Advanced Materials Research Vols. 194-196

Abstract: Early shrinkage of concrete includes plastic shrinkage before the final setting, drying shrinkage during hardening process and autogenous shrinkage. Concrete drying shrinkage which is caused by evaporation is a major factor for the concrete volume change. By ring constrained test and free shrinkage TONCEN test, this paper studies the impact of polypropylene fibers and SRA on the shrinkage properties of concrete at the early age. The test shows that the polypropylene fibers and SRA can significantly reduce the early shrinkage of concrete, and SRA works more evidently than polypropylene fibers.

Abstract: Combining with actual tunnel second lining crack field investigation and cracking reason analysis, on the basis of the simulation analysis of the carbon fiber reinforcement effect to the tunnel lining cracks of the tunnel segment intersection by use of finite element analysis software Ansys, proposed reinforcement solutions by grouting firstly for more than 0.05 mm cracks and then sticking carbon fiber on the concrete surface to reinforce. Epoxy resin stick carbon fiber in the tunnel crack zone to make carbon fiber and concrete structure work together, then reinforce and improve the mechanical properties. The determination of reasonable reinforcement solutions, choosing appropriate fiber materials and controlling of construction quality are effective measures to guarantee the carbon fiber reinforcement effect.

Abstract: This paper mainly studies the influence pattern of mechanical properties and anti-permeability and carbonation etc durability after adding the carbon fiber into the concrete. Results show that appropriate amount fiber seep into concrete can improve its mechanical properties and durability.

Abstract: Environmental Scanning Electron Microscope (ESEM) and Energy Dispersive X-ray Spectroscopy (EDS) were used to in situ observation microstructure character changes of hardened cement paste due to carbonation. Three types water-to-cement ratio of 0.53, 0.35 and 0.23 were research. When w/c=0.53, Carbonation enlarged the cracks, and some calcium carbonate spots appear on the calcium hydroxide crystals. When w/c=0.35, less cracks appear, and some white flocculent calcium carbonated appear on the calcium hydroxide crystals than above w/c=0.53 cement paste. When w/c=0.23, the microstructure character before and after carbonation have distinct changes, and some cracks become small or disappeared. Unhydrated cement clinkers continue to hydrate reactions and there are many white SiO₂•nH₂O (silica gel) after C-S-H gel carbonation in cement paste matrix.

Abstract: The rare earth complex terbium (III)-pyromellitic acid (H₄L)-1,10-phenanthroline (phen) nanorod was synthesized in the polyvinylpyrrolidone (PVP) matrix by a co-precipitation method. The chemical composition of the as-synthesized sample was speculated to be PVP/Tb₄L₃(phen)_0.75∙7H₂O by elemental analysis, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), and Fourier transform infrared spectroscopy (FTIR). The transmission electron microscopy (TEM) result exhibited that the as-synthesized sample was nanorods with diameters of ca. 150 nm. The X-ray diffraction pattern (XRD) of the sample showed that it was a crystalline complex. The thermogravimetric curve (TGA) analysis exhibited that the sample is stable below 450 °C. UV–Vis diffuse reflectance spectra exhibited that there is a broad and strong absorption band in the range of 280-350 nm. The photoluminescence analyses (PLA) indicated that the as-synthesized sample emitted the characteristic green fluorescence of Tb (III) ions under ultraviolet light excitation.

Abstract: Adopt the titanium sour D ester water solution legal system have of the Na rice TiO₂ does the zinc-air battery cathode catalyst. Shoot line Yan to cast light a table method(XRD) and scan an electronic microscope method(SEM) with the X, and deeply shoot an electronic microscope method(TEM) to carry on token to the TiO2 powder sample of making,[1] result enunciation titanium sour D ester water solution method legal system have of TiO₂ catalysts is the Rui titanium mineral type structure, grain the path be not the biggest over 50 nms.Adopt cathode very in the meantime to turn curve, the Heng electric potential turn on electricity with the Heng electric current turn on electricity etc. electricity chemistry test means, result detection,The TiO₂ has a better electricity catalyst an activity in the alkalescence lie the quality 6 mols/LNaOH, in keeping with do the zinc-air battery cathode catalyst.

Abstract: Replacement of steel fiber by scrap tires wire as shielding agent in cement-matrix composites was discussed in this paper. The electromagnetic shielding effectiveness (SE) of cement based composites materials containing FeCuNbSiB amorphous alloy powder and scrap tires wire were measured with coaxial planar－spectrum analyzer method. Results show scrap tires wire can effectively enhance the SE of cement composites in tested frequency range. The shielding effectiveness at 1.5GHz is 14.1 dB at a scrap tires wire content of 1.3 vol.% in cement paste. The SE of composites that simultaneously contain scrap tires wire and FeCuNbSiB powder is higher than singly use these shield agents.

Abstract: The objective of this study is to propose a light weight and suitable strength material as roof surface which can detain rainwater during rainy day and lower room temperature in sunny day by passive evaporative cooling. So blast furnace slag was used as the main raw material and clay as the subordinate ingredient to synthesize an alkali-activated cement matrix at room temperature. Furthermore the cement matrix were made into porosity by injecting prepared foam and attempted to improve strength by incorporation of short polypropylene fiber. Finally, the dry density of 453 kg/m3 and compressive strength of 4.5MPa porous roof material (slag-clay porous material) was gained. Variations of room temperature and heat flux transfer across porous material roof slab have been measured. The results showed that roof covered with slag-clay porous material can satisfactorily lower room temperature and reduce heat flux, as compared with OPC (ordinary Portland cement) roof layer simply. Covering slag-clay porous material layer as roof surface can create a more effective cooling system by utilizing its water absorption and evaporation capability during canicule, which provides a new approach to low carbon and energy saving technological development.

Abstract: We carried out experiments of the mechanical properties of frozen pipes under different temperatures (-5°C, -10°C, -15°C), obtained axial tensile stress - strain curves of the steel and performance of the overall bending under low temperature conditions. The results showed that: the freezing pipes bending capacity increased with the decrease of temperature, but the stiffness was decreased with the decreasing temperature; the steel yield strength and ultimate strength were both increased with the decrease of temperature, the elongation and sectional shrinkage were decreased with the decrease of temperature. The test results provided the basis for the further research of frozen pipes’ ductile-brittle transition, fracture and other acts in low temperature, and provided reference for the selection of frozen pipe and engineering design.

Abstract: In view of the phenomena that alkali-slag cement has high mechanical strength and good impermeability and they are closely related with the pore structure of cement stone,water glass was selected as the alkali activater, nitrogen adsorption method was adopted to study the pore structure of alkali-slag cement stone, while the pore surface fractal dimension was determined by fractal theory. The results show that the pore structure of alkali-slag cement stone posesses obvious fractal characters and that fits the Frenkel-Halsey-Hill(FHH) model quite well.So the pore surface fractal dimension can be used to synthetically evaluate the superior or inferior of the pore structure of cement stone.