Abstract: The paper presents the first scientific study of the stiffness, strength and energy absorption characteristics of the luffa sponge with a view to using it as an alternative sustainable engineering material for various practical applications. A series of compression tests on luffa sponge columns have been carried out. The stress-strain curves show a near constant plateau stress over a long strain range, which is ideal for energy absorption applications. It is found that the luffa sponge material exhibits remarkable stiffness, strength and energy absorption capacity that are comparable to those of some commonly-used metallic cellular materials. These properties are due to its light-weight base material, and its structural hierarchy at several length scales. Empirical formulae have been developed for stiffness, strength, densification strain and specific energy absorption at the macroscopic level by considering the luffa fiber as the base material. A comparative study shows that the luffa sponge material outperforms a variety of traditional engineering materials.
Abstract: As a new high performance construction material, concrete doped nano-TiO2 greatly expanded its application in engineering with the advantages of high strength and high durability. By compressive test of concrete block doped nano-TiO2 under the conditions of common conservation, this paper respectively studies the regulation of compressive properties of the concrete block affected by the factors such as concrete strength and nano-TiO2 dioxide.
Abstract: According to the axial compressive experiment of concrete cylindrical and quadrate specimens confined by Basalt fibers, the stress-strain curves, bearing capacity and peak strain were obtained. 12 quadrate and 12 cylindrical column specimens were prepared and wrapped with 2 to 4 layers of BFRP fibers. The results show that: (1) comparing with unconfined specimens, the compressive strength and peak strain of the specimens confined with Basalt fibers are improved significantly, not only cylindrical but also quadrate; (2) the compressive strength increases with the number of BFRP layers; with equal number of confinement layers, the compressive strength and peak strain of cylindrical specimens is higher than that of quadrate; (3) the wrapped fiber of quadrate specimens are more likely to rupture at the corners of specimen. Meanwhile, the compressive strength models of specimen confined by Basalt fibers were proposed, the theoretical values are in good agreement with the test data.
Abstract: The structure and properties of a kind of domestic continuous basalt fiber is analyzed in the paper. Chemical composition, crystal structure, thermal properties, flammability, mechanical properties and morphology of the fiber are investigated. Element analysis experiment shows that the basalt fiber is a kind of aluminosilicate fiber which mainly composed of the oxides of such elements as Fe, Si, Ca, Al, K, Mo, Ti, Ba and so on. X-ray diffraction indicates that the bulk structure of the fiber is non-crystal with short range order. SEM observation finds that basalt fiber is circular in cross-section and smooth in longitudinal direction. Solubility experiment reveals the superior resistance of the fiber to acids, alkaline and organic solvents. DGA demonstrates there are three weight loss stages in the process of elevating temperature. There are, respectively, evaporation of moisture in the fiber at about 100°C, decomposition of the residual carbonate minerals between 480°C and 630°C, and decomposition of newly generated carbonates between 850°C~995°C. In heatflow curve, there are also three endothermic peaks in which the first and the second correspond to the last two stages of weight loss and the third corresponds to melting process of the fiber and it onsets from 1122.14°C, comes to its peak value at 1194.96°C and ends at 1380°C. The tensile strength of the basalt fiber is better than S-glass fiber, worse than carbon fiber. Flammability of the fiber is also analyzed.
Abstract: In order to discuss the effectiveness of basalt fiber in reinforcing pavement performance of asphalt mixtures, the pavement performances of basalt fiber asphalt mixtures were investigated by tests of high temperature stability, water stability and low temperature crack resistance, and compared with the pavement performance of asphalt mixtures with polyester fiber and xylogen fiber, and that of reference mixture. The results show that pavement performance of fiber asphalt mixture are improved and optimized comparing with reference asphalt mixture, the performance of asphalt mixture with basalt fiber are excelled than those with polyester fiber and xylogen fiber while the dosage of fibers is keeping at the optimum.
Abstract: The steel-polypropylene hybrid fiber reinforced concrete can take full advantages of macro-scale crack resistance and toughening effect on the concrete matrix of steel and polypropylene fibers. The shortcomings of concrete are improved and there is a wide prospect application in engineering. This paper summarizes the enhancement theories of hybrid fiber reinforced concrete to explain its strengthening mechanism. The research status is reviewed including mix proportion design, working performance of fresh concrete, mechanical behaviors, durability (impermeability, shrinkage and others), and engineering applications etc. Some further researches are forecasted. It would be very useful to apply and popularize steel-polypropylene hybrid fiber reinforced concrete.
Abstract: This paper introduces the test results of the flexural performance of CF40 steel fiber reinforced concrete (SFRC) designed by the binary superposition mix design method. The flexural strength and flexural load ~ deflection curves were got from the test SFRC specimens with the different fraction of steel fiber by volume and the different thickness of cement paste wrapping steel fibers. The effects of the fraction of steel fiber by volume and the thickness of cement paste on the flexural strength and toughness of SFRC are analyzed. It is demonstrated that the flexural toughness of SFRC increases with the increase of the fraction of steel fiber by volume, the reasonable thickness of cement paste wrapping steel fibers is 1.0mm.
Abstract: In order to study the constitutive model of fiber reinforced concrete (FRC) for future, this paper emphasizes on three aspects. FRCs constitutive model based on damage mechanics has been reviewed. The knowledge and development of constitutive models is discussed based on its historical developments and logical relations. Damage model of FRCs which has been developed in recent years is summarized at macro and micro levels. The development trends of constitutive modeling for FRCs are suggested on the basis of our understanding of essential physical properties of FRC, e.g. its nonlinearity
Abstract: The tests were carried out to study the effects of the fraction of steel fiber by volume and the thickness of cement paste wrapping steel fibers on the axial tensile properties of steel fiber reinforced concrete (SFRC). The strength grade of SFRC was CF40 with the fraction of steel fiber by volume varying from 0.5% to 2.0%, and the thickness of cement paste wrapping steel fibers varying from 0.8mm to 1.2mm. The tests were conducted by WAW-600 electric-hydraulic servo-type test machine. The results show that the axial tensile properties such as the axial tensile strength, the fullness of stress-strain curve, the tensile energy and the axial tensile toughness ratio are all improved obviously by the adding of steel fiber in concrete. The reasonable thickness of cement paste wrapping steel fibers is 1.0mm. The formulas for stress-strain relationship of SFRC in axial tension are proposed.