Advanced Materials Research Vols. 168-170

Abstract: The joint section between steel and concrete box girders is the key localization of the super-long span hybrid girder cable-stayed bridge in the Edong Yangtze River, a high strength self-compacting concrete (SCC) was required to use in the joint section. This paper systematically investigated the performances of three types of C55 grade self-compacting concretes (SCCs), such as plain SCC, micro-expansion and polypropylene fiber reinforced SCC and steel fiber reinforced SCC. The results indicated that the steel fiber reinforced SCC had the best workability and mechanical properties. The flexural toughness of the steel fiber reinforced SCC was much better than that of the other two types of concretes. The addition of steel fiber, or polypropylene fiber and expansive agent improved the crack resistance of SCC, and the micro-expansion and polypropylene fiber SCC reinforced had better crack resistance than steel fiber reinforced SCC. The three types of SCCs have very high chloride penetration resistance and advanced freezing and thawing resistance. Moreover, the test achievement of concrete casting technology for the full-scale model of steel girder chambers in the joint section is introduced. The steel fiber reinforced SCC was preferred to be used in the steel-concrete joint section.

Abstract: Bi-stable structure can be stable in both its extended and coiled forms. For the elastic isotropic shell, a theoretical model in terms of only two parameters is proposed. Based on the principle of minimum potential energy, the conditions for bi-stability of isotropic shell are derived. The results indicate that, a pre-stressed shell will have its two stable states if the acting pre-stress satisfies some confined conditions. Further, the bi-stable model is improved taking into account boundary effect of the shell. The results show the rolled-up radius for the second stable state becomes larger. Meanwhile, using shell element in ABAQUS code, numerical simulation on bi-stable process is carried out. The numerical results of rolled-up radius characterizing the bi-stability agree well with the predicted results.

Abstract: Experimental data are obtained by a series of fundamental mechanical properties experiments on autoclaved sand-lime brick masonry such as compressive strength experiment， shear strength experiment, bending tensile strength experiment, they provide the experiment evidence for writing Hunan province engineering construction local standard named "Technical specification for autoclaved sand-lime brick masonry building ". And following conclusions are drawn through analyzing experiment data and experiment phenomenon: With mortar intensity increasing ,the masonry 's cracking load and ultimate load are approaching in the compression strength experiment; Except that the experiment average value in the bending tensile experiment of masonry along with joint section is lower than the calculated value of standardized formula obviously ,the other are bigger than that of standardized formula; There is a feature of optimal combination of strength for mortar and block; The author derived the formula of bending tensile strength of autoclaved sand-lime brick masonry.

Abstract: The volume parameter of matrix asphalt mixture is an important target in the design of the semi-flexible pavement. The research used volume-standar to design four kinds of matrix asphalt mixture, fulfilled mechanics performances and performances of semi-flexible pavement material with different aging, compared with common asphalt mixture and researched the effect by air void and pore structure. It proves that the compacted intensity, high-temperature stability and low temperature bend of the semi-flexible pavement material is better than common asphalt pavement material, the performances of matrix asphalt mixture with high air void is better. As for matrix asphalt mixture with same air void but different pore structure, the performances of homogenous grade design is prior to consecutive grade disign.

Abstract: to evaluate the influence of soil-water coupled and shield tunnel construction induced around soil disturbance damage on ground surface settlement, the process of shield tunnel construction induced around soil disturbance is analyzed, the FLAC3D numerical simulation are carried out, and a newly-modified tunnelling-induced ground settlement calculation method based on disturbance degree of around soil and soil-water coupled is presented, and these methods are applied in case of Beijing Metro 10^th Line. It is indicated that considering the influence of the shield tunnelling-induced around soil disturbance damage, and soil-water coupled induced soil properties weakening and the excess pore water pressure dissipating induced soil consolidation to the ground surface settlement are necessary, the calculating result of the newly-modified surface settlement prediction method, and the result FLAC3D numerical simulation all agree well with in-site observed data of Beijing Metro 10th Line.

Abstract: To establish an analytic model for carbon emission of building lifecycle, based on life cycle theory, a generic model for energy carbon emission of building materials was proposed. With the model, building materials were classified into several categories, such as cement, steel etc. Furthermore, some product from each category, such as PS325 in cement, was selected as a benchmark of this category. And then product coefficient and region coefficient were induced to express the differences in products and regions or manufacturers. With the proposed model, generic models for cement and steel were established. And it is found that energy carbon emission intensity of steel is around 30~40 times than that of cement. Energy carbon emission of PI525 and PO425 are 51% and 34% more than that of PS325, respectively. Carbon emission of large-scale steel and cold rolling strip is the most emitter in steel products.

Abstract: Effects of steel slag powder on properties of cement and concrete are investigated. Results show that with the increase of steel slag power, water requirement of normal consistency is decreased, and the setting times are prolonged. The early mortar strength is lower, but late strength rate of increase is great. Steel slag powder is compatible with blast furnace slag. Moreover，concrete，which has harmonious development strength and excellent workability can be obtained by mineral additives two-element compounding.

Abstract: In the damage research before on the CT image of quasi-brittle materials such as concrete, the damage evolution is often described by the change of average CT values or image threshold segmentation method. However, the evolution of average CT values is insensitive to the damage, and the threshold value is always not only, which grimly depends on the researchers’ judgment. Because CT image is a gray image and different grayscale expresses different density distribution, it is tried in the paper to express the variety of material density with variety of grayscale of CT image. A description index of Rd from fractal theory is introduced in the paper to describe the variety of grayscale. Thereby, a damage variable is defined by Rd index, which can be used to study the developing process and evolving rule of concrete damage.

Abstract: Cellulose treated with flame retardant was studied by thermogravimetry (TG), differential thermal analysis (DTA), limiting oxygen index (LOI) and IR. The kinetic parameters for the thermal degradation are obtained following the method of Broido. For the flame retardant cellulose, the activation energy and decomposition temperature were much decreased while char yield and LOI were increased. The main thermal decomposition of the samples with higher LOI occurs at lower temperatures, while that with lower LOI occurs at higher temperatures.

Abstract: The marked brittleness of concrete could be overcome by the addition of fibers. This paper experimentally investigated the mechanical properties and constitutive relationship of different fiber reinforced concrete. It is shown from the results that the compressive strength and peak strain of concrete with fiber have little improvement, but the ultimate strain, deformation capacity, toughness and energy dissipation capacity are improved greatly. The damage constitutive model recommended by the emendatory code for design of concrete structure (appendix C) (GB50010-2002) is applied for calculations and analyses according to the test results. The damage constitutive model and non-elastic constitutive model of different fiber reinforced concrete are established based on the test results. It is indicated from the analyses that the constitutive models established in this paper are in accordance with the characteristic of the fiber reinforced concrete in loading process. The damage constitutive model in appendix C in code could be applied directly in some low precision calculation and engineering application.