Expanding the world’s infrastructure drives up demand for building materials, particularly ordinary Portland cement (OPC) concrete, whose high carbon dioxide (CO₂) emissions have a detrimental effect on the environment. To address this issue, researchers looked into employing alternative supplementary cementitious materials (SCMs), including metakaolin (MK), which is derived from calcined kaolin clay with pozzolanic properties, to partially or completely replace OPC in concrete. This review article examines the MK’s application in alkali-activated materials (AAMs) and OPC-based concrete. By interacting with calcium hydroxide, MK functions as a pozzolanic additive for OPC concrete, enhancing its mechanical qualities and durability. The use of MK as a source material in AAMs, a newly developed class of sustainable binders, is also covered in this article. The effects of different combinations of MK with additional SCMs, including fly ash (FA), ground granulated blast furnace slag (GGBFS), silica fume, and rice husk ash, on the characteristics of alkali-activated concrete both in its fresh and hardened states, are compiled. The majority of the articles considered in this study are from the past decade, while some relevant articles from 2014 and earlier are also taken into account. The results showed that adding MK to concrete in combination with FA or GGBFS has excellent synergistic effects on microstructural development, pozzolanic activity, and strength increases. In particular, the MK–FA mix demonstrated the most encouraging performance gains. Because of its large surface area, the use of nano-MK helped achieve a denser geopolymer structure and improve mechanical properties. The best curing temperatures for MK-based geopolymers to gain strength were found to be between 40 and 80°C for a total of 28 days. The review also pointed out that the compressive strength and geopolymerization process of MK-based geopolymers were enhanced by increasing the mass ratio of Na₂SiO₃ to NaOH and NaOH concentration. Nevertheless, geopolymerization was hampered by unnecessarily high alkali concentrations. Moreover, the compressive strength was increased by partially replacing MK with TiO₂ or GGBFS. The synergistic effects of combining MK with other SCMs to improve concrete performance highlight the potential of MK-based solutions in lowering the environmental footprint of concrete buildings.

Reinforced concrete (RC) walls are mainly used in RC structures to resist gravity and lateral forces. These structural elements may need to be upgraded to withstand additional forces and extend their life cycle. Therefore, it is crucial to provide effective strengthening techniques using low-cost sustainable materials under optimal conditions to rehabilitate RC walls. This study presents an experimental and numerical investigation of reinforced normal concrete (NC) walls strengthened with near-surface mounted (NSM) steel bars, confined with or without an externally bonded reinforced (EBR) galvanized steel sheets (GSSs). A total of six RC walls were constructed, loaded, and tested to failure. The examined parameters included the type of strengthening technique, materials used, and the position and configuration of the strengthening. Both EBR and NSM techniques were applied using GSSs and steel bars, respectively. The configurations were introduced in vertical and horizontal positions to resist gravity and lateral forces, respectively. The experiments revealed that these parameters significantly influenced the crack control, energy absorption, mode of collapse, and ultimate load capacity. Nonlinear three-dimensional finite element models were developed and verified against experimental results, achieving a validation accuracy of 95% on average. This was followed by a parametric study investigating the effect of confinement with or without vertical reinforcements. Both experimental and numerical results confirmed that the strengthening could increase the ultimate load capacity from 20% to 38%.

A detailed examination was carried out by substituting waste ceramic powder (WCP) for specific ratios of cement in concrete. To achieve this, five different WCP percentages (10%, 20%, 30%, 40%, and 50%) were used in manufacturing of concrete. First, the workability and slump values in the fresh state of concrete were determined by performing a slump test. Subsequently, several tests, including compressive strength (CS), splitting tensile strength (STS), and flexural strength (FS), were conducted on the specimens to assess the effectiveness of concrete fabricated using WCP. Variations in the strength were determined in terms of the various amounts of WCP. The findings demonstrated that by including WCP at levels of 10%, 20%, 30%, 40%, and 50%, there were corresponding reductions in CS of 5.8%, 21.8%, 47.1%, 63.2%, and 73.6%, respectively. The decreases in STS were 6.3%, 13.8%, 35.2%, 49.7%, and 65.4%, respectively, when a concrete STS value of 1.59 MPa was considered. Similarly, when the WCP content increased, FS was reduced by 15.3%, 21.4%, 31.6%, 44.9%, and 54.1%, respectively. This is very significant because it represents one of the key issues in calculating the optimal quantity of WCP in relation to both the strength and the amount of WCP utilized. Furthermore, taking into account our experimental research and previous studies on concrete produced utilizing WCP, straightforward equations were provided for practical use to predict CS, STS, and FS. In addition, scanning electron microscopy was done to validate the findings obtained from the experimental part of the study. The artificial neural network modeling technique was adopted to estimate the concrete properties with average coefficients of determination (R²) as 0.945 (CS), 0.901 (STS), and 0.856 (FS) with K-fold cross-validation.

Recent years have witnessed a significant growth in the research and development of additive manufacturing methods involving concrete and cementitious materials, with technologies like three-dimensional (3D) printing becoming more widely used in the construction industry. Construction has the possibility to be revolutionized, not only in the context of cost savings but also in the context of increased sustainability and functionality. 3D printing of concrete is a cutting-edge technology that has the potential to speed up construction, reduce labor costs, give architects more creative freedom, improve precision, obviate requirements for formwork, and result in less construction wastes. In addition, 3D printing can be a long-term solution for both economy and environment. Even though 3D printing in concrete has made tremendous strides recently, developing an effective 3D-printable material that decreases material usage and enhances performance is critical for carbon dioxide reduction. Robust geopolymer formulations for 3D printing concrete technology in current construction applications have emerged as the subject of much research among scientists to find novel ways to circumvent this constraint. This study intends to highlight the current state of the art in developing 3D-Printed Geopolymer Concrete (3DPGC) with a comprehensive review related to the material composition, mix design, and mixing regimes on rheology of 3DPGC. The rheology of 3DPGC in terms of printability and buildability is discussed. The mixing regimes employed for the preparation of one-part and two-part 3DPGC are tabulated and commented on. Lastly, the research gaps are identified and summarized, and several research directions are also provided for future investigations to expedite the ubiquitous use of 3DPGC in versatile construction applications.

With concrete’s key role in construction and infrastructure, the reduction of its carbon footprint is critical for addressing global carbon emissions. One strategy to reduce environmental impact from concrete production is to replace cement clinker or fine aggregates in concrete with industrial wastes. Mine tailings, being a high-volume under-utilized resource, possess properties making it suitable for use as a partial substitute for cement or fine aggregates. This review article provides an overview of the recent findings within the topic of tailings-based concrete (TBC). Many of the identified publications aimed to describe the mechanical performance of TBC, and to optimize the concrete mix with respect to the strength and durability. The recommended cement replacement ranged from 5 to 25% and the recommended fine aggregate replacement ranged from 20 to 60%. In general, the compressive strength was decreased with increasing use of tailings as a replacement of cement. For the use of tailings as replacement for fine aggregates, the correlation was more complex, normally the mechanical performance enhanced at low replacement levels, until it reached an optimum after which it decreased. CO2 savings for replacing fine aggregate with tailings were up to 12% and for the cement replacement up to 30%. When assessing the environmental performance, most of the publications did not account for the loss of its mechanical performance, which could lead to the risk of underestimating the environmental impact. This review not only provides a basis for understanding the mechanical, toxicological, and environmental performances of TBCs, but also links the perspectives together, unveiling the connections between them. Moreover, this review presents an organized overview of the topic of TBC and points out topics for future research.

Bitumen, aggregate, and air void (VA) are the three primary ingredients of asphalt concrete. VA changes over time as a function of four factors: traffic loads and repetitions, environmental regimes, compaction, and asphalt mix composition. Due to the high as-constructed VA content of the material, it is expected that VA will reduce over time, causing rutting during initial traffic periods. Eventually, the material will undergo shear flow when it reaches its densest state with optimum aggregate interlock or refusal VA content. Therefore, to ensure the quality of construction, VA in asphalt mixture need to be modeled throughout the service life. This study aims to implement a hybrid evolutionary polynomial regression (EPR) combined with a teaching–learning based optimization (TLBO) algorithm and multi-gene genetic programming (MGGP) to predict the VA percentage of asphalt mixture during the service life. For this purpose, 324 data records of VA were collected from the literature. The variables selected as inputs were original as-constructed VA, 𝑉𝐴𝑜𝑟𝑖𝑔 (%); mean annual air temperature, 𝑀𝐴𝐴𝑇 (°F); original viscosity at 77 °F, 𝜂𝑜𝑟𝑖𝑔,77 (Mega-Poises); and 𝑡𝑖𝑚𝑒 (months). EPR-TLBO was found to be superior to MGGP and existing empirical models due to the interquartile ranges of absolute error boxes equal to 0.67%. EPR-TLBO had an R2 value of more than 0.90 in both the training and testing phases, and only less than 20% of the records were predicted utilizing this model with more than 20% deviation from the observed values. As determined by the sensitivity analysis, 𝜂𝑜𝑟𝑖𝑔,77 is the most significant of the four input variables, while time is the least one. A parametric study showed that regardless of 𝑀𝐴𝐴𝑇, 𝜂𝑜𝑟𝑖𝑔,77, of 0.3 Mega-Poises, and 𝑉𝐴𝑜𝑟𝑖𝑔 above 6% can be ideal for improving the pavement service life. It was also witnessed that with an increase of 𝑀𝐴𝐴𝑇 from 37 to 75 °F, the serviceability of asphalt concrete takes 15 months less on average.

Cross-laminated timber (CLT) is one of the most sustainable, robust, and green building materials nowadays and is normally used for walls, floors, or roofs. The number of studies on CLT has increased significantly since 2010, which shows the acceptance and needs of CLT. Connection systems, rolling shear performance, and sustainability are the popular and main research topics within CLT, including wooden connections, metallic connections, adhesive and rod connections, aspect ratio, bonding performance, life cycle assessment, carbon emission, and environmental impact. Based on these three branches, the current study conducts a literature review on CLT. This review article aims to provide a valuable view and better understanding of CLT, which are linked to (1) promoting the usage of CLT and (2) summarizing the weaknesses of the CLT’s research. This article presents a full background of the CLT research and gives potential research directions for CLT as a structural material. It revealed that the design and analytical methodologies for novel timber and steel connections are the main trends. As for the CLT’s rolling shear performance, standardized testing protocol, environmental impact, and bonding quality need further development. Furthermore, the data collection, selection, and influence of different policies are important for the CLT’s sustainability assessment.

In the pursuit of creating more sustainable and resilient structures, the exploration of construction materials and strengthening methodologies is imperative. Traditional methods of relying on steel for strengthening proved to be uneconomical and unsustainable, prompting the investigation of innovative composites. Fiber‐reinforced polymers (FRPs), known for their lightweight and high‐strength properties, gained prominence among structural engineers in the 1980s. This period saw the development of novel approaches, such as near‐surface mounted and externally bonded reinforcement, for strengthening of concrete structures using FRPs. In recent decades, additional methods, including surface curvilinearization and external prestressing, have been discovered, demonstrating significant additional benefits. While these techniques have shown the enhanced performance, their full potential remains untapped. This article presents a comprehensive review of current approaches employed in the fortification of reinforced cement concrete structures using FRPs. It concludes by identifying key areas that warrant in‐depth research to establish a sustainable methodology for structural strengthening, positioning FRPs as an effective replacement for conventional retrofitting materials. This review aims to contribute to the ongoing discourse on modern structural strengthening strategies, highlight the properties of FRPs, and propose avenues for future research in this dynamic field.

The purpose of this book is to expand the knowledge and skills of civil and structural engineers and researchers and help them better understand, design, and analyze civil engineering applications. This book examines advancements in structural integrity and failure and underground construction. It offers profound insights into the mechanisms that can lead to the integrity or failure of structures and result in safe underground construction. It provides details on the fundamental principles, theories, behavior, and performance of different structural elements and underground construction. The book delves into the mechanics, design, and construction of reinforced concrete structures. It explores the design principles applied to reinforced concrete structures and considers critical structural elements like beams, slabs, columns, and foundations. It also demonstrates various advances in reinforced concrete technology, including high-performance concrete, fiber-reinforced concrete, self-compacting concrete, and the use of nanomaterials. It describes methods for the analysis and evaluation of reinforced concrete structures, non-destructive testing methods, structural health monitoring, finite element analysis, and causes of failure. In addition, the book proposes a design model for determining the flexural bearing capacity of reinforced concrete beams having reinforcement steel with reduced modulus of elasticity. Moreover, the book investigates the effects of loading rates on the mechanical properties of structural steel. It also evaluates the formation of welding defects in the process of connecting steel structures, which is inevitable, from the aspect of failure mechanics. In addition, it utilizes an equivalent shell-wire model to propose a simple accurate technique for nonlinear assessment of reinforced concrete shear walls with less computational cost. The book introduces tunnel design theory and method, support structure systems, construction technology, and equipment under complex geological conditions. Furthermore, it highlights procedures to design efficient dewatering systems considering the working conditions, stability, and impacts generated in the vicinity of construction, and to examine the state of retaining walls by using hydrogeological tools. Finally, it outlines the online monitoring and intelligent diagnosis mechanism of key equipment in the subway ventilation system.

The dynamic analysis of municipal solid waste (MSW) is essential for optimizing landfills and advancing sustainable development goals. Assessing damping ratio (D), a critical dynamic parameter, under laboratory conditions is costly and time-consuming, requiring specialized equipment and expertise. To streamline this process, this research leveraged several novel ensemble machine learning models integrated with the equilibrium optimizer algorithm (EOA) for the predictive analysis of damping characteristics. Data were gathered from 153 cyclic triaxial experiments on MSW, which examined the age, shear strain, weight, frequency, and percentage of plastic content. Analysis of a correlation heatmap indicated a significant dependence of D on shear strain within the collected MSW data. Subsequently, five advanced machine learning methods—adaptive boosting (AdaBoost), gradient boosting regression tree (GBRT), extreme gradient boosting (XGBoost), random forest (RF), and cubist regression—were employed to model D in landfill structures. Among these, the GBRT-EOA model demonstrated superior performance, with a coefficient of determination (R2) of 0.898, root mean square error of 1.659, mean absolute error of 1.194, mean absolute percentage error of 0.095, and an a20-index of 0.891 for the test data. A Shapley additive explanation analysis was conducted to validate these models further, revealing the relative contributions of each studied variable to the predicted D-MSW. This holistic approach not only enhances the understanding of MSW dynamics but also aids in the efficient design and management of landfill systems.