Extending the service life of structures is an important strategy to mitigate the environmental impacts, in particular, the global warming potential, of the building sector. As a key factor ...determining service life, the durability performance of reinforced concrete has been investigated for decades. Yet, durability's impact on the eco-efficiency of materials and structures has not been well realized until the early 2010s. Today, an increasing number of publications focus on concrete durability coupled with life cycle assessment (LCA), an important tool for analyzing eco-efficiency. However, the gap between the two research fields, i.e., durability and LCA, has led to divergent methodologies, which hinders the consensus between studies. To bridge this gap, this review covers the recent advances in durability-based LCA. Three aspects were highlighted: 1) how durability influences the eco-efficiency of cementitious materials; 2) how LCA models these effects; and 3) how we come to more justified results. The review argues the necessity of a unified methodology in this field and identifies the importance of performance-based models in justifying durability-based LCA. Further, a framework grounded on the prescriptive and performance-based design methods was proposed to unify the existing divergent methodologies. This framework will facilitate improving the future engineering codes underlining sustainability.
This work investigates enhanced passivation and corrosion resistance of various Cr-modified rebars compared to carbon rebar. It also evaluates their service life through time-varying probability ...analysis based on Monte Carlo simulation, combined with the parameters obtained from sampling and testing reinforced concrete mortar samples exposed to various marine conditions over 5 years. The results show that the free energy required for oxide thickening of rebar decreases from 20.12 kJ/mol to 9.25 kJ/mol as the Cr content increases from 5 % to 11 % (wt.), which facilitates the developed Cr-modified rebars rapidly form a passive film, exhibiting a chloride threshold level 6–14 times higher than that of carbon rebar. In the harshest marine splash zone, sea sand concrete with Cr11 rebar ensures a theoretical 50-year service life, contrasting sharply with the much shorter lifespan estimated at 5–6 years for carbon rebar. The corrosion rate of Cr-modified rebars was notably lower than that of the carbon rebar, and the Cr oxides/hydroxides facilitate the transformation of FeO(OH) with larger volume expansion to Fe3O4 with smaller volume expansion, reducing from 130 μm in HRB to 70 μm in the case of the thinnest Cr11 rebar. The thin and dense rust layer of the developed rebars is advantageous in blocking Cl- and guarantees a smaller volume expansion of structure even if the rebars are corroded. This study underscores the suitability of Cr-modified rebars for sea sand concrete structures and sheds new light on rebar-reinforced concrete structure developments toward eco-efficient and sustainable infrastructures.
•Cr-modified rebar has lower free energy required for oxide thickening than carbon steel.•Cr significantly boosts the chloride threshold level of rebar.•The Cr oxides/hydroxides facilitate the transformation of FeO(OH) with larger volume to Fe3O4 with smaller volume.•The SSC with Cr11 rebars can guarantee a theoretical 50-year service life in the harshest marine splash zone.•Shedding new light on rebar-steel developments towards eco-efficient and sustainable infrastructures.
Chloride ingress induced depassivation of reinforcing steel leading to corrosion is a major durability concern for concrete structures. The influence of the presence of cracks commonly occurring in ...concrete structures on chloride ingress should be accounted to improve the accuracy of service life predictions. This study investigates the depassivation probability of the reinforcement in both cracked and uncracked concrete using both analytical and 1D numerical models. The probabilistic service life prediction is realized using the Monte Carlo simulation to incorporate the uncertainty and variability in the input variables. For uncracked concrete the result of the numerical model agreed well with the fib chloride model. For cracked concrete, the numerical simulation suggests that the optimal engineering approach to account for cracks in a service life analysis is the adaptation of crack depth. Although, the approach could lead to an overestimation of chloride concentration because the 1D numerical simulation did not consider lateral diffusion in cracked concrete.
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•Hydrothermal behavior and mechanism of TBF-wound composites, which have not yet been elucidated, were investigated.•The hydrothermal aging temperature more significantly affects the ...mechanical properties of the composites than humidity.•Hydrothermal aging significantly deteriorates the fiber/resin interface in the composites.•The mechanical properties of TBF-NOL composites in hydrothermal environments are predicted to remain at 40–50% over extended periods.•Understanding the hydrothermal aging mechanism of the composites helps predict their service life.
Twisted bamboo fiber (TBF) wound composites produced using filament winding exhibit excellent potential for applications in lightweight and high-strength rotary structural components. Hydrothermal aging crucially influences the durability of TBF-wound composites. The effects of hydrothermal aging on the microstructure, hygroscopic properties, and mechanical properties of TBF Naval Ordnance Laboratory (TBF-NOL) composites were examined in this study to elucidate the hydrothermal aging mechanisms of TBF-NOL composites and predict their service life. The moisture absorption behavior of the TBF-NOL composites conformed to Fick’s second law. After a 30 d water immersion test at 70 °C, the TBF-NOL composites exhibited a high moisture content, leading to a significant decrease in the tensile, bending, and shear properties. Hydrothermal aging significantly deteriorated the TBF/epoxy resin interface in the TBF-NOL composites. The effect of temperature on the hydrothermal aging of the TBF-NOL composites was more pronounced than that of humidity. This study predicts that the bending properties of TBF-NOL composites could be maintained at the 40–50% level for 5–10 years, depending on the degree of exposure to hydrothermal environments. The service-life prediction results can guide the practical application of TBF-wound composites.
Spalling is one of the most common contact fatigue failure modes on gear face. Although there are some prediction models for spalling formation, few prediction models have previously addressed the ...evolution from initial defects to spalling cavities. In this paper, a damage-connectivity spalling model (DCSM) is proposed to describe the formation and evolution of multiple irregular spalling cavities on the tooth face deriving from the initial defects. Subsequently, a type of TVMS-based indicator is established to represent the evolutionary severity of irregular spalling cavities. Finally, a service life prediction method is developed based on the proposed indicators. The correctness of the proposed DCSM model is verified by comparison with the extant gear spalling experiments. The effects of working load, depth ratio and quantify ratio of initial defect groups on the service life are discussed, which contributes to the service life improvements of gear pairs in the design stage.
•Relationship between freeze-thaw damage and pore structure deterioration is studied.•Low-field nuclear magnetic resonance and mercury intrusion porosimetry are used.•Mass loss rate and relative ...dynamic elastic modulus are used to evaluate damage.•Pore structure deterioration equations can predict residual life of mortar exposed freeze-thaw.
This study analyzes the deterioration process of mortar with three different water-cement ratios and compares the performances of mortar with and without air voids. The mass loss and relative dynamic elastic modulus of the specimens are the criteria for the macroscopic evaluation of freeze-thaw damage. Experimental methods combined rapid freeze-thaw testing, ultrasonic sound velocity, and low-field nuclear magnetic resonance (LF-NMR). The complete deterioration of mortar specimens is observed in detail to determine the relationship between freeze-thaw damage and pore structure deterioration. Results established a system to predict the residual life of mortar exposed rapid freeze-thaw cycles.
•Concrete reinforced with cellulose fiber, polyvinyl alcohol fiber or polyolefin fiber of different dosages has different durability performance.•Hybrid fiber is found to have a positive synergistic ...effect on concrete durability.•Hybrid fiber combination of 1.2 kg/m3 cellulose fiber, 2.0 kg/m3 polyvinyl alcohol fiber and 2.0 kg/m3 polyolefin fiber may achieve optimal synergistic effect on durability.•Hybrid combinations can prolong service life of concrete in carbonization and chloride ion corrosive environment.
The durability of concrete reinforced by cellulose fiber (CTF), polyvinyl alcohol fiber (PF) and polyolefin fiber (VS) is comprehensively studied in this paper. Relevant durability tests are conducted to explore the effect of different fiber types and dosages on durability performance demonstrated in the resistance to drying shrinkage, water permeability, crack, carbonization and chloride ion penetration. Besides single fiber reinforced concrete, synergistic effect of hybrid fibers on durability is also studied, and the service life of fiber reinforced concrete in carbonization environment and chloride ion corrosive environment is further predicted. In addition, the structure of fiber reinforced concrete is analyzed from the micro perspective by using the optical and electron microscope. The results showed that: (1) The addition of CTF can effectively enhance the all five aspects of durability performance, including the resistance to drying shrinkage, water permeability, crack, carbonization and chloride ion penetration. The addition of PF can enhance the durability properties except for chloride ion penetration resistance. Generally, though with few exceptions, the increased dosage of CTF or PF would improve the strengthening effect on the durability of single fiber reinforced concrete. The addition of VS can either enhance or weaken the above five aspects of durability properties, and its effect varies much with the fiber dosage. (2) Hybrid fiber is found to have a positive synergistic effect and enhance the above five aspects of durability properties of concrete. The concrete reinforced with the hybrid fiber combination of 1.2 kg/m3 CTF, 2.0 kg/m3 PF and 2.0 kg/m3 VS may achieve the optimal durability properties. (3) CTF, PF and VS, especially their hybrid combinations, are found to effectively prolong the service life of concrete structure in the carbonization and chloride ion corrosive environment. The research findings obtained in this paper can supplement the study on the durability of fiber reinforced concrete, and provide suggestions for suitable fiber type and dosage selection in actual engineering designs of fiber reinforced concrete.
This paper presents the durability performance of concrete incorporating high-volumes of fly ash exposed to a harsh marine environment for 19 to 24years. Concrete specimens (305×305×915mm 1×1×3ft.) ...were cast using W/CM in the range of 0.31 to 0.46, various types of fly ash with replacement levels of 56 or 58%, and various types of normal density and lightweight aggregates.
Surface erosion/scaling was seen on all specimens; the extent of erosion was slightly worse for fly ash concrete with normal density aggregate compared to the controls (without fly ash), but fly ash concrete with two of the three lightweight aggregates exhibited severe surface erosion.
Laboratory testing included taking cores from each block and determining the existing chloride profile, compressive strength and “chloride permeability” (ASTM C1202).
The depth of chloride penetration was found to be in excess of 100-mm (4in.) for the concrete specimens without fly ash, whereas the presence of fly ash significantly decreased the depth of penetration to approximately 30 and 40mm in specimens containing either normal density or lightweight aggregate, respectively. The increased penetration in the concrete with lightweight aggregates is attributed to the surface erosion observed with these concretes. The results from the chloride permeability testing also indicate significant increases in the resistance to chloride-ion penetration for fly ash concrete.
Degradation data have been broadly used for assessing product and system reliability. Most existing work focuses on modeling and analysis of degradation data with a single characteristic. In some ...degradation tests, interest lies in measuring multiple characteristics of the product degradation process to understand different aspects of the reliability performance, resulting in degradation data with multiple characteristics. The literature on modeling such data is scarce. Motivated by the photodegradation process of polymeric material, we propose a multivariate general path model for analyzing degradation data with multiple degradation characteristics (DCs). The model incorporates covariates for modeling the nonlinear degradation path. It also includes random effects that are correlated among the multiple DCs to capture the unit-to-unit variation in the individual degradation paths and to model the interdependence among the multivariate measurements. An expectation-maximization algorithm combined with the Markov chain Monte Carlo simulation is developed for estimating the model parameters and predicting system reliability with quantified uncertainty. The performance of the developed method is evaluated and compared with existing methods through a simulation study. The implementation of the method is illustrated through two examples with different forms of reliability functions. The main motivating example analyzes the coating degradation data with a closed-form reliability function, while the second example on analyzing the Device-B data demonstrates a more general simulation approach for dealing with analytically intractable reliability functions.
•Innovative ML models were integrated to predict the chloride resistance of RAC.•Model interpretability was improved by SRC and partial dependence analysis.•A mixture design method and a service life ...prediction approach were proposed.
This study investigates the feasibility of introducing machine learning algorithms to predict the diffusion resistance to chloride penetration of recycled aggregate concrete (RAC). A total of 226 samples collated from published literature were used to train and test the developed machine learning framework, which integrated four standalone models and two ensemble models. The hyperparameters involved were fine-tuned by grid search and 10-fold cross-validation. Results showed that all the models had good performance in predicting the chloride penetration resistance of RAC and among them, the gradient boosting model outperformed the others. The water content was identified as the most critical factor affecting the chloride ion permeability of RAC based on the standardized regression coefficient analysis. The model’s interpretability was greatly improved through a two-way partial dependence analysis. Finally, based on the proposed machine learning models, a performance-based mixture design method and a service life prediction approach for RAC were developed, thereby offering novel and robust design tools for achieving more durable and resilient development goals in procuring sustainable concrete.
