The aim of this paper is to investigate the effects of different activator -to-solid ratios on water consumption, setting time, fluidity, adhesion properties, bulk density and mechanical properties at standard consistency. The microstructural mechanisms of metakaolin geopolymer were also investigated by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The experimental results showed that for the different activator to solid ratios and mix designs used in this paper, higher ratios enhanced the fluidity, consistency, and setting time. Besides, the standard consistency water consumption of the metakaolin polymer mortar was reduced. SEM and FT-IR tests revealed macroscopic phenomena where the polyaluminum silicate structure improved with increasing activator -to-solids ratios. Excessive sodium silicate reduced strength, thus affecting mechanical properties.
Abstract This article aimed to research the effect of organic silicon on the density, mechanical strength, water absorption, porosity, and crack resistance of cementitious construction materials. Modified cement mortar was prepared by adding different amounts of organic silicon into control cement mortar. Mechanical strength was evaluated using bending and compressive strength tests. Porosity was evaluated to assess the inner structure of cement mortar. Furthermore, the micromechanism of modified cement mortar and control cement mortar was explored using the nitrogen-absorption test and a Scanning Electron Microscope (SEM). Experimental results showed that for the organic silicon and mix design used in this article, the incorporation of organic silicon generally reduced the mechanical strength and density and increased the water absorption, porosity, and crack resistance. In addition, the analysis of the nitrogen-absorption test and SEM test revealed the modified mechanism and the connection between the macroscopic properties and micromechanism of modified cement mortar.
Objective To explore a performance standard for hemolytic toxins in harmful bloom algae. Methods Using Chattonella marina as hemolytic substances producing organism, methods and conditions were compared and optimized including cell breakage, distillation temperature, blood origin and storage of algal pellets in extraction and activity determination of hemolytic toxins. Results The hemolytic activity of C. marina broken by supersonic method was 288.23 HU/L, higher than that by freezing--thawing method (94.89 HU/L), suggesting that supersonic method could be more optimal to break microalgal cells. When the supersonic treatment times were 5, 10, 20 and 30 min, the hemolytic activities were 80.57, 157.45, 288.23 and 279.17 HU/L, respectively, indicating that 20 min of supersonic treatment was suitable. When the distillation temperature were 40, 60 and 80 degrees C, the hemolytic activities were 288.23, 124.97 and 120.68 HU/L, respectively, meaning that high distillation temperature in extraction of hemolytic substances lowed the hemolytic activities of samples. Bloods from various animals such as human, fish, rat and rabbit exhibited different sensitivity to the hemolytic toxins, of which rabbit erythrocyte was the most sensitive. The hemolytic activities to human, fish, rat and rabbit were 244.98, 288.23, 266.35 and 195.47HU/L, respectively. The storage of algal pellets for 3 days at the temperature of 0 degrees C did not reveal a significant loss in hemolytic activity, while significant losses were observed at the temperature of 20 degrees C or -20 degrees C only after one day. Conclusion Supersonic method could be more optimal to break cell in comparison with freeze-thaw method. Optimal conditions for broken algal cells by supersonic method were 200 W for 20 min at the temperature of 4 degrees C. The distillation temperature in extraction of hemolytic substances should be maintained under the temperature of 40 degrees C. The rabbit erythrocyte could be the most optimal blood to detect hemolytic activity due to its high sensitivity. The algal pellets could be kept at the temperature of 0 degrees C for 3 days before determination of activity.
A laboratory experiment with orthogonal design was conducted to study the effects of factors salinity, temperature, and light intensity on the growth and toxin production of Chattonella marina. Three levels of salinity (22, 33, and 45), temperature (20 degrees C, 25 degrees C, and 30 degrees C) and light intensity (2000, 3000, and 4500 lx) were installed. In all treatments, the three factors had no significant effects on the growth of C. marina, but salinity significantly affected the toxin production of C. marina. Under salinity 45, temperature 30 degrees C and light intensity 2000 lx, C. marina had the maximal growth rate; under salinity 22, temperature 20 degrees C and light intensity 4500 lx, the toxin production of C. marina was the maximal. Low salinity was not favorable to the C. marina growth but favorable to its haemolytic toxin production. When the growth of C. marina was limited, its haemolytic toxin production increased.
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