The microstructure, phase composition, and thermal characteristics of various natural gypsums and the high-strength gypsum──the converted product of natural one are analysed.The formation mecbanism of high-strength ...The microstructure, phase composition, and thermal characteristics of various natural gypsums and the high-strength gypsum──the converted product of natural one are analysed.The formation mecbanism of high-strength gypsum is further discussed. It is found that the high-streugth gypsum is of hollow irregular hexagonal prism structure, which is almost free from tbe (010) and (100) cleavages and can form clustered fibrous crystals with high-strength.展开更多
Geophysical surveys are frequently applied in mining prospection to detect the presence and volume of ore bodies of different nature.Particularly,in gypsum ore bodies exploitation,electrical resistivity measurements a...Geophysical surveys are frequently applied in mining prospection to detect the presence and volume of ore bodies of different nature.Particularly,in gypsum ore bodies exploitation,electrical resistivity measurements are usually the most used methodology.However,it has been observed that different electrical resistivity values can be obtained depending on geometrical features and composition of gypsum.Indeed,electrical resistivity of gypsum rocks depends on several parameters,such as gypsum purity,nature of secondary minerals,porosity,saturation and interstitial fluid properties.Saturation and hydrogeological setting,in particular,were recognized as the most influencing parameters.Hydrogeological conditions of gypsum rock masses are also very relevant for exploitability,safety conditions and economic feasibility and should be accurately known during the prospection and planning phases of the quarries.In this work,a relationship between electrical resistivity and saturation degree of gypsum is proposed.The possibility to estimate gypsum porosity with the use of this relationship is also investigated.The reliability of laboratory measurements is finally verified in comparison with field and modelled resistivity data.The reported results underline the potentiality of the proposed approach to obtain a reliable characterization of the studied ore body.展开更多
Gypsum-bonded particleboard(GBPB) panels were made from various mixtures of particles of bagasse(Saccharum officinarum L.) and wheat straw(Triticum aestivum L.), bonded with different ratios of particle/gypsum. This s...Gypsum-bonded particleboard(GBPB) panels were made from various mixtures of particles of bagasse(Saccharum officinarum L.) and wheat straw(Triticum aestivum L.), bonded with different ratios of particle/gypsum. This study examined the feasibility of bagasse and wheat straw particles in the production of GBPB. One-layer experimental GBPBs with a density of 1.05 or 1.20 g·cm 3were manufactured at different ratios of bagasse/wheat straw, i.e., 100%/0%, 93.75%/6.25%, 87.5%/12.5%, 75%/25%, 50%/50%, 25%/75% and 0%/100% using two particle/ gypsum composite ratios, i.e., 1/2.75 and 1/3.25 by weight. Thickness swelling(TS), water absorption(WA), modulus of rupture(MOR), modulus of elasticity(MOE) and internal bond strength(IB) properties of the boards were evaluated and a statistical analysis was performed in order to examine the possible feasibility of these agricultural residues for use in commercial GBPB manufacturing. We determined that WA of panels decreases as the amount of straw increases to 100% and the LR/G(wood/gypsum) ratio decreases to 1/3.25, whereas the TS of panels decreases as the proportion of straw decreases to 0% and the LR/G ratio increases to 1/2.75. The experimental results also show that the MOR and MOE of panels containing 0%, 6.25% and 12.5% wheat straw with a LR/G ratio of 1/2.75 were higher than those of panels made from 25%–100% wheat straw with a LR/G ratio of 1/2.75, as well as those from all other percentages of straw with a LR/G ratio of 1/3.25. On the other hand, the IB of panels containing more than 12.5% straw with LR/G ratios of 1/2.75 and 1/3.25 were lower than those of panels made from 0–12.5% straw also with both LR/G ratios. Panels consisting of 0%, 6.25% and 12.5% wheat straw with LR/G ratios of 1/2.75 and 1/3.25 met the minimum EN standard requirements of mechanical properties for general purposes. All of the panels containing 0–100% wheat straw with a LR/ G ratio of 1/2.75 or 1/3.25 met the required level of TS for 24-h immersion.展开更多
粉煤灰和石膏粉复合掺入陶粒混凝土是一种新型材料,可以达到废渣利用、减少污染、提高强度等目的,为节能环保做出贡献。通过改变粉煤灰和石膏粉掺量的配合比,进行多龄期抗压强度试验,分析石膏粉掺量对掺粉煤灰陶粒混凝土抗压强度的影响...粉煤灰和石膏粉复合掺入陶粒混凝土是一种新型材料,可以达到废渣利用、减少污染、提高强度等目的,为节能环保做出贡献。通过改变粉煤灰和石膏粉掺量的配合比,进行多龄期抗压强度试验,分析石膏粉掺量对掺粉煤灰陶粒混凝土抗压强度的影响,并结合扫描电子显微镜(scanning electron microscope,SEM)技术,对微观结构进行分析。结果表明:当粉煤灰掺量为40%时,试样抗压强度随着石膏粉的掺量增加呈先上升后下降的趋势,石膏粉掺量为22%,试样抗压强度达到最大;22%的石膏粉和40%的粉煤灰复掺可以提高其抗压强度,使其微观结构更加紧密,对强度有利的水化产物较多,反之微观结构变得蓬松,其水化产物减少;强度较高的试样界面过渡区(interface transition zone,ITZ)更加紧密。展开更多
文摘The microstructure, phase composition, and thermal characteristics of various natural gypsums and the high-strength gypsum──the converted product of natural one are analysed.The formation mecbanism of high-strength gypsum is further discussed. It is found that the high-streugth gypsum is of hollow irregular hexagonal prism structure, which is almost free from tbe (010) and (100) cleavages and can form clustered fibrous crystals with high-strength.
文摘Geophysical surveys are frequently applied in mining prospection to detect the presence and volume of ore bodies of different nature.Particularly,in gypsum ore bodies exploitation,electrical resistivity measurements are usually the most used methodology.However,it has been observed that different electrical resistivity values can be obtained depending on geometrical features and composition of gypsum.Indeed,electrical resistivity of gypsum rocks depends on several parameters,such as gypsum purity,nature of secondary minerals,porosity,saturation and interstitial fluid properties.Saturation and hydrogeological setting,in particular,were recognized as the most influencing parameters.Hydrogeological conditions of gypsum rock masses are also very relevant for exploitability,safety conditions and economic feasibility and should be accurately known during the prospection and planning phases of the quarries.In this work,a relationship between electrical resistivity and saturation degree of gypsum is proposed.The possibility to estimate gypsum porosity with the use of this relationship is also investigated.The reliability of laboratory measurements is finally verified in comparison with field and modelled resistivity data.The reported results underline the potentiality of the proposed approach to obtain a reliable characterization of the studied ore body.
文摘Gypsum-bonded particleboard(GBPB) panels were made from various mixtures of particles of bagasse(Saccharum officinarum L.) and wheat straw(Triticum aestivum L.), bonded with different ratios of particle/gypsum. This study examined the feasibility of bagasse and wheat straw particles in the production of GBPB. One-layer experimental GBPBs with a density of 1.05 or 1.20 g·cm 3were manufactured at different ratios of bagasse/wheat straw, i.e., 100%/0%, 93.75%/6.25%, 87.5%/12.5%, 75%/25%, 50%/50%, 25%/75% and 0%/100% using two particle/ gypsum composite ratios, i.e., 1/2.75 and 1/3.25 by weight. Thickness swelling(TS), water absorption(WA), modulus of rupture(MOR), modulus of elasticity(MOE) and internal bond strength(IB) properties of the boards were evaluated and a statistical analysis was performed in order to examine the possible feasibility of these agricultural residues for use in commercial GBPB manufacturing. We determined that WA of panels decreases as the amount of straw increases to 100% and the LR/G(wood/gypsum) ratio decreases to 1/3.25, whereas the TS of panels decreases as the proportion of straw decreases to 0% and the LR/G ratio increases to 1/2.75. The experimental results also show that the MOR and MOE of panels containing 0%, 6.25% and 12.5% wheat straw with a LR/G ratio of 1/2.75 were higher than those of panels made from 25%–100% wheat straw with a LR/G ratio of 1/2.75, as well as those from all other percentages of straw with a LR/G ratio of 1/3.25. On the other hand, the IB of panels containing more than 12.5% straw with LR/G ratios of 1/2.75 and 1/3.25 were lower than those of panels made from 0–12.5% straw also with both LR/G ratios. Panels consisting of 0%, 6.25% and 12.5% wheat straw with LR/G ratios of 1/2.75 and 1/3.25 met the minimum EN standard requirements of mechanical properties for general purposes. All of the panels containing 0–100% wheat straw with a LR/ G ratio of 1/2.75 or 1/3.25 met the required level of TS for 24-h immersion.
文摘粉煤灰和石膏粉复合掺入陶粒混凝土是一种新型材料,可以达到废渣利用、减少污染、提高强度等目的,为节能环保做出贡献。通过改变粉煤灰和石膏粉掺量的配合比,进行多龄期抗压强度试验,分析石膏粉掺量对掺粉煤灰陶粒混凝土抗压强度的影响,并结合扫描电子显微镜(scanning electron microscope,SEM)技术,对微观结构进行分析。结果表明:当粉煤灰掺量为40%时,试样抗压强度随着石膏粉的掺量增加呈先上升后下降的趋势,石膏粉掺量为22%,试样抗压强度达到最大;22%的石膏粉和40%的粉煤灰复掺可以提高其抗压强度,使其微观结构更加紧密,对强度有利的水化产物较多,反之微观结构变得蓬松,其水化产物减少;强度较高的试样界面过渡区(interface transition zone,ITZ)更加紧密。
