Impact of Graphite Powder on The Properties and Microstructure of Conventional and Silica Fume Concretes

Abstract

Recently, the production of electrically conductive concrete (ECC) has becomewidespread by using carbon materials such as graphite powder GP. To eliminatethe negative impact of using graphite powder (GP) alone as an additive to concrete,one of the supplementary cementitious materials (SCMs), such as silica fume SF,is combined with graphite powder (GP). In this respect, research work wasconducted on concrete mixes with a cement replacement with silica fume with anSF ratio of 10% and with cement replacement levels with graphite powder (GP)ratio of 2.5, 5 and 7.5%. A control concrete mix (MCC) was made with 100%cement with no supplementary cementitious or carbon materials. Concrete mixeswere tested in rheological properties such as slump and in hardened properties suchas compression, indirect tension and flexural. Concrete samples were tested incompression at the ages of 3, 7, 28 and 90 days and were tested in indirect tensionand flexural at the ages of 7 and 28 days. The durability of the concrete sampleswas examined in both the rapid chloride penetrability (RCP) test and the scanningelectron microscopy (SEM) test. The compressive strengths of concrete mixes,MSF-GP2.5, MSF-GP5 and MSF-GP7.5 increase by about 11, -0.3 and -7%compared to MCC but were reduced by about 7, 18 and 21% when compared toMSF, respectively at the age of 28 days. Tensile strengths of concrete mixes, MSF-GP2.5, MSF-GP5 and MSF-GP7.5 were increased by about 19, 3 and -10%compared to MCC but, were reduced by about 7, 20 and 29% compared to MSF,respectively, at the age of 28 days. Flexural strengths of concrete mixes MSF-GP2.5, MSF-GP5 and MSF-GP7.5 increase by about 12, -0.3 and -6% whencompared to MCC but were reduced by about 7, 17 and 21% when compared toMSF, respectively, at the age of 28 days. Inclusion of graphite powder in silicafume concrete increases the rapid chloride penetration (RCP) and reduces thepozzolanic effect of silica fume on cement matrix.