Relationship between Defects of Recycled Aggregate and Mechanical Properties of Recycled Aggregate Concrete

Abstract:

This paper presents an experimental research on the influence of defects of recycled coarse aggregate on mechanical properties of recycled aggregate concrete (RAC). Concretes at two water/binder ratios (0.255 and 0.586) were broken into recycled aggregate (RA). A type of thermal treatment, i.e. heating to target temperature 620 °C, which was maintained for 3 hr, was employed to remove mortar from gravel in RA. Tests were conducted on RA and natural aggregate to measure their water absorption and crushing values, and on RAC and natural aggregate concrete (NAC) to measure compressive strength, tensile splitting strength, and fracture energy. The experimental results revealed that both gravel damage and mortar attached can significantly influence the water absorption and crushing value of RA, as well as strength and fracture energy of RAC. The mechanical properties RAC were obviously lower than those of NAC at an identical mix proportion. Moreover the removal of mortar caused additional change in mechanical properties of RA, which might be a decrease in mechanical properties in the case of low water/binder ratio, but might be an increase in mechanical properties in the case of high water/binder ratio. As to RAC at a low water/binder ratio, gravel damage was a main factor governing the decrease in fracture energy, which means a decrease in cracking resistance of hardened RAC, whereas the mortar attached had only a slight influence on fracture energy. However, as to RAC at a high water/binder ratio, mortar attached could significantly cause a greater decrease in cracking resistance of RAC than that caused by gravel damage.

• Periodical: Key Engineering Materials (Volumes 629-630)
• Pages: 314-320
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.629-630.314
• Online since: October 2014
• Authors: Gai Fei Peng, Jiu Feng Zhang
• Keywords: Fracture Energy, Gravel Damage, Mortar Attached, Recycled Aggregate (RA), Water Absorption

References

[1] Xiao J.Z., Li J.B., Lan Y. Research on recycled aggregate concrete – A review (in Chinese). Concrete, 2003, 10: 17-20.

[2] Chen Y.G., Cao B.B. Prospect of development of recycled aggregate concrete (in Chinese). International Building Materials Technology. 2004, 25 (3): 4-6.

[3] Zhu P.H., Wang X., Zhou J., He X. Main advances and tendencies in research on green high-performance recycled aggregate concrete (in Chinese). Proceedings of The 1st China Symposium on Research and Application of Recycled Aggregate Concrete, Shanghai, Beijing, 2008: 106-116.

[4] Poon C.S., Shui Z.H., Lam L. Effect of microstructure of ITZ on compressive strength of concrete prepared with recycled aggregates. Construction and Building Materials, 2004, 18: 461-468.

DOI: 10.1016/j.conbuildmat.2004.03.005

[5] Oliveira M.B., Vazquez E. The influence of retained moisture in aggregates from recycling on the properties of new hardened concrete [J]. Waste Management, 1996, 16 (1-3): 113-117.

DOI: 10.1016/s0956-053x(96)00033-5

[6] Topcu I.B., Sengel S. Properties of concrete produced with waste concrete aggregate. Cement and Concrete Research, 2004, 34: 1307-1312.

DOI: 10.1016/j.cemconres.2003.12.019

[7] Peng G.F., Shen D.Q., Zhu H.Y., Liu X.S. An experimental research on comparison of mechanical properties between recycled aggregate concrete and control concrete at identical mix proportions (in Chinese). Concrete, 2006, (2): 34-38.

[8] Quan H.Z., Ding J.D., Zhu Y.G., Yang X.N., Li Q.Y. Experimental study on effects different properties of recycled coarse aggregates on strength and durability of concrete (in Chinese). Proceedings of The 1st China Symposium on Research and Application of Recycled Aggregate Concrete, Shanghai, Beijing, 2008: 282-289.

[9] Mao G.F. Li Y.M., Zhang J., The influence of particle shaping on the quality of recycled aggregate concrete (in Chinese). ibid: 208-214.

[10] Li Q.Y., Li Y.X., Zhu C.J., Tian L. Research on strengthening technology of recycled aggregate from demolished concrete (in Chinese). Concrete, 2006, (1): 74-77.