Journal of Urban Environmental Management

Abstract Considering the three major problems of energy, raw material shortage, and waste, the development of environmentally friendly building materials is one of the development programs in the field of civil engineering. This study investigates the use of industrial and agricultural wastes in the development of sustainable clay blocks through activated geopolymerization technology with synthesized sodium silicate. Kaolinite clay was used as the initial matrix and supplemented with industrial fly ash, rice husk ash, and natural sands to synthesize sodium silicate additive. The alkaline activator was synthesized from silica sand through an optimized dissolution process with sodium hydroxide, and the SiO₂/Na₂O molar ratio was 1.5 and the H₂O/Na₂O ratio was 10. The samples were tested under different curing conditions and different concentrations of synthetic sodium silicate in clay blocks with different percentages of waste (0.5, 1, and 1.5%). Key findings show that: (1) compressive strength increased by 21–24% with 30 cc of alkaline activator at 150°C curing. (2) optimal substitution of 1% rice husk ash yielded maximum strength (1.81 MPa) that outperformed fly ash; (3) longer curing increased strength by 18–30% in 7-day specimens due to complete geopolymerization; (4) silica sand-derived activator was economically viable. The results confirm that waste-derived geopolymers reduce energy consumption while utilizing industrial/agricultural byproducts and provide a scalable route to environmentally friendly construction.

Abstract Corrosion inhibitor is an suitable and economical method to control the corrosion of metals in acidic environments. In this regard, green corrosion inhibitors based on plant essential oils have received a lot of attention as a usable alternative to common synthetic corrosion inhibitors, which are mostly not environmentally friendly. The presence of active compounds in eucalyptus essential oil has made it a source of green inhibitors in steel corrosion control. In this study, the inhibitory performance of eucalyptus essential oil has been investigated by extracting essential oils using steam method, electrochemical tests and surface analysis methods. Therefore, eucalyptus leaf essential oil has been used as a green inhibitor in the corrosive environment of sulfuric acid and hydrochloric acid to check the reduction of metal corrosion in this environment GC-Mass device was used to investigate the compounds present in the eucalyptus plant. The effect of steel corrosion inhibition by essential oils was investigated using weight measurement methods, electrochemical impedance spectroscopy and absorption isotherms and the results of metal immersed in acid solution with different concentrations were compared in the absence of inhibitor. The results of the tests showed that this substance has a good performance as an inhibitor and the percentage of inhibition on steel corrosion will increase with increasing concentration. The absorption of eucalyptus essential oil on steel follows the absorption isotherm and the amount of free energy of absorption indicates the spontaneous absorption of this substance with the predominance of chemical absorption on the surface.