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A series of innovative connections with the different combinations of steel plates and screws was developed for timber–concrete composite (TCC) system in this paper. Several groups have introduced vulcanized rubber layer to the jointing steel plate, which was used to be glued onto the timber beam surface. Push-out tests were carried out on the proposed connections and three replicates were prepared for each series. The study focused on the load carrying capacity, slip modulus, ductility and the role of some factors of the innovative connections. Moreover, the load-slip behaviour was evaluated based on an existing non-linear model and parametric analysis was also conducted. The research results showed that this connecting system looks suitable for structural application.

Few-layer vertical graphene (VG) was prepared on arrayed carbon nanotubes (CNTs) without a catalyst by using radio frequency sputtering deposition and microwave plasma enhanced chemical vapor deposition, and the field emission (FE) performance of VG–CNT composites was tested and optimized. The FE performance is found to be strongly dependent on the heights (but not the actual heights) and densities of CNTs, the shapes of VG, and the diameters of VG–CNT composites. The optimal shapes for FE are demonstrated to be CNTs with middle densities and small diameters and VG with high densities and small sizes. The optimal FE performance from our large area VG–CNT composites is found to have a low threshold field of 1.28 V/μm (at 10 mA/cm2), a high maximum emission current density of 87.63 mA/cm2 (4.28 times higher than that from our previously prepared graphene–CNT composites), and excellent stability at an extremely high mean emission current density of 36.28 mA/cm2 over a period of 50 h, far better than those of pristine CNTs, pure VG, and shape non-optimized VG–CNT composites.

This paper presents a summary of the experimental programmes and theoretical analysis of the bending performance of non-prestressed and prestressed timber-concrete composite (TCC) beams. Two non-prestressed and three prestressed composite beams were selected, and their flexural behaviour was evaluated. Three types of ductile fabricated connections were applied to the prestressed composite beams, whereas two types were applied to the non-prestressed beams. The concrete slabs with embedded steel plates and timber beams were connected together using coach screws. On the surfaces of the embedded steel plates, the portions in contact with the wooden beam were interspaced with a vulcanized rubber layer to improve the mechanical performance of shear connections and composite beams. A series of four-point bending experiments were performed until collapse failure occurred in a simply-supported scheme. The test results demonstrated that the TCC beams using steel plate + screw connections exhibited excellent structural performance. The flexural capacity of the prestressed specimens was improved by approximately 110% compared with the non-prestressed specimens. Due to the addition of the rubber layer in the TCC connections, the flexural capacity of the prestressed composite beams was improved by 25.2%. Based on the ‘γ–method’, a theoretical analysis was proposed for calculating the flexural capacity and bending stiffness for both non-prestressed and prestressed TCC beams. The theoretical results showed good agreement with the experimental evidence.

An investigation was conducted to compare the microbial community structures between contaminated and reclaimed mine tailings of Dexing copper mine, Jiangxi province, China. Sample T1 was obtained from tailings site, where reclamation of phytostabilization has been conducted for 20 years successfully whereas, the other one (sample T4) was obtained from the unreclaimed tailings site. Physico-chemical characteristics, chemical speciation of heavy metals Cu, Cd and Zn were revealed to compare the effects of reclamation. A polymerase chain reaction (PCR)-based cloning approach was employed to investigate the bacterial community composition in these two samples. Results indicate the improved physico-chemical conditions and decreased bioavailability of heavy metals Cd and Zn significantly in the sample collected from reclaimed site compared with the other unreclaimed mine tailings site. Phylogenetic analysis indicated that bacteria in these two samples fell into 12 putative phylogenetic divisions. Sample T1 had 12 phyla were present, and the community was predominated by Planctomycetes (20%), α-proteobacteria (16%), Chloroflexi (12%) and Acidobacteria (10%). On the other hand, sample T4 had only 4 phyla and was predominated by y-proteobacteria (86%). The diversity of microbes in sample T1 significantly increased when compared with sample T4. The structure of microbial community composition in the first sample also was optimized to sustain more phyla associated with a healthier soil after reclamation. From the results, it could be deduced that the inventories of bacterial populations such as Planctomycetes, Chloroflexi, α-proteobacteria, Acidobacteria and Actinobacteria predominated in sample T1, but were essentially absent in sample T4. This may serve as potential bioindicator for the reclamation evaluation of tailings.Keywords: Mine tailings, reclamation, bacterial community composition, bioindicatorsAfrican Journal of Biotechnology Vol. 12(30), pp. 4841-4849