Effect of sintering temperature on lightweight aggregates manufacturing from copper contaminated soil

Manufacturing lightweight aggregate (LWA) at high temperature is an effective way to immobilize heavy metals in solid waste. This work investigated the performance and solidification mechanism of LWA prepared from copper contaminated soil. The volume expansion of LWA could reach a maximum of 28%, and its lowest density accounted of 1.5 g/cm³, which met the standard requirements. Optical microscope and micro-CT test illustrated that the addition of Cu leaded to obvious phase separation in LWA. The Cu leaching result of LWA first increased and then dropped with the temperature. The XRD test found that the main formation phase of Cu in LWA were t-CuFe₂O₄ and amorphous phase that they had different acid resistance ability. XPS revealed that the main cause of the agglomeration of liquid phase in LWA was the chain broken reaction between Cu and Si–O tetrahedron. SEM-EDS results showed that the distribution of Cu and Si had a strong correlation, which meant that Cu mostly formed amorphous phase. This work showed the uniqueness of Cu in the high temperature immobilization and pointed out the best immobilization target phase.     

AlB12-AlB12C2-TiB2 hard and tough composites synthesized by reactive plasma activated sintering

AlB₁₂-AlB₁₂C₂-TiB₂-based hard and tough composites were fabricated using ball milled B, Al, and Ti powders as the starting materials, and sintered by reactive plasma activated sintering (PAS). The mechanical properties and microstructures were investigated, and the effects of the composition and microstructures on the reinforcing and toughening of the composites were determined. The results showed that the composite with 10 vol% TiB₂ showed excellent mechanical properties, a lightweight of 2.76 g cm⁻³, Vickers hardness of 37 GPa, and fracture toughness of 7.1 MPa m^1/2. In addition, the main strengthening and toughening mechanisms were due to the twin structures, dislocation defects, and stacking faults in the specimen in addition to grain pull-out, crack deflection, crack bridging, and crack branching caused by elongated TiB₂ particles.     

From magnesite directly to lightweight closed-pore MgO ceramics: The role of Si and Si/SiC

Partial/full replacement of traditional dense refractory aggregates (for furnace lining) with lightweight aggregates is considered to be an effective and promising strategy for energy saving and emission reduction. In this work, lightweight magnesia refractory ceramics with tailored closed porosity were prepared by one-step sintering at 1600 °C from high-purity magnesite added with silicon kerf waste in different ratios, with the emphasis on the evolution of their phase compositions, micromorphologies, and various properties. With the addition of additives, Mg_2–xFe_xSiO₄ solid solution was formed at the grain boundaries of the MgO matrix, and then the volumetric expansion effect (interfacial reaction) and activated sintering effect (vacancy defect) promote the decrease of apparent porosity and the increase of closed porosity, respectively. Consequently, MgO ceramics with apparent/closed porosity of 0.6%/6.5%, bulk density of 3.25 g cm⁻³, and lightweight index of 7.8% were successfully prepared, suitable for the working lining of metallurgical furnaces.     

Fibre reinforced lightweight aggregates

Carbon steel fibre reinforced lightweight aggregates (LWA) were produced in a pilot scale rotary kiln. Narrow size fractions as well as not-sieved (as received) material were investigated according to European standards with a main focus on strength and density and compared to a reference material without fibres. Depending on the size of the pellets a fraction of the fibres oxidized during firing. A strength increase proportional to the amount of non-oxidized fibres within the pellet was observed. The crushing resistance for as received fibre reinforced pellets (bulk density 452 kg/m³) was 3.0 MPa corresponding to an increase in strength of 140%. The enhanced strength was also confirmed by the single pellet compression test.     

生态建造：教育套餐和环境手册

生态建造是一个关注于传播建成环境中可持续性的需要以及促成可持续性的方式的项目。它针对于两个群体：16-19岁的学生，为他们制作了一个交互式的光盘；建造行业中的专业人员。光盘中提出了这样的问题--你的家和学校有多绿色？它说明了类似于建筑尺度和朝向的设计决策如何影响到建筑在能耗方面的表现和CO2的排放量。光盘包括了衡量如往宅温室节能效果的术语表，来解释它们对建筑的影响。这样学生们就可以对他们自己的学校和家进行评估，并提出怎样的设计可以提高它们的节能效果。如果我们想全球化地实现可持续性的未来，下一代的介入至关重要。环境手册中更深入地研究了这些问题，并关注到了其他建筑类型，如办公建筑。本文描述了正趋于完成的教育光盘和环境手册中涉及的一些根本的环境和教育因素。     

Long-term strength and durability parameters of lightweight concrete in hot regime: importance of initial curing

The paper presents results on strength development and durability of 35 and 50 MPa total lightweight concretes exposed to hot marine exposure conditions for a period of 7 years. An initial water curing of 7 days and subsequent seaside exposure was found more beneficial for the strength development of lightweight concrete. One day of initial curing and subsequent seaside exposure was not very conducive for the strength development. A marginal degradation in both the stiffness and the modulus of rupture of the concretes over the exposure period was observed. Likewise, the water penetrability of the two mixtures, for all the three initial curing regimes, increased over a period of 7 years. This establishes that the compressive strength of concrete is not synonymous with its durability. Overall, 3–7 days of initial water curing seems most desirable to enhance the durability of concrete exposed to hot salty marine exposure conditions.     

LC45轻骨料混凝土梁的力学特性

对比分析了同强度等级的普通混凝土及轻骨料混凝土矩形截面构件的应力应变特性和轻骨料混凝土预应力T梁受力特点。试验表明,对于非预应力混凝土配筋梁,LC45轻骨料混凝土构件的开裂荷载及破坏荷载分别高于C45普通混凝土构件;而预应力轻骨料混凝土试验梁的开裂荷载为规范计算值的1.6倍左右,并且在设计的荷载范围内,梁的荷载挠度曲线呈线性,梁在弹性工作状态中。     

Lightweight concrete made from oil palm shell (OPS): Structural bond and durability properties

The first part of this experimental program was to determine the structural bond properties of lightweight concrete incorporating solid waste oil palm shell (OPS) as coarse aggregate and also to compare its behaviour with other types of lightweight aggregate concretes. Other properties of OPS concrete namely the split tensile strength, modulus of rupture and modulus of elasticity were also determined. The structural bond properties were determined through pull-out test. The results showed that the experimental bond strength of OPS concrete was much higher than the design bond strength as stipulated by BS 8110. In general, the properties of OPS concrete compared well with that of other structural lightweight concretes and the results obtained encourage the use of OPS as aggregates for the production of structural lightweight concrete. The second part of the experimental program investigates the durability performance of OPS concrete through water permeability and water absorption tests.     

轻质高强沸石烧结砖的研制

我国沸石资源丰富，量多面广。以沸石为主要原料生产的烧结砖，是一种新型的节能墙体材料，它的最显著特点是：轻质、高强，节能效果好。