Flexural fatigue behaviors and damage evolution analysis of edge-oxidized graphene oxide (EOGO) reinforced concrete composites

Abstract

Edge-oxidized graphene oxide (EOGO) produced through a low-cost mechanochemical process has a high potential for bulk-scale applications. This study investigates the effect of EOGO on flexural fatigue behaviors of concrete composites. The results demonstrate that the fatigue performances of normal concrete and steel-fiber reinforced concrete (SFRC) are enhanced by EOGO of 0.1% by weight of cement. Single-logarithm fatigue equations are proposed for different mixtures and failure probabilities. The results show that EOGOs reduces the flexural strains over the fatigue life and increases the stiffness. By adding EOGOs, however, larger plastic deformation was observed in the SFRC than in the normal concrete as the fatigue damage is accumulated. For the EOGO-mixed SFRC, the fatigue damage propagation was mainly observed in the second half of fatigue life, whereas that of EOGO-mixed concrete appeared mostly in the first half. Morphological and elemental analyses of the EOGO-cement paste were performed. The analysis results indicated that EOGOs are mainly detected in the areas of calcium-silicate-hydrate (C–S–H) and calcium-aluminum-silicate-hydrate (C-A-S-H) as hydration proceeds. The experimental results support an interfacial bonding mechanism between EOGO and C–S–H/C-A-S-H through oxygen groups, creating the links of COO–Ca, O–Ca, and O–Al. As a result, EOGOs can bridge over microcracks; thus, not only reduce creep deformation but also delay crack initiation by extending the range of behavior before the macrocracks.