Applied Mechanics and Materials Vols. 438-439

Abstract: This paper presents results from an experimental study on the behavior of circular high-strength concrete (HSC)-filled fiber reinforced polymer (FRP) tubes (HSCFFTs). Concrete-filled FRP tubes (CFFTs) have received significant research attention over the last two decades and experimental investigations into the axial behavior are abundant for normal-strength concretes (NSC) confined by either carbon FRP (CFRP) or class FRP (GFRP). However, the same cannot be said for CFFTs filled with HSC or manufactured with other fiber types such as aramid or high-modulus carbon FRP (AFRP and HMCFRP), where experimental testing is very limited. To address this research gap, this study examined the compressive behavior of 24 test specimens prepared with three different fiber types (CFRP, HMCFRP and AFRP) and manufactured with HSC. The experimentally recorded stress-strain relationships are presented graphically and the influence of fiber type and other key experimental outcomes are discussed. The results indicate that fiber type has a significant influence on the axial compressive behavior of HSCFFTs.

Abstract: On the basis of the ultrasonic examination of concrete filled steel tube Pylon Bridge, comprehensive research and application analysis of nondestructive testing technology was carried out on the detection of micro-expansive concrete filled steel tube through the study of concrete filled steel tubular column (experimental section), which provide a theoretical basis for the detection of this kind of concrete.

Abstract: An experimental study has been conducted to investigate the effect of the fraction of PVA fiber on the mechanical properties of high-performance concrete. The mechanical properties include compressive strength, splitting tensile strength and compressive elastic modulus. On the basis of the experimental results of the specimens of six sets of mix proportions, the mechanism of PVA fiber acting on these mechanical properties has been analyzed in details. The results indicate that there is a tendency of increase in the compressive strength and splitting tensile strength when the fiber volume fraction is below 0.08%, and the compressive elastic modulus of high-performance concrete decreases gradually with the increasing volume fraction of PVA fiber with appropriate content.

Abstract: Advanced composite materials (ACMs) are also known as advanced polymer matrix composites. These are generally characterized or determined by unusually high strength fibers with unusually high stiffness, or modulus of elasticity characteristics, compared to other materials, while bound together by weaker matrices. These are termed advanced composite materials (ACMs) in comparison to the composite materials commonly in use such as reinforced concrete, or even concrete itself. The high strength fibers are also low density while occupying a large fraction of the volume. Advanced composites exhibit desirable physical and chemical properties that include light weight coupled with high stiffness (elasticity), and strength along the direction of the reinforcing fiber, dimensional stability, temperature and chemical resistance, flex performance and relatively easy processing. Advanced composites are replacing metal components in many uses, particularly in the aerospace industry.

Abstract: An investigation of early anti-cracking performance and permeability of hybrid cellulose fiber and PVA fiber reinforced concrete is presented in this article. The test results show that, both cellulose fiber and PVA fiber effectively improve the splitting tensile strength. The early anti-cracking performance of concrete is obviously improved by PVA and cellulose hybrid fibers, and there exists the synergistic effect for restrain matrix cracking with hybrid fibers. Based on the practical application of a subway station project during two years, result shows the underground concrete wallboard containing hybrid fibers does not produce obvious cracks and leakage problem.

Abstract: In order to study the effect of the fraction of PVA fiber on the axial compressive strength and flexural properties of high performance concrete, a series of tests have been conducted in this study. The middle span deflection was measured by a micrometer with dial indicator, and six different concrete mixes have been chosen. Flexural properties include flexural strength and flexural modulus of elasticity. The mechanism of PVA fiber acting on axial compressive strength, flexural strength and flexural modulus of elasticity has been analyzed in details. The results indicate that there is a tendency of increase in the axial compressive strength and flexural strength when the fiber volume fraction is below 0.08%, and the flexural modulus of elasticity of high-performance concrete decrease gradually with the increase of fiber volume fraction.

Abstract: To study the influence of polypropylene fiber on the strength of sandy soil stabilization with cement in flooded area of Yellow River, a series of experiments 7-day unconfined compressive strength have been done when samples reach 7-day standard curing. Based on the data, it is found that fiber content has an important influence than its length on unconfined compressive strength. As for failure modes, there are significant differences between the samples of adding fibers and those adding nothing. After adding 10 % cement, 1 fiber with 12 mm single length, the unconfined compressive strength of sandy soil stabilization with cement can be greatly improved with increase rate of 83%. It is concluded that the sandy soil can be successfully stabilized by the combined action of fibers and cement.

Abstract: Engineered cementitious composite (ECC) is a representative of the new generation of high performance fiber reinforced cementitious composites. To reveal the influence of mineral admixtures on the tensile mechanical characteristics of polyvinyl alcohol fiber reinforced engineered cementitious composites (PVA-ECC), the tensile properties of PVA-ECC with replacing cement by a significant amount of fly ash (FA), silica fume (SF) and metakaolin (MK) was experimentally investigated. Uniaxial tensile experiment was carried out using rectangular thin plate with sizes of 400×100×15mm³. Results from uniaxial tensile tests show that these mineral admixtures can improve the properties of PVA-ECC. The composite can achieve an ultimate strain of 2.0%, as well as an ultimate strength of 4.0MPa, with a moderate fiber volume fraction of 2.0%. In addition, the composites with FA, SF and MK show saturated multiple cracking characteristics with crack width at ultimate strain limited to below 175μm.

Abstract: In this paper, a new green hybrid fibre-reinforced cementitious composite with high volume fly ash and steel and bagasse fibres is developed. High volume fly ash is used to partly replace cement and make the composite greener. Eco-friendly bagasse fibres from industrial waste and steel fibres are utilized to improve the mechanical behavior. In particularly, the influence of the parameters such as the sand/cement ratio and fly ash/cement ratio on the mechanical properties of the composite is investidated by evaluating the essential mechanical properties such as compressive strength and modulus of elasticity. The new green composite is found to be sustainable with high compressive. It is found that compressive strength of the composite decreases while the Young's modulus increases with the increase of the sand content, and that compressive strength and Youngs modulus of the composite decreases with the increase of the fly ash content.

Abstract: This paper presents results of a series of shrinkage tests. Described tests were performed on asbestos-free plates. The shrinkage represents very important role in monitoring of length changes for different orientation of the fibers. The results showed that humidity significantly influenced dimensions change of tested fibrecement plates. Length change ratio of dried plates and saturated plates represented the most significant difference that reached 0.25 %. Influence of fibres orientation on the length change was not confirmed. The difference in both measured direction was the same because of varied humidity impact. Elimination of free shrinkage is predominantly given by matrix, influence of fibers is not significant.