Search Results (458)

The article presents research on concrete creep in bridge structures, focusing on the influence of concrete mix composition and the use of advanced rheological models with fractional-order derivatives. Laboratory tests were performed on nine mixes varying in blast furnace slag content (0%, 25%, and 75% of cement mass) and air-entrainment. The results were used to calibrate fractal rheological models—Kelvin–Voigt and Huet–Sayegh—where the viscous element was replaced with a fractal element. These models showed high agreement with experimental data and improved the accuracy of creep prediction. Comparison with Eurocode 2 revealed discrepancies up to 64%, especially for slag-free concretes used in prestressed bridge structures. The findings highlight the important role of mineral additives in reducing creep strains and the need to consider individual mix characteristics in design calculations. In the context of modern bridge construction technologies, such as balanced cantilever or incremental launching, reliable modeling of early-age creep is particularly important. The proposed modeling approach may enhance the precision of long-term structural behavior analyses and contribute to improved safety and durability of concrete infrastructure. Full article

Ferronickel slag and ground granulated blast-furnace slag (GGBFS) are solid waste by-products from the metallurgical industry. When incorporated into concrete, they help promote resource utilization, reduce hydration heat, and lower both solid waste emissions and the carbon footprint. To facilitate the application of ferronickel slag–GGBFS concrete in 3D printing, this study examines how aggregate size and nozzle diameter affect its performance. The investigation involves in situ printing, rheological characterization, mechanical testing, and scanning electron microscopy (SEM) analysis. Results indicate that excessively large average aggregate size negatively impacts the smooth extrusion of concrete strips, resulting in a cross-sectional width that exceeds the preset dimension. Excessively small average aggregate size results in insufficient yield stress, leading to a narrow cross-section of the extruded strip that fails to meet printing specifications. The extrusion performance is closely related to both the average aggregate size and nozzle diameter, which can significantly influence the normal extrusion stability and print quality of 3D printed concrete strips. The thixotropic performance improves with an increase in the aggregate size. Both compressive and flexural strengths improve with increasing aggregate size but decrease with an increase in the printing nozzle size. Anisotropy in mechanical behavior decreases progressively as both parameters mentioned increase. By examining the cracks and pores at the interlayer interface, this study elucidates the influence mechanism of aggregate size as well as printing nozzle parameters on the mechanical properties of 3D printed ferronickel slag–GGBFS concrete. This study also recommends the following ranges. When the maximum aggregate size exceeds 50% of the nozzle diameter, smooth extrusion is not achievable. If it falls between 30% and 50%, extrusion is possible but shaping remains unstable. When it is below 30%, both stable extrusion and good shaping can be achieved. Full article

The aviation industry is under increasing pressure to reduce its environmental impact while maintaining safety and performance standards. One promising area for improvement lies in the use of sustainable materials in airport infrastructure. One of the issues preventing uptake of emerging sustainable technologies is the lack of guidance relating to the opportunities, potential benefits, associated risks and an implementation plan specific to airport pavements. This research reviewed opportunities to incorporate waste materials into rigid airport pavements, focusing on concrete base slabs. Commonly used supplementary cementitious materials (SCMs), such as fly ash and ground granulated blast furnace slag (GGBFS) were considered, as well as recycled aggregates, including recycled concrete aggregate (RCA), recycled crushed glass (RCG), and blast furnace slag (BFS). Environmental Product Declarations (EPDs) were also used to quantify the potential for environmental benefit associated with various concrete mixtures, with findings showing 23% to 50% reductions in embodied carbon are possible for selected theoretical concrete mixtures that incorporate waste materials. With considered evaluation and structured implementation, the integration of waste materials into rigid airport pavements offers a practical and effective route to improve environmental outcomes in aviation infrastructure. It was concluded that a Triple Bottom Line (TBL) framework—assessing financial, environmental, and social factors—guides material selection and can support sustainable decision-making, as does performance-based specifications that enable sustainable technologies to be incorporated into airport pavement. The study also proposed a consequence-based implementation hierarchy to facilitate responsible adoption of waste materials in airside pavements. The outcomes of this review will assist airport managers and pavement designers to implement practical changes to achieve more sustainable rigid airport pavements in the future. Full article

This study aims to estimate the carbon footprint and relative uncertainties for design components of conventional and geopolymer concrete. All the design components of alkaline-activated geopolymer concrete, such as fly ash, ground granulated blast furnace slag, sodium hydroxide (NaOH), sodium silicate (Na₂SiO₃), superplasticizer, and others, are assessed to reflect the actual scenarios of the carbon footprint. The conjugate application of the life cycle assessment (LCA) tool SimPro 9.4 and @RISK Monte Carlo simulation justifies the variations in carbon emissions rather than a specific determined value for concrete binders, precursors, and filler materials. A reduction of 43% in carbon emissions has been observed by replacing cement with alkali-activated binders. However, the associative uncertainties of chemical admixtures reveal that even a slight increase may cause significant environmental damage rather than its benefit. Pearson correlations of carbon footprint with three admixtures, namely sodium silicate (r = 0.80), sodium hydroxide (r = 0.52), and superplasticizer (r = 0.19), indicate that the shift from cement to alkaline activation needs additional precaution for excessive use. Therefore, a suitable method of manufacturing chemical activators utilizing renewable energy sources may ensure long-term sustainability. Full article

The construction of concrete pavements has increased due to their better durability, lifespan, and lower maintenance costs. However, this has resulted in the increased consumption of Portland cement, which is one of the major contributors to carbon emissions. Consequently, the research on alternative binders such as geopolymer concrete has increased in recent times. There are several research studies that investigate the feasibility of geopolymer concrete as a construction material, with limited studies exploring its application in concrete pavements. Therefore, this review study explores the material properties of geopolymer concrete pertinent to the performance of concrete pavements. It also discusses the potential of various industrial and agricultural waste as precursor material in geopolymer concrete. The findings of this paper show that most of the studies used fly ash and ground granulated blast furnace slag (GGBFS) as precursor material in geopolymer pavement-quality concrete, and there is a vast scope in the exploration of other industrial and agricultural waste as precursor material. The mechanical and durability properties of geopolymer pavement-quality concrete are superior to conventional pavement concrete. It is also observed that the drying shrinkage and coefficient of thermal expansion of geopolymer pavement-quality concrete are lower than those of conventional pavement concrete, and this will positively benefit the long-term performance of concrete pavements. The results of fatigue analysis and mechanical load test on the geopolymer pavement-quality concrete indicate its improved performance when compared to the conventional pavement concrete. Full article

Ground granulated blast-furnace slag (GGBS), a waste product generated during steel production, can be added as a substitute for cement in concrete to mitigate the environmental impact of the cement and steel industries. However, the use of GGBS is limited because it decreases the early strength development of cement or concrete. This study evaluated the performance of incorporating synthesized C-S-H nanoparticles to enhance the compressive strength, early hydration, and microstructure of cement composite. The synthesized C-S-H nanoparticles were produced at standard atmospheric pressure and room temperature. Heat of hydration, X-ray diffraction, and thermogravimetric analyses were conducted to investigate the hydration and mechanical properties of the cement containing the C-S-H nanoparticles. Further, mercury intrusion porosimetry was conducted to examine the pore structures. The experimental finding demonstrated that adding C-S-H nanoparticles accelerated the early hydration progress in the cement composites, thereby increasing their initial compressive strength. Full article

The utilization of steel slag (SS) in construction materials represents an effective approach to improving its overall recycling efficiency. This study incorporates SS into a conventional ground granulated blast-furnace slag (GGBS)–fly ash (FA)-based binder system to develop a ternary system comprising SS, GGBS, and FA, and investigates how this system influences the static mechanical properties of ultra-high-performance geopolymer concrete (UHPGC). An axial point augmented simplex centroid design method was employed to systematically explore the influence and underlying mechanisms of different binder ratios on the workability, axial compressive strength, and flexural performance of UHPGC, and to determine the optimal compositional range. The results indicate that steel slag has a certain negative effect on the flowability of UHPGC paste; however, with an appropriate proportion of composite binder materials, the mixture can still exhibit satisfactory flowability. The compressive performance of UHPGC is primarily governed by the proportion of GGBS in the ternary binder system; an appropriate GGBS content can provide enhanced compressive strength and elastic modulus. UHPGC exhibits ductile behavior under flexural loading; however, replacing GGBS with SS significantly reduces its flexural strength and energy absorption capacity. The optimal static mechanical performance is achieved when the mass proportions of SS, GGBS, and FA are within the ranges of 9.3–13.8%, 66.2–70.7%, and 20.0–22.9%, respectively. This study provides a scientific approach for the valorization of SS through construction material applications and offers a theoretical and data-driven basis for the mix design of ultra-high-performance building materials derived from industrial solid wastes. Full article

As a promising and sustainable construction material, alkali-activated slag lightweight high-strength concrete (AAS-LWHSC) may be influenced by lightweight aggregate (LWA) content. In this study, the effects of hollow glass microspheres (HGM) replacing granulated ground blast furnace slag (GGBFS) under varying LWA dosages on the workability, dry apparent density, mechanical properties, and microstructure of AAS-LWHSC were investigated. The results indicated that the dry density of concrete was significantly reduced by HGM, while the “ball-bearing” effect of HGM was observed to enhance workability at a dosage of 6%. The 7-day mechanical properties of AAS-LWHSC were found to decline progressively with increasing HGM content. However, at the shale ceramsite sand replacement rates of 35% and 65%, the incorporation of 6% HGM slightly improved the 28-day mechanical properties. Due to the absence of the water-releasing effect from shale ceramsite, the pozzolanic reactions of HGM were restricted, resulting in coarse hydration products and a reduction in the mechanical performance of AAS-LWHSC. Full article

To address the challenges of concrete construction in polar regions, this study investigates the feasibility of fabricating cement-based materials under severely low temperatures using electric-induced heating curing methods. Cement mortars incorporating fly ash (FA-CM), ground granulated blast furnace slag (GGBS-CM), and metakaolin (MK-CM) were cured at environmental temperatures of −20 °C, −40 °C, and −60 °C. The optimal carbon fiber (CF) contents were determined using the initial electric resistivity to ensure a consistent electric-induced heating curing process. The thermal profiles during curing were monitored, and mechanical strength development was systematically evaluated. Hydration characteristics were elucidated through thermogravimetric analysis (TG), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR) to identify phase compositions and reaction products. Results demonstrate that electric-induced heating effectively mitigates the adverse effect caused by the ultra-low temperature constraints, with distinct differences in the strength performance and hydration kinetics among supplementary cementitious materials. MK-CM exhibited superior early strength development with strength increasing rates above 10% compared to the Ref. specimen, which was attributed to the accelerated pozzolanic reactions. Microstructural analyses further verified the macroscopic strength test results that showed that electric-induced heating curing can effectively promote the performance development even under severely cold environments with a higher hydration degree and refined micro-pore structure. This work proposes a viable strategy for polar construction applications. Full article

Geopolymer concrete (GPC) offers reduced carbon emissions and employs industrial by-products such as fly ash and ground granulated blast furnace slag (GGBFS). In this study, the synergistic augmentation of shear carrying capacity in steel-fiber-reinforced rubberized geopolymer concrete (FRGC) incorporating industrial by-products such as fly ash, GGBFS, and recycled rubber for sustainable construction is investigated. The reinforced rubberized geopolymer concrete (RFRGC) mixtures contained 20% rubber crumbs as a partial replacement for fine aggregate, uniform binder, and alkaline activator. The findings revealed that 1.25% steel fiber achieved optimal hardened properties (compressive strength, flexural, and split tensile strength), with 12 M sodium hydroxide and oven curing achieving maximum values. An increase in molarity improved geopolymerization, with denser matrices, while oven curing boosted polymerization, enhancing the bonding between the matrix and the fiber. The effect of steel fiber on the shear carrying capacity of RFRGC beams without stirrups is also discussed in this paper. An increased fiber content led to an increased shear carrying capacity, characterized by an improvement in first crack load and a delayed ultimate failure. These results contribute to sustainable concrete technologies for specifically designed FRGC systems that can balance structural toughness, providing viable alternatives to traditional concrete without compromising strength capacity. Full article

The aim of this work is to investigate the effect of curing temperature and time on the development of compressive strength in geopolymer mortars produced using ground granulated blast-furnace slag (GGBFS) and fly ash (FA). Considering curing circumstances, both the activation energy and the reference temperature could be used properly to build a reliable anticipated model for predicting the compressive strength of geopolymer-based products (mortar and concrete) using maturity-based techniques. In this study, the compressive strength development of geopolymer mortar made from (FA) and (GGBFS) under varying curing conditions. The mortar was prepared using an alkali solution of sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃) in a 1:1 ratio, with NaOH molarity of 12. Specimens were cast following ASTM C109 standards, with a binder/sand ratio of 1:2.75, and compacted for full densification. FA-based mortar was cured at 40 °C, 80 °C, and 120 °C, while GGBFS-based mortar was cured at 5 °C, 15 °C, and 40 °C for durations of 0.5 to 32 days. Compressive strength was evaluated at each curing period, and data were analyzed using ASTM C1074 procedures alongside a computational model to determine the best-fit datum temperature and activation energy. The Nurse-Saul maturity method and Arrhenius equation were applied to estimate the equivalent age and maturity index of each mix. A predictive model was developed for geopolymer concrete prepared at an alkali-to-binder ratio of 0.45 and NaOH molarity of 12. The final equation demonstrated high accuracy, offering a reliable tool for predicting geopolymer strength under diverse curing conditions and providing valuable insights for optimizing geopolymer concrete formulations. Full article

Rubberized concrete is a more environmentally friendly material than natural concrete as it helps to reduce rubber disposal issues and has superior impact resistance. Geopolymer concrete, on the other hand, is an economical concrete with higher mechanical properties than nominal concrete that uses fly ash and slag, among other industrial solid wastes, to lower carbon footprints. Rubberized geopolymer concrete (RuGPC) combines the advantages of both concrete types, and a thorough grasp of its dynamic compressive characteristics is necessary for its use in components linked to impact resistance. Despite the advantages of RuGPC, predicting its mechanical characteristics is sometimes difficult because of variations in binder type and combination. This research investigated the combined effect of ground granulated blast furnace slag (GGBFS) and fly ash (FA) on the workability, compressive strength, and stress–strain characteristics of RuGPC with rubber at 0%, 10%, and 20% fine aggregate replacement. Thereafter, energy absorption and ductile characteristics were evaluated through the concrete toughness and ductility index. Numerical models were proposed for the cube compressive strength, modulus of elasticity, and peak strain of RuGPC at different percentages of crumb rubber. It was found that RuGPC made with GGBFS/FA had similar stress–strain characteristics to FA- and MK-based RuGPC. At 20% of crumb rubber aggregate replacement, the workability, compressive strength, modulus of elasticity, and peak stress of RuGPC reduced by 8.33%, 34.67%, 43.42%, and 44.97%, while Poisson’s ratio, peak, and ultimate strain increased by 30.34%, 8.56%, and 55.84%, respectively. The concrete toughness and ductility index increased by 22.4% and 156.67%. The proposed model’s calculated results, with R² values of 0.9508, 0.9935, and 0.9762, show high consistency with the experimental data. RuGPC demonstrates high energy absorption capacity, making it a suitable construction material for structures requiring high-impact resistance. Full article

Facing sand and gravel shortages, construction waste accumulation, and the “double carbon” goals, improving the performance of recycled aggregate concrete (RAC) and utilizing mineral waste slag are key to the development of green, low-carbon building materials. To enhance the mechanical performance of RAC and facilitate the sustainable utilization of mineral waste, this study innovatively incorporated copper slag (CS), ground granulated blast furnace slag (GGBS), and basalt fiber (BF) into RAC. The modified RAC’s compressive, split tensile, and flexural strengths were systematically investigated. Experimental results indicated that incorporating appropriate amounts of CS or GGBS as single admixtures could effectively enhance the mechanical properties of RAC, with 20% (w) GGBS showing the most pronounced improvement. Compared with RAC, its 28 d compressive strength, split tensile strength and flexural strength were improved by 21.3%, 9.7% and 8.1%, respectively. As opposed to single admixture, 10% CS + 10% GGBS admixture can further improve the mechanical properties of recycled concrete. Compared with RAC, its 28 d compressive strength, split tensile strength, and flexural strength were improved by 25.6%, 29.7%, and 16.6%. The study also showed that 0.2% BF admixed on top of 10% CS + 10% GGBS could still significantly improve the mechanical properties of recycled concrete, and its 28 d compressive strength, split tensile strength, and flexural strength were improved by 31.3%, 35.9%, and 31.2%, compared with RAC, respectively. By XRF, SEM, and EDS techniques, the underlying mechanisms governing the mechanical behavior of RAC were elucidated from the microscale perspective of basalt fiber and industrial waste residues. These findings provide a solid theoretical foundation and a viable technical pathway for the widespread application of recycled aggregate concrete in civil engineering projects. Full article

Geopolymer concrete is a promising construction material that acts as an alternative to cement concrete. Unlike traditional cement concrete, geopolymers are environmentally friendly materials, the production of which does not involve significant carbon dioxide emissions. However, the structure formation and properties of geopolymers significantly depend on raw materials and are insufficiently studied. The aim of the study is to select the optimal combination of ground granulated blast furnace slag (GGBS) and fly ash (FA) as a binder and the optimal content of polypropylene fiber to create a sustainable, environmentally friendly and effective geopolymer concrete. To study various compositions of geopolymer binders selected by combining GGBS and FA, experimental geopolymer concrete mixtures and samples from them were manufactured. The density and slump of fresh concrete and the density and compressive strength of hardened composites were studied as mechanical characteristics. The microstructure of the geopolymer matrix was analyzed using optical and scanning electron microscopes. The most rational combination of GGBS 80% and FA 20% was determined, which allows obtaining a composite with the highest compressive strength of up to 31.5 MPa. A dispersion reinforcement study revealed that 0.8% polypropylene fiber (PF) is optimal. This allowed us to increase the compressive strength by 7.3% and the flexural strength by 48.7%. The geopolymer fiber concrete obtained in this study is a sustainable and environmentally friendly alternative composite material and has sufficient performance properties for its use as an alternative to cement concrete. Full article

The paper is devoted to the plasticization mechanisms of alkali-activated cement system Na₂O-CaO-Al₂O₃-SiO₂-H₂O. The fundamentals and basic factors determining the effectiveness of plasticizing surfactants for alkali-activated cement materials are discussed. The factors under consideration in the study were alkali-activated cement basicity (the content of granulated blast furnace slag), the anion of the alkaline component or activator, and the degree of dispersing of the cement particles in the system. The action effect of plasticizers was determined by finding the interrelation between the stability of its molecular structure, degree of adsorption, and molecular weight depending on mentioned basic factors. A systematic approach to the systematization of surfactants and their choice to be taken into consideration to control technology-related and physico-mechanical properties of alkali-activated cement-based heavyweight concretes, building mortars, and lightened grouts has been proposed. Full article