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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 11 Abstracts search results
October 1, 2008
Compared with other major industrial sectors, the construction industry has lagged behind in awareness of the potential for exploitation of nanotechnology.
Both the awareness and actual exploitation in construction are now increasing;
however, progress is uneven, especially in the current early stages of its practical exploitation. A roadmap then becomes a useful tool, a template, for predictions of trends and developments connecting nanotechnology and construction. The Roadmap for Nanotechnology in Construction (RoNaC) outlined in this paper is aimed at facilitating identifications of desirable aims/destinations for construction research and technical development (RTD) over a short-to-medium timescale (up to 25 years). The RoNaC was developed as an aid for forecasting research and investment directions. It provides guidance to construction industry, investors, and national/international bodies supporting research and development about the
diverse pathways toward current nanotechnology-linked expectations, aims, and targets in this very large and economically significant domain. The complexity of the construction domain is such that a single overall chart would be far too general in a scale so large that it would become incomprehensible. Sectorial or "topical" charts have been developed instead of a single "map", and three examples of such charts have been worked out to illustrate this approach. Requirements for adequate research infrastructures, effects of appropriate drivers, and diverse vehicles for RTD are considered together with an assessment of the "environment" conducive to progress along the pathways and directions indicated in the charts.
P. Mondal, S.P. Shah, and L.D. Marks
In this research, sample preparation techniques were developed to image
the nano- and microstructure of hardened cement paste and to determine local
mechanical properties. An atomic force microscope (AFM) was used to image the nanostructure of hardened cement paste. AFM and a Hysitron Triboindenter equipped with an in-situ scanning probe microscopy were used to determine the Young’s modulus of cement paste at the nanoscale.
Nano-technology based on depth-sensing microindentation apparatus was used to evaluate the elastic modulus and micro-hardness of the interfacial
transition zone (ITZ) and to estimate the extent of the ITZ around the aggregate-matrix interface for underwater concrete (UWC) and around steel reinforcement for selfconsolidating concrete (SCC) and vibrated concrete. The micromechanical properties of ITZ near to aggregates of concrete cast in water were lower than those of concrete cast in air. The modulus elasticity and the microstrength of concrete cast in water were lower than those of concrete cast in air. It is attributed to the dilution of paste cement and fines particles in water causing reduction of strength and increasing the porosity of concrete. The results of the interfacial properties between selfconsolidating
concrete and conventional concrete revealed that the elastic modulus
and the micro-strength of the ITZ were lower on the bottom side of a horizontal
steel bar than on the top side, particularly for the vibrated reference concrete. The difference of ITZ properties between top and bottom side of the horizontal steel bar appeared to be less pronounced for the SCC mixtures than for the corresponding control mixtures.
A. Gmira, J. Minet, A. Franceschini, N. Lequeux, R.J.-M. Pellenq, and H. Van Damme
On the basis of recent molecular simulation or experimental studies, we discuss two possible strategies for improving the mechanical properties of
cementitious materials by modifying the bonding scheme in the hydrates at
molecular level. We focus on the calcium silicate hydrates (C-S-H). A first strategy would be based on the strengthening of the cohesion forces acting between the individual C-S-H lamellae or between their crystallites. Monte Carlo simulations in the primitive model framework and ab initio atomistic calculations suggest that the cohesion of C-S-H is mainly due to a combination of sub-nano range ionic-covalent forces and meso-range ionic correlation forces. Both types of forces may be modified, at least in theory, by changing the nature of the interstitial ions, their hydration state, or the charge density on the C-S-H lamellae.
M. Drábik, L. Gáliková, S. Balkovic, and R.C.T. Slade
The latest research on the reactivity toward cross-linking of inorganic matrixes formed by cement-based materials, and the associated grafting at the nanoscopic and atomic levels, is highly promising. Macro-defect-free (MDF) materials and technologies were originally comprised of high-alumina cements cross-linked to poly(vinyl alcohol/acetate) or of portland cement with poly(acrylamide). Although the high-alumina system has shown promising results and is the more efficient system, it suffers from economic disadvantages; modern efforts to identify MDF systems focus on portland cement and a variety of polymer additives. We report recent findings regarding the potential and limitations of portland cement-based MDF materials, considering aspects of the associated chemistry (at the nanoscopic and atomic levels), of the mechanism linking polymer to the surface of cement grains, and of technologically relevant attributes such as moisture resistance of the formed MDF material.
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