Current Issue : April - June Volume : 2019 Issue Number : 2 Articles : 5 Articles
To optimize the main components of reactive powder concrete (RPC) for various curing methods, based on the fluidity and\ncompressive strength, an inclusive experimental research is conducted on 58 different mixture ratios. The results indicate that\nowing to the increase of the cement strength, the RPC fluidity decreases and the cement strength is not proportional to the\ncompressive strength. The addition of the fly ash and the nano-microbead is an effective way to improve the fluidity, and it is\nrequired at the low W/B ratio. However, the influence of the SF grade on the strength and fluidity is almost negligible. By\nconsidering the fluidity, strength, and economy of RPC as crucial design factors, SF90 is suggested. The contribution of the steel\nfiber to the compressive strength cannot be ignored. The upper envelope value of the steel fibers is required for the structure to\nresist appropriately against the fire. According to the test results, the mixture ratio formula is proposed through considering the\ncharacters of different compositions and curing methods. The strength coefficient k1 is introduced to verify the influence of the\nsteel fiber content, and the parameters...............
In this study, the effect of iron powder (Fe2O3) on the compressive strength,\ntensile strength, workability, and porosity of the binary blended concrete\nwere experimentally investigated. For this purpose, Portland cement was partially\nreplaced by 1.5%, 2.5%, 3.5%, and 5% by weighing of iron powder. The\namount of water-binder-ratio was considered constant. The workability of\nthe fresh composite concrete was determined using cone Abrams method;\nmechanical properties were determined included compressive and tensile\nstrengths at 7, 14, and 28 days and durability evaluated by water absorption\nand permeable porosity. It was observed that the compressive and tensile\nstrengths change with the replacement of iron powder by up to 5%. However,\nthe maximum improvement was gained at 2.5 wt% for compressive strength\nand 1.5 wt% for tensile strength. The workability of the fresh mixtures decreased\nwhen iron powder amount increased. It was observed that the porosity\ndecreased respectively by 21.88% and 26.77% at 1.5 wt% and 2.5 wt% replacement.\nMoreover, this present study shows the importance and benefits\nto improve concrete properties by using micro-particles materials....
This study aims to investigate the effect of water on the properties of cast in situ foamed concrete with a dry density of 300â??800 kg/m3\n(100 kg/m3 is a gradient). Firstly, the shrinkage deformation with the curing time and the volumetric moisture content is studied by\nthe drying shrinkage test and improved drying shrinkage test. Secondly, the influence of volumetric moisture content on mechanical\nproperties is assessed. At last, the effects of immersion time and immersion type on the mechanical properties of foamed concrete are\nstudied by considering the water-level conditions.Theachieved results show that the shrinkage deformations increase with the curing\ntime for the drying shrinkage test and the improved drying shrinkage test, while the variations are different. The shrinkage deformation\nincreases with the decrease of volumetric moisture content for six dry densities of foamed concrete. Besides, it gradually\nchanges in the early stage, while it changes fast in the later stage. The compressive strength and elastic modulus decrease with the\nincrease of volumetric moisture content for each density. For the water-level unchanged condition, the compressive strength and\nelastic modulus initially decrease and then slowly increase with the increase of the immersion time. For the water-level changed\ncondition, the compressive strength and elastic modulus of foamed concrete decrease with the increase of immersion time for each\ndry density, and the rate of early attenuation is high, whereas the rate of later attenuation is limited....
Landslides caused by earthquakes and other natural disasters may cause serious economic and personal losses. Slope protections\nare usually applied in engineering practice to prevent significant slope slides and damages. Based on the mechanical and ecological\nrequirements on slope protections, this paper put forward a new type of anchor + hinged block ecological slope and carried out\nshaking table tests on it and other three traditional slope protections for comparing. By shaking table tests, the acceleration\namplification factors and Fourier amplitude spectrums of four different slope types are analyzed and compared to verify the\nsuitability of this new slope protection under earthquakes. The results indicated that the natural frequency and the acceleration\nFourier amplitude spectrum of the four tested slope protections change according to internal materials. Theanchor + hinged block\necological slope has higher natural frequency comparing to traditional slopes, so the resonance cycle from earthquake excitation\ncan effectively be avoided and as a result the anchor + hinged block ecological slope can achieve better seismic performance....
Thin-walled member is structurally superior to a construction member.\nHowever, by reason of complexity in structure the stress and the deformation\nto yield the cross section are complicated. Specially, in case thin-walled\nmembers, such as thin-walled channel section columns, which are subjected\nto compressive force, these members produce the local buckling, distortional\nbuckling and overall buckling. A number of experimental and theoretical investigations\nsubjected to axial compressive force are generated for thin-walled\nchannel section columns with triangle-shaped folded groove by Hancock [1]\nand with complex edge stiffeners and web stiffeners by Wang [2]. In case\nthin-walled channel section column with folded groove which is subjected to\naxial compressive force, it is cleared that the buckling mode shapes are ordinarily\ngenerated for local buckling mode shape of plate-panel composing\ncross section of member in short member aspect ratio and overall buckling\nmode shape as column and distortional buckling mode shape interacting between\nlocal buckling and overall buckling similarly normal thin-walled\nmember. It is cleared analytically and experimentally that buckling strength\nand critical strength of thin-walled channel section column with folded\ngroove can increase sharply in comparison with that of normal thin-walled\nmember composing only plate-panel. In this paper a new cross section of\nshell-shaped curved groove [3] was proposed instead of the thin-walled\nlipped channel section column with triangle- and rectangle-shaped folded\ngrooves used ordinarily, and therefore the comparison and the examination\nof buckling strength and buckling behavior were generated in the case of\npreparing triangle-shaped folded and shell-shaped curved grooves to web and\nflange of thin-walled channel section column. And then in order to investigate\nthe buckling behavior on the thin-walled channel section column with\nfolded and curved grooves, exact buckling strength and the buckling mode shapes are generated by using the transfer matrix method. The analytical local\ndistortional and overall elastic buckling loads of thin-walled channel section\ncolumn with folded and curved grooves can be obtained simultaneously by\nuse of the transfer matrix method. Furthermore, a technique to estimate the\nbuckling mode shapes of these members is also shown....
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