A durability performance-index for concrete: developments in a novel test method

Implementation of both design for durability and performance-based standards and specifications are limited by the lack of rapid, simple, science based test methods for characterising the transport properties and deterioration resistance of concrete. This paper presents developments in the application of electrical property measurements as a testing methodology to evaluate the relative performance of a range of concrete mixes. The technique lends itself to in-situ monitoring thereby allowing measurements to be obtained on the as-placed concrete. Conductivity measurements are presented for concretes with and without supplementary cementitious materials (SCM’s) from demoulding up to 350 days. It is shown that electrical conductivity measurements display a continual decrease over the entire test period and attributed to pore structure refinement due to hydration and pozzolanic reaction. The term formation factor is introduced to rank concrete performance in terms of is resistance to chloride penetration.

Three-dimensional graphene-Co3O4 cathodes for rechargeable Li-O2 batteries

A three-dimensional (3D) graphene-Co₃O₄ electrode was prepared by a two-step method in which graphene was initially deposited on a Ni foam with Co₃O₄ then grown on the resulting graphene structure. Cross-linked Co₃O₄ nanosheets with an open pore structure were fully and vertically distributed throughout the graphene skeleton. The free-standing and binder-free monolithic electrode was used directly as a cathode in a Li-O₂ battery. This composite structure exhibited enhanced performance with a specific capacity of 2453 mA h g^-1 at 0.1 mA cm^-2 and 62 stable cycles with 583 mA h g^-1 (1000 mA h g_carbon^-1). The excellent electrochemical performance is associated with the unique architecture and superior catalytic activity of the 3D electrode. 

The application of early contractor involvement and its impact on project performance

Early contractor involvement is a topic that has attracted attention from construction practitioners and researchers in the UK since the 1990s. It has been adopted to introduce construction knowledge and experience to the design process, and to integrate design with construction. In contrast with the limited number of previous studies on early contractor involvement, which used case studies, a questionnaire survey was conducted in this study, to investigate the application of early contractor involvement in current practice and its impact on project performance in terms of time, cost and quality. From an analysis of the questionnaire results, early contractor involvement is found to be increasingly used in the construction industry, and to have a significant impact on cost and time performance. This research provides empirical evidence related to the practice of early contractor involvement. It demonstrates the major influence of early contractor involvement on management processes and working relationships during a project, which contribute to performance improvement and project success.