to predict pixel-wise crack detection. Some experiments on public crack databases using 118 images were performed and the results were compared with those obtained with other methods on the same images. The results show that the proposed U-HDN method achieves high performance because it can extract and fuse different context sizes and different levels of feature maps than other algorithms.

An advanced local calibration method for mechanistic‐empirical pavement design

AbstractModel calibration and validation is an important step of empirical modeling. The current local calibration (LC) method suggested by the AASHTOWare mechanistic‐empirical pavement design guide (MEPDG) is defective and can result in a completely distorted prediction of pavement reliability in design. This paper proposes an advanced LC method that integrates a jackknife sampling procedure and an iteratively weighted least squares technique into one coherent LC process. The jackknife sampling method, which has been recommended by AASHTO for model validation, is now used for identifying outliers of the data in order to ensure a homogeneous population. Meanwhile, an iteratively weighted least squares method is proposed to simultaneously estimate the LC coefficients and the standard deviation functions. Two LC case studies for Ontario roads are presented: one for the bottom‐up fatigue cracking models of asphalt concrete pavements and the other for the joint faulting models of Portland cement concrete pavements. The comparison with the traditional split‐data method has shown the effectiveness and efficiency of the proposed method. With little modification, the method can be introduced as a general calibration‐validation process for all empirical and mechanistic‐empirical models in engineering disciplines.

Quantification of embodied energy and carbon footprint of pervious concrete pavements through a methodical lifecycle assessment framework

This study provided a systematic lifecycle assessment (LCA) methodology that was used to quantify the total embodied energy and greenhouse gas (GHG) emissions involved in construction of a new pavement. Furthermore, a comparative LCA was performed to adjudge the benefits offered by pervious concrete pavement (PCP) over Portland cement concrete pavement (PCCP) for different mixing procedures, and distinct base layers. The system boundaries included the following phases of pavement LCA: raw material production, transportation, and pavement construction. The total embodied energy and GHG emissions were quantified for a functional unit of 1 km single lane road, 3.5 m wide, and 0.35 m thickness. The relative contribution of each component to energy consumption and GHG emissions was estimated and the variability of LCA model parameters was understood using sensitivity analysis. The results dictated that the total embodied energy and GHG emissions in PCP with aggregate base layer were reduced by up to 3% and 2.7%, respectively, compared to that of PCCP with similar configuration. Further, a capital cost analysis was conducted due to non-availability of maintenance and end-of-life data, which indicated that PCP is almost 1.21% costlier than PCCP for RMC mixing, and 4.13% cheaper for in-situ mixing. The conceptual approach developed in this study provided a generalized methodical framework that could be used to assess the environmental credibility of pavement systems for site-specific conditions.

Full-Scale Laboratory Evaluation of the Effectiveness of Subgrade Soil Stabilization Practices for Portland Cement Concrete Pavements Patching Applications

Adequate quality of subgrade under patched areas can extend the service life of concrete pavements and reduce their maintenance costs. In this study, the performance of various subgrade stabilization scenarios was evaluated and compared with each other in a full-scale laboratory-based setup. For this purpose, a test box with the footprint of 6 × 6 ft and a height of 4 ft was constructed using C steel channels. The test box was used to investigate the effects of various types of soil stabilization methods, such as chemical (cement) stabilization, use of aggregate base course (ABC), geogrid (GG) and geotextile (GT) with ABC, GT with cement-stabilized soil, GT with in-situ compacted soil, flowable fill, and lean concrete. The test results showed that all stabilization techniques successfully improved the performance of the subgrade layer by decreasing the deformation under the fatigue loading representing a single axle load of 9,000 lbf/tire. The use of GT with aggregate-based layers was found to significantly reduce the amount of settlement. Subgrade layers stabilized with GG also experienced lower values of deformations compared with the unmodified (control) section. However, GG was not as effective as GT. The use of cement-treated aggregate and lean concrete reduced the deformations to negligible levels.