Search Results (84)

The alkali–silica reaction (ASR) is an important mechanism of concrete deterioration, whereby reactive silica in aggregate interacts with cement alkalis to form expanding gel, which compromises the structural integrity of the concrete. Although the Republic of Korea has historically been classified as a low-risk region for ASR due to its geological stability, documented examples of concrete damage since the late 1990s have necessitated a rigorous reassessment of local aggregates. This study evaluated the ASR potential of 84 aggregate samples sourced from diverse Korean geological regions using standardized protocols, including ASTM C 1260 for mortar bar expansion and ASTM C 289 for chemical reactivity, supplemented by soundness, acid drainage, and weathering index analyses. The results indicate expansion within the range of 0.1–0.2%, classified as potentially deleterious, for some rock types. In addition to ASR reactivity, isolated high anomalies (e.g., high soundness, acid producing, and weathering) suggest the existence of other durability risks. Consequently, while Korean aggregates predominantly have a low ASR reactivity, the adoption of various validated ASR tests as a routine test and the integration of supplementary cementitious materials are recommended to ensure long-term concrete durability, highlighting the need for sustained monitoring and further investigation into mitigation strategies. Full article

This study investigates the use of Glass Fine Aggregate (GFA) and Fly Ash (FA) in mortar for Alkali–Silica Reaction (ASR) mitigation through a multidimensional evaluation. GFA was used to replace river sand in 20% increments up to 100%, while FA replaced cement at 10%, 20%, and 30%. Three GFA size ranges were considered: <1.18 mm, 1.18–4.75 mm, and a combined fraction of <4.75 mm. At 100% replacement, <1.18 mm GFA reduced ASR expansion to 0.07%, compared to 0.2% for <4.75 mm and 0.46% for 1.18–4.75 mm GFA. It also improved long-term strength by 25% from 28 days to 6 months due to pozzolanic activity. However, refining GFA to below 1.18 mm increased environmental impacts and resulted in a 4.2% increase in energy demand due to the additional drying process. Incorporating 10% FA reduced ASR expansion to 0.044%, had no significant effect on strength, and decreased key environmental burdens such as toxicity by up to 18.2%. These findings indicate that FA utilisation offers greater benefits for ASR mitigation and environmental sustainability than further refining GFA size. Therefore, combining <4.75 mm GFA with 10% FA is identified as the optimal strategy for producing durable and sustainable mortar with recycled waste glass. Full article

The concrete industry increasingly seeks sustainable alternatives to conventional materials to reduce the environmental impact while maintaining structural performance. This study evaluates the use of locally sourced rhyolite as a coarse aggregate combined with recycled supplementary cementitious materials (SCMs) to address the sustainability and durability. Due to its high silica content, rhyolite is prone to the alkali–silica reaction (ASR), which may affect concrete durability. Concrete mixtures incorporating rhyolite with silica fume (SF), Class F fly ash (FA), and slag cement (SC) were tested for compressive strength, porosity, density, absorption, mortar bar expansion, electrical resistivity, and rapid chloride permeability. All rhyolite-based mixtures—regardless of SCM incorporation—achieved higher 90-day compressive strengths than the conventional control mixture, with 10% SF reaching the highest value. Additionally, each recycled SCM effectively reduced ASR-induced expansion, with 20% FA showing the most significant reduction and superior durability, including the greatest decrease in chloride permeability and the highest electrical resistivity, indicating enhanced corrosion resistance. These results confirm that rhyolite aggregates, when combined with SCMs, can improve durability and reduce ASR. Therefore, rhyolite shows potential for use in structural concrete under standard exposure conditions. This strategy supports circular economy goals by incorporating regional and recycled materials to develop concrete with improved durability characteristics. Full article

The construction industry’s escalating environmental footprint, coupled with the underutilization of construction waste streams, necessitates innovative approaches to sustainable material design. This study investigates the dual functionality of recycled clay brick powder (RCBP) as both a supplementary cementitious material (SCM) and an alkali–silica reaction (ASR) inhibitor in hybrid mortar systems incorporating recycled glass (RG) and recycled clay brick (RCB) aggregates. Leveraging the pozzolanic activity of RCBP’s residual aluminosilicate phases, the research quantifies its influence on mortar durability and mechanical performance under varying substitution scenarios. Experimental findings reveal a nonlinear relationship between RCBP dosage and mortar properties. A 30% cement replacement with RCBP yields a 28-day activity index of 96.95%, confirming significant pozzolanic contributions. Critically, RCBP substitution ≥20% effectively mitigates ASRs induced by RG aggregates, with optimal suppression observed at 25% replacement. This threshold aligns with microstructural analyses showing RCBP’s Al³⁺ ions preferentially reacting with alkali hydroxides to form non-expansive gels, reducing pore solution pH and silica dissolution rates. Mechanical characterization reveals trade-offs between workability and strength development. Increasing RCBP substitution decreases mortar consistency and fluidity, which is more pronounced in RG-RCBS blends due to glass aggregates’ smooth texture. Compressively, both SS-RCBS and RG-RCBS mortars exhibit strength reduction with higher RCBP content, yet all specimens show accelerated compressive strength gain relative to flexural strength over curing time. Notably, 28-day water absorption increases with RCBP substitution, correlating with microstructural porosity modifications. These findings position recycled construction wastes and glass as valuable resources in circular economy frameworks, offering municipalities a pathway to meet recycled content mandates without sacrificing structural integrity. The study underscores the importance of waste synergy in advancing sustainable mortar technology, with implications for net-zero building practices and industrial waste valorization. Full article

In the present context of mitigating greenhouse gas emissions, interground portland-limestone cement (PLC) with elevated limestone filler (LF) replacement ratios (exceeding 15%) presents a feasible sustainable alternative, capable of diminishing clinker content. While LFs are known to modify the microstructure of concrete, the influence on ASR development has yet to be fully understood and requires further investigation. In this context, this work evaluates the effect of LFs replacement ratios between 15% and 25% on ASR development in concrete mixtures incorporating PLC. Analysis of expansion from accelerated mortar bar tests (AMBT) and concrete prism tests (CPT) indicate that increasing LF content from 15% to 25% does not substantially affect ASR-induced expansion. These findings underscore the viability of PLC as a sustainable construction material that does not compromise durability concerning ASR. Full article

Background: Pancreatic cancer (PC), the third leading cause of cancer-related mortality globally, exhibits a persistently low five-year survival rate (13%). While the global burden of PC among individuals aged 15–59 years has declined, trends in China remain understudied. This study evaluates global and national trends in PC incidence, mortality, and disability-adjusted life years (DALYs) from 1990 to 2021 and projects trajectories to 2045. Methods: Using data from the Global Burden of Disease (GBD) 2021 study, we calculated age-standardized rates (ASRs) for 204 countries/territories. Joinpoint (version: 5.3.0.0) regression identified temporal trends via average annual percentage changes (AAPCs), and Bayesian age-period-cohort (BAPC) modeling forecasted future burdens. Results: Globally, PC burden declined among 15–59-year-olds (AAPC for incidence: −0.8%, 95% UI: −1.2 to −0.4). However, China experienced a significant reversal after 2009, with incidence rising by 1.5% annually (95% UI: 0.9–2.1), disproportionately affecting males. Smoking (contributing to 22.2% of DALYs in China) and high fasting plasma glucose (15%) emerged as key modifiable risk factors, while elevated BMI exacerbated burdens in high SDI regions (3.1% of DALYs). Projections indicate a continued surge in China’s PC burden by 2045, particularly among males (incidence projected to increase by 50% from 2010 to 2045). Conclusions: High SDI regions exhibit concentrated PC burdens linked to lifestyle factors, whereas China’s rising trends align with healthcare expansion and metabolic disease proliferation. Targeted interventions—smoking cessation, glycemic control, and weight management—are imperative to mitigate growing burdens in younger populations. This study highlights the urgent need for region-specific strategies to address evolving epidemiological challenges in PC prevention and control. Full article

Enhancing the utilization rate of waste glass in concrete is crucial for achieving solid waste reduction and low carbon emissions in the construction industry. This study employs the method of simultaneously replacing fine aggregate and cementitious materials in concrete with glass sand and glass powder to prepare composite waste glass concrete (CGC). The compressive strength, alkali–silicate expansion, and thermal properties of CGC were investigated experimentally. The experimental results show that the pozzolanic activity of fine glass powder in CGC can effectively mitigate the ASR reaction, enhance glass utilization, and allow the glass content to reach up to 17.79% of the total concrete mass. The thermal conductivity of the compounded waste glass concrete decreased linearly with increasing temperature, and the specific heat capacity showed three distinct peaks in the range of 180–800 °C, which were caused by chemical dehydration, quartz phase transition, and CaCO₃ decarbonization, respectively. Furthermore, to examine the impact of replacement mode on the high-temperature resistance of waste glass concrete, the residual strength, physical properties, and microstructure of the concrete were evaluated. It was found that the residual strength ratio of CGC (0.73) exhibited a distinct advantage at 600 °C. At this time, the melting effect of glass can reduce the pore size of concrete and transform large pores into capillary pores. However, as the temperature rises to 800 °C, the melting effect of glass no longer alleviates the high-temperature damage to concrete, and the degree of decomposition of hydration products determines the concrete strength. Full article

Alkali–silica reaction (ASR) can create significant cracking, compromising the durability and structural integrity of concrete elements. Currently, there is no known way to halt or reverse ASR damage, and the expansion will continue until it impairs ride quality or structural capacity, requiring the replacement of the affected elements. For certain existing structures or structural elements, the progression of an alkali–silica reaction may slow down depending on the type, dimensions of the affected element, service conditions, and environmental factors. Early intervention with repairs, however, may delay the need for replacement and extend the service life of the structure. Repair methods, such as crack filling, sealing, and breathable coatings, help reduce moisture intake and slow expansion. These repairs can also be combined with strengthening techniques to counteract the expansive forces caused by ASRs. The primary goal of these repairs is to extend the life of the structure until replacement or abandonment is necessary. There is a lack of information regarding the long-term performance of repairs and the most widely accepted repair methods. However, the literature and knowledge from the field shows that the time gained through these repairs varies significantly depending on location and exposure conditions, indicating that replacement remains the only reliable solution. Still, given that repairs can cost only 10–20% of full replacement, they remain a viable option for agencies managing limited budgets for immediate replacement. Full article

This paper aims to support stakeholders in the sustainable construction sector by exploring the potential of unexamined aggregates from five distinct origins: the Jandol River, the Swat River, the Panjkorha River, the Kitkot Drain, and the Shavey Drain situated in Malakand division, North Waziristan, Pakistan, concerning Alkali–Silica Reaction (ASR) prior to their incorporation into large-scale construction practices. Petrographic examination for the determination of the mineralogical composition of all collected aggregates revealed that aggregates stemming from the Swat River, Panjkorh River, Kitkot Drain, and Shavey Drain exhibited no reactive minerals. In contrast, those from the Jandol River showed reactive mineral content. Physical analysis of the aggregates revealed that Jandol River aggregates had superior resistance to impact, crushing, and abrasion, having values of 18.53%, 18.53%, and 20.10%, respectively. Moreover, the chemical analysis exhibited the highest silica content (SiO₂) in Jandol River aggregates, i.e., 94.7%, respectively. Samples in the form of cubes, prisms, and mortar bars were prepared to study both the mechanical properties and the expansion tendencies of specimens prepared from different aggregate sources. Validation of the reactive nature of the Jandol River aggregates was corroborated by the expansion results obtained from the mortar bars and the reduction in compressive strength and flexure strength by 8.2% and 9.2%, respectively, after 90 days, higher than that of aggregates exposed to ASR sourced from the other four origins. It can be asserted that aggregates from the Jandol River source are more susceptible to ASR as compared to other aggregates. To mitigate the potential of ASR, various strategies, such as using low reactivity, natural, or processed aggregates; low alkali-containing cement; inducing pozzolanic substances in concrete; etc., are recommended. Simultaneously, an economic feasibility study and environmental assessments are recommended as future developments. Full article

F-doped PrBa_0.8Sr_0.2Co₂O_5+δ−xF_x (PBSCF_x, x = 0, 0.025, 0.05, 0.075, 0.1) cathode powder was synthesized by the sol–gel method. X-ray diffraction results showed that all the samples doped with F exhibited a typical tetragonal perovskite structure without a heterophase. F doping can effectively reduce the thermal expansion coefficient (TEC) of the cathode materials, which decreased from 25.3699 × 10⁻⁶ K⁻¹ of PBSC to 23.5295 × 10⁻⁶ K⁻¹ of PBSCF_0.1. The area-specific resistance (ASR) of PBSCF_0.05 was 0.0207 Ω·cm² at 800 °C, with a conductivity of 1637.27 S·cm⁻¹ and maximum power density of 856.08 mW·cm⁻². Its performance had slight decay after 100 h at 800 °C. F doping significantly improved the electrochemical performance of this cathode material for solid oxide fuel cells (SOFCs). Full article

Over the past few decades, a significant number of large concrete structures with deterioration problems related to the alkali–silica reaction (ASR) have been identified in Portugal and worldwide. Assessing the condition of ASR-affected concrete dams involves both diagnosis and prognosis. Diagnosis evaluates the structure’s current state, while prognosis predicts deterioration and safety implications. This is key to estimate the period during which the structure will effectively perform its function, and essential for the timely and cost-effective planning of the necessary mitigation, rehabilitation, and/or reconstruction works. This article aims to contribute to the ongoing discussion of this topic by the scientific and technical community and, therefore, presents the methodology adopted to assess the condition of a severely ASR-affected concrete dam in Portugal, the Alto Ceira dam, in which the concrete was produced with susceptible to ASR quartzitic aggregates and that was decommissioned and replaced by a new one in 2014. The article provides a brief review of the diagnosis and prognosis of the ASR in concrete dams, presents and analyses the results from laboratory testing (including chemical, microstructural, physical, mechanical, and expansion tests), in-situ testing, structural monitoring systems, visual inspections, and numerical modelling, aiming at assessing ASR impacts and evidencing the utility of the reported methodology on the appraisal of ASR-affected structures. Full article

Cracks and other defects in concrete will affect its durability, thermal insulation effect, and energy consumption. ASR is one of the common causes of concrete cracks. In this study, mortar specimens modified with fly ash were prepared using the mortar bar rapid method, and the inhibition effect of ASR in two alkali environments and the building energy efficiency characteristics were comparatively analyzed. SEM, EDS, and XRD were used to analyze the microstructure, elemental distribution, and products in the specimens’ interfacial transition zone comparatively. The results show that a replacement amount of 20–30% fly ash can restrain ASR expansion and maintain high mechanical strength. In both alkaline environments, K and Al are enriched in the interface transition zone and combine with SiO₂ and Al₂O₃ to form a stable framework aluminosilicate mineral. In addition to the inhibition effect of fly ash on ASR, the external wall heat dissipation flux decreased from 132.6 W/m² to 117.6 W/m², a decrease of 11.3%, and the overall envelope heat dissipation flux decreased by 9.2%, significantly reducing building energy consumption. This study provides a new perspective for the development of building energy-saving materials and helps green buildings and sustainable development. Full article

This study investigates the effect of calcined clays (metakaolin, metasilt, metaclay) on the chemical composition, distribution, and structure of alkali–silica reaction (ASR) gels. Using 10 wt% of calcined clays reduced concrete expansion and minimized cracking but did not inhibit ASR gel formation. Micro X-ray fluorescence mapping revealed an average ASR gel content of 3 wt% in concrete, incorporating up to two-thirds of K₂O and nearly all Na₂O from the binder. Raman spectroscopy indicated structural similarities among gels in different concrete mixes, with an increased degree of polymerization in the metakaolin-containing concrete. Automated mineralogy identified four gel phases: Si gel, Ca-Si gel, Al-Ca-Si gel, and Al-Si gel. Ca-Si gels are formed at binder interfaces, while non-swellable Al-bearing gels are mainly formed in metakaolin-containing concrete located within aggregates. This study shows that aluminum can be incorporated into gels in calcined clay concretes, altering their structure and potentially affecting their expansion behavior in concrete. Full article

Alkali–silica reaction (ASR) is an important factor that seriously affects the durability of reinforced concrete (RC) structures. The current research on alkali-aggregate mainly focuses on the deterioration mechanism of materials and the mechanical properties of standard specimens. However, there is a gap in the field of research on the effect of alkali-aggregate damage on the level of RC structures. In this study, five RC beams were tested, and the depth and location of alkali solution immersion were used as the test variables, with the aim of investigating how the steel reinforcement suppresses the expansion caused by ASR and evaluating the shear behavior of RC beams after non-uniform ASR damage. The results of the study showed that immersion in an alkali solution and an increase in immersion depth accelerated the rate of expansion development, while steel reinforcement inhibited the rate of expansion development. Compared with undamaged RC beams, ASR initially generates expansion stresses within the concrete, which increase the cracking and yield loads of RC beams and delay the cracking of RC beams, and ASR reduces the ultimate load-carrying capacity and ductility of RC beams due to the disruption of the concrete microstructure. Finally, a chemo-mechanical analysis method is proposed based on experimental results, which incorporate an ASR expansion model and a pore mechanics model. The efficacy and precision of this model are validated through comparison with experimental results. Full article

Arabic raw audio datasets were initially gathered to produce a corresponding signal spectrum, which was further used to extract the Mel-Frequency Cepstral Coefficients (MFCCs). The pronunciation dictionary, language model, and acoustic model were further derived from the MFCCs’ features. These output data were processed into Baidu’s Deep Speech model (ASR system) to attain the text corpus. Baidu’s Deep Speech model was implemented to precisely identify the global optimal value rapidly while preserving a low word and character discrepancy rate by attaining an excellent performance in isolated and end-to-end speech recognition. The desired outcome in this work is to forecast the next word and character in a sequential and systematic order that applies under natural language processing (NLP). This work combines the trained Arabic language model ARABERT with the potential of Long Short-Term Memory (LSTM) networks to predict the next word and character in an Arabic text. We used the pre-trained ARABERT embedding to improve the model’s capacity and, to capture semantic relationships within the language, we educated LSTM + CNN and Markov models on Arabic text data to assess the efficacy of this model. Python libraries such as TensorFlow, Pickle, Keras, and NumPy were used to effectively design our development model. We extensively assessed the model’s performance using new Arabic text, focusing on evaluation metrics like accuracy, word error rate, character error rate, BLEU score, and perplexity. The results show how well the combined LSTM + ARABERT and Markov models have outperformed the baseline models in envisaging the next word or character in the Arabic text. The accuracy rates of 64.9% for LSTM, 74.6% for ARABERT + LSTM, and 78% for Markov chain models were achieved in predicting the next word, and the accuracy rates of 72% for LSTM, 72.22% for LSTM + CNN, and 73% for ARABERET + LSTM models were achieved for the next-character prediction. This work unveils a novelty in Arabic natural language processing tasks, estimating a potential future expansion in deriving a precise next-word and next-character forecasting, which can be an efficient utility for text generation and machine translation applications. Full article