This research aims to provide a theoretical foundation for the temperature environments and facilitate the recycling of municipal tests of BA-MPC after exposure to temperatures from 20 to 1000 degrees C were carried out. Subsequently, the stress-strain curve, peak stress, peak strain, and deformation modulus were examined. The peak stress, peak strain, and deformation modulus, considering the influence of temperature factors, are proposed using regression analysis. Based on the continuum damage mechanics, the axial compression damage constitutive model of MPC is developed, accompanied by an analysis of its temperature damage characteristics. The results show that BA improves MPC strength and helps stabilize its deformation after exposure to high temperatures. The peak stress of MPC decreases after exposure to high temperatures, and the peak stress of BA-MPC is higher at the same temperature. At 1000 degrees C, the peak stress of MPC ranges between 15.86 and 28.38 MPa. After high thermal exposure, the peak strain fluctuation of the MPC with BA stays small, and the deformation modulus is higher than that of the MPC without BA. The developed MPC axial compression damage constitutive model can accurately describe the stress-strain relationship of MPC under axial compression following hightemperature exposure, with a correlation coefficient greater than mulates in the range of 20 to 200 degrees C. At 600 degrees C, the temperacertain extent.
The growing generation of construction and demolition waste necessitates the development of effective recycling strategies to address environmental concerns. This study investigated the replacement of natural fine aggregate (NFA) with recycled fine aggregate (RFA) at 0, 50, and 100% using two treatment methods: quantitative comparison of the aggregate and mortar quality was conducted for each method. The combined application of SS-T and OA-T demonstrated an 85% improvement in workability and a 68% reduction in water absorption for RFA. Mortar experiments revealed up to 76% improvement in compressive and flexural strengths compared with untreated RFA mortar. Microstructural analyses (scanning electron microscopy [SEM], energy-dispersive spectroscopy [EDS], X-ray diffraction [XRD], and Fouriertransform infrared spectrometer [FTIR]) confirmed the enhanced bond strength and mineral composition. This study highlights the potential of SS-T and OA-T to produce durable, high-performance RFA mortars using locally available, economical bio-additives.
Several approaches are currently used to proportion recycled aggregate concrete (RAC), each having limitations. An effective and universal way to proportion RAC is not only an important tool for developing high-quality concrete but also a critical milestone for promoting the wider use of recycled concrete aggregate (RCA) in concrete. A mixture design method based on particle packing and excess paste theory is proposed in this study. Given the focus on pavement concrete, the modified Box Test was used to quantify RAC workability. RAC mixtures with five different RCAs of varying quality, developed using the proposed method, showed excellent workability (Box Test Rating E1-S1), whereas mixtures developed with conventional mixture design methods failed to achieve adequate workability. Mechanical properties of optimized RACs were either comparable or improved. The adverse effect of RCA on concrete resistivity and shrinkage appeared negligible and was mitigated by the mixture design approach developed in this study. Compared with conventional direct weight replacement (DWR)/direct volume replacement (DVR) mixtures, the proposed design achieved a reduction of surface voids by more than 80%, up to 25% higher compressive strength, and 20% lower shrinkage at 28 days, while maintaining comparable resistivity.
As recycled concrete reaches the end of its service life, a new generation of coarse recycled aggregate (CRA) is created. Although the variables influencing the physical properties of CRA are well understood, the performance of multi-recycled concrete aggregate (MRCA) remains insufficiently explored, and it is essential to study how the modified properties could affect the performance of recycled concrete. This research involved five recycling cycles to evaluate the properties ofMRCA and its impact on the mechanical and durability performance of concrete made with 75% MRCA. The findings indicate that water absorption, porosity, and abrasion of MRCA increase with each recycling cycle. Although the mechanical behavior of the concretes appears to be unaffected by the number of recycling cycles, the elastic modulus is negatively impacted when MRCA is used. Furthermore, while some permeability properties are significantly influenced by each recycling cycle, both water penetration depth and resistance to sulfate attack remain largely unchanged.
The use of concrete composites with textile waste provides a sustainable path for circular construction. This paper reports the effects of the incorporation of textile-derived cellulose on the performance of cementitious composites. The study investigated the effect of the substitution of cement with microcellulose, 0 to 5%, on the compressive strength of cement paste. Isothermal calorimetry revealed cellulose delays initial hydration and increases the cumulative heat release over time. Chemical and microstructural analytical techniques such as thermogravimetric analysis, nuclear magnetic resonance, mercury intrusion porosimetry, and scanning electron microscopy were employed to examine the reaction kinetics of the cement when incorporating recycled cellulose. The research findings highlighted that recycled textile cellulose notably impacts the cement paste hydration process and the properties developed. Optimal cellulose content was identified as 1% by cement weight.
This study evaluated the effect of Class F fly ash (5, 10, 15, and 20%) and silica fume (20%) as partial cement replacements on bacterial crack healing. Concrete cylinders were prepared, cracked into 25.4 mm disks, and submerged in fresh water. Healing progress was monitored over 18 weeks using microscopy and quantified through a healing index. Results showed that bacterial activity substantially improved healing compared to natural hydration in control specimens. Fly ash replacement did not prevent healing, and several disks across all percentages achieved complete crack closure. However, higher fly ash levels shortened the duration of bacterial activity, indicating sensitivity to calcium availability. At 20% fly ash, healing progressed more slowly but remained active at 18 weeks. In contrast, specimens containing 20% silica exhibited significantly lower healing efficiency, with few disks achieving full closure and overall lower healing indexes. These results confirm that bacteria-based self-healing concrete remains effective with fly ash but is constrained by high silica fume content due to very low to zero calcium content in silica fume. The findings suggest that lower calcium levels in supplementary cementitious materials (SCM) replacements, caused by higher fly ash content or the use of silica fume, may significantly influence bacterial healing.
