An experimental study was carried out to understand the electrical percolation thresholds of different carbon-based nano-and micro-scale materials in cementitious composites. Multi-walled carbon nanotubes (CNTs), graphene nanoplatelets (GNPs) and carbon black (CB) were selected as the nano-scale materials, while 6 and 12 mm long carbon fibers (CF6 and CF12) were used as the micro-scale carbon-based materials. After determining the percolation thresholds of different electrical conductive materials, mechanical properties and piezoresistive properties of specimens produced with the abovementioned conductive materials at percolation threshold were investigated under uniaxial compressive loading. Results demonstrate that regardless of initial curing age, the percolation thresholds of CNT, GNP, CB and CFs in ECC mortar specimens were around 0.55%, 2.00%, 2.00% and 1.00%, respectively. Including different carbon-based conductive materials did not harm compressive strength results; on the contrary, it improved overall values. All cementitious composites produced with carbon-based materials, with the exception of the control mixtures, exhibited piezoresistive behavior under compression, which is crucial for sensing capability. It is believed that incorporating the sensing attribute into cementitious composites will enhance benefits for sustainable civil infrastructures.

No abstract

No abstract

The self-healing behavior of concrete elements with high risk of crack formation under various conditions from the moment of production has become a very important issue. In this study, the effectiveness of nano silica (NS) curing solutions in terms of self-healing behavior in engineered cementitious composites (ECC) was investigated. For this purpose, precuring was applied to the cementitious composite mixture prepared with four different contents for 7, 28, and 90 days and then half of the specimens were exposed to damage to certain extents of the mechanical strength loads. Half of the specimens were left in a 2% solution of NS for a further period of 7, 30, 60, and 90 days, and another portion was left in curing only in water (W). The mechanical properties of the sound and preloaded specimens were investigated with compressive and flexural tests, and the improvements in permeability were investigated with the help of water absorption and sorptivity tests. As a result of the experimental studies, it was observed that the nano silica solution applied to the specimens during the curing phase caused a more effective and rapid healing in the mechanical and permeability properties of the composites when compared with the water curing.

In this study, the self-healing behavior of engineered cemetitious composites (ECC) containing different types and quantities of fly ash (FA) under colloidal nano silica (CNS) curing conditions was investigated through the examination of their different permeability properties. FA in two different characters, Class F and Class C, were used in the preparation of the mixtures in high volumes (FA/ portland cement = 1.2 and 2.2). Self-healing capacities developed under CNS curing conditions were evaluated by changes in different permeability properties such as rapid chloride permeability test (RCPT) and electrical impedance measurement methods. In addition to these, the self-healing effects of the cracked composites were supported by microstructure analysis with the help of SEM-EDX and XRD tests on the sections taken from the crack interface of the sample. The results have showed that the CNS curing condition helps improve the permeability properties of composites by quickly and effectively covering their micro pores and cracks. In addition, the results of the experiment have revealed the effects of the use of different types and quantities of FA on the self-healing behavior of the ECC material. Finally, correlation analysis of ECC samples was applied according to the results obtained from EI and RCPT test methods and it was revealed that there was a negative significant relationship between test methods.