Fatigue and healing properties of nano-reinforced bituminous binders

The research work focused on fatigue and healing properties of bituminous binders containing carbon nanotubes (CNTs) and nanoclays (NCs) as reinforcing additives. Investigations were carried out by means of a dynamic shear rheometer and by employing specifically devised testing protocols. Experimental results were analysed with the specific goal of highlighting the role played by additive type and base bitumen. Although fatigue response of base bitumens was always improved by nano-modification, effectiveness of nano-particles was found to be highly dependent on the physico-chemical properties of blend components, which strongly influence the morphological configuration assumed by additives within bituminous media. Results obtained in healing tests were processed in order to discern between self-healing of cracks induced by fatigue damage and other artefact phenomena which are related to viscoelastic changes occurring in the bulk of the material. Outcomes of fatigue and healing tests were found to be coherent with interaction mechanisms which take place at the nano-scale.     

Improving the homogeneity and properties of ferrous powder mixes by a novel powder mixing process

Fe-2Cu-0.8C powder mixes were prepared by a wet mixing and spray-drying process using iron, copper, graphite and zinc stearate as main raw materials, and stearic acid, alcohol wax and amide wax as binders. The properties of the as-prepared binder treated powder mixes were investigated. The bonding efficiency of the binders was tested by measure the retention of graphite and copper in the powder mixes after dusting resistance test. The test results show that the wet mixing and spray-drying process can realise the bonding of different particles and improve processing properties of the powder mixes. A flow rate of 30.6?s/50?g and an apparent density of 3.18?g/cm³ were obtained for powder mixes with alcohol wax as binder. The results of dusting resistance test demonstrated that alcohol wax and amide wax have better bonding effect for Cu and graphite powders, respectively, which was reflected by the difference value of electronegativity between Fe, Cu, C elements and functional groups. Compared with mechanically mixing powder mixes, using binder treated powder mixes can also reduce the friction coefficient during compaction by 0.012–0.026. The addition of different binders also has a great influence on the properties of sintered parts.     

Microstructure and mechanical properties of ternary mortars with brick powder,glass powder,slag, fly ash,and limestone

The objective of this research is to study the effects produced by ternary binders which combine the addition of waste brick powder with fly ash, limestone, ground granulated blast furnace slag or waste glass powder in the microstructure and mechanical properties of mortars. In these ternary binders, the ordinary Portland cement was partially replaced by 10% of waste brick powder and 10% of another of the abovementioned additions. Mortars prepared with ordinary Portland cement without additions were also prepared. The microstructure was characterized with mercury intrusion porosimetry, electrical resistivity, and thermogravimetric analyses. Ultrasonic pulse velocity, compressive and flexural strengths were also determined. Mortars made using ternary binders with two active additions showed higher pore refinement and higher electrical resistivity at 250 days. Furthermore, their compressive strength and ultrasonic pulse velocity were relatively similar or even higher than that noted for reference specimens.     

Formulation of new materials based on geopolymer binders and different road aggregates

The study of bitumen substitution in the field of road construction is necessary to overcome the effects of limited oil resources and economic problems. The elaboration of new materials based on geopolymer binders and aggregates was investigated in this work. Two series of formulations of geopolymer binders based on sodium or potassium were prepared with the incorporation of granite or diorite. The formulation of these binder was investigated by the study of (i) the effect of the nature of the alkaline solution by modify the pH value with base and (ii) the mass percentage of the incorporated aggregates. The time evolution study shows different aspects of the synthesized materials, which depend essentially on the composition of the activating solutions and the nature of the alkaline solutions. The formulations using these ratios (Si/Na=1.55; Si/K=1.94 and 2.96) appear the best. Moreover, it was evidenced that materials based on the potassium alkaline solution present a consolidated aspect faster than the materials based on the sodium alkaline solution. Additionally, it is possible to incorporate diorite or granite until 60 w% with some formulations. These various formulations are promising to be use not as a substitute of bitumen but in addition between bitumen and ground.     

A Robust Ion‐Conductive Biopolymer as a Binder for Si Anodes of Lithium‐Ion Batteries

Binders have been reported to play a key role in improving the cycle performance of Si anode materials of lithium‐ion batteries. In this study, the biopolymer guar gum (GG) is applied as the binder for a silicon nano­particle (SiNP) anode of a lithium‐ion battery for the first time. Due to the large number of polar hydroxyl groups in the GG molecule, a robust interaction between the GG binder and the SiNPs is achieved, resulting in a stable Si anode during cycling. More specifically, the GG binder can effectively transfer lithium ions to the Si surface, similarly to polyethylene oxide solid electrolytes. When GG is used as a binder, the SiNP anode can deliver an initial discharge capacity as high as 3364 mAh g^?1, with a Coulombic efficiency of 88.3% at the current density of 2100 mA g^?1, and maintain a capacity of 1561 mAh g^?1 after 300 cycles. The study shows that the electrochemical performance of the SiNP anode with GG binder is significantly improved compared to that of a SiNP anode with a sodium alginate binder, and it demonstrates that GG is a promising binder for Si anodes of lithium‐ion batteries.     

Microstructure evolution of TiC cermets with ferritic AISI 430L steel binder

From the outlook of healthcare, economic importance and supply risk, utilisation of raw materials like tungsten, cobalt and nickel should be reduced or replaced with other metals. Nontoxic titanium carbide and iron are the top-of-the-line solution for displacing these materials. Our focus was on conventionally fabricated titanium carbide-based cermets with a chromium ferritic steel binder. To study microstructural evolution, specimens were sintered at different temperatures (600–1500°C). We used a scanning electron microscopy, X-ray diffraction and differential scanning calorimetry to analyse the microstructure and phase formation of the cermets. Our results showed that during the solid and liquid phase sintering of the TiC–FeCr cermet, chromium ferrous complex carbides M₇C₃ are formed and as a result, chromium content in the binder phase is decreased. Alloying TiC–FeCr cermets with strong carbide formers improves the structural homogeneity of the cermets. Also, mechanical characteristics (hardness, fracture toughness) were evaluated.     

Chemical activation of hybrid binders based on siliceous fly ash and Portland cement

The hydration of Portland cement (PC) blended with a high amount of a siliceous fly ash (70% fly ash, 30% PC) has been examined. The fly ash contributes significantly to the long-term strength development, when compared to a reference sample with quartz powder. However the long setting time and the poor early strength prevent the use of such binders. Therefore the effect of different activators (sodium carbonate, potassium sodium silicate, potassium citrate and sodium oxalate) on the setting, the hydration kinetics and the strength development of the fly ash-PC blend has been investigated.The addition of the activators increases the pH and decreases thus the calcium concentrations in the pore solution, which leads to a faster reaction of alite and thus to early setting and increased early strength. On the long term, the high alkali concentrations lower the compressive strength and lead to a (partial) destabilization of ettringite.Sodium oxalate and potassium sodium silicate accelerate both the setting of the fly ash-PC blend and increase the early compressive strength. Furthermore, they show better compressive strengths at later ages compared to the other activators. Based on these findings, they can be considered as the most suitable accelerators among the investigated activators.     

Plate Water Absorption as an Assessment Tool for Organic Binders

Plate water absorption has been traditionally used to assess the binding ability of bentonite clay binders for iron ore concentrate pelletization. Until 1997, there was an accepted test by ASTM, but due to inconstant data this method was withdrawn. This value, however, is still used by some pelletization operations to gauge the efficacy of their bentonite. This test procedure has only been investigated on inorganic binders and never organic binders. This paper seeks to confidently prove that PWA can be used to accurately determine the efficacy of starch binders both alone and in conjunction with bentonite. The role of bentonite as a binder for iron ore concentrate is not only to hold agglomerates together during high temperature operations. But during pelletization it can also mitigate many times its own weight in water. This water absorption capacity aids in retarding the growth rate of pellets, as faster growing pellets tend to be weaker. The value of this water absorption, known as plate water absorption (PWA), is used as a metric to determine the strength and quality of the resulting pellets by industrial pelletizing facilities. As new low silica binders seek to replace bentonite, they too must take on the role of moisture mitigation. This study has shown that starches with lower water absorption capacities tend to have lower compressive strengths. As the water absorption capacity increases so too does the compressive strength. When using only starch, higher absorption capacities lead to lower compressive strengths of pellets exposed to elevated temperatures. When bentonite is used in conjunction with starch, higher water absorption mixtures do exhibit an increase in strength when heated.     

粘结剂对纯铁磁粉芯性能的影响

采用粉末冶金工艺制备纯铁磁粉芯,研究了粘结剂含量、组成对磁粉芯综合性能的影响.结果表明,粘结剂含量为2.7%～3.6%,无机与有机粘结剂组成为3∶2～3∶1时,粘结剂的包覆效果较好,样品的力学性能得到较大改善,抗压强度达到了480 MPa;粘结剂含量为2.8%～3.5%,无机与有机粘结剂组成为2∶1时,磁粉芯磁性能较好...     

沥青品种对沥青混合料路用性能的影响

采用具有代表性的3种沥青和AC-13C级配矿质混合料拌制沥青混合料并进行了一系列室内试验研究。结果表明:TLA改性沥青混合料和SBS改性沥青混合料都比普通沥青混合料具有更好的高温稳定性、低温抗裂性和水稳定性。TLA改性沥青混合料比SBS改性沥青混合料具有更好的高温稳定性和水稳定性,但低温抗裂性略差一些。