Theory

Online Publications

You can access the following publications online. Corresponding PDF document files can be downloaded, and some of them are available in HTML format as well.  For viewing and printing PDF files, get the free Adobe Acrobat Reader.

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1. Modeling of Concrete Performance, Maekawa, K. Chaube, R.P. and Kishi, T.

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Published by E&FN SPON, 1999

2. Coupled Mass Transport, Hydration and Structure Formation theory for durability design of Concrete Structures, Maekawa, K. Chaube, R.P. and Kishi, T.

Available

consec.docconsec.zip (83 KB)

Printed in the book, entitled 'Integrated Design and Environmental Issues in Concrete Technology' edited by K.Sakai, E&FN SPON 1996.

3. Service-life Evaluation of Reinforced Concrete under Coupled Forces and Environmental Actions, Maekawa, K. and Ishida, T.

Available

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Submitted to International Conference on Ion and Mass Transport in Cement-based Materials, Univ. of Toronto, 1999.

4. Multi-component Model for Hydration Heating of Portland Cement, Kishi, T. and Maekawa, K.

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Concrete Library of JSCE*, No.28, 1996.

5. Multi-component Model for Hydration Heating of Blended Cement with Blast Furnace Slag and Fly Ash, Kishi, T. and Maekawa, K.

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Concrete Library of JSCE*, No.30, 1997.

6. Micro-physical Approach to Coupled Autogenous and Drying Shrinkage of Concrete, Ishida, T. Chaube, R.P., Kishi, T. and Maekawa, K.

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Concrete Library of JSCE*, No.33, 1999.

7. An Integrated Computational System for Mass/Energy Generation, Transport, and Mechanics of Materials and Structures, Ishida, T. and Maekawa, K.

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pdfdoc.gif (266 ???) download (124KB)

Concrete Library of JSCE*, No.36, 2000.

8. A Computational Method for Performance Evaluation of Cementitious Materials and Structures under Various Environmental Actions, Ishida, T. and Maekawa, K.

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Submitted to Integrated Life-Cycle Design of Materials and Structures -ILCDES2000-, Helsinki, 2000.
9. Modeling of pH profile in pore water based on mass transport and chemical equilibrium theory, Ishida, T. and Maekawa, K.

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pdfdoc.gif (266 ???) download (124KB) Concrete Library of JSCE*, No.38, 2001.
10. Multi-scale modeling of concrete performance -Integrated material and structural mechanics, Maekawa, K., Ishida, T. and Kishi, T.

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pdfdoc.gif (266 ???) download (1.77MB) Journal of Advanced Concrete Technology, 1 (2) pp.91-126, 2003.
11. Theoretically Identified Strong Coupling of Carbonation Rate and Thermodynamic Moisture State in Micropores of Concrete, Ishida, T. Maekawa, K. and Masoud , S.

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pdfdoc.gif (266 ???) download (505KB) Journal of Advanced Concrete Technology, 2 (2) pp.213-222, 2004.
       
* Concrete Library of JSCE (Concrete Library International) is the English publication transrated from selected technical papers in Proceedings of JSCE, which is one of the most autoritative Civil engineering journals in Japan.  You can also find other papers related to WCOMD and COM3 in the Concrete Library International. To access online order for this journal, click here.

Online Presentations

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1. Modeling of Structural Performance under Coupled Environmental and Weather Actions, Maekawa, K. and Ishida, T.

Available

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UEF Conference on Advances in Cement and Concrete: Materials Aspects of Concrete Repairs and Rehabilitation, Quebec, 2000

Background

Strength and microstructure development of cementitious materials are generally the crucial factors that influence several deterioration mechanisms controlling the durability of concrete. While individual processes leading to deterioration have been studied extensively, an integrated approach to quantitatively predict the durability parameters of concrete is lacking. To accomplish this task, the major governing phenomenon's of interest must be studied in detail. For example, during the hardening phase of concrete - it is the risk of cracking due to thermal as well as drying shrinkage strains that needs to be investigated. Therefore, heat generation problems due to hydration should be carefully examined. In the hardened state, transport of external agents into the internal microstructure of concrete governs the deterioration phenomenon. In this regard transport processes in concrete with special emphasis on moisture transport needs to be investigated. Furthermore, economic considerations in project cost optimizations require that a construction schedule minimizes the curing periods of concrete as far as possible. To know the impact of curing conditions on concrete durability performance, we must study the phenomenons due to which the hydration and strength development processes might get affected.

Motivation

Consideration of all the aforementioned requirements in a durability evaluation system, calls for an integrated approach. The aim of the research on this line in our laboratory, is to attempt the establishment of such an integrated rational analytical framework for tracing the physio-chemical properties of concrete structures and to raise discussion for future performance based durability design.

Framework

This is done by studying the durability of concrete, starting from the stages of early age development of concrete. The fruits of various researches have been compiled into the computational simulation tool DuCOM.

DuCOM offers a computational platform on which structural concrete performance and quality at early age are examined in both space and time domains under environmental actions. In this approach, concrete is treated as a composite material consisting of growing micro-scale pores in geometry, which governs basic mechanical and physical features of concrete with respect to long-term durability. On this line, the thermo-dynamic modeling of concrete forms the fundamental core of the theoretical approach to achieve both the scientific knowledge and engineering simulations of altering materials.

Methodology

Basically, in the case of aging concrete, we have attempted to bring three thermo-dynamic technicalities of green and young aged concrete from its birth to several months. One is hydration heat of cementitious powders and its mathematical expression under arbitrary environments in micro-pores with respect to temperature and water. The second is hysteretic state equilibrium of liquid water, vapor and other idealized gases in micro-scale pores and its migration / percolation in space. The third one is geometrical formation of micro-pores built by cement hydrates. The thermo-dynamic interaction of the physical chemistry is an engineering highlight of the computational model. Currently, efforts are under progress towards linking the physio-chemical system of concrete with deformational field associated with mechanical stresses. This could be thought of as a "future bridge" between material science and structural engineering for reinforced concrete.

The microstructure development model assumes a mono sized particle dispersion and uses a particle expansion model based upon the degree of hydration. Furthermore, assuming a linear nature of bulk porosity variation in the expanding cluster of a particle, important microstructural parameters like the surface area and bulk porosity distribution parameters are computed with time. Moisture transport model is based on the multi-component division of concrete space porosity and is applicable to any arbitrary paths of drying and wetting. Moisture transport related characteristics are directly evaluated from the microstructure of the matrix. Since, long term durability of concrete is primarily influenced by its mass transport characteristics, therefore, special attention has been given to the relationships of its transport characteristics to the microstructure by taking into account the composite nature of concrete. The hydration model is based upon a multi-component division of cement and pozzolanic powder materials and obtaining the rate of heat generation for each of these components based on modified Arrhenius's law. Mutual interactions among the reacting constituents during hydration and their dependence on the availability of water in the concrete micro pore is also quantitatively formulated. Simultaneously, applying these three basic phenomenon's at any point, enables the tracing of microstructure development with increase in the degree of hydration for arbitrary temperature and moisture content history. The computational models of structure formation, moisture transport and hydration are then integrated into a FE simulation program. The simulation method typically starts from the casting stage of concrete and computes development of several properties like strength, porosity and microstructure etc., along with the temperature and pore moisture content history with time.

Viewpoint

We view the current status and progress as just an incomplete platform consisting of crude technical and scientific elements to be further investigated. As a matter of fact, we are just standing by an entrance approaching to the long-term performance of concrete structures and its prediction.