Improvement of residual compressive strength and spalling resistance of high-strength RC columns subjected to fire

This paper investigates the spalling properties of high-strength concrete in order to improve the residual compressive strength and spalling resistance in specimens subjected to 3 h of unloading fire conditions. This study consists of three series of experiments with eighteen different specimens varying in fiber type and content, finishing material and simultaneous fiber content and lateral confinement. They were fabricated to a 300 × 300 × 600 mm mock-up size. Results of the fire test showed that the control concrete was explosive, while the specimens that contained more than 0.1 vol% of polypropylene (PP) and polyvinylalcohol (PVA) fibers were prevented from spalling. One specimen, finished by a fire endurance spray, exhibited even more severe spalling than the control concrete. The specimen containing 0.1 vol% of PP fiber and using a confining metal fabric at the same time, showed the most effective spalling resistance; in particular, the residual compressive strength ratio was even higher than that of the control concrete before the fire test. It was demonstrated that adding fibers in concrete prevented the spalling occurrence and confining metal fabric around the main bars of concrete specimens can secure the strength of structures during the conditions of elevated temperature.     

Novel Nafion/Hydroxyapatite composite membrane with high crystallinity and low methanol crossover for DMFCs

Summary Novel Nafion/Hydroxyapatite (HA) composite membrane with high crystallinity was fabricated to suppress methanol crossover for direct methanol fuel cell (DMFC) applications. In this study, water and methanol diffusivity were evaluated through water-methanol sorption/desorption test and methanol permeation experiments. It was shown that the water-methanol diffusivity and methanol crossover for the composite membranes decrease as HA increases. Structural variation was investigated with wide-angle x-ray. As a result, it was found that the crystallinity of composite membranes increases with HA whereas water uptake content decreases gradually. Methanol permeability using a diffusion cell reduced in the composite membranes, suggesting that high crystallinity and low water uptake of composite membrane result in the suppression of methanol crossover due to the incorporation of HA into Nafion structure.     

Synergistic effect of combined fibers for spalling protection of concrete in fire

This study demonstrates the synergistic effect of some particular combination of fibers that can provide significantly better spalling protection of concrete in a fire than single fiber by themselves at the same fiber content level. Various combinations of polypropylene, polyvinyl alcohol, cellulose and nylon fibers were investigated. Fire tests were conducted in accordance with ISO-834. The combination of nylon (9 mm length) and polypropylene (19 mm length) fibers found to provide the most optimum results. By combining these two fibers, the same level of spalling protection was achieved by three times less fiber content than the single type of 0.10% polypropylene fiber commonly prescribed. A “fiber effectiveness parameter” is proposed which is a function of total number of fibers per unit volume and length of fiber. This parameter is useful in providing quantitative explanations of various fiber additions and their spalling results in fire.     

Relationship between inter-aggregate spacing and the optimum fiber length for spalling protection of concrete in fire

Addition of polypropylene fibers in concrete for spalling protection in fire is well known, where the fibers melt in fire and percolate the concrete. However, the optimum fiber characteristics for spalling protection are not well understood. In this study, the optimum fiber length for spalling protection of concrete is found to be related to the inter-aggregate spacing of coarse aggregates, which is critical for the interconnectivity of adjacent aggregates surrounded by porous interfacial transition zones. The experimental test results showed that, for the concrete with maximum 20 mm of graded aggregates, with optimum 30 mm length fibers, almost no spalling was found; whereas other fiber concretes lost up to 92% of weight due to spalling. By evaluating the criteria of the optimum fiber length, this study also found the critical threshold of fiber numbers per unit volume.     

Soundproofing effect of nano particle reinforced polymer composites

In this paper, the effects of soundproofing by polymer and carbon-nanotube (CNT) composites were investigated. The specimens for sound insulation measurement were fabricated with Acrylonitrile Butadiene Styrene (ABS)/CNT composites. Tests showed that sound transmission loss of ABS/CNT 15 vol.% composite was higher by 21.7% (4.1 dB) than that of pure ABS specimen at a frequency of 3400 Hz. It was found that the principal factor influencing the improvement of sound insulations of ABS/CNT composites was increased stiffness by CNT additives. To demonstrate the practical applicability of polymer/CNT composites, tests were conducted for the reduction of operational noise from mechanical relay.     

Application of pulsed corona induced plasma chemical process to an industrial incinerator

Pulsed corona induced plasma chemical process (PPCP) has been investigated for the simultaneous removal of NO(x) (nitrogen oxides) and SO2 (sulfur dioxide) from the flue gas emission. It is one of the world's largest scales of PPCP for treating NO(x) and SO2 simultaneously. A PPCP unit equipped with an average 120 kW modulator has been installed and tested at an industrial incinerator with the gas flow rate of 42 000 m3/h. To improve the removal efficiency of SO2 and NO(x), ammonia (NH3) and propylene (C3H6) were used as chemical additives. It was observed that the pulsed corona induced plasma chemical process made significant NO(x) and SO2 conversion with reasonable electric power consumption. The ammonia injection was very effective in the enhancement of SO2 removal. NO removal efficiency was significantly improved by injecting a C3H6 additive. In the experiments, the removal efficiencies of SO2 and NO(x) were approximately 99 and 70%, respectively. The specific energy consumption during the normal operation was approximately 1.4 Wh/m3, and the nanopulse conversion efficiency of 64.3% was achieved with the pulsed corona induced plasma chemical process.     

Hydroxyapatite forming ability of electrostatic spray pyrolysis derived calcium phosphate nano powder

A novel fabrication technique, i.e., electrostatic spray pyrolysis (ESP), has been used in this study to prepare calcium phosphate nano powders. Final annealing was done at 400°C for 30 min in air. The hydroxyapatite-forming ability of the annealed powder has been investigated in Eagle’s minimum essential medium solution. X-ray diffracton, field emission scanning electron microscope, energy dispersive X-ray spectroscope, and Fourier transform infrared spectroscope were employed to characterize the annealed powders after immersion. The powder with an amorphous structure induced hydroxyapatite formation on their surfaces after immersion for 15 days.     

Surface modification of polymethyl methacrylate intraocular lenses with the mixture of acrylic acid and acrylamide via plasma‐induced graft copolymerization

An approach is presented for the graft copolymerization of acrylic acid (AAc) and acrylamide (AAm) mixture onto the surfaces of polymethyl methacrylate intraocular lenses (PMMA IOLs) treated with an Argon gas plasma, followed by the exposure to the oxygen atmosphere. In this case, peroxides formed by the plasma treatment are likely to be responsible for initiating the graft copolymerization. The amount of peroxides on the surface of PMMA IOLs was determined using 1,1‐diphenyl‐2‐picrylhydrazyl, and the maximum amount was found with the plasma treatment at 30 W for 20 s under 5 mTorr pressure. The surfaces of the grafted PMMA IOLs were characterized using Fourier transform infrared spectroscopy‐attenuated total reflectance (FTIR‐ATR), electron spectroscopy for chemical analysis, and contact angle meter. The FTIR‐ATR spectrum of PMMA‐g‐AAc‐AAm showed the characteristic band of PAAc at 1580 cm^?1 together with those of PAAm at 1670 and 1630 cm^?1, confirming that the copolymer of AAc and AAm was successfully grafted onto the surfaces of PMMA IOLs. The experimental data of O1s/C1s and N1s/C1s reasonably concurred with the calculated data, a strong indication that the pH value of the reaction medium at 3.77 could produce a graft with an equal molar ratio. Surface tension of the samples increased to 52 dyn/cm due to the graft of the hydrophilic monomers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2361–2366, 2002