2) Fundaci6n Labein, Spain iiiiir 1. ABSTRACT The paper is an extended summary of the state-of-the-art report on Application of Nanotechnology in Construction, which is one of the main tasks of a European project -Towards the setting up of a Network of Excellence in Nanotechnology in Construction (NANOCONEX). The paper first presents background information and current developments of nanotechnology in general. Then, the current activities and awareness of nanotechnology in the construction industry are examined by analysing results of a survey of construction professionals and leading researchers in the field. This is followed by results of a desk study of nanotechnology development and activities focussing on key areas relevant to construction and the built environment.Examples of nanotechnology-enabled materials and products that are either on the market or ready to be adopted in the construction industry are provided. Finally, the future trend/potential and implications of nanotechnology development in construction are discussed. INTRODUCTION BackgroundNanotechnology has recently become one of the 'hottest' areas in research and development worldwide, and has also attracted considerable attention in the media and investment community. It is essentially about new ways of making things through understanding and control over the fundamental building blocks (i.e. atoms, molecules and nanostmctures) of all physical things. This is likely to change the way almost everything is designed and made [1]. With the backing of unprecedented funding, nanotechnology is fast emerging as the industrial revolution of the 21 st century [2]. What is nanotechnology?In contrast to other technologies, nanotechnology is much less well-defined and well-structured. Nano, which comes from the Greek word for dwarf, indicates a billionth. One nanometre is a billionth of a metre, that is, about 1/80,000 of the diameter of a human hair. Nanotechnology can best be considered as a 'catch-all' description of activities (any application of science and technology) at the nanometre scale that have applications in the real world [3]. Definitions of 'nanotechnology' vary, but it generally refers to understanding and manipulation of matter on the nanoscale, say, from 0.1 run to 100 nm.The significance and importance of controlling matter at the nanoscale is that at this scale different laws of physics come into play (quantum physics); traditional materials such as metals and ceramics show radically enhanced properties and new functionalities, the behaviour of surfaces starts to dominate the behaviour of bulk materials, and whole new

Cement-based materials are ubiquitous in almost all built environment. In spite of this, little is known about the formation and the role played by the silicate chains always present in the cement nanostructure. By means of first principles simulations we provide compelling evidence on the pivotal role played by certain ionic species in the formation of the silicate chains inside the cementitious matrix. Moreover, we corroborate the experimental evidence which shows that the length of the most stable chains with m Si atoms follows a magic-number sequence: m =3n − 1 with n =1,2,... Our results have been applied in the development of new higher performance cement-based materials by adding nanosilica.

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