Advanced Materials Research Vols. 168-170

Abstract: The binary superposition mix design method is constructed to quantitatively calculate the compositions of steel fiber reinforced concrete (SFRC), which brings into sufficient cement paste wrapping steel fibers to strengthen the boundary surfaces of steel fibers with base concrete. The principle of the method is firstly introduced. The experiments were carried out to evaluate the validity of the method. In the experiment, the cubic and axial compressive strength as well as the splitting tensile strength of SFRC affected by the fraction of steel fiber by volume and the average thickness of cement paste wrapping steel fibers were tested. The results are analyzed on the basis of former studies specified in the current technical specification for fiber reinforced concrete structures, which show that the larger strengths especial the splitting tensile strength of SFRC in grade CF50 can be got by the method, but the less splitting tensile strength of SFRC in grade of CF40 should be further studied.

Abstract: The paper is the second part of the study on binary superposition mix design method for steel fiber reinforced concrete (SFRC), which introduces the experimental results of flexural tensile strength and flexural toughness of SFRC. Based on the test, the effects of fraction of steel fiber by volume and average thickness of cement paste wrapping steel fibers on flexural tensile strength and toughness of SFRC are analyzed. The effect coefficient of steel fiber on flexural tensile strength of SFRC is suggested on the basis of the formula specified in current technical specification for fiber reinforced concrete structures. The flexural toughness of SFRC raises with the increase of fraction of steel fiber by volume, but less affected by the average thickness of cement paste wrapping steel fibers.

Abstract: In order to make clear of the effects of the change in fineness of fly ash on air-entrained concrete, 2 series of laboratory experiments were carried out using 6 kinds fly ash with the specific surface area in the range from 2500 to 4400cm2/g. The test results indicated higher slump and lower air-entraining content and higher dosage of air-entraining agent for fly ash with higher specific surface area. Compressive strength was found to increase with the increases of specific surface area of fly ash, while drying shrinkage and carbonation were found to show different tendency with change in fineness of fly ash.

Abstract: The validity of the wet-sieving concrete technique for building the reinforced composite concrete wall are demonstrated in the paper. The fine aggregate concrete made by ordinary concrete passing the sieve with square mash of 15 mm was cast for the surface layer, the recomposed concrete mixed by the residual concrete stayed on the sieve with the ordinary concrete was cast for the reinforced concrete structural wall. The mechanical properties such as the cubic and compressive strengths, the elastic modulus and the splitting and flexural tensile strengths of the fine aggregate concrete, the recomposed concrete and the ordinary concrete were tested and analyzed. The results show that the elastic modulus and splitting tensile strength of fine aggregate concrete reduce in some extent compared with that of ordinary concrete, the mechanical properties of recomposed concrete are almost the same as that of ordinary concrete.

Abstract: six partial bonded concrete beams prestressed with CFRP tendons are tested under monotonic loads. deformation of this kind of beams with varying unbonded length are systematically investigated. full-range analysis for deflection performance of partial bonded CFRP prestressed beams is performed by using ADINA. The analytical results agree well with the experimental results.

Abstract: Adopting the two systems-common base and base isolation and inputting El-Centro wave as the earthquake wave, in this paper, comparative analysis of structure’s earthquake-resistant performance was conducted on a 6-layer custom steel structure residence in Changzhou area. The result shows that the gradually matured isolated technology can be applied to steel structure as well, which means the isolated steel structures possess the same characteristics as other isolated structures. With the satisfaction of required bearing capacity, the structural reaction to earthquake has been effectively reduced and its safety has been guaranteed after considering the isolation of steel structure residence; moreover, the storey accelerations reaction has also been greatly declined, meeting higher requirements towards comfortableness of residence structure. Meanwhile, by nonlinear dynamic analysis of simple Bouc-Wen hysteretic model, the requirement towards the biggest ductility was discussed and a brief analysis of the life cycle cost of this residence was worked out. The analysis result demonstrates that the isolation layer has effectively controlled the vibration of superstructure, which would contribute to the reduction of seismic hazard.

Abstract: Aminobenzenesulfonic-based superplasticizer is a kind of high range water reducer synthesized by sodium aminosulfonate, phenol and formaldehyde, as the expensive phenol and the bad workability of concrete added with it, so its application is limited. Bamboo tar is one of the byproducts from bamboo charcoal production, and for its complicated components it isn’t utilized effectively until now. Crude phenols extract was obtained from bamboo tar by using sodium hydroxide solution, and the synthesis of modified aminobenzenesulfonic-based superplasticizer by using crude phenols extract to substitute part of phenol was optimized, and the fluidity of cement paste, compressive strength and water-reducing rate of concrete added superplasticizers were also determined in this paper. The research results indicated that the fluidity of cement paste, concrete compressive strength during the same period, the water-reducing rate and the workability of concrete added with modified aminobenzenesulfonic-based superplasticizer synthesized by using crude phenols extract to substitute 10% phenol were better than that added with aminobenzenesulfonic -based superplasticizer synthesized by only phenol.

Abstract: Self-igniting gangue concrete from C15 to C40 was successfully produced with fine and coarse aggregate of coal gangue through mix design method of lightweight aggregate concrete. It concluded that Self-igniting gangue concrete with reasonable grading can reach to the target strength. The basic properties of Self-igniting gangue concrete between Coal Gangue Portland cement and Portland cement were investigated, and mechanism was analysis. The coal gangue content was from 705 to 80% in the concrete. The technology can not only relief the scarcity of natural aggregate, but also employed the solid waste, and it was suitable for sustainable development in 21 century.

Abstract: Fiber Reinforced Polymers (FRP) is a new composite material with characteristic of high tensile strength, light weight and perfect resistance to corrosion. Therefore, it is a perfect reinforcing material. To make good use of FRP, its mechanics need to be severely studied. We study the mechanics of FRP by means of experiment. The Yong’s modulus and the ultimate tensile strength of GFRP, which will be used in a bridge, are measured.

Abstract: Through the three-point bending test on the specimens of steel fiber reinforced high strength concrete (SFHSC) and plain high strength concrete (HSC) with the size of 100 mm×100 mm×515 mm, the effects of influencing factors including the fiber volume fraction (ρf) and relative notch depth (a/W) upon the fracture energy and the work of applied force (gravity and external force) were studied. The results show that the effect of ρf upon the fracture energy is more obvious; the variation tendencies for the increment ratio of the fracture energy and that of the work of applied force are different under different factors; the fracture energy is dependent on the work of external force. Based on the test results, the formula was established for calculating the fracture energy.