Construction and Building Materials 

Abstract: This paper reviews the state of the field of nanotechnology in concrete. Definitions of nanotechnology, including nanoscience and nano-engineering in concrete, are provided. The impact of recent advances in instrumentation and computational materials science and their use in concrete research is discussed. Recent progress in nano-engineering and nanomodification of cement-based materials is presented.

Abstract: This review brings together research on life cycle assessment (LCA) applied within the building sector. More than ever, the construction industry is concerned with improving the social, economic and environmental indicators of sustainability. By applying LCA it is possible to optimise these aspects, from the extraction of raw materials to the final disposal of waste building materials. Firstly, this review details LCA concepts and focuses on the LCA methodology and tools employed in the built environment. Secondly, this paper outlines and discusses the differences between the LCA of building materials and components combinations versus the LCA of the full building life cycle. Finally, this work can be used by stakeholders as an important reference on LCA including up to date literature on approaches and methodologies to preserve the environment and therefore achieve sustainable development in both developed and developing countries. The present review has tried to compile and reflect the key milestones accomplished in LCA over the last 7 years, from 2000 to 2007 within the building sector. In summary, it can be stated that the application of LCA is fundamental to sustainability and improvement in building and construction. For industrial activities, SMEs must understand the application of LCA, not only to meet consumer demands for environmentally friendly products, but also to increase the productivity and competitiveness of the green construction markets. For this reason, this review looks at LCA because of its broad international acceptance as a means to improve environmental processes and services, and also for creating goals to prevent adverse environmental impacts, consequently enhancing quality of life and allowing people to live in a healthy environment.

Abstract: External confinement by the wrapping of FRP sheets (or FRP jacketing) provides a very effective method for the retrofit of reinforced concrete (RC) columns subject to either static or seismic loads. For the reliable and cost-effective design of FRP jackets, an accurate stress–strain model is required for FRP-confined concrete. In this paper, a new design-oriented stress–strain model is proposed for concrete confined by FRP wraps with fibres only or predominantly in the hoop direction based on a careful interpretation of existing test data and observations. This model is simple, so it is suitable for direct use in design, but in the meantime, it captures all the main characteristics of the stress–strain behavior of concrete confined by different types of FRP. In addition, for unconfined concrete, this model reduces directly to idealized stress–strain curves in existing design codes. In the development of this model, a number of important issues including the actual hoop strains in FRP jackets at rupture, the sufficiency of FRP confinement for a significant strength enhancement, and the effect of jacket stiffness on the ultimate axial strain, were all carefully examined and appropriately resolved. The predictions of the model are shown to agree well with test data.

Abstract: The influence of nano-SiO 2 (NS) addition on properties of hardened cement paste (hcp) as compared with silica fume (SF) has been studied through measurement of compressive and bond strengths of hcp, and by XRD and SEM analysis. Results indicated that the influence of NS and SF on consistency and setting time of fresh cement paste showed different. NS made cement paste thicker and NS accelerated the cement hydration process. Compressive strengths of hcp and bond strengths of paste–aggregate interface incorporating NS were obviously higher than those incorporating SF, especially at early ages. And with increasing the NS content, the rate of bond strength increase was more than that of their compressive strength increase. With 3% NS added, NS digested calcium hydroxide (CH) crystals, decreased the orientation of CH crystals, reduced the crystal size of CH gathered at the interface and improved the interface more effectively than SF. The results suggest that with a small amount of added NS, the CH crystals at the interface between hcp and aggregate at early ages may be effectively absorbed in high performance concrete (HPC).

Abstract: Concrete for construction has traditionally been based on an Ordinary Portland Cement (OPC) binder. Geopolymers, an alternative binder based on fly ash (a fine waste collected from the emissions liberated by coal burning power stations) that is activated by an alkaline activator, have potential to lower the significant carbon footprint of OPC concrete. This paper presents the results of comprehensive carbon footprint estimates for both geopolymer and OPC concrete, including energy expending activities associated with mining and transport of raw materials, manufacturing and concrete construction. Previous studies have shown a wide variation of reported emission estimates: the results of this study are benchmarked with data from those studies.