No abstract

No abstract

Surfaces of hydraulic concrete conduits where significant abrasion of waterborne sediment can occur often degrade and need a regular repair to maintain their serviceability. In this research, thin overlay made of fiber reinforced cement mortar was introduced as a repair measures. Its resistance to underwater abrasion was therefore experimentally evaluated following the procedures of ASTM C 1138. This research utilized three types of fiber: steel fiber, polypropylene fiber, and micro polypropylene fiber (the micro polypropylene fiber was used only in a combination with either the steel or the polypropylene fiber). The influence of these fibers on the abrasion resistance of fiber reinforced cement mortar was then determined in terms of weight loss. The weight loss results showed that the fibers added to mortar specimens can enhance the abrasion resistance. Between the steel and polypropylene fiber, the latter provided better abrasion resistance. In case of the combination mixes, the micro polypropylene fiber increased abrasion resistance when combined with the polypropylene fiber but had no benefit when combined with the steel fiber.

Currently, nano-scale zero valent iron particles (nZVI) are being increasingly used in many types of environmental remediation. Due to their usage, nZVI can be left in the environment and may cause toxic effects to living beings, especially surrounding microorganisms. Environmental bacteria in soil and water are some of the main factors affecting plant productivity and other microorganisms in ecosystems. This study evaluated the toxicological effects of nZVI and aged nZVI on bacteria commonly found in the environment. Bacterial, namely E. coli, P. aeruginosa, S. aureus, B. subtilis, and Rhodococcus sp., were treated with different concentrations of nZVI at different times of exposure in in vitro conditions, and bacterial cell viability was determined in order to analyze the toxic effects of nZVI over the course of treatments. The data revealed that at the highest nZVI concentration (1,000 mg/L), B. subtilis and Rhodococcus sp. had the highest resistance to nZVI (49.35% and 48.31% viability) and less resistance in P. aeruginosa (2.26%) and E. coli (0.50%) was observed. The growth of microorganisms significantly increased after exposure with seven and 14-day aged nZVI particles. Therefore, the toxicity of aged nZVI to microbial organisms was reduced. Hence, this study demonstrated the toxic effects of nZVI and aged nZVI particles on several species of bacteria in vitro. Less toxicity to bacteria was observed in aged nZVI. These findings provide more understanding in the toxic effect of nZVI to microorganisms.

The objective of this research is to study equilibrium adsorption, adsorption isotherm and the amount of the phytochemical called Micronice Bio MEX 3, which is adsorbed on various supporters. Micronice is a biodegradable chemical liquid product collected from Technogreen Company Limited. The supporters in this work are activated carbon, zeolite and brick which are used as adsorbents. The supporters were immersed in the Micronice with various periods to find out their adsorption equilibrium time. The results show that the adsorption equilibrium time for all supporters is 60 minutes and the mass adsorption percentages of activated carbon, zeolite and brick are 14.05%, 1.58% and 2.24%, respectively. An adsorption isotherm can be described by the Langmuir and Freundlich models. The Freundlich constants of activated carbon, zeolite and brick are KF= 4.76 x10-8(mg/g)(L/mg)1/n, 7.15x10-8(mg/g)(L/mg)1/nand 1.10x10-4(mg/g)(L/mg)1/n, n = 0.772, 0.619 and 0.922, respectively. The Langmuir constants of activated carbon, zeolite and brick are KL= 756.62 L/mg, 12,924 L/mg and 3,918.60 L/mg, qo= 1,428.57 mg/g, 44.25 mg/g and 303.030 mg/g. The results present that the adsorption mechanism of all supporters can be well described by both Langmuir and Freundilch models and the best supporter is activated carbon.