Evaluation of strength properties of high volume fly ash concrete incorporating nanomaterials

This paper presents the results of experimental study on the combined effect of colloidal Nanosilica (CNS) and Carbon nanofibers (CNF) on mechanical properties of High volume fly ash concrete (HVFAC). High strength concrete (control concrete), HVFAC, HVFAC incorporating NS, HVFAC incorporating NS and CNF were considered for the study. Experimental programme was divided into two phases. Phase – 1 consists of, obtaining mix proportion for control concrete that produces strength above 60 N/mm² at 28days. The cement content obtained for control concrete was partially replaced by HVFA to produce HVFAC. Further, cement content in HVFAC was partially replaced with NS in varying percentages of 1%, 2%, 3%, and 4% by weight of cementitious material. The optimum dosage of NS that produces high compressive strength in HVFAC was considered as optimum dosage of NS. Phase – 2 consists of adding CNF in HVFAC incorporating optimum dosage of NS in percentages of 0.15% and 0.2% by weight of cementitious materials. Compressive strength, split tensile strength and flexural strength tests were performed on all the test samples in both the phases. It was concluded that with increase in NS content, mechanical properties of HVFAC increases and 3% NS is obtained as optimum dosage. Addition of CNF increased the compressive strength of HVFAC incorporating optimum dosage of NS, but the increase was marginal. It did not show any significant strength improvement in split tensile and flexural strength tests. This may be due to improper dispersion of CNF in HVFAC incorporating optimum dosage of NS.