Overlay Performance Research Articles

Comparative Studies on In-Plane Shear Behavior of Masonry Wallettes Retrofitted with Mortar, UHPC, and ECC Ferrocement: Shotcrete and Prefabricated Panels

Masonry walls, prevalent in many historical and contemporary structures, often require retrofitting to meet modern safety and performance standards. Motivated by the need for efficient and reliable retrofitting solutions, this research investigates the potential of various types of ferrocement, reinforced with high-strength steel meshes, to enhance the in-plane shear behavior of brick masonry walls. Through rigorous diagonal compression tests on nine masonry wallettes, the study evaluated the performance of ferrocement overlays in terms of overlay configuration (asymmetric or symmetric), cementitious material type (mortar, ECC, or UHPC), the presence or absence of steel mesh, and construction method (shotcrete or prefabricated panels). The results indicated that UHPC and ECC overlays significantly enhanced post-cracking deformation capacity. Compared to the asymmetric retrofit, the symmetric retrofit led to more uniform deformation in the retrofitted wallette, effectively improving the maximum shear by up to 119 %. While UHPC shotcrete was more effective in improving the shear strength, ECC shotcrete led to the highest rupture shear strain and pseudo-ductility for the retrofitted wallette, reaching 0.83 % and 17.2, respectively. Moreover, although steel mesh inclusion in the ferrocement overlay was crucial in enhancing post-peak ductility, its impact on shear strength of the retrofitted wallettes was minimal. The test results also demonstrated that the developed prefabricated UHPC panels emerged as an effective retrofitting solution to simultaneously improve the strength, deformation capacity, and ductility for masonry wallettes. In addition to the experimental investigation, a new strength model, accounting for various key design variables, was developed, offering reliable shear strength predictions for the retrofitted wallettes.

Effects of Macro Fibers on Crack Opening Reduction in Fiber Reinforced Concrete Overlays.

Macro fibers have been extensively used in the construction of various concrete structures, including bridges, dams, tunnels, industrial floors, and pavements. However, their effectiveness in reducing crack opening widths in concrete pavements has not been fully explored. This study aims to delineate the role of fibers by identifying the optimal types and volumes for effectively controlling cracks in concrete pavement structures, particularly in thin overlays. The research investigates how different fiber types, such as synthetic and steel, and their respective volumes can mitigate crack propagation in concrete overlays. Additionally, it evaluates the performance of fiber-reinforced concrete overlays compared to conventional dowel bar systems in terms of crack width reduction and overall pavement durability. The findings aim to provide specific design criteria for incorporating macro fibers in concrete overlays to enhance structural integrity and longevity.

Overlay and Virtual Private Networks Security Performances Analysis with Open Source Infrastructure Deployment

Overlay and Virtual Private Networks Security Performances Analysis with Open Source Infrastructure Deployment

Neural network driven sensitivity analysis of diffraction-based overlay metrology performance to target defect features

Overlay (OVL) is one significant performance indicator for the lithography process control in semiconductor manufacturing. The accuracy of the OVL metrology is extremely critical for guarantee the lithography quality. Currently, diffraction-based overlay (DBO) is one of the mainstream OVL metrology techniques. Unfortunately, the accuracy of the DBO metrology is largely affected by the defect features of the OVL target. Therefore, there is a strong need to investigate the impacts of these target defects on the DBO metrology performance. However, efficiently investigating the statistical and interactive impacts of various DBO target defects remains challenging. This study aims to address this issue through proposing an intelligent sensitivity analysis approach. A cumulative distribution based global sensitivity analysis (GSA) method is utilized to assess the nonlinear influences of multiple defects in the OVL target on the DBO inaccuracy. The scenarios with both known and unknown distributions of the OVL target defects are considered. For the former, a neural network driven forward model is constructed for fast calculating the optical diffraction responses to accelerate the GSA process. For the latter, another neural network based inverse model are built for efficiently estimating the distribution of the target defects. Finally, a series of simulation experiments are conduct for typical DBO targets with multiple common defect features. The results demonstrate the effectiveness and robustness of the proposed approach as well as give valuable insights into the DBO defect analysis. Our study provides a strong tool to assist the practitioners in achieving intelligent and efficient DBO analysis and thus in enhancing OVL metrology performance.

Erosion Potential of Stabilized Support Layers for Concrete Pavements and Overlays

The performance of concrete pavements and overlays is highly dependent on the uniformity, durability, and stability of the underlying support layers. Erosion of support layers can lead to pavement distresses and a reduction in pavement life. A review of existing erodibility performance tests that assessed stabilized support layers was first conducted to identify and evaluate their suitability for adaptation. The Hamburg wheel tracking device (HWTD) test was selected to assess the erosion potential of asphalt and cement stabilized support layers. Field testing with distress surveys, falling weight deflectometer, and coring was completed to obtain HWTD specimens and link laboratory results to pavement performance. The HWTD test was performed on cores obtained from in-service cement and asphalt stabilized support layers, a cold in-place recycling (CIR) mixture, and cement stabilized laboratory mixtures. As expected, an increase in cement content within cement stabilized mixtures decreases the likelihood of erosion with the HWTD. Additionally, conventional asphalt stabilized base layers were highly erosion resistant. Erosion resistant cement stabilized bases (including full-depth reclamation) should target an average HWTD erosion depth ≤2 to 4 mm (0.08 to 0.16 in.) after 10,000 load cycles based on the functional classification and expected traffic volume of the pavement section. Likewise, asphalt stabilized bases (including CIR and support layers for concrete overlays) should target an average HWTD erosion depth ≤12.5 mm (0.5 in.) after 7,500 load cycles with performance grade 64 binder.

Overlay Mark Design Using Irregular Grating Patterns

Overlay refers to controlling the vertical alignment and misalignment between circuit patterns manufactured in the previous process and circuit patterns manufactured in the current process during the stacking process of circuit patterns in the semiconductor manufacturing process. A critical factor in ensuring precise overlay measurements is using an optimized overlay mark design. Many semiconductor manufacturers have put considerable effort into optimizing overlay measurement marks to reduce high costs. However, image-based overlay measurement encounters several challenges, including resolution degradation, image distortion, and noise introduction during digital data conversion. These issues can amplify the uncertainty of overlay measurements, impair optical resolution, and heighten the risk of mismeasurement. In this paper, we introduce irregular grating patterns designed to address the principal challenges faced by the commonly utilized Advanced Imaging Metrology (AIM) marks, namely large overlays and image distortion. Furthermore, we propose an overlay mark capable of precisely identifying overlays exceeding half a pitch and incorporating as much data as possible within the limits of optical resolution. This aims to improve overlay measurement performance. The experimental findings demonstrate that the proposed Pulsated Grating Target (PGT) mark enhances overall measurement uncertainty by approximately 17% compared to the AIM mark. The practical applicability of the PGT was validated through experiments, and we achieved enhanced precision and reliability in overlay measurements by resolving the issue of large overlays—the most significant challenge with grating patterns—and simultaneously enhancing mark performance.

Field Performance and Cost-Effectiveness of Ultrathin Asphalt Overlay in Hot and Humid Climates

Field Performance and Cost-Effectiveness of Ultrathin Asphalt Overlay in Hot and Humid Climates

Fatigue performance of geosynthetic-reinforced asphalt using DIC

The main objective of this study is to evaluate the influence of geosynthetic reinforcement on the fatigue performance of asphalt overlays using double-layered specimens extracted from experimental sections. Notched beam fatigue tests were conducted, together with Digital Image Correlation (DIC) technique to assess the initiation and propagation of cracks, along with strains mobilized at the geosynthetic interface. The geosynthetic-reinforced specimen demonstrated notable improvement compared to the unreinforced counterpart in reducing vertical deformations with an increase in fatigue life by a factor of 7. DIC analysis demonstrated that geosynthetic reinforcement absorbed the tensile stresses from the crack tip and reduced the tensile strains, contributing to minimize the propagation of reflective cracks into the asphalt overlay. Overall, research findings contribute to understanding the factors that enhance fatigue life through the incorporation of geosynthetic reinforcements in asphalt overlays.

Case Study on Using Warm Mix Asphalt at Reduced Production Temperatures for Balanced Mix Design

This study provides a case study to illustrate the feasibility of using warm mix asphalt (WMA) at lower production temperatures to design asphalt mixtures with balanced rutting and cracking resistance in a laboratory setting. Two balanced mix design (BMD) modification approaches were evaluated to modify an existing Superpave mix design with unbalanced performance because of inadequate cracking resistance: (1) adding asphalt binder and (2) using WMA with a surfactant-based chemical additive. The modified mix designs were tested with the indirect tensile asphalt cracking test and high-temperature indirect tensile strength test to determine compliance with the Alabama Department of Transportation’s (ALDOT’s) BMD performance requirements. The original and modified mix designs were then tested in the modified overlay test to characterize their reflective cracking resistance, and the results were input into the Texas Asphalt Concrete Overlay Design System (TxACOL) software for theoretical asphalt overlay design simulations. Finally, asphalt binder testing was conducted to determine the impact of BMD modifications on the rheological properties of extracted binders. Laboratory testing showed that both BMD modifications improved the cracking resistance of the mix design but through different mechanisms. All the modified mix designs met ALDOT’s BMD requirements with balanced rutting and cracking resistance at their corresponding optimum binder content (OBC), which was 0.4%–0.7% higher than the volumetric OBC, respectively. TxACOL simulations showed that BMD modifications significantly improved the predicted reflective cracking performance and service life of asphalt overlays, but the improvement varied depending on the underlying pavement and traffic conditions.

Investigations on the role of Inconel 82 additions on improving fatigue and corrosion behaviour of gas tungsten arc AISI 316L stainless steel claddings

In the present work, single- and double-weld layers of Inconel 82 were added to 316L stainless steel claddings using the gas tungsten arc welding process with the aim of improving the fatigue and sensitization performance of such clad overlays. These overlays were subjected to a high-temperature sensitization treatment of 750˚C/24 h (air-cooled) to induce precipitation, and then solution treated at 1050˚C/2 h (furnace-cooled) to mitigate the ill effects of intermetallic precipitation. Carbides of types Cr23C6 and Cr7C3 were detected in the aged 316L clad, which occurred interdendritically. These deleterious phases decreased the fatigue crack growth resistance of conventional 316L, but the addition of Inconel 82 resulted in inducing crack-arresting tendencies in it and thus significantly increasing its resistance against fatigue crack propagation. Solution annealing treatment resulted in the dissolution of deleterious phases, due to which the fatigue performance of these clads improved significantly. Among all the specimens, 316L clad with the double layer of Inconel 82 in the solution-annealed condition offered the highest resistance to fatigue crack growth. Corrosion performance evaluated via sensitization studies shows that ageing degraded the corrosion performance of 316L weld overlays, but the addition of Inconel 82 improved it. This study establishes that the addition of Inconel 82 can significantly improve the fatigue and corrosion performance of conventional 316L weld claddings.

Impact of vehicle fire exposure on polymer concrete overlays

This study investigates the performance of polymer concrete (PC) overlays after short-duration vehicle fire exposure. A vehicle fire test was conducted on a reinforced concrete slab with polyester PC overlay. Test results show a notable decline in overlay performance after the fire. In high-exposure areas, average reductions ranged from 13.3% to 23.1% in skid resistance, abrasion resistance, chloride penetration resistance, and surface hardness. Heat exposure heightens the bond failure risk and causes overlay delamination. Water penetration tests, done separately, show extended fire worsens PC overlay damage. These findings guide future performance improvements of PC.

Installation of geosynthetic interlayers during overlay construction: Case study of Texas State Highway 21

Geosynthetic interlayers in the form of geotextiles, geogrids, and geocomposites have been used to minimize reflective cracks and enhance overlay performance through functions such as stress relief, reinforcement and moisture barrier. However, proper geosynthetic installation and asphalt overlay construction practices are essential to the adequate performance of geosynthetic-reinforced asphalt overlays. In this study, various factors determining the successful construction of a geosynthetic-reinforced asphalt overlay are discussed in light of experiences during the construction of experimental test sections constructed in Texas State Highway 21. The project included nine different types of geosynthetic interlayers including four polymeric geogrid composites, three fiberglass geogrid composites, one fiberglass grid, and a fiberglass paving mat. The experimental test section included both sensor- and non-instrumented sections. The constructability evaluation of such experimental sections revealed that the primary factors influencing tack coat type and application rates include the pre-existing surface condition, geosynthetic type and their asphalt retention capacities. The geosynthetic installation procedures adopted in the experimental sections were proficient and comprised a specialized installation equipment that is capable of pre-tensioning the geosynthetics during the installation to minimize wrinkles and irregularities. Additionally, particularly high temperature of the pre-existing asphalt surface resulted in blistering of geotextile backing and subsequently leading into an excessive bleeding of tack coat through the geosynthetic apertures that resulted in tracking of construction equipment wheels. Recommendations on efficient geosynthetic installation and overlay construction techniques include adopting the tack coat type and application rates based on project-specific conditions, and using such tack coat to determine the asphalt retention capacity of the geosynthetic interlayer to be used in the project. Additional recommendations include minimizing the movement of construction vehicles on top of the geosynthetic interlayer, and adopting asphalt sanding technique to restore the friction between the paver and surface to minimize possible damage to the geosynthetic interlayer.

Experimental and statistical investigation on the performance of asphalt overlays reinforced with geocomposite in controlling the reflective cracks under different loadings and temperatures

One of the easiest method to repair the old pavement is to apply an overlay on them. However, the deteriorated pavement affects the overlay performance by propagating the existing cracks upwards to the overlay due to the stress and strain concentration from the loading and temperature variations. Today, using the asphalt overlays reinforced with geosynthetic interlayers is one of the most effective methods to prevent the reflective cracking. This paper investigates the effects of the temperature, bending fatigue loading frequency and geocomposite tensile strength on the asphalt overlays performance experimentally. The crack initiation and its propagation rate were analyzed by the help of image processing technique and statistically. The obtained results revealed that the temperature has the greatest effect on the reflective cracking rate, so that by increasing the temperature from 20 to 40 °C in addition to increasing the crack growth rate and changing the vertical deformation under the load, the direction of crack formation changes, and besides the reflective cracks, the top-down cracks also appear. Furthermore at the higher loading frequency more than 10 Hz, even in samples reinforced with geocomposite, increasing the temperature from 0 to 20 and 40 °C will increase the crack growth rate between 5 and 30 times. The obtained coefficients of determination (R2) and Adjusted R2 are equal to 0.9936 and 0.9907, respectively, indicating the satisfactory prediction of the model compared to the real observations.

Development of an indoor test method for evaluating the anti-reflection crack performance of asphalt overlay

Fatigue tests conducted in an indoor environment for evaluating the anti-reflection crack performance of asphalt overlay are associated with large specimen size and significant dispersion in the test results. To overcome these drawbacks, a test method based on small composite specimens and composite-specimen interface-cracking (CSIC) samples was developed to evaluate the anti-reflection crack performance of asphalt overlays. The effect of glass fiber gratings with three different sizes and no glass fiber grating on the anti-reflection crack performance of the asphalt overlays was compared and analyzed through fatigue tests. The results showed an evident anti-reflection crack effect in the specimens with glass fiber grating; the fatigue test with the CSIC specimens could effectively improve the precision of the test method and reduce the dispersion in the test results. Based on a fatigue test conducted through the ABAQUS finite element analysis software simulation, the feasibility of the evaluation method could be effectively verified. Our study can serve as a basis for the reasonable selection of reinforcing materials to extend the service life of asphalt overlays.

P-273 Heavy oil and conventional mineral oil produce similar Day 5 embryological outcomes. A prospective, single centre case study on 546 sibling 2PN zygotes

Abstract Study question Does heavy oil improve embryological outcomes compared to conventional mineral oil? Summary answer Heavy oil produces no improvement in embryological outcomes. What is known already Oil overlays are integral part of the culture system as they buffer gas and temperature exchanges in the culture media and reduce the risk of contamination and evaporation. However, slight variations in their composition, oxidative status, storage and utilisation can have a direct effect on culture system performance, eventually resulting in reduced embryo development and subsequent decrease in clinical outcomes. In an attempt to improve the performance of oil overlays, new formulations have recently reached the market. Nonetheless, their positive impact on embryological outcomes, as well as best practice in handling them, are yet to be broadly recognised. Study design, size, duration This is a prospective case-study conducted as part of routine consumable validation procedures undertaken when evaluating the use of new products in the IVF laboratory of a public hospital. A total of 546 sibling 2PN zygotes derived from 52 treatments were cultured to Day5 of development. All cases attending the clinic between March 2022 and January 2023 and leading to the collection of more than 10 oocytes were enrolled in this validation exercise. Participants/materials, setting, methods Sibling oocytes from IVF and ICSI treatments were cultured under the same conditions until fertilisation check (IVF) or after ICSI. Oocytes from each treatment were then equally split between conventional mineral oil (CONTROLS) and heavy oil (CASES) study groups. All embryos were individually cultured in 25µL drops of single step media at 37 °C, 5% CO2 and 5% O2. Embryological outcomes on Day3 and Day5 were compared across the study groups using Chi-square test. Main results and the role of chance CONTROLS and CASES showed similar embryological outcomes, including fertilisation (for ICSI only; 77.2% vs. 79.77%, respectively p = NS), good quality Day3 (69.5% vs. 75.6%, p = NS), good quality Day5 (30.2% vs. 24.0%, p = NS), blastulation (58.9% vs. 53.9%, p = NS) and utilisation rates (34.9% vs. 29.5%, p = NS). However, a sub-analysis was performed on the basis of oil handling/storage method. When heavy oil was pre-aliquoted and stored in 15mL tubes prior to usage, negative effects were measured on embryological parameters. In this subset of cases (n = 28 treatments; n = 304 2PN zygotes), although fertilisation and good quality Day3 rates were comparable (80.0% vs 81.6% and 69.1% vs. 73.0% in CONTROLS and CASES, respectively), CASES revealed a significantly lower rate of good quality Day5 blastocysts (Gardner grade ≥B for ICM and TE and expansion ≥grade3) compared to CONTROLS (32.2% vs. 21.7%, p = 0.04). Moreover, CASES showed significant lower embryo utilisation (36.8% vs. 25.7%, CONTROLS and CASES, respectively, p = 0.03) and a trend towards lower blastulation rate (61.2% vs. 50.7%, respectively, p = 0.06). Although the equal split of sibling oocytes between the two groups has minimised population bias, multiple variables may have influenced the performance of the tested product. We note that adequate storage/handling of products is required to avoid suboptimal results. Limitations, reasons for caution Although designed with sibling oocytes/embryos, this study is limited in population size. Moreover, only one product brand has been tested, limiting the universality of the conclusions about heavy oil performance in IVF culture systems. Wider implications of the findings Introducing a new product in the IVF laboratory should undergo a reliable validation exercise. Despite the commercial claims, heavy oil failed to improve our results. Untested variations may have detrimental effects on clinical performance and, if implemented without control, their effects may become impossible to identify at later stages. Trial registration number not applicable

Clinical outcome of CAD/CAM overlays of MIH affected young permanent molars

BackgroundRestoration of first permanent molars with MIH is considered a challenge for dentists because the enamel has less flexibility and hardness with increased porosity and organic content. Materials and methodsThe current study was a randomized control trial in which fifty-two first permanent molars were distributed equally into two groups (Z) teeth that received zirconia overlays and (EC) teeth that received IPS e.max CAD overlays. Clinical assessments were carried out at baseline, 6, and 12 months using modified FDI World Dental Federation criteria. ResultsAfter the observational period of one year, all restorations were still in function with no significant differences in the esthetic, functional, and biological performance of overlays fabricated with zirconia and IPS e.max CAD except one case have been fractured in the group (EC) and three cases have been de-bonding in the group (Z). ConclusionsUsing monolithic zirconia and IPS e.max CAD overlays could be a viable selection for restoring MIH-affected posterior teeth. In further studies, it is advisable to assess the restoration that combines strength with adhesive properties like zirconia-reinforced lithium silicate glass ceramic restoration.

Survival Analysis of Concrete Overlays on Low-Volume Roads in Iowa

Concrete overlays are an important component of Iowa’s rural road network. More than 2,000 centerline miles of concrete overlays have been paved in Iowa over the last few decades, including many overlays on low-volume roads serving 400 vehicles per day or less. In this study, a survival analysis was performed using automated pavement condition data collected on Iowa’s concrete overlays to obtain a probabilistic assessment of concrete overlay service life, paying particular attention to the performance of overlays on low-volume roads. Concrete overlays were found to perform very well, with a 30-year survival probability of 85.3% for all projects to rehabilitation or reconstruction, and 76.6% for overlays only on low-volume roads. Survival life was reduced when the survival condition was changed to performance thresholds based on a pavement condition index (PCI) of 60/100 and an International Roughness Index (IRI) value of 170 in./mi, but was still good overall. Overlays tended to reach the failure condition for PCI before IRI, indicating that cracking is a more common distress than surface roughness. Another important finding was that concrete on asphalt overlays had a longer median survival life and a greater 30-year survival probability than concrete on concrete-unbonded overlays. Overall, concrete overlays have performed well in Iowa and are well suited to low-volume roads and rural county highways.

Effect of bridge deck surface preparation on the consolidation and bond of UHPC overlays

This investigation studies the effect of concrete substrate surface preparation methods on ultra-high performance concrete (UHPC) overlay bonds. Substrate surface roughnesses were analyzed using profile chips and a laser. After applying overlays to the substrates, direct tensile pull-off testing was performed to assess bond strength. Scanning electron microscopy was then used to observe representative interfaces. The study found that UHPC rheology and consolidation can significantly affect UHPC overlay bond with a high-amplitude roughness concrete substrate, particularly for thixotropic UHPCs. Surface retarder finishes were found to offer reasonably similar overlay bond performance to that of a hydromilled concrete substrate.

Image-based overlay target design using a grating intersection

Background: An overlay target design is essential before performing overlay metrology and has a great impact on overlay performance. In addition, accurate overlay metrology is required to achieve high product yields in semiconductor manufacturing. When asymmetry of the overlay target occurs, it is necessary to increase the area of the pattern existing in the target and stabilize the optical aberration for stable measurement. For this reason, we propose an image-based overlay target design that can secure a larger area compared with the existing overlay target and stabilize the optical aberration by overlapping and exposing the upper and lower patterns of the overlay target.Aim: The effective area of the existing mark design is improved by proposing an overlay target and a measurement method used in image-based overlay measurement.Approach: The proposed overlay target design is configured by arranging different marks orthogonally to the upper and lower layers, and different two-dimensional information can be inserted in the same area. When necessary, single-dimensional information desired by the user can be obtained through a technique called projection, and it has the advantage of using a larger effective area than the existing overlay target.Results: Overlay can be measured using projected signal components, and the possibility and performance of the proposed target can be confirmed through simulation and test wafer. In addition, it was possible to bring about a 15% improvement in total measurement uncertainty performance compared with the existing advanced imaging metrology (AIM) target by taking a wider effective area.Conclusions: An overlay target design is proposed to solve the technical problems of the existing overlay target design. The proposed overlay target has a method that is capable of minimizing the size of the overlay target while maximally maintaining the signal density, a way of reducing the influence of aberration, and various other advantages.In addition, the proposed method provides a design rule that breaks the “lower pattern and upper pattern must not overlap” framework.

Field Performance and Cost-Effectiveness of Chip Seals and Asphalt Concrete Overlays with and without Asphalt Concrete Stripping Damage

The objective of this study was to evaluate the effects of asphalt concrete (AC) stripping damage on the field performance and cost-effectiveness (CE) of chip seals and AC overlays in pavement maintenance and rehabilitation. To achieve this objective, in-service pavement sections were selected from the Louisiana pavement management system (LaPMS) database and the presence of moisture damage was confirmed through the visual inspection of extracted cores. Sections were categorized according to traffic volume and their pavement condition index before treatment (PCI-). Road sections in each group were then divided into two groups as stripped and non-stripped sections. The average deterioration rate (ADR), extension in pavement service life (ΔPSL), average condition improvement over the treatment service life (PI), and CE were compared for stripped and non-stripped sections. Results showed that for chip seal sections, moisture damage negatively affected the performance of the sections with PCI- < 80 and low traffic volumes. For sections with PCI- > 80, similar performance was observed for stripped and non-stripped sections. For AC overlays, moisture-induced damage significantly affected the long-term pavement performance at all traffic levels. On average, moisture-induced damage decreased ΔPSL, PI, and CE of AC overlays by 5 years, 24%, and 0.5%, respectively. Overall, results of the study demonstrated that moisture damage has a significant effect on the performance of chip seal and AC overlay. Therefore, it is critical to identify and repair stripped sections before the maintenance and rehabilitation of in-service pavements to ensure adequate performance and optimum CE.