International Concrete Abstracts Portal

ABOUT THE 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.

International Concrete Abstracts Portal

Showing 1-10 of 11 Abstracts search results

Document: 

SP254-10

Date: 

October 1, 2008

Author(s):

M. Drábik, L. Gáliková, S. Balkovic, and R.C.T. Slade

Publication:

Special Publication

Volume:

254

Abstract:

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.

10.14359/20216


Document: 

SP254-09

Date: 

October 1, 2008

Author(s):

H. Li, H. Xiao, and J. Ou

Publication:

Special Publication

Volume:

254

Abstract:

The electrical properties of nanophase carbon black-filled cement-based composites are sensitive to moisture content. Previous studies indicate that cementbased composites filled with 120 nm carbon black (CB) in the amounts of 15% (A-15) and 25% (A-25) by weight of cement have promising strain self-sensing properties (that is, piezoresistance properties), thus, this study investigated the effects of moisture on the electrical properties of A-15 and A-25. The results indicate that the initial resistance of composites increases with moisture content. Additionally, the resistance of specimens with certain moisture content increases with measurement time. These two phenomena are mainly attributed to a polarization effect. A waterproof measurement (that is, a specimen encapsulated by epoxy) was developed to insulate the composites from ambient moisture for the composites as strain self-sensing materials. The initial resistance of the specimens encapsulated with epoxy and dipped into water stayed constant during measurement time, and their piezoresistance properties were almost the same as those of the specimens exposed to ambient moisture.

10.14359/20215


Document: 

SP254-08

Date: 

October 1, 2008

Author(s):

B.H. Green

Publication:

Special Publication

Volume:

254

Abstract:

This paper describes the development of a high-strength, high-density cementitious rock-matching grout mixture for use in a field project. This portland cement-based grout incorporated silica nanoparticles in the form of an ultra-fine amorphous colloidal silica (UFACS) along with hematite fine aggregate, silica fine aggregate, silica fume, water, and other chemical admixtures to match as closely as possible the given in-situ high-strength rock properties at a given field site. The new admixture, UFACS, was used as a viscosity-modifying agent to prevent aggregate segregation and was used to replace sodium bentonite clay, which frequently leads to a decrease in unconfined compressive strength. The resultant rock-matching grout (RMG) mixture was then placed in the field with over 65 individual batches to fill the annular space surrounding instrumentation packages previously placed in drilled boreholes. The resultant mechanical properties of this field-placed RMG included unconfined compressive strengths of 91.2 MPa (13,230 psi), hardened densities of 2680 kg/m3 (4,520 lb/yd3), and ultrasonic pulse velocities of 4.40 km/s (14,500 ft/s).

10.14359/20214


Document: 

SP254-07

Date: 

October 1, 2008

Author(s):

K. Sobolev, I. Flores, R. Hermosillo, and L.M. Torres-Martínez

Publication:

Special Publication

Volume:

254

Abstract:

Nanotechnology has changed our vision, expectations, and abilities to control the material world. The developments in nanoscience can also have a great impact on the field of construction materials. Portland cement, one of the largest commodities consumed by mankind, is obviously the product with great, but not completely explored, potential. Better understanding and engineering of complex structure of cement-based materials at nanolevel will definitely result in a new generation of concrete, stronger and more durable, with desired stressstrain behavior and, possibly, with the whole range of newly introduced "smart" properties. The reported research examined the mechanical properties of mortars with nano-SiO2 synthesized by sol-gel method. Experimental results demonstrate an increase in compressive strength of mortars with developed nanoparticles at early stages of hardening followed by the strength reduction at later age (versus the reference). Addition of superplasticizer was proposed to overcome this obstacle. Superplasticized mortars with selected nano-SiO2 demonstrated a 15-20% increase of compressive strength, reaching up to 144.8 MPa (21 ksi) at 90-day age. Mechanochemical activation was found to be effective method to improve the strength of cement-based materials. It was proposed that this process is governed by the solid state interaction between the organic modifiers and cement. During this process, the surface of cement particles attaches the functional groups introduced from the modifiers; so the organo-mineral nano-layers or nano-grids are formed on the surface of cement. The developed high-performance cements demonstrate the 28-day compressive strength at the range of 93 - 115 MPa (13.5-16.7 ksi), which is higher than 72 - 89 Mpa (10.4-12.9 ksi), the strength of reference cements.

10.14359/20213


Document: 

SP254-06

Date: 

October 1, 2008

Author(s):

H.J.H. (Jos) Brouwers

Publication:

Special Publication

Volume:

254

Abstract:

The present paper addresses several topics in regard to the sustainable design and use of concrete and the role of nanotechnology. First, major features concerning the sustainable aspects of the material concrete are summarized. Then the major constituent, cement, (from an environmental point of view), is discussed in detail, particularly the hydration and application of slag cement. The intelligent combining of mineral oxides, which are found in clinker, slag, and fly ashes, is designated as mineral oxide engineering. It results, among others, in environmentally friendly binders, recipes for soil stabilization (new building products), and impermeable/durable concretes. Subsequently, the mixture design of concrete is treated, whereby distinction is made between self-consolidating concrete and earthmoist concrete. By combining the particle sizes of all components, including the powders (cement, fillers), optimum mixtures in regard to workability/compactability and hardened state properties are obtained. This so-called particle size engineering results in concretes that meet all technical requirements, but that also make optimum use of the cement it is containing. This paper concludes with summarizing the opportunities and challenges involved with the introduction of both approaches, viz. mineral oxide engineering and particle size engineering, in the construction industry.

10.14359/20212


Document: 

SP254-05

Date: 

October 1, 2008

Author(s):

M. Sonebi

Publication:

Special Publication

Volume:

254

Abstract:

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.

10.14359/20211


Document: 

SP254-04

Date: 

October 1, 2008

Author(s):

P. Mondal, S.P. Shah, and L.D. Marks

Publication:

Special Publication

Volume:

254

Abstract:

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.

10.14359/20210


Document: 

SP254-03

Date: 

October 1, 2008

Author(s):

A. Gmira, J. Minet, A. Franceschini, N. Lequeux, R.J.-M. Pellenq, and H. Van Damme

Publication:

Special Publication

Volume:

254

Abstract:

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.

10.14359/20209


Document: 

SP254-02

Date: 

October 1, 2008

Author(s):

P. Balaguru and K. Chong

Publication:

Special Publication

Volume:

254

Abstract:

Nanotechnology is one of the most active research areas that encompasses a number of disciplines including civil engineering and construction materials. The most active fields are electronics, biomechanics, and coatings. Interest in nanotechnology concept for portland-cement composites is steadily growing. Currently, the most active research areas dealing with cement and concrete are: understanding of the hydration of cement particles and the use of nano-size ingredients such as alumina and silica particles. There are also a limited number of investigations dealing with the manufacture of nanocement. If cement with nanosize particles can be manufactured and processed, it will open up a large number of opportunities in the fields of ceramics, high-strength composites ,and electronic applications. This will elevate the status of portland cement to a high-tech material in addition to its current status of the most widely used construction material. Very few inorganic cementing materials can match the capabilities of portland cement in terms of cost and availability. The main objective of this paper is to outline promising research areas. Basic background information on nanotechnology research, state of the art on use of this technology in concrete, opportunities, and challenges are discussed.

10.14359/20208


Document: 

SP254-01

Date: 

October 1, 2008

Author(s):

P.J.M. Bartos

Publication:

Special Publication

Volume:

254

Abstract:

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.

10.14359/20207


12

Results Per Page