Using Microwave Heating to Completely Recycle Concrete

Heesup Choi, Myungkwan Lim, Hyeonggil Choi, Ryoma Kitagaki, Takafumi Noguchi

Department of Architecture, The University of Tokyo, Tokyo, Japan.
Department of Civil Engineering, Kitami Institute of Technology, Hokkaido, Japan.

DOI: 10.4236/jep.2014.57060                

Abstract

The aim of this study was to develop a technique for the complete recycling of concrete based on microwave heating of surface modification coarse aggregate (SMCA) with only inorganic materials such as cement and pozzolanic materials (silica fume, fly ash). The mechanical properties of SMCA, which was produced using original coarse aggregate (OCA) and inorganic admixtures, as well as its separation from the cement matrix and recovery performance were quantitatively assessed. The experimental results showed that micro structural reinforcement of the interfacial transition zone, which is a weak part of concrete, by coating the surface of the OCA with cement and admixtures such as pozzolanic materials can help suppress the occurrence of micro-cracks and improve the mechanical performance of the OCA. Microwave heating was observed to cause micro-cracking and hydrate decomposition. Increasing the void volume and weakening the hydrated cement paste led to the effective recovery of recycled coarse aggregate.

Keywords

Recycling, Surface Modification, Interfacial Transition Zone, Pozzolanic Reaction, Microwave, Recovery

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Noguchi, T. and Tamura, M. (2001) Concrete Design toward Complete Recycling. Structural Concrete, 2, 155-167.
[2]	Noguchi, T. (2008) Resource Recycling in Concrete: Present and Future. Stock Management for Sustainable Urban Regeneration, 4, 255-274.
[3]	Hendriks, Ch.F. and Janssen, G.M.T. (2001) Construction and Demolition Waste: General Process. HERON, 46, 79-88.
[4]	Shima, H., Tateyashiki, H., Matsuhashi, R. and Yoshida, Y. (2005) An Advanced Concrete Recycling Technology and its Applicability Assessment through Input-Output Analysis. Journal of Advanced Concrete Technology, 3, 53-67. http://dx.doi.org/10.3151/jact.3.53
[5]	Choi, H.S., Kitagaki, R. and Noguchi, T. (2014) Effective Recycling of Surface Modification Aggregate using Microwave Heating. Journal of Advanced Concrete Technology, 12, 34-45. http://dx.doi.org/10.3151/jact.12.34
[6]	Choi, H.S., Kitagaki, R. and Noguchi, T. (2012) A Study on the Completely Recovery of Surface Modification aggregate using Microwave and Effective Utilization. Proceedings of the 5th ACF International Conference, Pattaya, October 2012, Session 1-2, ACF2012-0093, 41-46.
[7]	Kunio, Y. (2003) A Study on the Manufacturing Technology of High-Quality Recycled Fine Aggregate. Japan Concrete Institute, 25, 1217-1222.
[8]	Shima, H. and Tateyashiki, H. (1999) New Technology for Recovering High-Quality Aggregate from Demolished Concrete. Proceedings of the 5th International Symposium on East Asian Recycling Technology, The M.M.P.I. in Japan 1999, 106-109.
[9]	Tamura, M., Tomosawa, F. and Noguchi, T. (1997) Recycle-Oriented Concrete with Easy-to-Collect Aggregate. Cement Science and Concrete Technology, 51, 494-499.
[10]	Tsujino, M., Noguchi, T., Tamura, M., Kanematsu, M. and Maruyama, I. (2007) Application of Conventionally Recycled Coarse Aggregate to Concrete Structure by Surface Modification Treatment. Journal of Advanced Concrete Technology, 5, 13-25. http://dx.doi.org/10.3151/jact.5.13
[11]	Value Engineering Benefits (2010) Concrete Recycling.org. Retrieved 2010-04-05.
[12]	Mehta, P.K. and Moneiro, P.J.M. (2006) Concrete: Microstructure, Properties and Materials. McGraw-Hill Companies, New York.
[13]	Diamond, S. and Huang, J. (2001) The ITZ in Concrete. Cement and Concrete Composite, 23, 59-64.
[14]	Elsharief, A., Cohen, D. and Olek, J. (2003) Influence of Aggregate Size, Water Cement Ratio and Age on the Microstructure of the Interfacial Transition Zone. Cement and Concrete Research, 33, 1837-1849. http://dx.doi.org/10.1016/S0008-8846(03)00205-9
[15]	Robin, P.J. and Austin, S.A. (1995) A Unified Failure Envelope from the Evaluation of Concrete Repair Bond Tests. Magazine of Concrete Research, 47, 57-68. http://dx.doi.org/10.1680/macr.1995.47.170.57
[16]	Austin, S., Robins, P. and Pan, Y.G. (1999) Shear Bond Testing of Concrete Repair. Cement and Concrete Research, 29, 1067-1076. http://dx.doi.org/10.1016/S0008-8846(99)00088-5
[17]	McGill, S.L., et al. (1988) The Effects of Power Level on the Microwave Heating of Selected Chemicals and Minerals. Proceedings of the MRS Symposium, Nevada, April 1988, 124.
[18]	Schneider, U. (1982) Behavior of Concrete at High Temperatures. Deutscher Ausschuss für Stahlbeton, Berlin, 28-33.
[19]	Bazant, Z.P. and Kapaln, M.F. (1996) Concrete at High Temperatures: Material Properties and Mathematical Models. Prentice Hall, Upper Saddle River.
[20]	Takeo, A., Fukujiro, F., Kuniyuki, T., Kenji, K. and Isao, K. (1999) Mechanical Properties of High-Strength Concrete at High Temperatures. Architectural Institute of Japan, 515, 163-168.
[21]	Tsujino, M., Noguchi, T., Kitagaki, R. and Nagai, H. (2010) Completely Recyclable Concrete of Aggregate-Recovery Type by a New Technique Using Aggregate Coating. Architectural Institute of Japan, 75, 17-24.