Fly ash from coal represents the foremost waste product of fossil fuel combustion. These waste materials are most widely utilised in the cement and concrete industries, but the extent of their use is insufficient. This study investigated the physical, mineralogical, and morphological characteristics of non-treated and mechanically activated fly ash. The possibility of enhancing the hydration rate of the fresh cement paste by replacing part of the cement with non-treated and mechanically activated fly ash, and the hardened cement paste’s structure and early compressive strength performance, were evaluated. At the first stage of the study, up to 20% mass of cement was replaced by untreated and mechanically activated fly ash to understand the impact of the mechanical activation on the hydration course; rheological properties, such as spread and setting time; hydration products; mechanical properties; and microstructure of fresh and hardened cement paste. The results show that a higher amount of untreated fly ash significantly prolongs the cement hydration process, decreases hydration temperature, deteriorates the structure and decreases compressive strength. Mechanical activation caused the breakdown of large porous aggregates in fly ash, enhancing the physical properties and reactivity of fly ash particles. Due to increased fineness and pozzolanic activity by up to 15%, mechanically activated fly ash shortens the time of maximum exothermic temperature and increases this temperature by up to 16%. Due to nanosized particles and higher pozzolanic activity, mechanically activated fly ash facilitates a denser structure, improves the contact zone between the cement matrix, and increases compressive strength up to 30%.

The growing demand for low-carbon cementitious materials has increased interest in natural zeolite as a supplementary cementitious material capable of reducing clinker consumption while modifying cement system performance. This study presents an integrated experimental evaluation of natural zeolite-modified cementitious materials by combining rheological behavior, hydration, compressive strength, density, scanning electron microscopy (SEM), and X-ray diffraction (XRD) within a single experimental framework. Natural zeolite was used as a partial replacement for cement at dosages of 5–12.5 wt.%. The results showed that zeolite significantly affected both fresh-state and hardened-state properties. Zeolite increased the rheological resistance of fresh mixtures, shifted the exothermic hydration peak from 12 h to 8–10 h, and reduced the maximum hydration temperature by approximately 8–12%. Among the investigated compositions, the mixture containing 7.5% zeolite exhibited the highest compressive strength (44.9 MPa at 28 days) together with increased hardened density, suggesting more efficient particle packing and matrix development than the reference mixture. SEM observations indicated a more uniform distribution of hydration products in mixtures containing moderate zeolite dosages, while XRD analysis confirmed changes in the crystalline phase assemblage associated with zeolite incorporation. The results demonstrate that moderate natural zeolite replacement, particularly at 7.5%, provides an effective balance between rheological behavior, hydration characteristics, mechanical performance, and microstructural development, highlighting its potential as a sustainable supplementary cementitious material for low-carbon cement-based composites.

The integration of modern computer technologies into the construction industry is transforming design and building processes, offering professionals numerous advantages. One of the most significant advancements is the adoption of virtual modeling tools, which enhance design accuracy, improve project quality, and reduce implementation time. These technologies also optimize material costs, making construction more efficient and cost-effective. A major milestone in this digital transformation is the widespread use of Building Information Modeling (BIM) technologies, such as Revit and Archicad. These programs create a unified software environment that streamlines project management across all stages, from initial design to construction and operation. Additionally, they enable the development of complex architectural forms through 3D printing, further expanding the potential of modern construction methods. The success of 3D printing in construction depends heavily on advanced materials, particularly fine-grained concrete with inorganic binders. While these materials enhance durability and structural integrity, their development remains a challenge due to strict technical requirements. Overcoming these challenges requires a scientifically grounded approach to optimizing material composition and ensuring seamless integration into additive manufacturing processes. In conclusion, the fusion of digital tools with construction methodologies significantly improves efficiency, precision, and sustainability. These innovations not only advance the design and building processes but also pave the way for the successful realization of complex and economically viable projects, shaping the future of the construction industry.

Additive manufacturing technologies in construction, particularly concrete 3D printing, offer new opportunities to automate building processes and improve material efficiency. However, the use of agricultural waste in cement-based composites for 3D printing remains limited, and the combined effects of such waste on rheology, interlayer bonding, mechanical performance, and thermal insulation are still insufficiently studied. This study aims to develop 3D-printable cement-based composites incorporating ground rice husk (GRH) as a multifunctional filler. GRH was introduced at dosages of 0–40% by mass of cement while maintaining constant workability. Because GRH is hydrophilic and water-absorbing, increasing its content required progressively higher amounts of added mixing water. Consequently, GRH dosage and water adjustment were not independent variables, and the reported effects represent the combined response of the composite to GRH incorporation and the associated water adjustment required to preserve printability. Under these conditions, increasing the GRH content reduced the compressive strength from 45.6 to 5.2 MPa, the flexural strength from 8.0 to 1.9 MPa, and the interlayer bond strength from 0.56 to 0.13 MPa, while thermal conductivity decreased from 0.85 to 0.35 W/(m·K) and water absorption increased by 98%. SEM confirmed the transition from a dense cementitious matrix to a highly porous structure, with filler particles connected by thin films of cement paste. The study demonstrates the potential of using rice husk in 3D-printable cement-based composites and highlights the trade-off between mechanical performance and thermal insulation as GRH content increases.

This study comparatively evaluated lightweight structural and thermal-insulating concrete containing unground rice husk (RH) and commercially supplied ground rice husk (GRH). Two comparative mixture series, one containing unground rice husk (RH) and the other containing ground rice husk (GRH), were produced at four binder levels using cement, fly ash, quartz sand, a polycarboxylate superplasticizer, and an organosilicon water repellent. The study assessed particle characteristics, fresh and hardened density, 28-day compressive strength, thermal conductivity, water absorption, and microstructure. The commercially supplied GRH consisted of fragmented particles with a median size of approximately 0.72 mm, facilitating its incorporation into the granular skeleton. The hardened density remained within 1402–1478 kg/m³, while the average compressive strength increased from 7.38 MPa for RH mixtures to 10.43 MPa for GRH mixtures. Depending on the composition, the GRH mixtures exhibited 26.7–65.0% higher compressive strength than the corresponding RH mixtures at comparable densities. Thermal conductivity remained within the range of 0.36–0.42 W/(m·K), and water absorption varied only from 28.0 to 29.5%. Scanning electron microscopy (SEM) observations revealed more uniform particle distribution, improved particle–matrix contact, and fewer pronounced interfacial defects in GRH composites. The GRH-4 mixture demonstrated the best overall performance, combining a compressive strength of 11.47 MPa, a density of 1462 kg/m³, and a thermal conductivity of 0.42 W/(m·K). These findings show that the investigated GRH-based formulations achieved higher structural efficiency than the corresponding RH-based formulations while largely maintaining their thermal insulation performance; however, the differences reflect the combined effects of particle characteristics, husk dosage, moisture conditions, and associated mixture adjustments.

Mechanical activation is a promising approach to improving the performance of low-calcium fly ash (FA) in cementitious materials; however, its effect on time-dependent rheology remains insufficiently quantified. This study investigates the influence of mechanical activation of fly ash from the Almaty combined heat and power plant No. 3 (CHP-3) on the rheological, hydration, mechanical, and microstructural properties at cement replacement levels of 5–20 wt.%. Grinding increased the specific surface area from 3710 to 6134 cm²/g. Cement mortars containing as-received FA or mechanically activated fly ash (AFA) were evaluated by rotational rheometry after 5 and 90 min of resting using the Herschel–Bulkley model, while cement pastes were examined by semi-adiabatic exothermic measurements and microstructural analysis. Mechanical activation generally increased flow resistance and affected the time-dependent rheological response, with pronounced changes in viscosity and hysteresis after 90 min that remained detectable after standardized remixing. At identical replacement levels, AFA pastes exhibited maximum temperatures 1.3–7.0 °C higher than FA pastes (temperature rise higher by 2.1–6.8 °C), indicating enhanced early hydration. At 28 days, AFA mortars reached compressive strengths of 43.7, 41.4, 36.8 and 35.0 MPa at 5, 10, 15, and 20% replacement, respectively, remaining above the reference mortar (33.3 MPa), whereas FA mortars exceeded the reference only at 5–10%. The semi-quantitative X-ray diffraction (XRD) portlandite-to-quartz intensity ratio was approximately 18–31% lower for AFA15-P than for FA15-P, consistent with enhanced portlandite consumption, while scanning electron microscopy (SEM) of the same 15% pastes revealed a denser matrix and improved ash–hydrate intergrowth after activation. Overall, mechanical activation extended the fly ash replacement level at which the 28-day strength remained above the reference from 10% to 20%, while increasing rheological resistance.