# Frontiers of Structural and Civil Engineering

 Front. Struct. Civ. Eng.    2019, Vol. 13 Issue (4) : 821-830     https://doi.org/10.1007/s11709-019-0518-6
 RESEARCH ARTICLE
Optimizing the compressive strength of concrete containing micro-silica, nano-silica, and polypropylene fibers using extreme vertices mixture design
Department of Civil Engineering, Hakim Sabzevari University, Sabzevar 9617976487, Iran
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 Abstract Many studies have evaluated the effects of additives such as nano-silica (NS), micro-silica (MS) and polymer fibers on optimizing the mechanical properties of concrete, such as compressive strength. Nowadays, with progress in cement industry provides, it has become possible to produce cement type I with strength classes of 32.5, 42.5, and 52.5 MPa. On the one hand, the microstructure of cement has changed, and modified by NS, MS, and polymers; therefore it is very important to determine the optimal percentage of each additives for those CSCs. In this study, 12 mix designs containing different percentages of MS, NS, and polymer fibers in three cement strength classes(CSCs) (32.5, 42.5, and 52.5 MPa) were designed and constructed based on the mixture method. Results indicated the sensitivity of each CSCs can be different on the NS or MS in compressive strength of concrete. Consequently, strength classes have a significant effect on the amount of MS and NS in mix design of concrete. While, polymer fibers don’t have significant effect in compressive strength considering CSCs. Corresponding Authors: Hamid ESKANDARI-NADDAF Online First Date: 12 March 2019    Issue Date: 10 July 2019
 Cite this article: Fatemeh ZAHIRI,Hamid ESKANDARI-NADDAF. Optimizing the compressive strength of concrete containing micro-silica, nano-silica, and polypropylene fibers using extreme vertices mixture design[J]. Front. Struct. Civ. Eng., 2019, 13(4): 821-830. URL: http://journal.hep.com.cn/fsce/EN/10.1007/s11709-019-0518-6 http://journal.hep.com.cn/fsce/EN/Y2019/V13/I4/821
 Fig.1  Construction and testing process of the specimens Tab.1  Mix design of concrete containing, MS and NS and polypropylene fibers Fig.2  Cox response trace plots for concrete specimens (a) CSC 32.5 MPa; (b) CSC 42.5 MPa; (c) CSC 52.5 MPa Fig.3  Mixture contour plot of compressive strength (a) 32.5 MPa; 42.5 (b) MPa; and 52.5 (c) MPa Fig.4  Response optimization plots showing the optimized mixture for the maximum production compressive strength for CSCs (a) 32.5 MPa; (b) 42.5 MPa; and (c) 52.5 MPa