Search Results (2)

The early strength of geopolymers (GPs) and their composites is higher, and the hardening speed is faster than that of ordinary cementitious materials. Due to their wide source of raw materials, low energy consumption in the production process, and lower emissions of pollutants, they are considered to have the most potential to replace ordinary Portland cement. However, similar to other inorganic materials, the GPs themselves have weak flexural and tensile strength and are sensitive to micro-cracks. Improving the toughness of GP materials can be achieved by adding an appropriate amount of fiber materials into the matrix. The use of discrete staple fibers shows great potential in improving the toughness of GPs. Sisal is a natural fiber that is reproducible and easy to obtain. Due to its good mechanical properties, low cost, and low carbon energy usage, sisal fiber (SF) is a GP composite reinforcement with potential development. In this paper, the research progress on the effect of SF on the properties of GP composites in recent decades is reviewed. It mainly includes the chemical composition and physical properties of SFs, the preparation technology of sisal-reinforced geopolymers (SFRGs), the microstructure analysis of the interface of SFs and the GP matrix, and the macroscopic mechanical properties of SFRGs. The properties of SFs make them have good bonding properties with the GP matrix. The addition of SFs can improve the flexural strength and tensile strength of GP composites, and SFRGs have good engineering application prospects. Full article

The aim of our study was to identify appropriate multiparametric fluorescence ratios to evaluate the response of tomato (Solanum lycopersicum) genotypes to salinity. In this context, we hypothesized that the fluorescence indices BFRR_UV, FLAV, NBI and SFR provided by the multiparametric fluorescence technique reveal the impact of salinity on tomato leaves. For this purpose, the tomato genotypes H-2274, Harzfeuer and Rio Grande were grown in the greenhouse under standard or saline conditions. As reference measurements, we recorded the maximum photochemical efficiency of photosystem II (Fv/Fm) via pulse-amplitude-modulated (PAM) chlorophyll fluorescence (ChlF) and analyzed the concentrations of sodium (Na), potassium (K), magnesium (Mg), proline and chlorophyll (Chl). In general, “Harzfeuer” showed a more pronounced response to salinity, as revealed by the increase in Na and proline as well as the decrease in K concentration. Significant differences between the control and the salt treatment were also assessed with Fv/Fm. The ratios BFRR_UV, FLAV, SFR_G and NBI_G increased significantly in the salinity-exposed plants. These ratios, compared with Fv/Fm, also provide precise but more rapid information about the impact of salinity on tomato leaves. On this basis, we demonstrate that the multiparametric fluorescence indices provide a valuable, rapid and practical tool for the in situ monitoring of the physiological status of plants exposed to salinity. Full article