Advanced Materials Research Vols. 374-377

Abstract: The cement powder materials are evaluated by fractal theory. Fractal characteristic parameters are analysed and evaluated by the method of laser particle size analyzer, microscope, transmission electron microscope. In this paper, cement powder materials has good self-similarity. Fractal dimension of grading is tested and evaluated by laser particle size analyzer, fractal dimension of cluster is tested by microscope, fractal characteristic of particle distribution is tested by transmission electron microscope. Compared with traditional weight of screen residue and specific surface area, those methods are more careful. Fineness fractal parameters and activity of ultra fine fly ash and pulverized slag have good linear dependence relation that is evaluated by fractal dimensions. Fractal characteristics provide an important basis to further explore the inherent relation of cement powder materials and concrete material density effect.

Abstract: A and B two-component solid chemical cleanser was prepared in order to clean the fouling in floor heating pipe effectively. In stated cleaning conditions, the fouling removal rate of this cleanser was greater than 97%, cast iron corrosion rate was much lower than 6 g/(m²•h) and brass corrosion rate was much lower than 2 g/(m²•h). The cleanser is solid, so its storage and transportation are convenient and its usage is easy and safe.

Abstract: Anchor bolts are set in some elastomeric bearings of large-span column-supported spatial steel roofs. Besides helping the bearing in-site assembly, the bolts play the roles of sliding position limitation and vertical anchorage. To analyze the effect of bearings on nonlinear structural behavior, the bearing stiffness change is studied just before and after the elastomer pad is in contact with the bolts. For the bearing that the pad is glued with the top/bottom steel plates, three kinds of relation of pad and bolts are discussed and an approximate horizontal stiffness formula is obtained with parametric analysis method. Based on the analysis results a stiffness expression for sliding elastomeric bearings is deduced. To solve the computational problem caused by the bearing stiffness changes, an improved imbalance force vector formula is proposed. Case study shows that the bolts have influence upon the computed results more significantly.

Abstract: This paper made a study on the effect of different vibrating parameters on the air content and compressive strength of concrete by the test of using the combining method of vibrating and forced mixing, and compared it with common forced mixing and mixing with air entraining agent. It indicated that the blade of the mixer, also as the vibrating source of vibrating mixing, had a significant effect on the air content of fresh concrete and compressive strength of hardened concrete; the air content of the fresh concrete could be up to 3.0%~3.5% when the vibrating strength was 4~8, and meanwhile the compressive strength of the hardened concrete was higher; different with improving the air content by adding air entraining agent, the vibrating mixing could increase the air content in the concrete by more retained air from bubbles refined in the mixing process and make the diameters of pores inside in the decreasing direction. In this case, it could not only improve the air entraining effect to achieve the high value of air content required by the construction, but it also could increase the compressive strength of the concrete comparing with the forced mixing with air entraining agent.

Abstract: In order to describe the damping characteristics of building materials and members, the formula for calculating loss factor which concerns with the internal loss factor and edge losses was derived from the concise physical relationship and, calculations of loss factor of some common building materials and members are presented. Therefore, the loss factor curves of among the walls which made of different materials are gained. It is shown that at low frequency total loss factor (damping) of a building material gradually decreases with the frequency and is also dependent on the thickness of the wall and its longitudinal wave speed, and at high frequency it tends to a constant.

Abstract: Carbonation is one of the key factors that result in the corrosion of the reinforcing steel embedded in concrete. In this work, a novel method to improve the resistance to carbonation of concrete was presented, i.e. the surface of the concrete specimens were treated by Super-absorbent resin (SAR) synthesized in situ, the prepolymer solution of poly (acrylic acid-co-acrylamide) with initiator and crosslinker was impregnated in the capillary-pores of concrete, then the acrylic acid and acrylamide copolymer by self-crosslingking under the initiator to synthesize SAR of poly (acrylic acid-co-acrylamide). The backbone of SAR is characterized by FTIR spectrum; the resistance to carbonation of the concrete with and without treatment by SAR was studied and the carbonation depth of concrete after the accelerated carbonation testing was measured. The results show that the concrete specimens treated with SAR have higher resistance to carbonation than that of the blank concrete specimens due to the synthesized SAR being swollen after absorbing water, filling the capillary-pores of concrete and reducing the ingress of CO2 and H2O.

Abstract: The Chaidaer-Muli Railway (abb., Chaimu Railway) was constructed in the Qilian Mountains, where middle-latitude swampy permafrost regions are developed. About 20km embankment was equipped with heat pipes. Taking into account the characteristics of local climate, the interaction between heat pipe and ground soils and secondary standard adopted by the Chaimu railway in accordance with the national railway, the structure and design parameter of the heat pipe were optimized. The wick structure and the adiabatic section were removed; the condensing section was reduced to 1.5m in length. In order to examine the cooling effect of heat pipe in the middle-latitude swampy permafrost, a testing field was built up in the middle part of the Chaimu Railway in the year of 2008. According to the field data from 2008 to 2010, cooling radius of heat pipe is 2.4m if it is treated as a standard that mean annual ground temperature at 3.0m deep was cooled down by -0.5°C. The results proved that design interval between heat pipes can meet the demands of cooling frozen soil roadbed in the Chaimu Railway.

Abstract: Before the construction of hydraulic structure, aggregate must be cooled or heated by air (we call it aggregate air cooling or heating in this paper) or other technologies to the required temperature. Previous model of aggregate air cooling or heating cannot provide the center temperature of each aggregate. So a more accurate mathematical model is developed to determine the thermal performance of aggregate, and the surface heat transfer coefficient of wet aggregate is revised. This model can predict the center temperature of an aggregate and can accurately calculate the cold down time or temperature distribution of aggregate, so that the refrigeration or heating capacity can be reasonably supplied. It’s significant for foundation engineering of hydraulic structure.

Abstract: In order to study the mechanical performance of self-compacting reinforced concrete beam with recycled coarse aggregates, recycled concrete and recycled gravel were taken as coarse aggregates with the particle size from 50 to150mm, two groups of specimen of self-compacting reinforced concrete beams with recycled coarse aggregates were made. After seven days, their bending strength were tested using method of one-third point loaded of simple beam on the testing machine. The results showed that the recycled coarse aggregates are bonded closely with the self-compacting concrete, its bond performance is good; Compared to ordinary reinforced concrete beam, it shows a smaller stiffness and a bigger mid-span deflection. In addition, the different combination of recycled concrete could reduce the self-compacting reinforced concrete’s stiffness with recycled coarse aggregate and increase its deflection.

Abstract: A type of small-scale fibers with dumbbells on two ends and notches in the middle was first designed to improve the workability and crack resistance of fresh high performance steel fiber reinforced concrete (HPSFRC). By using the fiber, the HPSFRC was continuously pumped to 306 meter high Sutong bridge tower. To ensure crack resistance of HPSFRC, tests concerning both non-loaded crack and structural crack were systematically performed, respectively. Then, the mechanisms behind the macro-behaviors were explored. Finally, life assessment method of HPSFRC that focused on the fatigue loading coupled with chloride and carbonation environment was presented by considering the effects of different fatigue degree on concrete durability. The results demonstrate that the steel fiber has the remarkable ability to restrain shrinkage and resist structural crack. It was also shown that the small-scale steel fiber can greatly improve the fracture toughness and fatigue property. In addition, the increased degree of damage due to fatigue loading would shorten the service life of concrete and the service life of HPSFRC under the multi-damage of fatigue loading and environmental loading would be longer than that of plain concrete.