The effect of nano sized additives to the electrical resistance strain relationship of concrete

In our country, thousands of citizens were dead, injured and thousands of structures were either collapsed or became useless due to the earthquakes in the last 20 years. Earthquakes, material deteriorations and other factors adversely affect the structural health. Structural health monitoring is important to secure the lives and assets. The strain gages which are used in structural health monitoring can take pointwise measurement, for this reason they have to be used in vast numbers and they are costly; they are not durable. In this project, smart concrete which can sense its strain and damage was produced for structural health monitoring. In order to determine smart concrete, mixtures having different conductive fillers with different volume percent were designed. For every mixtures were tested with compression test. During the compression tests, electrical resistance change and strain measurements were conducted. The most sensitive mixtures which had nano and macro scaled conductive materials to strain were determined. Split tensile and bending test were applied to the samples. The most sensitive mixture to strain and crack length was determined as Smart Concrete. Smart concrete was tested with different load rates, effects of temperature and moisture were investigated, circumferential electrode and alternative current effects were investigated. Transverse loading effect which had strain perpendicular to electrical resistance change was investigated. Smart concrete had a strong linear relationship between strain and electrical resistance change. The electrical resistance increased when temperature increased. Strain sensitivity decreased with moisture. The mechanisms governing strain and electrical resistance change relationship for compression, split tensile and their transverse loadings were determined. Embedded electrode was found to be better than circumferential electrode. Direct current gives higher sensitivity with respect to alternative current. In the long term, strain sensitivity decreased; smart concrete which waited longtime and immersed in water to increase moisture, had a higher strain sensitivity with respect to same age samples. In the high scale compression and bending tests of smart concrete, strong linear relationship between strain and electrical resistance change was found. Smart concrete will be used for structural health monitoring of prefabricated and important structures.