Effect of Matrix Modification on Durability of Cementitious Composites in an Acid Rain Environment

The durability of silane-modified mortar, a cementitious composite, in acid rain environment was investigated given its extensive usage as a structural material. The results indicated that the addition of silane decreased the compressive strength of the cementitious composite. Wetting angle was increased by incorporating silane into the matrix. Decrease in both water absorption ability and coefficient of capillary suction confirmed hydrophobicity as induced by silane addition. Results of mechanical testing, scanning electron microscopy and X-ray diffraction showed that the sulfuric acid resistance of mortar was enhanced by silane. Based on these results, it is revealed that silane addition inhibits the diffusion of water, and consequently, sulfate ion diffusion rate decreases, thereby resulting in reduction in the rate of corrosion of cementitious composites by sulfuric acid.

Numerical Study on Effects of Door-Opening on Airflow Patterns and Dynamic Cross-Contamination in an ISO Class 5 Operating Room

The contamination diffusion to the operating room when the door is open was simulated with a computational fluid dynamic(CFD) method,to give the extent of the contamination diffusion.The influence of the door-opening procedure was ignored since the door of the operating room is normally a sliding one.The flow field in the case of the 16 s course of opening the door was simulated.The simulated and the experimental results demonstrate that the extent of the contamination diffusion is around 1.5 m when there is no temperature difference between indoor and outdoor,and there is hardly any contamination diffusion when the temperature difference is 1 ℃.It can be concluded that the positive pressure difference in the operating room lost its function in preventing the contamination when the door is open.That the temperature of corridor is lower than that of operating room contributes to contamination control.Keeping 1 ℃ temperature difference between corridor and operating room and increasing positive pressure and air flow are suggested.It is more secure to set up an anteroom if persons come in or out of the operation room at the course of surgery.

Red Cement-based Decorative Mortar Prepared with Dry Electroplating Sludge Containing Pb as Red Pigment

Red cement-based decorative mortars were prepared with different content electroplating sludge containing Pb （EPSP）, and their colors, water absorption, strengths, hydration characteristics and heavy metal leachabilities were investigated. The experimental results show that EPSP can adjust the mortar color well as the red pigments exclusively used in the decorative mortarS. EPSP will result in the increase of water absorption, but the mortar produced with 5% EPSP still has the very satisfactory water absorption. The mortars with EPSP are provided with nearly the same compressive, flexural and tensile bond strengths as those of the control. EPSP has no notable influence on the paste hydration. But it can densify the mortar microstructures. It is also evident that heavy metal concentrations in leachates of the mortars with EPSP are far lower than the recommended in the GB5085.3-2007.

Numerical Controlled Processing Techniques for Optical Components

Comparied to traditional optical processing methods,numerical controlled surfacing techniques have irreplaceable effects especially in spherical and aspherical optics. In this paper,fabricating methods,mechanisms and processes are analyzed. Also,some processing difficulties and problems are discussed. The possible improvements and feasible methods are given.

UV Photodegradation of Polypropylene Thick Bars Containing Rutile-type TiO_2 Nanorods

Surface modified rutile-type titanium dioxide （CST） nanorods were used as a UV absorber in polypropylene （PP） thick bars in combination with the hindered amine light stabilizer （HALS） Chimassorb 944 （C944）. For all of the tested samples, the photodegradation was mainly limited in the region near the exposed surface, as proved by the carbonyl index and molecular weight. Compared with the typical HALS photostabilization system containing organic hindered phenol UV absorber Tinuvin~ 328 （T328）, the thickness of photodegradation region for PP/C944/CST was only a quarter to that for PP/C944 and PP/C944/T328, while the rates of reduction in molecular weight and increase in carbonyl index were much lower. Optical microscopic observation showed that the evolution of surface micro-cracks in PP/C944/CST was quite different from that in the other samples, while scanning electronic micrographs revealed that the depth of the micro-cracks in PP/C944/CST was much shorter than that in the others. It is therefore concluded that the protection of CST on PP thick bars is mainly attributed to the outstanding UV-shielding and cracks-blocking abilities.