In order to reduce the negative impact on the environment caused by the massive accumulation of red mud (RM) and Yellow River sand (YRS), new alkali-excited granulated blast-furnace slag (GGBS)/RM/YRS (AGRY) geopolymer cementitious materials were prepared by combining RM and YRS with GGBS in different ratios and using sodium silicate as the alkali exciter. The effects of YRS dosage and different curing conditions on the mechanical properties, hydration products, and pore structure of cementitious materials were investigated and analyzed in terms of cost and carbon emissions. The results showed that when the dosage of YRS was 40%, the compressive strength of the prepared AGRY cementitious material could reach 48.8 MPa at 28 d under standard curing, which showed mechanical properties comparable to those of the cementitious material without YRS. The cementitious material has a more compact internal structure, and the combination of RM and YRS promotes the chemical reaction of Al and Si elements and generates the (N, C)-A-S-H gel products, which are the key to the strength enhancement of the cementitious material. In addition, the prepared cementitious material is only 90% of the cement cost for the same strength and has low carbon emission accounting for only 43% of the cement carbon emission. This study not only provides a new way for the resource utilization of RM and YRS, but also contributes an excellent new environmentally friendly material for the construction industry to achieve the goal of low carbon development.

Aiming at the mechanical response of geomembrane (GEM) in membrane-faced rockfill dam (MFRD) to different ambient temperatures, the mechanical properties in axial tension of polyvinyl chloride (PVC) GEM were studied by experiment and theoretical analysis. First, fifteen groups of axial tensile tests for longitudinal/transverse specimens were conducted at different temperatures in the temperature environment laboratory, the stress–strain curve and Young’s modulus were obtained, and the variation of Young’s modulus with temperature was analyzed by Boltzmann function fitting. Second, the glass transition temperature of PVC GEM was obtained by differential scanning calorimetry (DSC), and the difference in mechanical properties between longitudinal and transverse specimens of PVC GEM was analyzed by thermomechanical analyzer (TMA) thermodynamic test. The results showed that the lower the temperature, the greater the Young’s modulus, and the smaller the linear interval of stress and strain, while the higher the temperature, the result is opposite. The difference in mechanical properties between the two directions is related to the ambient temperature. The orientation of polymer structure accounts for the difference in mechanical properties by theoretical analysis. The fitting results of Boltzmann function have a certain reference value for numerical simulation. In design of the membrane impervious structure in MFRD, the ambient temperature should be considered fully, and the longitudinal/transverse welding splicing should be avoided as far as possible. The current test specification should test the mechanical performance of GEM at normal operating temperature of reservoir instead of the test and quality evaluation at a single temperature. The temperature should be considered comprehensively in construction to avoid damaging the performance of impervious structure and ensure the service life.

The mechanical properties of polyvinyl chloride (PVC) geomembrane (GM), particularly its elastic modulus, are of the utmost importance in engineering design and evaluation of performance. The existing test methods make it difficult to provide an accurate elastic modulus of PVC GM. This research presents the establishment of an improved method for analysing the true stress–strain by non-contact measurement technology to determine the elastic modulus. Digital image correlation (DIC) was used to measure the axial and transverse strain, and it was found to give measurements of strain with a high degree of accuracy. The variation of Poisson's ratio is discussed and the true cross-sectional area is determined, allowing the true stress to be calculated theoretically. In accordance with the true stress–strain curve, the elastic modulus and linear range are established, which can provide designers with the tools to evaluate the true performance of GM and help them to select anti-seepage materials in design.

This study explores the durability of plasticized polyvinyl chloride (PVC-P) geomembranes in hydraulic engineering anti-seepage structures, particularly under varying operational temperature conditions. Employing accelerated thermal air aging tests on three distinct PVC-P geomembrane variants, the study assesses their mechanical properties, specifically axial tensile strength, using an electronic universal testing machine. A comprehensive thermal air aging model, based on the Arrhenius equation, has been developed, offering insights into the lifespan prediction of these geomembranes. Results demonstrate that factors such as annual average temperature, plasticizer content, and membrane thickness significantly influence the geomembranes' service life. Post-aging observations include a notable yellowing and increased brittleness of the geomembranes, coupled with a decline in tensile strength and elongation. Elongations exhibit a decreasing trend, aligning with a first-order degradation kinetics equation. Under conditions of 50℃ over a period of 120 days, the elongation of polyvinyl chloride (PVC)-HX, PVC2.0-JT, and PVC2.5-JT geomembranes was reduced to 255.88%, 430.11%, and 434.58%, respectively. Predictions indicate that at an operational temperature of 20℃, the expected lifespans for these geomembranes are 19, 45, and 48 years, with material failure correlating to plasticizer loss rates of 58.2%, 32.5%, and 24.8%, respectively. These findings offer valuable guidance for the selection of geomembrane materials in hydraulic engineering projects, considering various designed service durations.

Stress relaxation properties have a significant impact on the performance of polyvinyl chloride (PVC) geomembranes (GMBs) at the peripheral joints of the membrane faced rockfill dam (MFRD). This paper presents a fractional order viscoelastic model (FOVM) to measure the relaxation stress as a function of time. Model parameters were obtained by best fit to results from wide-width strip tensile tests conducted at three tensile rates and three initial strains for 48 h. The results of a 90 d stress relaxation test demonstrate the applicability of the model to describe the stress relaxation behavior of PVC GMBs. The tensile rate and initial strain marginally influenced the relaxation modulus rate, while having no effects on the fractional derivative order. Residual stress could account for the difference in relaxation stress between the longitudinal and transverse specimens. Finally, the FOVM could be used for predicting the service cycle under specifying failure stress criteria. Furthermore, it has great potential for applications in predicting the long-term deformation of PVC GMBs at the peripheral joints of MFRD. Furthermore, it has great potential for applications in predicting the long-term deformation of PVC GMBs at the peripheral joints of MFRD.