چكيده به لاتين
In recent years, various researches have been conducted on the use of graphene oxide (GO) in cement composites. Although GO has a good dispersion in aqueous solutions, it agglomerates in alkaline cementitious environments. In order to improve the dispersion of GO nanosheets in cementitious environments, some solutions have been investigated by previous studies such as using polycarboxylate ether (PCE) based superplasticizers or using pozzolanic materials like silica fume. In this study, the effect of metakaolin (MK) microparticles on the dispersion of GO nano sheets in water and simulated cement pore solution (SCPS) was investigated. Then based on the results of dispersion tests, cement paste and mortar specimens were prepared. The fluidity, compressive and flexural strengths, flexural elastic modulus, toughness, ultrasonic pulse velocity of cement paste and mortar samples and also the porosity of cement paste specimens were measured. The results of dispersion tests showed that the addition of MK leads to the GO agglomeration in water. Also, MK particles have no obvious influence on the dispersion of GO sheets in SCPS. So, to ameliorate the dispersion of GO and MK particles in SCPS, PCE was used. The results showed that the good dispersion and stability of GO and MK in SCPS could be guaranteed by PCE copolymers. Also, MK particles improved PCE-GO dispersion and stability in SCPS. The results of fluidity tests showed that MK and GO decrease the fluidity of cement paste and mortar samples. The results of compressive strength, flexural strength, flexural elastic modulus and ultrasonic pulse velocity tests on MK-GO incorporated cement paste samples after 28 days of curing showed an increase by 27.6%, 36.3%, 49.8% and 5.0%, respectively compared with the reference sample. Also, the porosity of MK-GO sample after 28 days of curing was decreased by 27.2% in comparison with the reference sample. The results of this study can pave the way for effective use of GO and MK in cement-based composites.
