Issue 45

P. Jinchang et alii, Frattura ed Integrità Strutturale, 45 (2018) 156-163; DOI: 10.3221/IGF-ESIS.45.13 162 C ONCLUSIONS raphene oxide solution was prepared using the improved Hummers method and mixed with cement mortar to form cement-based composite material to investigate the effects of different mix proportion on the mechanical properties and microstructure of graphene oxide reinforced cement based composite material. The following conclusions were obtained. (1) When the water cement ratio was fixed. The mechanical strength of cement mortar increased with the increase of the content of graphene oxide and reached the maximum when the content of graphene oxide was 0.03%; the increase of the bending strength (23.83%) was the most obvious. Those findings suggested the addition of graphene oxide could greatly improve the toughness of cement. (2) When the content of graphene oxide was 0.03%, cement mortar was the same with the traditional cement; the larger the water cement ratio, the lower the strength. But the specimens which were added with graphene oxide effectively slowed the decline of the strength of the specimens with high water cement ratio (W/C=0.5). Compared to the blank specimens, the bending and compressive strength of the specimens which was mixed with graphene oxide had an improvement of 73.09% and 72.35%. (3) The analysis of the microstructure suggested that the addition of graphene oxide could affect the growth form and number distribution of cement hydration products. The filling effect, hydration effect and nucleation effect of graphene oxide was notable when the content of graphene oxide was within a certain range. Graphene oxide became the zone for various hydration reactions because of its large specific surface area, which provided a better growth space for hydration products. It could reduce the porosity of the hardened cement paste and make the structure of cement mortar tighter; leading to the improved strength and ductibility. The above research results which were similar to the research results of Xu et al. [22] were meaningful to improve the bending strength and crack resistance of cement-based materials and extend their service life, which can provide a reference for the future studies. A CKNOWLEDGMENTS his study was supported by the Key Laboratory of Architectural Structure (project no. CP12015005). R EFERENCES [1] Boulekbache, B., Hamrat, M. and Chemrouk, M., et al., (2012). Influence of yield stress and compressive strength on direct shear behaviour of steel fibre-reinforced concrete, Construction and Building Materials, 27(1), pp. 6-14. [2] Wille, K., Naaman, A.E. and Parra-Montesinos, G.J. (2012). Ultra-high performance concrete and fiber reinforced concrete: achieving strength and ductility without heat curing, Materials and Constructure, 3, pp. 1-16. [3] Han, Y. (2015). Study on properties of cement based composites based on grapheme, Low Temperature Architecture Technology, 2, pp. 4-6. [4] Nobili, A., Lanzoni, L. and Tarantino, A.M. (2013). Experimental investigation and monitoring of a polypropylene- based fiber reinforced concrete road pavement, Construction and Building Materials, 47, pp. 888-895. [5] Liu, X.H., Duan, Y., Zhou, W., et al. (2013). Modeling the piped water cooling of a concrete dam using the heat-fluid coupling method, Journal of Engineering Mechanics, 139(9), pp. 1278-1289. [6] Freyne, S., Ramseyer, C. and Giebler, J. (2012). High-performance concrete designed to enhance durability of bridge decks: oklahoma experience, Journal of Materials in Civil Engineering, 24(7), pp. 933-936. [7] Yu, H.Y., Zhao, R.X. and Zou, H.F. (2005). Development and Prospect of Cement-based Composite Materials. Henan Building Materials, 3, pp. 21-19. [8] Feng, N.Q. (2003). Development and Application of High Performance Concrete, Construction Technology, 32(4), pp. 1-6. [9] Cao, M.L. (2015). Effect of graphene on mechanical properties and microstructure of cement paste, Journal of Harbin Institute of Technology, 47, pp. 26-30. G T