Concrete Design Research Articles

Advances and applications of the strut-and-tie method in reinforced concrete design: A state-of-the-art review

The Strut-and-Tie Method (STM) is a versatile and powerful approach widely used in the design and analysis of reinforced concrete structures, particularly in regions with complex stress distributions and discontinuities. This review article delves into the theoretical foundations, practical applications, and experimental validations of the STM. The article begins by exploring the fundamental principles of the STM and its historical development, with a focus on its application in predicting the capacity of reinforced concrete members. Additionally, the STM efficacy in designing deep beams and comparisons with other analytical methods are thoroughly examined. Notably, the review includes a discussion on the application of STM in concrete beams, highlighting its ability to accurately predict capacity. Several studies investigating the behavior of reinforced concrete deep beams with openings, shear-strengthened deep beams, and continuous deep beams using the STM approach are critically analyzed, providing valuable insights into its reliability and practicality. Furthermore, the review delves into advancements in computational tools and finite element analyses that have been integrated with the STM, offering a more comprehensive and robust approach to design and analysis. The article also evaluates practical applications of STM in engineering scenarios, such as the design of bridge pier caps and complex regions, showcasing its versatility and adaptability. In conclusion, this review underscores the pivotal role of the Strut-and-Tie Method in modern reinforced concrete design and analysis. It serves as a valuable resource for engineers, researchers, and practitioners seeking to apply this method effectively in various structural configurations and challenging scenarios. Ultimately, the article emphasizes the significance of STM as a reliable and efficient tool for optimizing the design and ensuring the safety and performance of reinforced concrete structures.

Experimental investigation and machine learning models for predicting flexural and tensile strengths of recycled concrete: Bridging the gap between sustainable materials and structural design

The sustainability of structural components requires recycled aggregate concrete (RC) to achieve adequate flexural and split tensile strengths for practical use. These strengths depend on mix design and the properties of recycled coarse aggregates (R-CA). The variability in R-CA sources and the inherent heterogeneity of RC complicate strength predictions. No existing model accounts for this variability, leaving a gap between sustainable materials and structural design. This study develops machine learning-based models to predict the flexural and split tensile strengths of RC, regardless of R-CA source and properties. Key factors such as water absorption, effective water-to-cement ratio, coarse aggregate-to-cement ratio, and R-CA replacement ratio are used for predictions. The impact of different R-CA types on RC and natural aggregate concrete (NC) is also experimentally analyzed. A dataset of 353 test results from this study and 33 prior studies is used, and various machine learning algorithms (MLA) are evaluated. Results show a 41 % and 23 % reduction in flexural and split tensile strengths of RC compared to NC, but acid and mechanically treated R-CA can recover up to 94 % and 93 % of NC's strengths, respectively. Among all MLA models, the gradient boost model depicted the highest accuracy in predictions for the flexural and tensile strengths of both RC and NC. This research introduces new equations and a C/C++ tool for predicting RC and NC strengths, contributing to sustainable concrete design and bridging the gap between research and practical application.

Inovasi Desain Roster Beton dengan Mengutamakan Unsur Privacy dan Estetika

A roster is a nonstructural construction that plays a role in regulating the temperature and humidity of the air in the room; not only that, a roster is also often used as a room divider. The number of roster product designs on the market allows roster manufacturers to make products whose designs tend to prioritize less privacy and only prioritize aesthetic factors in the design of the roster structure. This research was conducted to create changes in roster design to improve the function of the roster, where the roster itself must have optimal air circulation and an element of privacy that is maintained. This research uses an experimental method by making its concrete roster design innovation and comparing it with existing products on the market; as a comparison, 2 product design samples were taken from the market and tested. Tests are carried out in the form of air circulation testing, facade testing, compressive strength testing, and water absorption testing. AutoDesk CFD software is used as a means for testing air circulation and as a success parameter for testing compressive strength and water absorption per SNI 03-1570-1989. The value of the air circulation test is 866343.0 cm3/s = 866.343 Liter/s for the 1st design, 842725.0 cm3/s = 842.725 Liter/s in the 2nd design, 7964661.0 cm3/s = 796.4661 Liter/s in the 3rd design. The compressive strength result obtained is 1.25 N/mm2. The results of the test values of compressive strength and water absorption show that they can meet the specified requirements. This concrete roster design innovation can make the right solution for consumers when choosing a more optimal concrete roster.

Sketching Versus Digital Design Tools in Architectural Design

Sketching is a design tool that can be assumed to be ill-structured, does not offer exact solutions, is intuitive, and is open-ended in the initial stages of architectural design. Sketching creates an opportunity for architects to release their creativity and intuition, giving rise to spontaneous ideas and concepts in an organic and natural way. During the initial design phases, like in the conceptual stage of the design, designers receive aid from conventional sketching as their concepts and ideas can easily transform into tangible, real-world forms. With the development of digital design methods like CAD (computer-aided design) in pursuit of AI (artificial intelligence), it has been accepted that manual sketches are no longer the only method used in the design process, and the trend toward using new methods has begun. The diversity and evolution of tools used in architectural design, together with the integration of CAD, AI, and traditional sketching techniques, have contributed to the development of architectural design and facilitated enhanced collaboration, visualization, and efficiency across the design process. As a result, it has evolved to embrace the use of CAD, which was the first method adopted from these developments, as a basic skill in the field of architectural design education. This shift places a strong emphasis on the professional field of architectural design while also encouraging students to explore the innovative potential of CAD for design purposes. CAD presents architects with a robust platform that facilitates the creation of intricate designs and precise measurements during the initial stages of the design process. Following CAD, the development of AI-driven design tools motivates architecture students and designers to transform their concepts into concrete designs. Although it is known that each method mentioned has its own positive or negative aspects, it is not possible to say that any of them is used alone in architectural design processes. At this point, combining the design process with CAD and AI-supported design tools, as well as traditional manual sketching in architecture, helps develop a diverse and adaptable skill set in design. Integrating digital design tools into the architectural field emphasizes the enduring importance of traditional sketches, especially in terms of inspiration and conceptualization in architectural design, while also updating the design process. This document aims to explore the progression of employing diverse design tools, namely manual sketching, CAD, and AI-driven design tools, throughout the architectural design process. This paper undertakes a comparative analysis of using computational design tools instead of traditional sketching with pen and pencil, aiming to juxtapose their respective benefits and drawbacks. In conclusion, although it is not yet possible to assert the superiority of one method over the other, it is evident that traditional sketching continues to hold significant relevance and effectiveness in the design process despite its long-term use.

Importance of pumice amount in the design of self-compacting lightweight concrete

Although concrete has high compressive strength values, it has a heavy unit volume and low tensile strength. In this study, the normal-weight aggregate, which takes up the most space in concrete by volume and mass, was partially replaced with pumice aggregate, and macro steel fiber (30 mm) was also added to the mixtures. This experimental work aims to investigate the effect of pumice aggregate amount on the fresh and hardened properties, as well as the flexural performance of the self-compacting lightweight concrete (SCLC). The replacement proportions of pumice aggregate with crushed sand were arranged as 45%, 50%, and 55% of the entire aggregate by weight. Three mixtures, each with 1% macro steel fiber reinforcement and without fiber, were prepared for each mixture scenario. The mix design of these six mixtures was arranged to achieve the self-compacting ability and the workability tests recommended by EFNARC (slump-flow, T50, J-ring) were taken into account. To investigate the mechanical properties (compressive, splitting tensile, and flexural strengths) and flexural toughness of the samples, the specimens were cured in water at 23±2 °C for 28 days. As a result, the unit volume weights of the specimens produced from pumice-substituted mixtures decreased with the increase in the pumice dosage, while the compressive, splitting tensile, and flexural strengths decreased. However, it has been determined that all SCLC mixtures including pumice aggregate provided workability properties in general and had enough compressive strength to be used in the production of structural bearing elements, regardless of fiber content. As a result, the optimum pumice aggregate replacement percentage with crushed sand was found to be 45% and the best flexural performance values of the specimens having macro steel fiber were observed in the ones having 45% pumice aggregate substitution.

Flexural behaviour and post-cracking performance of polypropylene fibre-reinforced waste cardboard blended concrete

The requalification of recycled materials has become of significance owing to a global shift towards net zero emissions and the severe environmental impact of misused recyclable waste. Cardboard and polypropylene have evolved into significant waste products, and the purpose of the study was to focus on the repurposing of both waste materials in determining the structural behaviour of an eco-efficient fibre-reinforced waste concrete. The study extended upon the findings of a precursor study in the development of an eco-efficient fibre-reinforced waste concrete mix. Finely processed municipally collected waste cardboard and recycled polypropylene macro-fibres were incorporated into a concrete mix design for which an experimental program was realised. To achieve this, uniaxial compressive strength, modulus of rupture, modulus of elasticity, and indirect tensile strength of the waste and reference mixtures were determined for 7- and 28-day intervals. Crack mouth open displacement testing was achieved to assess the post-cracking response, and retaining wall beams were prepared and loaded to determine the efficacy of the concrete mixture for low load-bearing structures. Mechanical and post-cracking properties of the hybrid waste concrete underscored excellent performance in comparison to other waste fibre-reinforced concrete mixtures, and superior to those blended with similar kraft fibre volume fractions. Moreover, the structural performance of beams cast from the hybrid mixture closely matched those of the reference mixture, emphasising the viability of the mixture and the role waste materials have in the construction and building industry.

Методы прогнозирования долгосрочного поведения преднапряженных железобетонных мостов

Purpose: to analyze the causes of long-term deformations of prestressed concrete bridge spans and the problems associated with their prediction. To provide a brief overview of existing methods for predicting the long-term behavior of prestressed concrete bridges. The relevance of the problem is due to the need to ensure the reliability and durability of these structures, which are widely used in modern bridge construction. The objective of this paper is to identify factors that influence the development of long-term deformations and to develop approaches for their accurate prediction. Methods: the study examines the long-term deformations of prestressed concrete bridge spans and the problems associated with their prediction using existing bridge structures as examples. Existing methods for predicting long-term deformations in prestressed concrete are evaluated. In particular, the effects of high-strength reinforcement relaxation and the effects of concrete creep and shrinkage are analyzed. Results: accurate prediction of long-term deformations is a complex task that requires consideration of many factors, such as prestress losses, environmental conditions, material properties, and structural characteristics of bridges. The methods discussed in this paper, including the multiplier method and the approximate time interval method, demonstrate their effectiveness in evaluating long-term deformations. However, further research is needed to improve the prediction methods and increase the efficiency of prestressed concrete bridge design. Practical significance: provides design engineers with specific methods and approaches for evaluating the long-term behavior of prestressed concrete bridges. Application of these methods can reduce the risk of excessive deformations and deflections, ultimately ensuring the safety and reliability of bridge structures.

Balancing public interest, fundamental rights, and innovation: The EU’s governance model for non-high-risk AI systems

The question of the concrete design of a fair and efficient governance framework to ensure responsible technology development and implementation concerns not only high-risk artificial intelligence systems. Everyday applications with a limited ability to inflict harm are also addressed. This article examines the European Union's approach to regulating these non-high-risk systems. We focus on the governance model for these systems established by the Artificial Intelligence Act. Based on a doctrinal legal reconstruction of the rules for codes of conduct and considering the European Union's stated goal of achieving a market-oriented balance between innovation, fundamental rights, and public interest, we explore our topic from three different perspectives: an analysis of specific regulatory components of the governance mechanism is followed by a reflection on ethics and trustworthiness implications of the EU´s approach and concluded by an analysis of a case study from an NLP-based, language-simplifying artificial intelligence application for assistive purposes.

Advanced Predictive Modeling of Concrete Compressive Strength and Slump Characteristics: A Comparative Evaluation of BPNN, SVM, and RF Models Optimized via PSO

This study presents the development of predictive models for concrete performance, specifically targeting the compressive strength and slump value, utilizing the quantities of individual raw materials in the concrete mix design as input variables. Three distinct machine learning approaches—Backpropagation Neural Network (BPNN), Support Vector Machine (SVM), and Random Forest (RF)—were employed to establish the prediction models independently. In the model construction process, the Particle Swarm Optimization (PSO) algorithm was integrated with cross-validation to fine-tune the hyperparameters of each model, ensuring optimal performance. Following the completion of training and modeling, a comprehensive comparison of the predictive accuracy among the three models was conducted, with the aim of selecting the most suitable model for incorporation into an optimized objective function. The findings reveal that among the chosen machine learning techniques, BPNN exhibited superior predictive capabilities for the compressive strength of concrete. Specifically, in the validation set, BPNN achieved a high correlation coefficient (R) of 0.9531 between the predicted and actual outputs, accompanied by a low Root Mean Square Error (RMSE) of 4.2568 and a Mean Absolute Error (MAE) of 2.6627, indicating a precise and reliable prediction. Conversely, for the prediction of the concrete slump value, RF outperformed the other two models, demonstrating a correlation coefficient (R) of 0.8986, an RMSE of 9.4906, and an MAE of 5.5034 in the validation set. This underscores the effectiveness of RF in capturing the complexity and variability inherent in slump behavior. Overall, this research highlights the potential of integrating advanced machine learning algorithms with optimization techniques for enhancing the accuracy and efficiency of concrete performance predictions. The identified optimal models, BPNN for compressive strength and RF for slump, can serve as valuable tools for engineers and researchers in the field of construction materials, facilitating the design of concrete mixes tailored to specific performance requirements.

Conceptual design of sandwich walls for shielding against secondary neutrons using MC simulations with FLUKA

FLUKA Monte-Carlo transport code was employed to evaluate the secondary neutron spectra emerging from spherical sandwich shielding configurations composed of concrete and soil, similar to that used at the particle therapy facility MedAustron. This study provides a comparative analysis of neutron spectra attenuated by a concrete-soil-concrete (CSC) sandwich wall shielding configuration versus a full concrete wall design (CCC). Furthermore, we enhanced the shielding performance of the CSC configuration by adding an additional concrete layer (CCSC) to achieve results comparable to the CCC shielding. Two scenarios were tested for shielding performance: (1) primary protons at 100 MeV, and (2) primary carbon ions (C-ions) at 190 MeV/u. Our simulations with primary protons of 100 MeV showed that adding additional internal concrete wall to the CSC configuration, therefore designing the CCSC configuration, the RP performance becomes slightly improved – the HE-peak drops from (1.43 ± 0.11)10−11 to (5.62 ± 0.3)10−12, about 2.5 times. Still, the HE-peak of the exiting neutron spectrum from CCC -(6.29 ± 1.87) 10−13 is about 9 times lower than that exiting CCSC - (5.62 ± 0.3) 10−12.Our simulations with primary C-ions showed that by placing an additional internal concrete wall to the CSC configuration (CCSC) the RP performance becomes slightly improved – the exiting HE peak can be further attenuated from (6.92 ± 0.40)10−9 for CSC to (3.79 ± 0.15)10−9, becoming comparable to the one exiting the CCC configuration, (0.92 ± 0.04)10−9, only 4 times higher. Future research should be focused on improvements of the RP performance of the CCSC, by increasing the soil layer thickness and taking into consideration the humidity (water content) in the soil and concrete and also improve the number of primaries to 109 or even 1010 for better statistical outcome.

Edifices Created with Precast and Prefabricated Components

Typically, the precast and prestressed concrete courses encompass various topics vital for understanding and applying the principles of prestressed concrete design and construction. This paper is designed to educate students on precast and prestressed concrete's theory and practical aspects, emphasizing the importance of understanding the mechanics, design principles, and construction techniques involved. By the end of this paper, one will have a solid foundation in working with these materials and be prepared to apply their knowledge in real-world scenarios. Comprehending the basic principles of prestressing, encompassing a range of systems and techniques employed within the field, is crucial for professionals in the industry. By delving into the core concepts of prestressing, individuals can gain a deeper insight into how this method enhances the structural integrity of various construction projects. Understanding the different systems and strategies utilized in prestressing allows engineers and architects to make informed decisions when designing and implementing their projects.

A review of mixture design and preparation methods for high-performance recycled aggregate concrete

Recycled aggregate concrete (RAC) has been widely investigated for recent decades, during which there are a great deal of findings on the modification of RAC to overcome the drawbacks of RA, i.e. high absorption and low strength. In this paper, four methods for designing and preparing RAC are reviewed, including the particle packing method (PPM), equivalent mortar volume (EMV) method, two-stage mixing approach (TSMA) and distributing-filling coarse aggregate (DFCA) process, and their effects on the properties of RAC is compared to reveal the effective approaches to high-performance preparation of RAC. Among these methods, only TSMA presents a positive effect on the workability of RAC. In terms of the properties of hardened RAC, TSMA improves the compressive strength and penetration resistance by densifying the ITZs around RA, and the developed TSMAsc containing silica fume exhibits better efficiency in improving the properties of RAC. The EMV method and DFCA process are beneficial to the compressive strength, elastic modulus and volumetric stability of RAC, and the effectiveness of the DFCA process is superior to the EMV method, indicating that enhancing the coarse aggregate interlocking effect is an effective approach to obtain high-performance RAC. Furthermore, the combination of TSMA and EMV methods can synthesize the enhancements of ITZs and coarse aggregate interlocking effect, contributing to a further improvement in the properties of hardened RAC. It is conceived that the TSMA and DFCA process can be integrated as a promising combination to realize the high performance of RAC.

An explainable machine learning approach to predict the compressive strength of graphene oxide-based concrete

Graphene oxide (GO) has shown promise in improving concrete strength. Despite its frequent use in cement composites, its effect on concrete properties is less explored. The influence of GO on concrete remains unclear due to various interactions among constituents such as GO type and percentage, Superplasticiser (SP) type and percentage, dispersion technique, and curing age. Therefore, making prediction of compressive strength using simple mathematical formation is challenging. This study represents the first-ever attempt at developing a comprehensively validated machine learning model to predict GO-concrete's compressive strength characteristics by considering all key variable parameters. A comprehensive laboratory experiment program was conducted to collect the data required for training the machine learning (ML) models. Once the ML models were trained, they were used to predict the relationship of each of those input variables towards the compressive strength properties. Four machine learning models—(a) multiple linear regression (MLR), (b) k-nearest neighbour (KNN), (c) random forest (RF) and (d) extreme gradient boost (XGB)—were utilised to model the relationship between input parameters and compressive strength. Also, explainable machine learning (XML) methods were employed to elucidate the impact of mixed constituents on the compressive strength of GO concrete. The results from test predictions showcase that the XGB has attained a coefficient of determination (R2) of 0.981, coefficient of correlation (R) of 0.99, mean square error (MSE) of 0.9, mean normalised bias (MNB) of 0.004, scatter index (SI) of 0.2 with mean absolute error (MAE) of 0.8 MPa for the predictions, outperforming the remaining models. XML highlighted the true impact of GO and the remaining variables, emphasising that the presence of GO significantly improves compressive strength. The optimum GO content and optimum superplasticiser content observed from the experimental work agreed with results obtained from the XML analysis, showing the consistency of the explanation with the experimental results. This implies the superiority of using XML methods in concrete mix design applications in industry.

Resistance to acid, alkali, chloride, and carbonation in ternary blended high-volume mineral admixed concrete

The World Bank study predicts that 4 °C warming will bring high temperatures, sea-level rise, and saltwater intrusion to coastal areas, damaging coastal concrete structures. Increased CO2 from industrialization exacerbates this, necessitating durable, low-carbon concrete. Combined use of fly ash (FA) and ground granulated blast furnace slag (GGBFS) as high-volume OPC replacements boosts performance while reducing concrete’s carbon footprint. In this perspective current study examines the durability of concrete against aggressive agents (H2SO4, MgSO4, NaCl, and CO2) causing premature deterioration of concrete structures. Initially, three cost-effective sustainable concrete mix designs were developed, incorporating 50% replacement of OPC with locally available supplementary cementitious materials, specifically FA and GGBFS. These mixes were then evaluated for their mechanical and durability performances. The impact of aggressive ions (SO4 2−, Cl−, and CO3 2−) was studied by examining the changes in mechanical performance and phase assemblages. Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) techniques were used to estimate the phase compositions. Ternary blended concrete having 50% OPC+ 30% GGBFS + 20% FA exhibited optimal synergistic performance, enhancing pozzolanic and hydraulic reactions for better resistance to harmful ions. The sorptivity test confirmed that as the GGBFS content increased, the sorption rate decreased, indicating the higher reactive nature of GGBFS to that of FA. Deleterious compounds formed due to the action of SO4 2-, Cl-, and CO3 2- were identified to be ettringite (Ca6Al2(SO4)3(OH)12.32H2O, AFt) and gypsum (CaSO4.2H2O, Gy), Friedel’s salt (Ca4Al2(OH)12Cl2.4H2O, Fs) and polymorphs of calcium carbonate (CaCO3), respectively through TG mass loss curve. These results were corroborated by FTIR analysis, which showed predominant characteristic bands at 662 cm−1 for SO4 2−, 459 cm−1 for Mg–O stretching, 790 cm−1 for Al–OH bending, and 1431-1443 cm−1 for C–O, confirming the presence of the deleterious compounds.

Long-term study on the mechanical properties of the ITZ in coral aggregate concrete and its impact on material durability

The rich coral reef resources on the island make coral aggregate concrete (CAC) widely applied in marine engineering construction. This study extensively investigates the mechanical properties of the interfacial transition zone (ITZ) within CAC and its consequential influence on the overall mechanical performance of concrete. This article uses the interface bonding strength method, microscopic hardness technology, and X -ray diffraction (XRD) test. It is found that the performance of ITZ is critical to the overall performance of CAC. Optimizing the formation of cement paste and regulating the generation of hydrophilic products can significantly enhance the interface strength and durability of concrete. Our findings demonstrate a clear mathematical correlation between the splitting tensile strength of interface bonding and the microhardness value of the ITZ, offering a novel theoretical framework and practical approach for concrete structure design. The characteristics of hydrophilic products within the ITZ, such as the orientation and dimensions of CH crystals, directly influence the intricate properties of concrete. Therefore, in the process of concrete preparation and construction, attention should be paid to the control and optimization of these micro-structural parameters.

Calcined Clays as Concrete Additive in Structural Concrete: Workability, Mechanical Properties, Durability, and Sustainability Performance.

Calcined clays (CCs) as supplementary cementitious materials (SCMs) can be a promising option to reduce clinker content and CO2 emissions in eco-friendly concretes. Although CCs as components of composite cements in combination with Ordinary Portland Cement (OPC) and limestone powder (LSP) have attracted industry interest, their use as concrete additives is limited. This study investigates the effects of the addition of CCs on the fresh and hardened properties of industry-standard ready-mixed concretes. Four concrete mix designs, each with three superplasticizer dosages, were tested, resulting in 12 variations. The CCs used, which are typical of 2:1 bentonite clays with low metakaolin content, reflect the clays available in Germany. The results showed that CCs significantly influenced the workability, which could be controlled with a high superplasticizer dosage. Increased CC contents reduced bleeding tendencies, which was beneficial for certain structural applications. Early age strength decreased with CCs, but the 28-day strength exceeded that of pure OPC concretes up to 30 wt% CCs. Resistance to CO2-induced carbonation decreased with higher levels of CCs but was comparable up to 15 wt%. Freeze-thaw damage decreased, and chloride migration resistance improved due to a denser microstructure. The global warming potential (GWP) of the concretes tested is in line with that reported in the literature for concretes made from highly blended cements, suggesting that CCs can improve the sustainability of concrete production.

Assessment of residual bonding performance for bimetallic steel bar-seawater concrete after exposure to high temperature

The bimetallic steel bar (BSB) is a new type of corrosion-resistant reinforcement material composed of carbon steel and stainless steel, which can effectively improve the durability of structures. Reinforced concrete structural strength depends on the bond between steel bars and concrete. This mechanism can be compromised after exposure to a fire, but it has been less considered in research, and is not addressed in concrete design codes. To evaluate the residual bearing capacity of BSB reinforced concrete structures after a fire, it is necessary to clarify the bonding performance between BSBs and concrete after exposure to high temperatures. In this study, 45 BSB-seawater concrete (BSBSC) pull-out specimens were prepared, and the bonding performance of BSBSC after high temperature was studied by heating treatment and pull-out tests. The results showed that the BSBSCs changed from bluish-gray to grayish-yellow with the increase in heat treatment temperature. After exposure to 400 °C, cracks appeared on the surface of BSBSCs. As the heat treatment temperature increased, the slope of the rising and descending stages for the bond stress-strain curve decreased gradually. In addition, as the thickness of the concrete cover increased, the bonding strength of BSBSCs also improved. The higher the heat treatment temperature, the less significant the improvement effect. Based on test results, a predictive model for the bonding performance characteristics of BSBSCs after high temperature was proposed, and a constitutive model for bonding stress-slip relationship was established.

Geotechnical Forensic Investigations of a Gravity Dam: Addressing Seepage and Sliding Problems in the Basalt Foundations of Karjan Dam, Gujarat, India

Geotechnical forensic engineering plays a crucial role in identifying and mitigating potential issues in large gravity dams. The Karjan Dam in Gujarat, India, a 100-meter-high gravity dam built 38 years ago on Deccan basalt, encountered significant geotechnical challenges during construction due to early investigation oversights. These oversights failed to detect sub-horizontal weathered rock seams within the basalt during the pre-construction investigations, which could have posed significant seepage and sliding risks during the dam's operation. Subsequent detailed investigations during the construction phase revealed that these seams extended throughout the foundations of the dam blocks. In-situ shear tests were conducted to determine the shear parameters, namely cohesion (C) and the angle of internal friction (ϕ) of the seams. The test results indicated low shear strength parameters, necessitating a re-evaluation of the dam's safety. Stability analysis revealed that the spillway and certain non-overflow blocks were at risk of sliding and seepage after reservoir filling. To address these geotechnical challenges, a combination of treatments—including concrete shear keys, grouting, and design enhancements—was implemented to prevent sliding and control seepage. The timely forensic investigation and treatment during the construction stage ensured the dam's safety, which has operated without issues since 1986. This study underscores the critical importance of integrating engineering and geological assessments at various stages of dam construction. Re-evaluating and addressing evolving foundation conditions, particularly during construction, is essential for applying effective treatments to prevent dam failure during operation. The findings from this case study provide valuable geotechnical insights required for enhancing the safety and resilience of dam infrastructure globally.

Report of RILEM TC 281-CCC: A critical review of the standardised testing methods to determine carbonation resistance of concrete

The chemical reaction between CO2 and a blended Portland cement concrete, referred to as carbonation, can lead to reduced performance, particularly when concrete is exposed to elevated levels of CO2 (i.e., accelerated carbonation conditions). When slight changes in concrete mix designs or testing conditions are adopted, conflicting carbonation results are often reported. The RILEM TC 281-CCC ‘Carbonation of Concrete with Supplementary Cementitious Materials’ has conducted a critical analysis of the standardised testing methodologies that are currently applied to determine carbonation resistance of concrete in different regions. There are at least 17 different standards or recommendations being actively used for this purpose, with significant differences in sample curing, pre-conditioning, carbonation exposure conditions, and methods used for determination of carbonation depth after exposure. These differences strongly influence the carbonation depths recorded and the carbonation coefficient values calculated. Considering the importance of accurately determining carbonation potential of concrete, not just for predicting their durability performance, but also for determining the amount of CO2 that concrete can re-absorb during or after its service life, it is imperative to recognise the applicability and limitations of the results obtained from different tests. This will enable researchers and practitioners to adopt the most appropriate testing methodologies to evaluate carbonation resistance, depending on the purpose of the conclusions derived from such testing (e. g. materials selection, service life prediction, CO2 capture potential).

Effect of Concrete Mix Design Factors on Static Yield Stress Changes due to Vibration

Effect of Concrete Mix Design Factors on Static Yield Stress Changes due to Vibration