Characterising aggregate surface geometry in thin-sections of mortar and concrete

Measurement of microstructural gradients at the aggregate/cement paste interfacial transition zone (ITZ) in hardened mortar and concrete is commonly performed via quantitative image analysis of multiple micrographs of specimen surfaces, using a scanning electron microscope. However, due to the random orientation of interfaces sectioned by the specimen surface, measurements of the microstructural gradients at the interface have an unknown angular component, and thus have an unknown error. We present a method for the identification of interfaces that are perpendicular to the specimen surface, and therefore, are more suitable for accurate ITZ analysis. This method employs simple optical and electron imaging techniques on petrographic thin-sections. Use of 3D laser scanning confocal microscopy helped to validate the method. Quantitative 2D image analysis of backscattered electron micrographs, captured over three angular classes of interface gives an indication of this error in the determination of interfacial porosity and anhydrous cement content.     

炼铜反射炉水淬渣工艺矿物学

采用XRF, XRD, SEM-EDS, M?ssbauer及金相显微分析等对炼铜反射炉水淬渣进行了工艺矿物学研究. 结果表明,渣中含铜1.06%(w),主要以冰铜存在;全铁量为36.41%(w),Fe2SiO4占53.5%(w),Fe3O4为32.5%(w),Fe2O3为14.0%(w),且铜、铁、硅矿物紧密共生,呈细粒不均匀嵌布. 热力学分析表明,在CaO和O2存在条件下,硅酸铁转化为磁性氧化铁的趋势较大. 采用浮选回收铜-高温脱硅-磁选分离铁的选冶工艺处理炉渣,当磨矿细度-0.074 mm含量从75%增加到95%时,一次粗选铜回收率从18.6%增至39.02%,粗选精矿铜品位为4.6%. 炉渣在CaO/SiO2摩尔比0.9、1350℃氧化30 min、10 K/min缓冷速度下脱硅后,经破碎、磨矿、磁选,铁回收率为71%,铁精矿品位达62%.     

Impact load-induced micro-structural damage and micro-structure associated mechanical response of concrete made with different surface roughness and porosity aggregates

The relationship between the nature of micro damage under impact loading and changes in mechanical behavior associated with different microstructures is studied for concretes made with two different coarse aggregates having significant differences mainly in roughness and porosity — sintered fly ash and uncrushed gravel. A range of techniques including X-ray diffraction, digital image analysis, mercury porosimetry, X-ray computed tomography, laser surface profilometry and scanning electron microscopy were used to characterize the aggregates and micro-structures. The concrete prepared with lightweight aggregates was stronger in compression than the gravel aggregate concrete due to enhanced hydration as a result of internal curing. In the lightweight concrete, it was deduced that an inhomogeneous micro-structure led to strain incompatibilities and consequent localized stress concentrations in the mix, leading to accelerated failure. The pore structure, compressibility, and surface texture of the aggregates are of paramount importance for the micro-cracking growth.     

钢渣-杂填土基层材料的性能研究

将钢渣、矿渣微粉与废弃混凝土碎料混拌制备钢渣-杂填土基层,并对其性能开展研究。体积安定性试验表明,矿渣微粉具有明显抑胀作用,掺入50%(质量分数,下同)钢渣、50%杂填土以及外掺钢渣质量30%矿渣微粉的试件的10 d高温水浴膨胀率仅为1.32%,而未掺矿渣微粉的试件3~5 d膨胀率均超过2%限值。7 d无侧限抗压强度和28 d劈裂强度正交试验表明:7 d无侧限抗压强度、28 d劈裂强度影响因素大小顺序为钢渣、水泥掺量、混凝土碎料占比、土壤固化剂;各组试件中7 d无侧限抗压强度、28 d劈裂强度最大值分别为12.41 MPa、2.24 MPa;钢渣-杂填土基层最佳配比为50%钢渣、50%杂填土(m(混凝土碎料)∶m(素土)=6∶4),外掺钢渣质量40%的矿渣微粉、5%水泥、0.018%固化剂,此时试件具有良好的水稳定性。强度影响因素试验表明,矿渣微粉对试件强度的增幅影响最大。X射线衍射及扫描电子显微镜分析表明,在矿渣微粉和土壤固化剂的作用下,钢渣中f-CaO被有效消解,团聚体与混凝土碎料、钢渣颗粒的密实包裹阻止了内部水分的挥发和外部自由水的侵入,既保证了钢渣-杂填土基层的强度,又有效抑制了膨胀。     

Utilisation of steel furnace slag coarse aggregate in a low calcium fly ash geopolymer concrete

This paper evaluates the performance of steel furnace slag (SFS) coarse aggregate in blended slag and low calcium fly ash geopolymer concrete (GPC). The geopolymer binder is composed of 90% of low calcium fly ash and 10% of ground granulated blast furnace slag (GGBFS). Mechanical and physical properties, shrinkage, and detailed microstructure analysis were carried out. The results showed that geopolymer concrete with SFS aggregate offered higher compressive strength, surface resistivity and pulse velocity than that of GPC with traditional aggregate. The shrinkage results showed no expansion or swelling due to delayed calcium oxide (CaO) hydration after 320 days. No traditional porous interfacial transition zone (ITZ) was detected using scanning electron microscopy, indicating a better bond between SFS aggregate and geopolymer matrix. Energy dispersive spectroscopy results further revealed calcium (Ca) diffusion at the vicinity of ITZ. Raman spectroscopy results showed no new crystalline phase formed due to Ca diffusion. X-ray fluorescence result showed Mg diffusion from SFS aggregate towards geopolymer matrix. The incorporation of Ca and Mg into the geopolymer structure and better bond between SFS aggregate and geopolymer matrix are the most likely reasons for the higher compressive strength observed in GPC with SFS aggregate.     

Understanding the mechanical and interfacial properties of core–shell structured bamboo–plastic composites

Core–shell structured bamboo–plastic composites (BPCs) were directly prepared with a single‐screw/single‐screw coextruder system. The effects of different shell layers, such as high‐density polyethylene (HDPE), bamboo pulp fiber (BPF)/HDPE, and white mud (WM)/HDPE, were studied in the context of the mechanical properties and the characteristics of the interfacial transition zone (ITZ) of BPC. The mechanical properties of the core–shell structured BPC were characterized by flexure, short‐beam shear, and impact tests. The surface morphologies of BPC were analyzed with field emission scanning electron microscopy. The ITZ properties were studied with dynamic mechanical analysis and nano‐indentation testing. The results show that the flexural properties, short‐beam strength, and impact strength decreased profoundly in the presence of BPF or WM. The dynamic mechanical analysis results suggest that the ITZ properties decreased, as indicated by the reductions in the storage modulus, loss modulus, and loss factor; the nano‐indentation results show that on the addition of BPF or WM, a gradient in the hardness and modulus of elasticity appeared across ITZ. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43053.     

Effect of hexabromocyclododecane and antimony trioxide on flame retardancy of bisphenol A epoxy resin

In the present work, the hexabromocyclododecane and the antimony trioxide were introduced into the bisphenol A epoxy resin to improve its flame retardancy. The effects of hexabromocyclododecane and antimony trioxide on flame retardancy of bisphenol A epoxy resin were estimated according to ASTM D2512-95 (2008). The specimen cured by T-31, with the addition of hexabromocyclododecane, did not show any flash and explosion during the 20 times of mechanical impact, whereas slightly empyreumatic scent was detected. The explosion was observed for the other specimens. The resin particles on the surface of the specimen after the mechanical impact were more than that before the mechanical impact, which was attributed presumably to the mechanical impact at the low temperature resulted in the crushing of the resin materials. It also indicated that bisphenol A epoxy resin cured by 593 with antimony trioxide at the low temperature had low flexibility. The XPS analysis confirmed that the surface of the specimen observed explosion was readily reacted with liquid oxygen. The O/C ratios of the specimen cured by T-31, with the addition of hexabromocyclododecane, before and after the mechanical impact were statistically approximate to 0.223 and 0.238, respectively, which revealed that the specimen was compatible with liquid oxygen.     

Effect of ZnO on the crystallization behavior and properties of SiO2–CaO–Al2O3–Fe2O3 glass-ceramics prepared from simulated secondary slag after reduction of copper slag

The feasibility of preparing low-cost glass-ceramics from Zn-containing dust and secondary molten slag generated during the carbothermal reduction of copper slag was investigated. Analytical-grade agents, such as ZnO, Fe₂O₃, SiO₂, CaO, and Al₂O₃, were used to simulate the dust and secondary slag. The effect of ZnO content on the crystallization behavior, structure, and mechanical properties of the glass-ceramics was investigated through X-ray diffraction analysis, scanning electron microscopy-energy dispersive spectrometry, differential scanning calorimetry, Fourier transform infrared spectroscopy, and Raman spectroscopy. The results showed that with increased ZnO content from 0 to 6 wt%, the crystallization activation energy of base glass increased from 386.05 to 425.89 kJ/mol. Meanwhile, the average value of the crystal growth index increased from 1.91 to 4.10, and the highest crystallization rate of the glass-ceramics increased from about 1.44 to 23.11 mm³/min. The increased ZnO in glass-ceramics promoted the precipitation of gehlenite, but inhibit the crystallization of anorthite. When the ZnO content was 6 wt%, the comprehensive properties of the glass-ceramics were better; the flexural strength, microhardness, volume density, water absorption rate, and open porosity were 58.67 MPa, 738.35 HV, 2.92 g/cm³, 0.44% and 1.27%, respectively.     

Meso-scale computational modeling of the plastic-damage response of cementitious composites

Concrete is considered as a 3-phase composite material; mortar matrix, aggregates, and interfacial transmission zone (ITZ). In order to investigate the contribution of each phase to the strength and damage response of concrete, 2-D and 3-D meso-scale simulations based on a coupled plasticity-damage model are carried out. The aggregates are modeled as a linear-elastic material, whereas the mortar matrix and ITZ are modeled using a coupled plasticity-damage model with different tensile and compressive mechanical behavior. Aggregate shape, distribution, and volume fraction are considered as simulated variables. The effect of the ITZ thickness and the strength of the ITZ and mortar matrix are also evaluated. It is shown that the behavior of concrete is merely dependent on the aggregate distribution and the strength of the mortar matrix, but dependent on aggregate shape, size, and volume fraction, and the thickness and strength of the ITZ.     

中间包镁质干式振动料蚀损机理研究

采用相图分析了中间包溶渣对于式振动料的侵蚀机理,并用扫描电镜、能谱及X-ray衍射对中间包干式振动料残衬进行显微观察和分析.结果表明:在中间包使用初期,熔渣对中间包工作衬侵蚀的途径为渗透;在渗透的同时,熔渣对干式料产生化学侵蚀及干式料对熔渣产生化学过滤作用、方镁石溶于熔渣改变了熔渣的性质,提高了熔渣的熔点和粘度,在干式振动料/熔渣界面形成致密的结构,阻碍熔渣的进一步渗透;此后,熔渣对干式料侵蚀的主要途径是对界面致密层的溶蚀.     

纳米SiO2对钢渣水泥基胶凝材料的影响

钢渣和水泥具有相似的矿物组成,可以作为一种潜在的胶凝材料,然而钢渣掺量较高时并不利于混凝土早期性能的发展。以钢渣质量分数为30%的钢渣水泥基胶凝材料为研究对象,探讨纳米SiO₂对其早期性能的影响。主要通过测量流动度、凝结时间和抗压强度评估物理力学性能,并利用微量热分析、X射线衍射(XRD)、差热分析(DSC-TG)等方法对掺有纳米SiO₂的钢渣水泥基胶凝材料的水化过程和水化产物进行分析。结果表明,当纳米SiO₂掺入的质量分数为3%时,纳米SiO₂可充分发挥火山灰活性,消耗大量Ca(OH)₂,同时由于纳米SiO₂颗粒的结晶成核作用和微集料填充作用,促进了钢渣和水泥的水化,水化初期的放热速率有所提高,从而提高钢渣水泥基胶凝材料的力学性能,28 d的抗压强度提高了14.0%。     

Studies on the adhesion of polyimide coatings on copper foil

The peel strength and the color of the copper foil peeled at 90 degrees from five different polyimide films were studied. The interfacial surfaces of copper foil and polyimide were examined by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and energy dispersion analysis by X-ray (EDAX). There is a correlation between peel strength, and the color of the interfacial side copper caused by oxygen diffusion. Study of the imidization process carried out in vacuum indicates that the geometric arrangements of the atoms of polyimide also play a very important role in peel strength.     

预煅烧铜渣对生物质催化热解动力学的影响

采用热重分析仪考察了预煅烧铜渣对生物质催化热解动力学的影响. 结果表明,催化剂的使用可明显降低生物质热解的活化能;随煅烧温度提高和1000℃下煅烧时间延长,催化剂活性先增强后减弱. 不同预煅烧条件下铜渣矿物的表征显示,由于Fe2SiO4、硫化物和磷化合物的氧化,铜渣质量先增加后降低;预煅烧使Fe从铜渣的Fe2SiO4中脱出,以Fe3O4和a-Fe2O3形式存在;随煅烧温度提高,Fe2SiO4的特征峰逐渐减弱直至消失,Fe3O4先增强后减弱,a-Fe2O3增强. 由此推断,Fe3O4的形成是预煅烧铜渣催化活性提高的原因.     

利用微观测试手段评价磷渣的活性

通过化学分析、X射线衍射分析以及扫描电镜分析等测试手段研究磷渣的化学成分和物相，结合其物理特性，评价磷渣的活性。研究结果表明，磷渣本质结构使得其活性很低，大量应用还需合理激发。     

Impact strength elastomer composites based on polystyrene components separated from waste electrical and electronic equipment

The reuse of plastic components of waste electrical and electronic equipment (WEEE) is an important concern both for environmental issues and to preserve the material resources, with minimum energy consumption. Considering that polystyrene fraction was reported as approximate 80% of the total amount of WEEE plastic, this article aims to evaluate the recycling of this fraction, without separation by components, by melt compounding with styrene-butadiene block-copolymer (SBS) and hydrogenated and maleinized SBS, the blend of the two elastomers acting both as an impact modifier and compatibilizer. The composites are characterized by mechanical analysis, impact tests, dynamic mechanical analysis, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction. The recycling conditions of the polystyrene fraction as composites without eliminating the WEEE additives for improved UV and flame resistance, with physical mechanical properties comparable to those of high-impact polystyrene resulted from the study. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48329.     

The influence of cooling rate on the adhesion of polyethylene coatings applied to metals as a hot melt

The quenching from the melt of polyethylene coatings on steel, polished copper and black-oxidized copper increased their adhesion. The fracture surfaces examined in a scanning electron microscope showed the quenched polymer had a more fibrous texture. Quenching lowered the crystallinity and yield strength of the polymer but greatly increased its elongation at break requiring a greater energy for fracture. The tear strength also was higher. The increased adhesion is attributed to the changed mechanical properties of the quenched polymer, particularly to its increased fracture energy.     

太阳盐/钢渣定型复合相变储热材料的制备与性能研究

全球范围内的能源短缺和环境污染问题迫使人们积极开发可再生新能源.储热技术是解决新能源不稳定性问题的关键技术.相变材料是重要的储热介质之一.熔盐相变材料因其储热密度高,可操作温度范围广的优势,成为储热材料领域研究的热点.为解决熔盐液相易泄漏、低导热和高成本的问题,选择钢渣为基体材料,制备了太阳盐/钢渣定型复合相变储热材料...     

Life cycle assessment of a ceramic glaze containing copper slags and its application on ceramic tile

Even though copper slags have many possible applications, their disposal is still practiced, creating long-term waste management problems. This led to the investigation of new products for residential applications, taking advantages of the interesting chemical properties of copper slag. This study aims to assess the environmental impact of the use of copper slag as secondary raw material in a ceramic glaze composition and to compare it with a traditional glaze. A manufacturing process was designed, through an industrial scale up operation from experimental laboratory data and the entire life cycle of the products was analyzed using the Life-cycle assessment (LCA) methodology. Considering the production of a ceramic glaze containing copper slag, the most impacting process resulted the one related to frit production, due to the large amount of thermal energy necessary for the raw materials melting. The comparative LCA analysis carried out between the frit obtained from metallurgical slags and a traditional one, demonstrated that the innovative ceramic frit has a greater environmental advantage. The LCA analysis allowed to highlight the most impactful stages of an industrial process using copper slag as a secondary raw material for glaze production and to quantify the potential environmental advantages of this operation.     

铜渣催化气化木屑的实验研究和热力学分析

以木屑为原料,在铜渣催化气化木屑的实验平台上研究了气化剂和载气对气体产物成分及热值的影响。根据实验结果,当水蒸气当量比为0.058时,焦油产率降低了约50%,氢气产率提高了63.04%,气化效率达75.03%。在优化的实验条件下基于能量平衡建立熔融铜渣催化气化木屑的热力学分析方法,得到铜渣、木屑及水蒸气之间的耦合关系,1250℃的熔融铜渣的余热高达1.773 MJ/kg,充分利用铜渣显热和潜热气化木屑产生的合成气热值可高达13319 kJ。在最优气化工况下,1 kg原料气化需要1.92 kg铜渣,热态铜渣催化气化木屑的能量利用率可达62.94%。     

铜矿渣在水泥混凝土应用的研究进展

铜矿渣应用于水泥与混凝土中可降低炼铜企业成本,又有利于环境保护.介绍了铜矿渣的物理与化学性质,对铜矿渣在水泥和混凝土领域的研究进展进行了综述.铜矿渣可作为铁质原料配置生料,配置的生料易烧性好,并能改善熟料的岩相结构和力学性能;也可作为水泥熟料混合材,所制成的水泥具有早期水化放热低、后期强度发展高等优点.铜矿渣可作为细骨料应用于混凝土中,铜矿渣混凝土具有与普通混凝土相当的工作性、力学性能与耐久性能.铜矿渣和水泥熟料有相似的化学成分,可通过物理或化学方式激发铜矿渣的活性作为胶凝材料应用于混凝土中,与Ca(OH)2反应生成与水泥水化相似的水化产物.铜矿渣可降低混凝土的脆性系数,具有减脆的作用.