The incorporation of construction and demolition (C&D) waste in concrete production has gained great importance toward sustainability, especially in geopolymer concrete. In this study, ground granulated blast-furnace slag (GGBFS) and fine aggregate of normal geopolymer concrete were partially replaced by clay brick powder (CBP) and fine clay brick (FCB) derived from C&D waste, respectively, aiming to produce high-strength geopolymer concrete (HSGC). Fly ash (FA) was also used as a partial replacement for GGBFS in normal geopolymer concrete. Twenty HSGC mixtures were designed using the response surface methodology with three variables, including CBP (0–25%), FA (0–25%), and FCB (0–50%). The performance of the proposed HSGC mixtures was assessed by measuring several mechanical and durability properties. In addition, a variety of physicochemical methods, including X-ray fluorescence spectroscopy, X-ray diffraction, and scanning electron microscopy, were used to examine the mineralogical and microstructural characteristics of the control and the developed mixtures. The findings revealed that the compressive, splitting tensile, and flexural strengths of the HSGC made with C&D waste ranged from 38.0 to 70.3 MPa, 4.1 to 8.2 MPa, and 5.2 to 10.0 MPa, respectively. The results also indicated that the incorporation of FA is an essential parameter to eliminate the negative impacts of C&D waste addition on concrete workability. The optimal proportions for the HSGC were 5% for CBP, 5% for FA, and 40% for FCB, which were determined to generate the optimized HSGC with the highest mechanical performance, according to the verified models and optimization findings. The physicochemical analyses showed that the thick amorphous geopolymeric gel predominated the nonporous structure of the optimized HSGC, which had good mechanical characteristics. Furthermore, the anti-carbonation performance and freezing resistance of the optimal HSGC increased by 17.7% and 14.6%, respectively, while the apparent porosity decreased by 8.4%.

A viable strategy for promoting sustainable development and a cleaner environment is the reuse of demolition-related ceramic waste and ceramic manufacturing byproducts in the production of concrete. The purpose of this study is to assess the possibilities for using ceramic waste in the production of concrete as a fine aggregate and cementitious material. The effectiveness of concrete mixtures incorporating 20–100% ceramic waste fine (CWF) as a replacement for natural fine aggregate and 10–30% ceramic waste powder (CWP) in place of cement was evaluated. Their influence was assessed with respect to workability, mechanical performance, durability, and elevated temperature resistance. The results were analyzed via energy dispersive x-ray (EDX) and scanning electron microscopy (SEM). The findings illustrated that the increase in the replacement levels of CWP and CWF decreases the concrete workability. The mechanical performance of concrete mixtures is enhanced under compression and flexural tests as the replacement ratios of CWF and CWP increase up to 50% and 10% as replacements of sand and cement, respectively. The increases in compressive and flexural strength were 5.33% and 8.14%, respectively, at age 28 days. The concrete water permeability significantly increases as the CWF replacement ratio increases, and the incorporation of CWP reduces this negative impact. After exposure to 200, 400, 600, and 800 °C, the residual compressive strengths of concrete mixtures incorporating CWF and CWP were up to 95.02%, 89.66%, 74.33%, and 51.34%, respectively, compared to control mixtures, which achieved 84.25%, 76.03%, 59.36%, and 35.84% of their initial strength. Microstructure analysis revealed that combining CWP and CWF significantly improves cement hydration when compared to the reference mixture. Thus, the use of CWF and CWP in the production of masonry mortar might be an economical alternative that would aid in raising the recycling rate of demolition and construction debris and supporting sustainable growth in the building sector.

One of the most important challenges in developing the concrete industry is to use sustainable materials that are able to improve concrete properties. Magnetized water (MW) is a type of water that can replace tap water (TW) in conventional concrete and enhance its mechanical properties. However, the performance of MW in geopolymer concrete has not been well investigated up to now. The goal of this study is to measure the effect of using an alkaline activator (AA) made of MW on the mechanical properties and durability of fly ash (FA)-based geopolymer concrete. The AA was a mixture of sodium hydroxide (SH) solution and sodium silicate (SS) solution. Eighteen geopolymer concrete mixes were tested for several fresh, hardened, and durability properties. Of these mixes, nine were prepared with AA made of MW and the other nine were the same but prepared with AA made of TW. The preparation of MW was simply carried out by passing TW across permanent magnets of 1.6 Tesla, and then 1.4 Tesla intensities for 150 cycles. The MW-based AA properties were analyzed and compared to those of the conventional TW-based AA. Several mechanical and durability properties were measured. Scanning electronic microscopy (SEM) analysis was also conducted on selected mixes. The outcomes of the hardened concrete tests demonstrated that while using MW to prepare AA solution contained SH with a molarity of 16 M, an SS/SH ratio of 2, an AA/C ratio of 0.4, a W/C ratio of 10%, and a curing temperature of 115 °C could display the best outcomes in this study when used in geopolymer concrete. Using MW in a geopolymer concrete AA could increase its slump by up to 100% compared to that made of TW. Using MW in the AA enhanced the compressive strength by up to 193%, 192%, and 124% after 7, 28, and 56 days, respectively. The SEM analysis showed that using MW clearly enhanced the surface morphology of geopolymer concrete. The proposed geopolymer concrete made using the MW-based AA in this study sheds the light on a new class of eco-friendly concrete that could possibly be used in many structural applications.

The aim of this study is to experimentally investigate the mechanical characteristics of concrete combining silica fume (SF) and magnetized water (MW). A total of nine concrete mixes were prepared and tested for workability, compressive strength, splitting tensile strength, and flexural strength. Ordinary tap water (TW) and MW that was prepared with five proposed different methods were utilized in the concrete mixes. The MW was prepared by passing TW through a permanent magnetic field (having intensities of 1.4 Tesla and/or 1.6 Tesla) for a different number of cycles, namely 100, 150, and 250 cycles. Water characteristics were analyzed after being magnetized using the proposed different methods and compared with the TW characteristics. Non-destructive concrete testing (ultrasonic pulse velocity, and Schmidt hammer) was also conducted to determine the effect of MW on the prediction of concrete compressive strength. Scanning electron microscopy (SEM) analysis and energy dispersive X-ray (EDX) analysis were carried out on the produced mixes. Regardless of the method utilized to prepare the MW, the results revealed a considerable improvement in concrete compressive strength, splitting tensile strength, and flexural strength by up to 80%, 98%, and 22%, respectively, when MW was prepared with 150 cycles. The best water magnetization method found in this study was the passing of water through magnetic fields of 1.6T then 1.4T intensities for 150 cycles. The ultrasonic pulse velocity test resulted in good prediction of the concrete compressive strength with overall error ranged between −12.6% and +5.8%. MW significantly improved the concrete microstructure and produced a denser structure in comparison to the control conventional concrete.

Developing longer-lifespan concrete with minimized surface cracking is crucial for sustainable construction. This study investigates self-healing rubberized concrete incorporating 15% recycled rubber waste as a sand replacement. To enhance strength and flexibility through crack closure, bacteria Sporosarcina Pasteurii and Rhizobium Leguminosarum were introduced at 20% of the water volume. Slump, compressive and flexural strength, SEM, and EDX were the tests performed to identify the effects of bacteria and rubber on the concrete characteristics. The results illustrated that the use of rubber as a partial replacement for sand significantly reduced concrete workability and mechanical performance, with slump, compressive strength, and flexural strength decreasing by up to 77%, 49%, and 47%, respectively. However, incorporating SpP and RL bacteria, particularly at concentrations of 10¹⁰ + 10¹⁰ and 10¹⁴ + 10¹⁰, effectively mitigated these negative effects. The improvement in compressive strength and flexural strength was up to 98.7% and 137.4%, respectively for mixture containing SpP and RL bacteria at concentration 10¹⁰ +10¹⁰ compared to mixture containing 15% rubber only. Complete crack self-healing was achieved in SHRC mixtures after 80 days. Microstructure analysis revealed that the formation of calcium carbonate in large quantities within the concrete matrix, which works to heal cracks and fill voids. Thus, using rubber with bacteria to heal cracks could be a cost-effective solution that helps to increase tire rubber recycling rates.

The durability and fire resilience of concrete structures are increasingly critical in modern construction, particularly under elevated-temperature exposure. With this context, the current study explores the thermal and microstructural characteristics of geopolymer-based ultra-high-performance concrete (G-UHPC) incorporating quartz powder (QP) and silica fume (SF) after exposure to elevated temperatures. SF was used at 15% and 30% to partially replace the precursor material, while QP was used at 25%, 30%, and 35% as a partial replacement for fine sand. The prepared specimens were exposed to 200 °C, 400 °C, and 800 °C, followed by air cooling. Mechanical strength tests were conducted to evaluate compressive and flexural strengths, as well as failure patterns. Microstructural changes due to thermal exposure were assessed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Among the prepared mixtures, the 30SF35QP mixture exhibited the highest compressive strength (156.0 MPa), followed by the 15SF35QP mix (146.83 MPa). The experimental results demonstrated that G-UHPC underwent varying levels of thermal degradation across the 200–800 °C range yet displayed excellent resistance to thermal spalling. At 200 °C, compressive strength increased due to enhanced geopolymerization, with the control mix showing a 29.8% increase. However, significant strength reductions were observed at 800 °C, where the control mix retained only 30.8% (32.0 MPa) and the 30SF25QP mixture retained 28% (38.0 MPa) of their original strengths. Despite increased porosity and cracking at 800 °C, the 30SF35QP mixture exhibited superior strength retention due to its denser matrix and reduced voids. The EDS results confirmed improved gel stability in the 30% SF mixtures, as evidenced by higher silicon content. These findings suggest that optimizing SF and QP content significantly enhances the fire resistance and structural integrity of G-UHPC, providing practical insights for the design of sustainable, high-performance concrete structures in fire-prone environments.