Current Issue : October - December Volume : 2019 Issue Number : 4 Articles : 5 Articles
Calcium carbonate (CaCO3) whisker, as a new type of microfibrous material, has been extensively used in the reinforcement of\ncementitious materials.However, the combined effect of CaCO3 whisker and fly ash on mechanical properties of cementitious\nmaterials under high temperatures was still unknown. In this study, the coupling effect of CaCO3 whisker, and fly ash on\nmechanical properties of the cement was investigated. Two sets of cement mortars were fabricated, including CaCO3 whiskerbased\nmortar which contained 0 wt.%, 5 wt.%, 10 wt.%, 15 wt.%, and 20 wt.% CaCO3 whisker as cement substitution and CaCO3\nwhisker-based fly ash mortar which contained 30 wt.% fly ash in addition to 0 wt.%, 5 wt.%, 10 wt.%, 15 wt.%, and 20 wt.% CaCO3\nwhisker as cement substitution. Mass loss, compressive strength, and flexural strength of these two sets of specimens before and\nafter being subjected to high temperatures of 200°C, 400°C, 600°C, 800°C, and 1000°C were measured. Based on the results of the\naforementioned tests, load-deflection test was performed on the specimen which exhibited the superior performance to further\nstudy its mechanical behavior after exposure to high temperatures. Moreover, microstructural analysis, such as mercury intrusion\nporosimetry (MIP) and scanning electron microscopy (SEM), was conducted to reveal the damage mechanism of high temperature\nand to illustrate the combined effect of CaCO3 whisker and fly ash on high-temperature resistance of the cement. Results\nshowed that fly ash could improve the high-temperature performance of CaCO3 whisker-based mortar before 600°C and limit the\nloss of strength after 600°C....
In order to preserve natural resources, the use of waste and alternative materials in the construction and maintenance of roads is\nincreasingly investigated. .is paper presents the results of testing wearing course asphalt mixtures (AC 11s SURF 50/70) made\nwith various percentages of fly ash, used as a partial or complete substitute for mineral filler. .e properties of fly ash were\ndetermined to assess their suitability for use in asphalt mixtures. .e experimental research was performed on asphalt samples\ncontaining fly ash from three different sources, with 25%, 50%, 75%, and 100% of mineral filler substitution. .e control mixture\nwas prepared with 100% of mineral filler. .e paper presents the volumetric composition, stability, and flow of asphalt mixtures\ntested on standard Marshallâ??s samples, water sensitivity, and resistance to permanent deformation. .e results of this study\nindicate that a satisfactory volumetric composition can be achieved by adding fly ash, while the bulk density and voids of the\nmineral and asphalt mixture generally depend on the type of fly ash and its content. .e stability and flow of mixtures with fly ash\nare favourable compared with the control mixture. .e water sensitivity of mixtures with fly ash is generally lower compared with\nthe control mixture and depends on the type and percentage of fly ash. .e resistance to permanent deformation of the asphalt\nmixtures depends on the fly ash type and percentage. .e results obtained in this study are an important step towards broader\nimplementation of fly ash in asphalt mixtures....
Installing geosynthetic reinforcement at the bottom of the embankment will provide positive support for subgrade stability and\nsettlement control, if there is a void or a weak foundation. In routine design work, the geomembrane effect must be well estimated\nand the tensile strain should be precisely predicted. Conventional analytical methods often adopt the limit state method to\ncalculate the overlying load on the deflected geosynthetic. However, this assumption does not necessarily apply to all conditions,\nespecially when the foundation soil can provide certain resistance. In this study, a semiempirical prediction method for evaluating\nthe geomembrane effect of the basal reinforcement was proposed, and an iterative solution for calculating tensile strains of a\ndeflected geosynthetic was deduced. In derivation, a virtual inclined slip surface and interaction between the geosynthetic and soil\nwere quantitatively evaluated by coupling the arching effect and the geomembrane effect. Moreover, the development of shear\nstress along the slip surface can be considered, as well as different segments of the basal reinforcement. *en, the proposed method\nwas validated by two large-scale experiments. Comparison of the results of this method with measurements and results of other\nanalytical models confirmed that this analytical method can take good care of the varying process of the localized sinking,\nregarding the overlying loads on the geosynthetic and the subsequent tensile strains....
Bridges, especially highway bridges, are a key factor in nationsâ?? development\nand flourish. Thus, great care should be taken to maintain and inspect their\nsafety and serviceability. An immediate repair will prevent the loss of life and\nvehicles damage while crossing underpass and over passing the heavy deteriorated\nbridges. Reinforced or pre-stressed concrete bridge girders become\nstructurally deficient because of severed reasons including, increasing in the\nload requirements, corrosion of pre-stressing strands or reinforcement bars\nand collision of over-height trucks with the bulb of the concrete girders. The\npurpose of this case study is to evaluate and assess the damages of the highway\nbridges in Jordan. Since there is no mandatory program in Jordan for\ninspection of bridges and evaluating their conditions, this paper presents an\ninspection and assessment of two highway bridges along the desert highway\nwhich is the essential nerve connecting Jordan cities, and it also serves as an\ninternational road between many middle east countries. These two Bridges\nhave never been investigated or checked since their construction in the late\n1980s. The study results showed that the main factor causing the deterioration\nof these bridges is the collision of the over-height trucks with their elements.\nRelying on the collected data, solutions and repair methods were introduced\nto rehabilitate these bridges and assure their structural safety....
This paper presents the study on the properties of high-ductility fiber reinforced concrete\nmade with desert sand from Chinaâ??s Mu Us desert. The workability and uniaxial tensile/compression\nproperties of undisturbed desert sand-based fiber reinforced concrete (DS-FRC) with the change\nof water-to-binder ratio (W/B), sand-to-binder ratio (S/B) and desert sand replacement rate (DSRR)\nwere experimentally investigated. Experimental results reveal that the appropriate W/B and\ndesert sand content are conducive to the workability development of DS-FRC. The uniaxial\ntension/compression properties of DS-FRC are mainly affected by the W/B. Especially, the highest\nuniaxial tensile/compression stresses and corresponding strains are obtained at the W/B of 0.29.\nThe S/B has similar effects on the uniaxial tensile/compression properties, and an S/B of 0.36 is the\noptimal ratio. In terms of the DSRR, it shows less effect on the uniaxial tensile/compression properties,\neven for the DSRR of 100%. The results of the tests indicate that undisturbed desert sand can be used\nas silica sand in high-ductility fiber reinforced concrete....
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