An increased interest in decreasing the environmental impact of the construction sector andin vertical urbanization has renewed attention to timber as a primary structural materialin multi-story buildings. This study investigated whether an existing 10-story reinforcedconcrete (RC) residential building can be redesigned as an equivalent mass-timber structurewhile satisfying the same structural performance requirements. It addressed the lackof like-for-like building-scale comparisons that redesigned an existing multi-story RCresidential building into a functionally equivalent mass-timber scheme. A real RC buildingin Gävle, Sweden, was modeled, analyzed, and designed using StruSoft FEM-Designsoftware in accordance with the Eurocodes and the Swedish National Annex, after whichall main structural elements were systematically replaced with timber. Through iterativeadjustments of member sizes, support conditions, and added reinforcing elements, both theRC and timber schemes were verified with respect to load-bearing capacity, serviceability,and global stability under identical load combinations. The RC and timber buildingsreached maximum utilization ratios of 99% and 98%, respectively; displacements werehigher in the timber building but remained within serviceability limits, and both systemswere classified as globally stable. The timber alternative reduced the total structural weightto about 19% of the RC building and roughly halved the maximum vertical reaction forces,at the expense of additional beams, columns, and basement wall segments. Moreover, thisarticle developed an equivalent-design methodology for material substitution, a bottom-upreinforcing elements logic that resolved serviceability and stability constraints in tall timber,and a performance trade-off map based on structural performance, offering guidance forfuture mass-timber design.

Decarbonization of the concrete industry has arisen as one of the main priorities for the construction sector in order to mitigate the negative climate impact associated with construction. The carbon emissions of concrete mainly originate from the production of cement, and it is essential to find supplementary cementitious materials (SCMs) to achieve eco-friendly construction materials. The use of tailings as SCMs could reduce the carbon footprint of concrete, as well as improve the environmental impact of waste management within the mining sector. To investigate the effects of using lead–zinc tailings as a partial replacement for ordinary Portland cement (OPC), an experimental study was conducted. Two types of lead–zinc tailings were utilized in the experiments to replace 10% and 20% of OPC. A mechanical activation method was adopted using a vibratory cup mill. The effects of activation on the tailings’ particle size distributions and mineralogy were evaluated. The results indicated that the activation was insufficient to promote the pozzolanic activity in T1 and only partially promoted it in T2. A total of 18 different tailing-based mortar (TBM) specimens were produced from the raw and activated tailings, and their flowability, setting time, and compressive strengths after 7, 28, and 90 days were evaluated. The microstructures of the specimens were analyzed using scanning electron microscopy with energy dispersive X-ray spectroscopy. No alteration of mineralogy was observed in T1 after activation; however, a reduction in muscovite was observed in T2. The TBM specimens with 10% activated tailings exhibited comparable 28-day compressive strengths to the control specimen. For the replacement level above 10%, there was a loss of compressive strength at 28 days, both for the activated and raw tailings and for both T1 and T2. Evaluation of the microstructure showed that the use of tailings caused regions in the cement matrix with high metal concentrations. Microcracks could be observed in or around such grains in several cases. The study demonstrated that 10% of OPC can be replaced by lead–zinc tailings while retaining the compressive strength of the specimens.

Sometimes only a portion of the surface of a concrete element is loaded, which causes stressconcentration in that region. To safely transfer concentric loads to concrete componentssuch as column bases, short cantilevers, superstructure piers, post-tensioned elements,and support anchors, it is imperative to investigate the local compressive characteristics ofconcrete. To learn more about this subject, further research is required, as there are currentlyinsufficient studies in this field. Therefore, the local compressive behavior of concrete underconcentric stresses is the main focus of this work. Concrete is represented as block sampleswith dimensions of 200 × 200 × 250 mm. A stiff steel plate is used to apply concentricloading on the surface of the samples. The primary parameters are the bearing platedimensions, shape (square, rectangle, and circular with varying areas), and rectangularity. Additionally, the bearing plate’s movement is examined. The stress-slip curves, ultimatebearing strengths, failures, and related slippages of the tested samples are discussed. The findings revealed that the upper surface of the concrete samples exhibited localizeddeterioration beneath the bearing plate. Additionally, the ultimate bearing strength of thesample loaded with the 6 × 6 cm square plate was 163% greater than that of the sampleloaded with the 10 × 10 cm square plate. Furthermore, the sample loaded with the circularplate with a diameter of 4 cm had an ultimate bearing strength that was 181% greater thanthe sample loaded with the circular plate with a diameter of 11 cm. It is clear that thesamples loaded with a circular plate of varying diameters had an ultimate bearing strengththat was 8.5–11% higher than the samples loaded with a square plate of varying lengths.

The integrity of the structure and load capacities of reinforced concrete (RC) columns are severely impacted by corrosion-induced reinforcing steel losses. This study examines an innovative strengthening technique incorporating near-surface mounted (NSM) steel or glass fiber-reinforced polymer (GFRP) bars, combined with an external layer of engineered cementitious composite (ECC) or ultra-high-performance concrete (UHPC) reinforced with a GFRP mesh. The experimental results demonstrated that UHPC provided superior confinement compared with ECC jackets, leading to the highest load capacity enhancement. Incorporating NSM steel bars with ECC (Group 3 (G3)) significantly improved performance, increasing ultimate load capacity by 25%–32%, with energy absorption increasing up to 3.9 times compared with the control column. The combination of NSM bars with external jacketing proved to be the most effective, particularly when NSM GFRP bars were used alongside UHPC, resulting in a 49% increase in load capacity and a substantial improvement in energy absorption. Additionally, finite element models were developed and showed good agreement with the experimental findings, further validating the proposed strengthening technique. The model was extended for a parametric study examining the effect of main reinforcement diameter. The results highlight the important role of the reinforcement diameter in enhancing column strength. Increasing the reinforcement diameter led to progressive strength improvements, but the efficiency of additional reinforcement decreased at larger diameters.

This study presents a comprehensive analysis of self-healing concrete technologies, focusing on autogenous and autonomous self-healing methods, through a systematic literature review of peer-reviewed articles. The autogenous self-healing method relies on the natural hydration and carbonation processes of unhydrated cement particles, enhanced by additives such as fly ash, slag, and superabsorbent polymers. It is effective for small cracks (<200 μm), environmentally favorable, and cost-efficient, although it is limited by relatively slow healing rates and reduced performance over time. The autonomous self-healing method incorporates external agents, primarily bacteria like Bacillus cohnii and Bacillus sphaericus, encapsulated in protective carriers. These bacteria precipitate calcium carbonate (CaCO3) upon activation, sealing cracks up to approximately 1240 μm. While generally more effective in terms of healing efficiency and durability, the autonomous self-healing method involves higher production costs. Life cycle assessment results indicate that the autonomous self-healing concrete can exhibit up to 85% higher environmental impact during the production phase than conventional concrete. However, during the production phase, the autogenous self-healing method shows about 32% higher CO2 emissions than the autonomous method. Results from investigating the mechanisms, performance, repairability, environmental impacts, and economic aspects in this study demonstrate that bacterial concentration and nutrient type critically influence mechanical properties, with optimal strength gains at 105 cells/mL. Both techniques reduce corrosion risk and extend service life, with the autonomous self-healing method displaying superior performance in harsh environments. However, the autogenous self-healing method is more feasible for large-scale applications due to lower costs and simpler implementation. The study concludes that method selection should align with project-specific durability, sustainability, and economic goals.

Reinforced concrete (RC) columns with insufficient steel reinforcement present a significant structural concern. This issue is most commonly found in aging buildings, poorly constructed members, or structures designed before the adoption of modern codes. This study investigates the effectiveness of external hybrid strengthening techniques in enhancing the axial load-bearing capacities of such deficient columns. A series of rectangular RC column specimens with intentionally reduced longitudinal reinforcement ratios were tested under axial compression in the laboratory and simulated using ABAQUS software to evaluate structural performance. The specimens were strengthened using a combination of near-surface-mounted (NSM) steel or glass fiber-reinforced polymer bars with externally bonded glass fiber textile mesh covered with different types of high-strength concrete to form a hybrid strengthening solution. The influence of different strengthening configurations on the columns’ ultimate load, energy absorption, and failure modes was evaluated. The results show that the proposed hybrid systems improve the structural behavior of deficient RC columns. They also demonstrate that these systems significantly enhance the structural performance of deficient RC columns, achieving increases in the axial load-bearing capacity ranging from 11% to 78% compared with the deficient specimens. Additionally, the energy absorption capacity improved by up to 382%, highlighting the effectiveness of the combined NSM and external confinement techniques. Furthermore, these systems provide a practical solution for field engineers by helping them strengthen existing structures with inadequate internal reinforcement.

Bearing layers are commonly produced using coarse aggregates, gravel, and filler, where excessive filler content can reduce drainage performance. This study investigates an alternative production method for converting a standard 0/32 bearing layer into a draining bearing layer through the controlled removal of fines at two NCC rock quarries (Släsh and Hammarby, Sweden), where the current product typically contains approximately 4–5% filler. Freshly crushed 0/32 material (with a moisture content of 1–2%) was processed using a vibration-free harp screen that was designed and built. The standard product was run through the harp under full-scale quarry conditions (5 t per test and a 45° inclination) using four different grid and board-cover configurations. The produced material was analyzed in the laboratory to determine the resulting filler content. Digiroad finite element simulations were performed to compare harp layouts and the expected generation of residual material. The results showed that harp sieving reduced the measured filler (< 0.063 mm) from 3.7% to between 1.8 and 2.6%. The 25% grid and 75% board configuration provided the best performance, achieving 2.6% filler, with the lowest observed amount of residual material and a grading most closely matching AMA DCB.33/1. Similarly, the simulations indicated the lowest residual-material mass for the 25% grid layout (71.30 kg). The developed harp screen offers a practical solution for improving drainage performance, thereby contributing to more sustainable and safer infrastructure.

Cast-in-place ground-supported concrete slabs (GSCSs) are used as floors in many facilities such as factories, workshops, garages, and airports (i.e., rigid pavements). These slabs may be subjected to repeated impact loads caused by vehicle loads, the dropping of heavy loads, and aircraft landing loads on runways. This research presents an experimental and numerical study to investigate the behavior of these slabs under impact loads. The experimental program consists of 18 concrete slabs with dimensions of 400 mm × 400 mm × 100 mm. Some variables were studied experimentally, such as the reinforcement ratio of these slabs and the amount of the impact force (represented by the drop height). Unreinforced slabs and slabs reinforced with steel reinforcement or a geogrid mesh made of knitted polyester ribs were tested. ABAQUS software was employed to study the failure mode and crack distribution of these slabs numerically. The accuracy of the proposed numerical model was verified by modeling the tested slabs and comparing the numerical results with the experimental results. From the study results, it is clear that the reinforcement significantly improves the impact performance of GSCSs, transforming their failure behavior from brittle to more ductile and tough. The combined use of impact strength and ductility factors provides an integrated measure of slab performance, offering valuable guidance for the design of protective structures, pavements, and industrial flooring under impact loading.

This study explores the feasibility of using municipal solid waste incineration bottom ashes (MSWIBAs) as a partial replacement for cement in concrete with respect to the fresh and hardened properties of concrete. MSWIBA samples from five Swedish incineration plants (BA1–BA5) were collected and analyzed for their mineral composition and particle size distribution (PSD). The samples (BA3 and BA5), exhibiting better pozzolanic behavior and particle sizes closer to those of conventional cement, were selected for further detailed study. Mechanical activation was performed on the BA3 and BA5 samples. Concrete mixes were prepared with 10% and 20% (by mass) cement replacements utilizing raw and activated BA3 and BA5 samples. The resulting concrete specimens were evaluated through slump, density, and compressive strength tests at 7, 28, and 56 days. The results showed that activated MSWIBAs improved the workability of the concrete specimens compared with the control concrete mix, and the density of the concrete decreased with increasing the MSWIBA content. The compressive strength of the concrete mixes generally decreased as the replacement level of MSWIBAs increased. At 56 days, the concrete mix with 10% raw BA5reached about 77% of the compressive strength of the control concrete mix, whereas mixes with 20% raw or activated MSWIBAs reached about 58%. The concrete mix with BA3 performed better than the mix with BA5 at 7 days, while the concrete mix with BA5 showed higher later-age compressive strength. In addition, mechanical activation of MSWIBAs did not significantly improve compressive strength of concrete mixes. Despite the reduction in compressive strength when using MSWIBAs, this sustainable concrete contributes to the development of climate-friendly concrete and offers potential environmental benefits.

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.