This paper aims to develop geopolymer concrete (GPC) with flash-calcined soils cured under ambient conditions. Flash calcination is a heat thermal technique used to eliminate pollutants and organic content in excavated soils and allow them to be used in cementitious formulations. To develop GPC, the materials used in the development of the GP precursor binder should be rich in silicon (Si) and Aluminum (Al) that can react with alkaline silicates to yield Si-O-Al bonds that would form cementitious materials. The GP precursor binder is composed of Metakaolin (MK), flash-calcined soils, and granulated blast furnace slag (GBFS). The thermally treated soils are flash-calcined dredged sediments (FCS) and flash-calcined excavated clays (FCC) while potassium silicate is used as the alkaline reagent. This study aims to use the materials above to develop GPC cured under ambient conditions with high strength, good durability, and microstructure properties. Seven formulations are done to evaluate the effect of replacing MK with either FCS or FCC and GBFS on the mechanical compressive strength, water absorption, and freeze-thaw test. The findings reveal that using only metakaolin (MK0) in the formulation yielded the highest compressive strength. These results align with the porosity test outcomes, which show correlations between micropore and macropore percentages. Analysis of the durability freeze-thaw test suggests that as the proportion of macropores increases, formulations incorporating FCS and FCC exhibit improved resistance to extreme temperatures. Conversely, an increase in GBFS content leads to a finer microstructure and reduced resistance. Water absorption testing indicates that formulations with FCS and FCC display favorable sorptivity coefficients compared to MK0, with increased GBFS content enhancing durability. SEM/EDS and calorimetry tests were conducted to investigate the impact of substituting FCS and FCC for MK within the geopolymer matrix.

A large quantity of waste slurry (WS) is produced during the process of drilled grouting piles, which is mainly composed of bentonite, clay, and metal ions. Improper disposal of WS will bring about serious environmental problems. In this study, flocculation technology and solidification technology were combined to treat WS using three types of flocculant solution, and waste slurry geopolymer concrete (WS-GPC) was prepared using treated WS, slag powder (SP), fly ash (FA) and alkali activator. The results showed 100 mL WS treated with 25 mL APAM flocculant solution with a concentration of 0.1 % had the lowest filtrate turbidity and the lowest mud moisture content (50.30 %). The bone-glue ratio, sand rate and water-to-cement ratio of the concrete samples was 3.0, 0.4 and 0.42, respectively. Taking into account the 7-day compressive strength of WS-GPC and the maximum application rate of WS, the optimal slurry cake content was 35 %. At this time, the total amount of slag powder and fly ash used was 65 %. The effects of slag powder dosage (SPD), alkali activator dosage (AAD), and alkali activator modulus (AAM) on the compressive, flexural, and splitting properties of WS-GPC were discussed. And X-ray diffraction (XRD), scanning electron microscope (SEM), and mercury intrusion porosimetry (MIP) tests were also taken to analyze the phase composition, microstructure, and pore structure of WS-GPC. There was a positive correlation between the mechanical strength of WS-GPC and SPD. While when the AAD or AAM increased, the mechanical strength of WS-GPC first increased followed by a decrease. The mechanical properties of WS-GPC with 60 % SSD, 29 % AAD and AAM being 1.3 were optimal due to more hydration products, smoother and denser microstructure, lower porosity and smaller average pore diameter of the WS-GPC. This study is expected to create a new way of green treatment of WS and provide a theoretical basis for the application of WS-GPC.

This research explores the application of Artificial Intelligence (AI) techniques to assess the mechanical properties of geopolymer concrete made from a blend of Banana Peel-Ash (BPA) and Sugarcane Bagasse Ash (SCBA), using a sodium silicate (Na2SiO3) to sodium hydroxide (NaOH) ratio ranging from 1.5 to 3. Utilizing three AI methodologies-Artificial Neural Networks (ANN), Adaptive Neuro-Fuzzy Inference System (ANFIS), and Gene Expression Programming (GEP)-the study aims to enhance prediction accuracy for the mechanical properties of geopolymer concrete based on 104 datasets. By optimizing mix designs through varying proportions of BPA and SCBA, alkaline activator molarity, and aggregate-to-binder ratios, the research identified combinations that significantly enhance mechanical properties, demonstrating notable international relevance as it contributes to global efforts in sustainable construction by effectively utilizing industrial by-products. The experimental results demonstrated that increasing the molarity of the alkaline activator from 4 to 10 M significantly enhanced both the compressive and flexural strengths of the geopolymer concrete. Specifically, a mixture containing 52.5% SCBA and 47.5% BPA at a 10 M molarity achieved a maximum compressive strength of 33.17 MPa after 20 h of curing. In contrast, a mixture composed of 95% SCBA and 5% BPA at a 4 M molarity exhibited a substantially lower compressive strength of only 21.27 MPa. Additionally, the highest recorded flexural strength of 9.95 MPa (77.25% SCBA and 22.5 BPA) was observed at the 10 M molarity, while the flexural strength at 4 M was lowest, at 4.12 MPa (95% SCBA and 5% BPA). Microstructural analysis through Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (ED-SEM) revealed insights into the pore structure and elemental composition of the concrete, while Thermogravimetric Analysis (TGA) provided data on the material's thermal stability and decomposition characteristics. Performance analysis of the AI models showed that the ANN model had an average MSE of 1.338, RMSE of 1.157, MAE of 3.104, and R2 of 0.989, while the ANFIS model outperformed with an MSE of 0.345, RMSE of 0.587, MAE of 1.409, and R2 of 0.998. The GEP model demonstrated an MSE of 1.233, RMSE of 1.110, MAE of 1.828, and R2 of 0.992, confirming that ANFIS is the most accurate model for predicting the mechanical and rheological properties of geopolymer concrete. This study highlights the potential of integrating AI with experimental data to optimize the formulation and performance of geopolymer concrete, advancing sustainable construction practices by effectively utilizing industrial by-products.

Excavated rock and soil from tunnelling (ERST), fly ash (FA), and slag are one of the largest sources of solid waste and play an important role in reducing dependence on natural resources and solving the problem of solid waste accumulation. This study verifies the feasibility of highperformance ecological geopolymer concrete (HPEGC) incorporating ERST, FA and slag for engineering applications. The effects of different binding material to machine-made sand ratio (BMMSR) and SN/FS (the total mass of sodium silicate and NaOH solids to the total mass of the powdered raw material) on the slump, compressive strength, tensile strength, drying shrinkage, salt corrosion resistance of concrete and the microstructural deterioration process before and after salt corrosion were analysed by indoor tests and microscopic tests. The results showed that the hydration products generated at SN/FS of 10, 12, and 15 % could effectively fill the pores of HPEGC and improve the pore structure and interfacial properties of HPEGC by microminiaturisation of the pore size. HPEGC formed a dense three-dimensional reticulated polysilicaaluminate-like structure due to the coexistence of C-S-H gel, C-A-S-H gel, N-A-S-H amorphous gel, and Na2Al2Si3O10. 2 Al 2 Si 3 O 10 . HPEGC with SN/FS of 12 % and BMMSR of 0.36 showed 29.5 % and 18.9 % improvement in compressive and tensile strengths, better resistance to sulfate attack, and 4.5 % and 45 % reduction in economic cost and GHG emission, respectively, compared with ordinary Portland cement concrete (OPCC). The results of the study proved that the engineering application of HPEGC incorporating ERST, FA and slag as raw materials is promising, providing new solutions for global underground excavation materials and industrial solid waste, and effectively promoting the sustainable development of the construction industry.

The environmental impact of non-biodegradable rubber waste can be severe if they are buried in moist landfill soils or remain unused forever. This study deals with a sustainable approach for reusing discarded tires in construction materials. Replacing ordinary Portland cement (OPC) with an environmentally friendly geopolymer binder and integrating crumb rubber into pre-treated or non-treated geopolymer concrete as a partial replacement of natural aggregate is a great alternative to utilise tire waste and reduce CO2 emissions. Considering this, two sets of geopolymer concrete (GPC) mixes were manufactured, referred to as core mixes. Fine aggregates of the core geopolymer mixes were partially replaced with pre-treated and non-treated rubber crumbs to produce crumb rubber geopolymer concrete (CRGPC). The mechanical properties, such as compressive strength, stress-strain relationship, and elastic modulus of a rubberised geopolymer concrete of the reference GPC mix and the CRGPC were examined thoroughly to determine the performance of the products. Also, the mechanical properties of the CRGPC were compared with the existing material models. The result shows that the compressive strength and modulus of elasticity of CRGPC decrease with the increase of rubber content; for instance, a 33% reduction of the compressive strength is observed when 25% natural fine aggregate is replaced with crumb rubber. However, the strength and elasticity reduction can be minimised using pre-treated rubber particles. Based on the experimental results, stress-strain models for GPC and CRGPC are developed and proposed. The proposed models can accurately predict the properties of GPC and CRGPC.

Climate change is a catastrophic phenomenon that negatively impacts the planet. Temperature variation is a major cause of climate change which results in melting glaciers and expanding waterbodies leading to increasing sea water levels. The Mediterranean coastline is at risk of flooding, shoreline erosion, and intrusion of seawater into the groundwater table due to the increase of seawater levels placing our coastal structures in danger. To alleviate the negative impacts of climate change, several preventive and remedial measures will be proposed and assessed using a simulation to compare them with the already existing conditions of a case study in Alexandria, Egypt. The objective of this study is to investigate the possibility of protecting coastal structures against the increasing effects of climate change by using an environmentally friendly, low-permeability concrete mix design to endure the chloride attacks in the sea water. Furthermore, soil injections using polyurethane will be analyzed to validate their effectiveness in decreasing the soil porosity protecting the structure's foundations against the seepage of sea water into the groundwater as it rises. Several concrete mixes incorporating metakaolin, a pozzolanic material to reduce permeability, with 5 and 10% replacement of the ordinary Portland cement will be studied. Moreover, the potential use of geopolymer concrete consisting of fly ash, sodium hydroxide, and sodium silicate as a binder will also be assessed through three different mixes with varying molarities and alkaline-activator solution-to-fly ash ratios and compared to the metakaolin mixes. To evaluate the performance of the aforementioned mixes, several fresh tests as well as hardened tests were conducted. Results reveal that the mixes achieve superior mechanical properties when compared to ordinary Portland concrete, namely, higher compressive and tensile strength in addition to increasing durability. As for the early concrete properties, both the geopolymer and metakaolin concrete mixes exhibit a considerable amount of full strength during the first 7 days. Regarding the soil impregnation, polyurethane was successful in reducing the soil permeability by a thousand times. In line with the previous results, it was concluded that such actions are indispensable to alleviate the negative impacts of climate change.