基于复合胶凝材的喷射混凝土抗渗性能研究

喷射混凝土的抗渗性能与喷射混凝土的使用年限、承受水压力、喷射混凝土的龄期等因素密切相关。以喷射混凝土的渗水高度作为其抗渗性能的评价指标,通过室内试验研究了基于复合胶凝材的喷射混凝土渗水高度与加压时间、承受水压力、混凝土龄期的相关关系;并进一步研究了喷射混凝土回弹率、吸水率等,以及这些指标与抗渗性能的相关性。通过研究得到,掺加复合胶凝材对提高喷射混凝土的抗渗性能有显著作用;加压时间和水压力量值对渗水高度的影响很大,加压时间与渗水高度呈正比关系,水压力大小与渗水高度成近似正比关系;随着龄期的增加,渗水高度逐步减小,28 d龄期后渗水高度趋于稳定;单掺复合胶凝材的喷射混凝土吸水率低于掺加复合胶凝材和聚丙烯纤维的喷射混凝土,抗渗性更好一些;但是加入聚丙烯纤维后,与只掺加复合胶凝材的混凝土比较,其回弹率大大降低。

基于模糊决策理论的衬砌混凝土胶凝材组成优化研究

在胶凝材中掺入矿物掺合料是实现混凝土高性能的一条必要途径。混凝土的高性能主要包括高工作性能、高力学性能和高耐久性能,因此混凝土性能的评价指标和影响因素是多方面的,故很难依据诸多评价指标直观判断混凝土综合性能的优劣。通过对不同矿物掺合料配方胶凝材混凝土性能试验以及成本核算,对比分析矿物掺合料种类和掺量对混凝土性能以及工程造价的影响,并利用模糊多属性决策理论对混凝土性能进行综合评价,从中优选出适用于侵蚀环境条件下隧道衬砌高性能混凝土胶凝材配方(即矿物料合料掺入种类和掺量范围)。试验和理论分析表明:多掺矿物掺合料混凝土综合性能最优,复掺矿粉、粉煤灰混凝土性能次之,又因矿粉和粉煤灰是炼钢、发电等工业副产品,将其等量掺入水泥中,可大大节约资源,有效利用了工业废料,实现节能减排。

镍铁矿热炉渣制备胶凝材的可行性试验与分析

本文分析了镍铁矿热炉渣的化学组成、物理性能和性能特点。研究了镍铁矿热炉渣微粉的基础性能和非金属磨料的基础性能,探讨了其与普硅水泥、高炉矿粉比例复合制备复合胶凝材的可行性,试验证明,镍铁矿热炉渣可以作为非金属磨料使用,而用于制备复合胶凝材具有可行性。

粉煤灰复合胶凝材硬化浆体微观孔隙特征研究

目前工程渗漏水问题已经得到了工程界的广泛重视,而调研得知,不同的掺和料有助于改善混凝土的结构特性。因此,文章以粉煤灰为主要掺和料,采用压汞法为主,低场核磁共振法为辅的测试手段,分别对单掺和复掺粉煤灰胶凝材硬化浆体微观孔隙的孔径分布、平均孔径和孔隙率进行了测试。结果显示:①掺入适量的粉煤灰,可以细化复合胶凝材硬化浆体的微观孔隙,降低孔隙率;②硬化浆体的孔径分布范围、最可几孔径、平均孔径和孔隙率均表现出随龄期延长而减小的趋势,且早龄期时,下降速率快,后期降幅变缓;③多掺粉煤灰的硬化浆体在28 d龄期后,其最可几孔径略有增大;④在早龄期时,多掺粉煤灰复合胶凝材的孔隙率更小,而长龄期时,单掺粉煤灰的孔隙率更小。论文研究成果有助于从微观上解决混凝土的渗漏水问题。

镍铁矿热炉渣复合胶凝材的研究

本文总结了目前镍铁的冶炼工艺、综合利用现状,分析了镍铁矿热炉渣的化学组成、物理性能和性能特点。研究了镍铁矿热炉渣微粉的基础性能,探讨了其与普硅水泥、高炉矿粉比例复合制备复合胶凝材。试验结果表明,镍铁矿热炉渣活性较低,不适合单独作为水泥和混凝土掺合料使用,而用于制备复合胶凝材具有可行性。

矿山充填胶凝材料发展现状与方向

充填胶凝材料在充填成本构成中占很大比例,本文从充填胶凝材料入手回顾了充填胶结材料的发展状况和与之相应技术特点,更依据发挥材料性能和降低成本两方面指出充填胶凝材料的发展方向:加强胶凝材料和充填技术的协同发展;深化激发机理研究,利用"固废"发展更高性能碱激发材料;研发与充填胶凝材料相适用的外加剂,提升材料性能。上述途径降低了水泥耗量或简化了工艺流程,并提升了材料胶结性能,能够促进充填胶凝材料的革新发展和降低充填成本。

基于复合胶凝材配制隧道高性能湿喷混凝土试验研究

针对目前铁路、公路等交通隧道施作初期支护时湿喷混凝土性能不足、回弹大等问题,通过在胶凝材中掺入矿物掺合料,借助高效外加剂,配制高性能湿喷混凝土尤为迫切。通过对不同掺量和不同种类的矿物掺合料混凝土进行力学性能和耐久性能试验,依据试验结果探寻适用于隧道初期支护的高性能湿喷混凝土的最优胶凝材配方。试验结果表明:复掺矿粉、粉煤灰混凝土性能最好,单掺矿物掺合料混凝土的综合性能比复掺差,但是优于基准混凝土,纤维素纤维对混凝土力学性能具有负效应,而单掺矿物掺合料自然养生的混凝土最差。掺入矿物掺合料或掺入纤维使混凝土内部孔径发生细化作用,改善混凝土内部孔径分布,提高了混凝土的密实性。

基于复合胶凝材配制隧道衬砌高性能混凝土试验研究

我国大部分山岭隧道在运营后,均出现了不同程度的病害,特别是在富含地下水地区,隧道结构开裂、渗漏水、溶蚀和化学腐蚀严重。导致隧道结构耐久性不足的首要原因是混凝土胶凝材以硅酸盐水泥为主,其成分单一、级配差、品质不高。根治隧道结构耐久性病害,必须从原材料抓起,提出采用多元复合胶凝材配制高性能混凝土,复合胶凝材中主要粉体材料采用分别粉磨集中配送的模式等对策。试验结果表明,以矿物掺合料为主要成分的复合胶凝材配制高性能混凝土具有很好的工作、力学和耐久性能,同时还具有节能、环保和降低成本之功效。

隧道单层衬砌高强喷射混凝土试验研究

近年来,单层衬砌作为新的隧道结构形式,由于其具有经济、低碳、环保特点,广泛应用于隧道及地下工程中。但对于组成单层衬砌结构主要材料的喷射混凝土的力学和耐久性能要求比以往喷射混凝土要求更高。该文围绕提高喷射混凝土强度和密实度进行了相关的试验研究,研究证实采用聚羧酸高性能减水剂、无碱速凝剂和低水胶比以及单掺或双掺矿物掺合料可有效提高混凝土的强度和密实性。

消除黄磷厂废渣污染环境的有效途径

利用黄磷厂废渣作煅烧水泥熟料的矿化剂、水泥混合材和利用黄磷厂废渣生产胶凝材、白水泥是消除黄磷渣污染环境的有效途径;通过影响黄磷渣作水泥混合材和生产胶凝材因素的研究,推荐了提高黄磷渣作水泥混合材的掺量及生产优质胶凝材的工艺条件;黄磷渣的开发利用不仅可使企业获得显著的经济效益,而且可减少磷渣堆放占用耕地和消除磷渣对环境的污染,具有显著的经济效益、社会效益和环境效益。

Three-dimensional MoS_2/reduced graphene oxide aerogel as a macroscopic visible-light photocatalyst

Photocatalysis is regarded as an ideal technology for solving the urgent environmental and energy issues that we face today.Among the reported photocatalysts,molybdenum disulfide（MoS2） is very promising for applications in hydrogen production and pollutant photodegradation.However,its lack of active sites and the difficulty of recovering catalysts in powder form have hindered its wide application.Here,we report the successful preparation of a macroscopic visible-light responsive MoS2/reduced graphene oxide（MoS2/RGO） aerogel.The obtained MoS2/RGO aerogel exhibits enhanced photocatalytic activity towards hydrogen production and photoreduction of Cr（Ⅵ） in comparison with the MoS2 powder.In addition,the low density（56.1 mg/cm^3） of the MoS2/RGO aerogel enables it to be used as an efficient adsorption material for organic pollutants.Our results demonstrate that this very promising multifunctional aerogel has potential applications in environmental remediation and clean energy production.

Influence of pH value and chelating reagent on performance of Li_3V_2(PO_4)3/C cathode material

The Li3V2（PO4）3/C composite cathode material was synthesized via sol-gel method using three different chelating agents （citric acid, salicylic acid and polyacrylic acid） at pH value of 3 or 7. The crystal structure, morphology, specific surface area and electrochemical performance of the prepared samples were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, cyclic voltammetry （CV）, electrochemical impedance spectroscopy （EIS） and galvanostatic charge/discharge test. The results show that the effects of pH value on the performance of the prepared materials are greatly related to the chelating agents. With salicylic acid or polyacrylic acid as the chelating reagent, the structure, morphology and electrochemical performance of the samples are greatly influenced by the pH values. However, the structure of the materials with citric acid as the chelating agent does not change as pH value changes, and the materials own uniform particle size distribution and good electrochemical performance. It delivers an initial discharge capacity of 113.58 mA·h/g at 10C, remaining as high as 108.48 mA·h/g after 900 cycles, with a capacity retention of 95.51%.

钢渣在外墙饰面砂浆中的应用研究

经研究确定转炉钢渣粉作为胶凝材,粒径<0.8 mm的电炉钢渣作为填料,与水泥及其他添加剂复配制备外墙饰面砂浆,各项指标均可满足建材行业标准。这样,既节约了天然石材,减少了水泥用量,又符合国家循环经济利用政策,具有明显的社会效益。

Effect of Mn-doping on performance of Li_3V_2(PO_4)_3/C cathode material for lithium ion batteries

Li3V2-2/3xMnx（PO4）3（0≤x≤0.12） powders were synthesized by sol-gel method. The effect of Mn2＋-doping on the structure and electrochemical performances of Li3V2（PO4）3/C was characterized by XRD, SEM, XPS, galvanostatic charge /discharge and electrochemical impedance spectroscopy（EIS）. The XRD study shows that a small amount of Mn2＋-doped does not alter the structure of Li3V2（PO4）3/C materials, and all Mn2＋-doped samples are of pure single phase with a monoclinic structure （space group P21/n）. The XPS analysis indicates that valences state of V and Mn are ＋3 and ＋2 in Li3V1.94Mn0.09（PO4）3/C, respectively, and the citric acid in raw materials was decomposed into carbon during calcination, and residual carbon exists in Li3V1.94Mn0.09（PO4）/C. The results of electrochemical measurements show that Mn2＋-doping can improve the cyclic stability and rate performance of these cathode materials. The Li3V1.94Mn0.09（PO4）3/C cathode material shows the best cyclic stability and rate performance. For example, at the discharge current density of 40 mA/g, after 100 cycles, the discharge capacity of Li3V1.94Mn0.09（PO4）3/C declines from initial 158.8 mA·h/g to 120.5 mA·h/g with a capacity retention of 75.9%; however, that of the Mn-undoed sample declines from 164.2 mA·h/g to 72.6 mA·h/g with a capacity retention of 44.2%. When the discharge current is increased up to 1C, the intial discharge capacity of Li3V1.94Mn0.09（PO4）3/C still reaches 146.4 mA·h/g, and the discharge capacity maintains at 107.5 mA·h/g after 100 cycles. The EIS measurement indicates that Mn2＋-doping with a appropriate amount of Mn2＋ decreases the charge transfer resistance, which is favorable for the insertion/extraction of Li＋.

Mechanical properties of anti-seepage grouting materials for heavy metal contaminated soil

Cement-based composite grouting materials were used to construct grouting cutoff wall for heavy metal contaminated soil in non-ferrous metal mining areas. Cement, fly ash, and slag as principal ingredients were mixed with water glass in different ways to produce three composite grouting materials. In order to investigate the effect of water glass mixing ratio, Baume degree, fly ash and slag contents on the mechanical properties of the composite grouting materials, particularly their gel time and compressive strength, the beaker-to-beaker method of gel time test and unconfined compressive strength test were conducted. In addition, the phase composition and microstructure of the composite grouting materials were analyzed by the X-ray diffraction（XRD） and scanning electron microscope（SEM） techniques. The test results show that their gel time increases when water glass mixing ratio and Baume degree increase. The gel time increases dramatically when fly ash is added, but decreases slightly if fly ash is partly replaced by slag. When the mixing ratio of water glass is below 20%, their compressive strength increases with the increases of the ratio; when the ratio is above 20%, it significantly decreases. The compressive strength also tends to increase as Baume degree increases, and improves if fly ash and slag are added.

Target effects on electrical properties and laser induced voltages of La_(0.72)Ca_(0.28)MnO_3 thin films prepared by pulsed laser deposition

La0.72Ca0.28MnO3 thin films were deposited on untilted and 15° tilted LaAlO_3 （100） single crystalline substrates by pulsed laser deposition. The polycrystalline targets used in the deposition process were synthesized by sol-gel and coprecipitation methods, respectively. The structure, electrical transport properties and surface morphology of the targets and films were studied. It is found that, compared with coprecipitation method, the sol-gel target has more homogeneous components and larger density and grain size, thus the higher insulator-metal transition temperature and larger temperature coefficient of resistivity. The thin film prepared by sol-gel target has a uniform grain size and higher quality. The metal-insulator transition temperature is higher and the laser induced voltage signal is larger. Preparing the target by sol-gel method can largely improve the properties of corresponding thin films in pulsed laser deposition process.

Synthesis and characterization of hybrid organic-inorganic materials based on EA-MAn-APTES and silica

Poly (EA-MAn-APTES)/silica hybrid materials were successfully prepared fromEthyl acrylate (EA), maleic anhydride (MAn) and tetraethoxysilane (TEOS) in the presence of acoupling agent 3-aminopropyltriethoxysilane (APTES),by free-radical solution polymerization and insitu sol-gel process. The mass fraction of TEOS varied from 0 to 25%. The hybrid materials werecharacterized by the methods of FT-IR spectra, solvent extraction, scanning electron microscope (SEM), transmission electron microscope (TEM), differential scanning calorimetry (DSC) andthermogravimetric analysis (TGA) measuring apparatus to get their structures, gel contents,morphologies, particle sizes and thermal performances. The results show that the covalent bonds arebetween organic and inorganic phases, gel contents in the hybrid materials are much higher, theSiO_2 phase is well dispersed in the polymer matrix, silicon dioxide exist at nanoscale in thecomposites and have excellent thermal stability.

Synthesis of LiMnPO_4/C composite material for lithium ion batteries by sol-gel method

The LiMnPO4/C composite material was synthesized via a sol-gel method based on the citric acid. The X-ray diffraction （XRD）, scanning electron microscopy （SEM） and electrochemical performance tests were adopted to characterize the properties of LiMnPO4/C. The XRD studies show that the pure olivine phase LiMnPO4 can be obtained at a low temperature of 500 °C. The SEM analyses illustrate that the citric acid used as the chelating reagent and carbon source can restrain the particle size of LiMnPO4/C well. The LiMnPO4/C sample synthesized at 500 °C for 10 h performs the highest initial discharge capacity of 122.6 mA-h/g, retaining 112.4 mA-h/g over 30 cycles at 0.05C rate. The citric acid based sol-gel method is favor to obtain the high electrochemical performance of LiMnPO4/C.

隧道衬砌高性能混凝土性能试验研究

混凝土作为最大宗的建筑材料,已不能单纯从力学性能指标来对其进行评价。本文主要以矿渣粉、粉煤灰、石膏及纤维素为外掺料,在使用聚羧酸高效减水剂的情况下,除纤维素直接外掺外,其他掺合料等量取代相应比例的水泥,研究单掺和复掺矿物掺合料对混凝土的力学和耐久性等各方面的性能。试验结果表明矿渣粉、粉煤灰的掺入可以满足胶凝材料及混凝土的基本物理力学性能,并改善了耐久性,其抗冻性较差,寒区隧道中慎用。

Mechanical properties of pervious cement concrete

Compressive and flexural strength,fracture energy,as well as fatigue property of pervious cement concrete with either supplementary cementitious materials (SCMs) or polymer intensified,were analyzed.Test results show that the strength development of SCM-modified pervious concrete (SPC) differs from that of polymer-intensified pervious concrete (PPC),and porosity has little effect on their strength growth.PPC has higher flexural strength and remarkably higher flexural-to-compressive strength ratio than SPC at the same porosity level.Results from fracture test of pervious concrete mixes with porosity around 19.5% show that the fracture energy increases with increasing the dosage of polymer,reflecting the ductile damage features rather than brittleness.PPC displays far longer fatigue life than SPC for any given failure probability and at any stress level.It is proved that two-parameter Weibull probability function describes the flexural fatigue of pervious concrete.