Tamer Ibrahim Ahmed

This research aims to develop self-healing geopolymer concrete (SHG) to address the limitations of conventional repair methods, including reduced thermal conductivity and density, while promoting sustainable construction. The incorporation of the self-healing method (SHM), crushed brick (CB), and minced water bottles (F-PET) resulted in reduced thermal conductivity, maintenance costs, and environmental impact. This study investigated the effects of varying amounts of CB, F-PET, and SHM on several properties, including flowability, setting times, densities, ductility index (DI), and mechanical strengths, across 13 different mixtures. Additionally, water absorption (WA%), residual weight loss (WL%), and relative dynamic modulus of elasticity (RDME%) were assessed following freeze–thaw cycles, alongside SEM analysis and thermal transport measurements of the SHG mixtures. The inclusion of up to 50% CB enhanced density and thermal conductivity but negatively affected other properties. In contrast, incorporating 25% F-PET led to modest improvements in mechanical, thermal, and durability properties; however, it did not reduce density and thermal conductivity as effectively as CB. Among the three mixtures containing both CB and F-PET, the formulation with 37.5% CB and 12.5% F-PET exhibited the lowest density (1650 kg/m³) and thermal conductivity (1.083 W/m·K). The self-healing capacity of SHM was demonstrated through its ability to close cracks, facilitated by the deposition of CaCO₃ under combined durability conditions. Incorporating 2%, 3%, and 4% SHM into the 37.5% CB and 12.5% F-PET mixture significantly improved key properties, including strength, water absorption, freeze–thaw resistance, SEM characteristics, density, and thermal conductivity. The addition of 4% SHM enhanced the mechanical performance of the geopolymer concrete (GVC) after 28 days, resulting in increases of 27% in compressive strength, 40.5% in tensile strength, 81% in flexural strength, and 61.6% in ductility index. Further, the inclusion of SHM improved density, reduced WA% and WL%, and enhanced RDME% after 300 freeze–thaw cycles. Specifically, thermal conductivity decreased from 1.8 W/m·K to 0.88 W/m·K, and density reduced from 2480 kg/m³ to 1760 kg/m³. Meanwhile, WA%, WL%, and RDME% improved from 3%, 4.5%, and 45% to 2%, 2.5%, and 50%, respectively.

Because cement is the primary component of concrete, the production of concrete results in a significant amount of carbon dioxide emissions. Concrete, thus, has an impact on the environment. Concrete may undergo a change in its nanostructure if it contains even a trace number of nanoparticles (NPs). Constructions made of concrete would be more long-lasting and would have a smaller impact on the environment. Researchers know very little about NPs before they are utilized, and the findings of their investigations have been inconsistent despite the fact that a large number of studies have been conducted. In contrast to the inclusion of metals, NPs, particularly nano-silica (NS) and nano-ferrite (NF), have garnered a lot of attention. Due to the fact that NPs perform more effectively in concrete than metal complexes. To evaluate bids, it is essential to provide background information on the most common methods for the manufacture and fabrication of nanomaterials. The parameters that influence the behavior of NPs in cement-based materials have also been the subject of extensive research. There are also processes for mixing and dispersion, as well as super-plasticizers and nanoparticle agglomeration. The mechanical properties of mixtures containing NPs are also assessed. This encompasses modulus of elasticity, splitting tensile strength, compressive strength, and flexural strength. An assessment is conducted to ascertain the penetration of chloride ions in water, permeability, and fire resistance. This study examines various methods for dispersing NS and NF particles to reduce the probability of agglomeration. The investigation also examines how the buildup of NS particles affects the properties of nano-modified concrete. The study revealed that augmenting the nanoparticle substitution by 3–5% can enhance compressive strength. The hydration process is enhanced by extensively disseminated NPs, which also provide a denser microstructure. The incorporation of NF into concrete enhances tensile strength, permeability, and durability, even at concentrations as minimal as 2%. The graphical abstract encapsulates the research conducted in this article.

Construction sites may be exposed to crisis conditions during the casting process, resulting in delays of several hours and causing destruction of ready-mix concrete. This study suggests an experimental analysis of the possibility of using a specific additional dose of retardant admixtures, which may be used to ready-mix concrete before the initial setting of the concrete occurs. The effect of this additional dose on concrete characteristics in terms of workability, setting time, and compressive strength is also being studied. To conduct this investigation, three types of retardant admixtures from three branded companies were used. In addition, a penetration resistance experiment was conducted on the concrete to determine its setting time. The setting time of concrete was measured at different period intervals depending on when the additional dose of the retardant admixtures was added from the start of the concrete mixing. The results showed that concrete maintained proper workability for a period of more than 5 hours after using the additional dose of retarding admixtures. The additional dose of retarding admixtures not only delayed the concrete setting but also improved the compressive strength of the concrete. This implies that the use of an additional dose of retardant admixtures specifically tailored for ready-mix concrete is an effective option to avoid the return of ready-mixed fresh concrete.