Issue 53

H. Fawzy et al, Frattura ed Integrità Strutturale, 53 (2020) 353-371; DOI: 10.3221/IGF-ESIS.53.28 369 C ONCLUSIONS n experimental program concerning the effect of high temperature on the characteristics of rubberized concrete and the bond behavior of concrete filled steel tubular sections was discussed in this research. The following conclusions can be outlined based on this study:  Partial substitution of crumb rubber aggregate in concrete caused gradual decrease in compressive, tensile and flexural strengths of concrete. The degree of reduction depended on the replacement ratio of the rubber aggregates. The effect of fine rubber aggregate on concrete tensile and flexural strength was less than its effect on compressive strength.  Under high temperature, crumb rubber helps to relieve the inception and growth of cracks in concrete. The inclusion of rubber particles reduces the rate of compressive, splitting tensile and flexural strengths loss.  Circular rubberized CFST sections had more bond strength and ductility compared to square specimens. Partial substitution of crumb rubber aggregate in concrete caused a gradual decrease in bond strength of concrete. The degree of reduction depended on the replacement ratio of the rubber aggregates.  Exposure of rubberized CFST sections to a temperature of 70° C; as in hot countries; caused a slight decrease in bond strength for less amounts of rubber content, however higher content of rubber improves the bond strength. A bond strength recovery was observed after cooling the specimens down.  The increase in rubber replacement ratio in rubberized CFST sections to 12% and 16% enhanced the bond strength in fire and post fire conditions. Less amounts of rubber content caused reduction in the bond strength during exposing to high temperature and after cooling down.  Strength and ductility recovery were observed in rubberized CFST specimens tested after cooling from exposing to different degrees of high temperature. A CKNOWLEDGMENTS he research described in this paper was financially supported by the Faculty of Engineering, Zagazig University. R EFERENCES [1] Abendeh, R., Ahmad, H.S. and Hunaiti, Y.M. (2016). Experimental Studies on the Behavior of Concrete-Filled Steel Tubes Incorporating Crumb Rubber, Journal of Constructional Steel Research. 122, 251-260. DOI: 10.1016/j.jcsr.2016.03.022 [2] Torgal, P., Ding, F.Y. and Jalali, S. (2012). Properties and Durability of Concrete Containing Polymeric Wastes (Tyre Rubber And Polyethylene Terephthalate Bottles): An Overview, Construction and Building Materials, 30, 714-724. DOI: 10.1016/j.conbuildmat.2011.11.047 [3] Siringi, G., Abolmaali, A. and Aswath, P.B., (2015). Properties of Concrete With Tire Derived Aggregate Partially Replacing Coarse Aggregates, The Scientific World Journal, 2015, ID 863706. DOI: 10.1155/2015/863706 [4] Batayneh, M.K., Marie, I. and Asi, I., (2008). Promoting the Use of Crumb Rubber Concrete in Developing Countries, Waste management, 28(11), 2171-2176. DOI: 10.1016/j.wasman.2007.09.035 [5] Yüksel, İ ., Siddique, R. and Özkan, Ö. (2011). Influence of High Temperature on The Properties of Concretes Made with Industrial By-Products as Fine Aggregate Replacement, Construction and building materials, 25(2), 967-972. DOI: 10.1016/j.conbuildmat.2010.06.085 [6] Gintautas, S., Audrius, G. and Benjaminas, C., (2007). Deformation Properties of Concrete with Rubber Waste Additive, Material Science, 13(3), 219-223. [7] Al-Tayeb, M., Abu Bakar, B.H., Akil H.M. and Ismail, H., (2013). Performance of Rubberized and Hybrid Rubberized Concrete Structures Under Static and Impact Load Conditions, Experimental Mechanics, 53(3), 377-384. DOI 10.1007/s11340-012-9651-z. A T