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Ultra-high-performance concrete (UHPC) has emerged as a suitable material for pavement rehabilitation, particularly in the context of bridge engineering. This material' attributes and performance-related characteristics have attracted attention due to the numerous advantages and potential for enhanced long-term durability of deteriorated pavements, either cementitious or asphaltic. Because of its relevance and increased use in recent years for pavement engineering applications, this paper presents a comprehensive review of recent case studies that investigate the application of UHPC in bridge pavement rehabilitation or reconstruction projects. The selected case studies include projects conducted in America, Asia, and Europe, and provide valuable insights into the design, construction, and performance of UHPC overlays. These showcase the effectiveness of UHPC in addressing common issues such as cracking, rutting, and structural deficiencies in bridge pavements. Furthermore, these highlight the superior flexural and compressive strength of UHPC, which contributes to improved load-carrying capacity and resistance to permanent deformation. Moreover, some environmental benefits derived from UHPC such as smaller carbon footprint are highlighted in the paper as well as cost-effectiveness considerations in light of the long-term performance and reduced maintenance obtained with UHPC overlays. Overall, the comprehensive literature review and case studies presented in this paper provide valuable data on material properties, project types, construction techniques, and post-rehabilitation evaluations. These findings can guide future research and assist practitioners in making informed decisions regarding the implementation of UHPC overlays for pavement rehabilitation. Finally, this paper contributes to the existing body of knowledge on UHPC overlays and emphasizes their significance in improving the longevity and sustainability of bridge pavements. • UHPC overlays enhance pavements: cracking, rutting, and structural issues addressed. • UHPC delivers strength and durability: improved load capacity and reduced deformation. • UHPC's environmental benefits: smaller carbon footprint, cost-effectiveness. • Efficient construction with UHPC: reduced time and costs using specialized machinery. [ABSTRACT FROM AUTHOR]

The Multiple Stress Creep Recovery (MSCR) test has been proposed and implemented over the last two decades as an alternative to traditional tests, especially the elastic recovery (ER) test, to better capture rutting resistance. This paper presents a study on predicting asphalt binder ER using MSCR test results through ensemble learning methods, based on a database of more than 700 points for mostly polymer-modified binders. The ensemble approach involved tree-based Bagging (Random Forest and Extra Trees) and Boosting (Adaboost, gradient boosted decision tree, XGBoost, LightGBM, and CatBoost). The findings revealed the effectiveness of ensemble learning methods in capturing complex relationships within the data. Extra Trees and XGBoost emerged as the most accurate models based on coefficient of determination, mean absolute error, and root-mean-square error, compared to the other mentioned models and Neural Networks. These models offer precise predictions of asphalt binder ER from MSCR test results, surpassing the ER-DSR test proposed in the literature. Recovery at stress levels of 0.1 and 3.2 kPa were identified as the top influential features. In addition, clustering methods were employed to detect patterns within the dataset. The outcomes highlighted difficulties in discerning binders based on existing MSCR parameters, suggesting opportunities for refining MSCR analysis, and exploring additional tests to improve the distinction among asphalt binders. This investigation provides practical implications for states still utilizing PG-Plus, promoting the adoption of MSCR specifications for asphalt binder characterization. • Bagging and boosting models predicted elastic recovery from binder MSCR and PG. • MSCR shows promise for replacing elastic recovery by predicting it. • Percent recovery was most critical for predicting ER; J nrdiff was least important. • Clustering did not reveal any specific trends in binder categories. [ABSTRACT FROM AUTHOR]

Concrete-to-concrete interfaces are common in new reinforced concrete structures with different casting stages and or with precast members with cast-in-place parts, as well as in rehabilitation of existing reinforced concrete structures. Their longitudinal shear strength has been studied in the last five decades. Today, it is established that this is ensured by a combination of adhesion, aggregate interlock, friction, and dowel action. Being all these resistant mechanisms, but mainly friction, highly dependent on the surface roughness, the quantification of the latter is of paramount importance. This paper investigates the correlation between the friction coefficient and the surface roughness of concrete-to-concrete interfaces. An experimental campaign of direct shear tests, performed on specimens with different surface treatments (smooth, rough and corrugated), was carried out. The surface's texture was analysed using a 2D Laser Scan and different roughness parameters (extreme, mean and segments) were calculated, then correlated with the corresponding shear strength and, lastly, based on the latter, correlated with the friction coefficient. Results showed that the extreme roughness parameters, as well as the peaks' height related parameters, have poor or no correlation with the magnitude of the friction coefficient. The average roughness of the profile, its mean square, the mean valley depth, and the mean peak-to-valley height turned out to have the strongest positive correlation with the friction coefficient. Based on these, a novel combined roughness parameter with an optimized correlation with the friction coefficient was derived and proposed. • Roughness and friction in concrete-to-concrete interfaces are investigated. • Concrete's surface roughness is analyzed using a 2D laser scan. • A novel roughness parameter for more precise estimation of friction is proposed. [ABSTRACT FROM AUTHOR]

Modeling an accurate bond-slip model between concrete and reinforcement is a significant challenge in fiber reinforced polymer (FRP) strengthened reinforced concrete (RC). This paper presents a novel method for developing and validating an accurate bond-slip model. By employing a numerical procedure based on the finite difference method and a metaheuristic optimization algorithm, this method eliminates the need for a specific bond-slip law shape. This unique feature enables the prediction of bond-slip laws for various strengthening methods, including EBR and NSM, as demonstrated in this study. Furthermore, the methodology allows for the prediction of bond-slip laws associated with premature failure. The numerical and experimental results obtained confirm the accuracy of the methodology. • Prediction of bond-slip laws of strengthening methods with general applicability. • Inverse analysis approach to determine the bond-slip law from load-slip curve. • Applicable to tests that experience premature failure. • Validation against synthetic data generated by Finite Element Model. • Exemplification on single-shear bond tests using EBR strengthening method. [ABSTRACT FROM AUTHOR]

Graphene has been considerably studied as a reinforcing nanomaterial in cementitious composites to improve their mechanical properties under quasi-static loading. However, there is still lack of knowledge in graphene cementitious composites under high strain rate loadings. This paper reports the reinforcing effect of graphene on the mechanical behaviour of mortar at high strain rates. Different graphene contents were incorporated into the mortar to study their effect on the behaviour of mortar quasi-statically and dynamically. Compressive and split tensile strengths were measured under low and high strain rates using a universal testing machine and split-Hopkinson pressure bar (SHPB), respectively. It was found that adding 0.05% and 0.01% of graphene to the mortar enhanced the dynamic compressive and split tensile strengths up to 30% and 9.5% at 175 s-1 and 2–5 s-1 strain rates, respectively. Moreover, to understand the macroscale mechanical behaviour of the graphene mortar, Scanning Electron Microscopy (SEM), Energy Dispersive Spectrometer (EDS) and Mercury Intrusion Porosimeter (MIP) were employed to explore the morphology, porosity and hydration products of graphene mortar. The results indicated that graphene acted to fill the voids as well as to impede the crack path. • Mechanical properties of graphene mortar were evaluated at high strain rates. • Graphene can enhance the strengths of mortar quasi-statically and dynamically. • Dynamic increase factors were determined for both compression and tension. • Microscopic analysis proved graphene fills the voids and impedes the crack path. [ABSTRACT FROM AUTHOR]

The pavement surface sediments are continuously transported into the pore structure of permeable pavement under hydraulic power, resulting in the loss of permeability function. Obtaining the siltation behavior of the permeable asphalt mixture is the key and foundation to achieving siltation prevention and control technology for permeable asphalt pavement. In this paper, a self-developed laboratory accelerated siltation test was designed, and X-ray diffraction (XRD), computed tomography (CT) experiments, intrinsic frequency tests were employed to explore the siltation behavior of permeable asphalt mixture. The test results reveal that the density of pavement surface sediments is approximately 15.2 g/m2 per day, and pavement surface rainwater contains 27.6% clay minerals, which exhibits induration consolidation property with dry-wet cycles. The blockage behavior caused by sand particles is 7.5% higher than that caused by clay. For the siltation contribution of permeable asphalt mixture, sand particles account for 81%, clay particles represent 7%, and the induration consolidation contributes 12% of the siltation. CT test results indicate that the lower 1/3 of permeable asphalt mixture is silted up with continuous adhesive deposition of clay. The dry-wet cycle is one of the key factors of hardening blockage, the hardening blockage primarily experiences three stages: stagnation and hardening, erosion and collapse, and deposition blockage. Intrinsic frequency test explores that the intrinsic frequency of permeable asphalt pavement is between 14,000 Hz and 15,000 Hz, and the intrinsic frequency of pavement surface sediment is 3968.83 Hz. The intrinsic frequency of pavement increases continuously with the transportation of surface sediment, and there is a good correlation between the siltation degree and intrinsic frequency of permeable asphalt mixture. • We analyzed the composition of surface sediments. • We analyzed the influence of clay hardening effects. • We visualized the distribution of blockage materials within the specimens. • There is a correlation between blockage level and natural frequencies. [ABSTRACT FROM AUTHOR]

Carbonation cured calcium silicate binders can be considered an alternative material to reduce the carbon footprint of the construction industry. Carbonation at elevated temperatures is used to enhance carbonation reaction; however, it accelerates drying, which could result in drying shrinkage induced cracking. The effect of hydrogel on the microstructure and properties of carbonated wollastonite pastes was discussed in this paper. The teabag test and flow test showed that hydrogel absorption was notably higher in wollastonite paste than in OPC paste. The phase analysis based on Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA), revealed calcite as the primary polymorph of calcium carbonate in the carbonated product. The micro-CT analysis showed crack formation in the control pastes while no or significantly fewer cracks were observed in the hydrogel modified pastes. The hydrogel modified pastes exhibited lower water loss and drying shrinkage compared to the control paste at early carbonation stage. The above results provided evidence that cracking was caused by drying shrinkage in the control carbonated pastes and hydrogel was effective in mitigating such cracking by lowering water loss at early stage of carbonation. The results of the nitrogen adsorption test indicated a higher specific surface area and pore volume in the hydrogel modified pastes. The hydrogel modified pastes exhibited a slightly reduced compressive strength due to the presence of hydrogel macrovoids in these pastes. • Hydrogels reduced drying shrinkage and cracking in carbonated wollastonite. • Calcite is the primary polymorph of calcium carbonate in the microstructure. • Hydrogel demonstrated significant water absorption in wollastonite. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study of the flexural performance of reinforced concrete (RC) beams externally bonded with hybrid fiber-reinforced polymer (FRP) laminates made of carbon and polyethylene terephthalate (PET) fibers. Ten beam specimens were subjected to four-point bending tests, with a focus on assessing the effects of the stacking sequence and the elastic modulus of hybrid carbon-PET FRP laminates on the flexural performance of the strengthened beams. The failure modes, load-bearing capacities, displacement ductility of the specimens and strain distributions in the FRP laminates were examined and discussed. The experimental results showed that the load-carrying capacities of the FRP-strengthened specimens were significantly increased by 10.18∼27.98%, while the displacement ductility decreased by 51.36∼77.85%. The peak load and ductility of the beam specimens strengthened with PC (i.e., PET-C FRP) and CPC (i.e., C-PET-C FRP) stacking sequences were higher than those of their counterparts strengthened with two or three layers of hybrid FRP laminates. The accuracy and reliability of the calculation methods specified in ACI 440.2R-17, CNR DT 200 R1/2014 and GB 50608–2020 for estimating the flexural strengths of the strengthened RC beams were evaluated through a comparison of theoretical predictions with experimental results. The average predicted-to-tested ratios for the flexural strengths of the strengthened beams using ACI 440.2R-17, CNR-DT 200 R1/2014 (based on PE debonding failure), CNR-DT 200 R1/2014 (based on IC debonding failure), and GB 50608–2020 are 0.994, 0.704, 0.946, and 0.930, respectively. • Flexural behavior of RC beams strengthened with hybrid carbon-PET FRP laminates was studied. • Effects of the stacking sequence and the elastic modulus of hybrid FRP laminates were examined and compared. • The hybrid FRPs achieved a significant increase in load-carrying capacity accompanying with a displacement ductility reduction. • The design methods specified in current guidelines reasonably predicted the flexural strengths of the tested specimens. [ABSTRACT FROM AUTHOR]

Triethanolamine (TEA) is a multifunctional organic additive, applied chiefly to a grinding aid and accelerator for cement. Its effect on cement paste in a sulfate-rich environment remains still unclear and elusive. In this paper, the expansion and mechanical performance of cement paste under external sulfate attack were measured. Thermodynamic model lent itself to estimate the correlation between triethanolamine and generated products content ahead of quantified phase analysis. The transformation of internal component was surveyed by multiple technologies of thermal gravimetric (TG), scanning electron microscope (SEM), X-ray diffraction (XRD), and nuclear magnetic resonance (NMR), while inductively coupled plasma (ICP) was applied to investigate the evolution of interstitial ion concentration. Furthermore, the changes of pore structure over immersion time were separately figured and tabulated by virtue of mercury intrusion porosimetry (MIP). The above analysis shows that when cement paste suffers sulfate attack, triethanolamine intensifies the formation of calcite and exacerbates the decalcification of C-S-H, promoting a large quantity of insoluble precipitation including mirabilite of abundant crystalline water which accounts essentially for severe damage. Determined after comprehensive evaluation, the addition of TEA is conducive to the emergence of physical sulfate attack and an increment of the total porosity and permeability, contributing to an extension of microcracks and a more fragile structure, ultimately makes cement paste appear as a reduction in strength and stiffness. • Triethanolamine correlates adversely with the resistance to sulfate attack of cement paste • The complex of sulfate and aluminum ions occupied by the TEA intensifies decalcification of C-S-H • Triethanolamine loosens internal structure and permeability paths inside cement paste within sulfate attack [ABSTRACT FROM AUTHOR]

• The effects of hysteresis were highlighted at several scales. • A new hysteresis implementation method was proposed and validated using a bi-climatic chamber. • Considering the hysteresis phenomenon improved the accuracy of prediction of the developed numerical model. • Significant deviations in relative humidity and heat flux were observed in the habitable ambience between simulation cases. Experimental measurements of sorption isotherms show a difference between the water contents in the adsorption phase and the desorption one. This is mainly due to the hysteresis phenomenon. Not considering this phenomenon in hygrothermal behaviour models impacts the reliability of the latter. In this paper, we have studied the effects of hysteresis on the hygrothermal behaviour at the building scale. For this purpose, a new implementation method of a hysteresis model was proposed and validated at the material and wall scales using a bi-climatic chamber which controlled the indoor and outdoor climate conditions. Then, the effect of the hysteresis phenomenon at the building scale was evaluated following a COMSOL/TRNSYS co-simulation approach to consider the gains and losses in the hydric fluxes going through walls. The results showed significant differences in terms of the relative humidity of the living environment. However, no difference was noticed in the temperature variations. On the other hand, the total heat fluxes were also affected by the hysteresis phenomenon due to latent heat parts, that were driven by variations in relative humidity. The maximum gain and loss discrepancies (with and without hysteresis) in total heat fluxes of 1121 kJ/h and 1086 kJ/h, respectively, were obtained during the first week of February (winter period). The results also revealed that these discrepancies are sensitive to the number of persons in the living environment. [ABSTRACT FROM AUTHOR]