Application of Cement-Based Sensor on Compressive Strain Monitoring in Concrete Members

Abstract

The aim of this research was to implement cement-based sensors in monitoring the change of strain in concrete structures in particular where a compression applies. The experiment was conducted in a laboratory by embedding a cement-based sensor in a 150x150x150 mm normal strength concrete cube. When the sensor-installed concrete cube was loaded, the relation between the fractional change in resistivity (FCR) and strain of the sensors was evaluated. In this study, all cement-based sensors were made of cement paste containing carbon fiber at 2% by volume fraction. They were then varied with the addition of graphite powder at 4% and silica fume at 15% by weight of cement. Thus, there were total four mix proportions. From the experimental results, all sensors provided a good corelation between the FCR and compressive strain. Among them, the carbon fiber plus graphite powder (no silica fume) cement-based sensor yielded the most excellent piezoresistive response.

The Utilization of Pearson’s Method to Analyze Piezoresistive Effect in Self-Sensing Cement Composite with Graphite

“…Following the literature [45][46][47] four mortar specimens were prepared for the piezoresistive test, in cubic shape samples with a 40 mm edge, dimensions recommended in NBR 16868-2 48 for compression test. The mortar mix rate was made in the following proportions of cement, sand, and graphite: T1C=1:4:0; T2C=1:4:0.125; T3C=1:4:0.250; and T4C=1:4:0.375, in proportions to the cement mass, and these graphite proportions are within the range (0-0.4) used by 49 .…”

“…The samples were tested by compression in a manual press, for three repetitions of each sample 45,52 , with a maximum load of nearly 2 kN 31,32 , since this load would not cause rupture of the samples, because it is a non-destructive test. The voltage (U) changes and force (compression) applied were recorded synchronously at a sampling rate of 10 Hz, using the scheme in Figure 6, which had a data acquisition system (DAQ) model 8000-8-SM (Micro-Measurements), a load cell, and a laptop.…”

A Three-Dimensional Strain Rosette Sensor Based on Graphene Composite with Piezoresistive Effect

“…However, these sensors have some problems, such as single testing direction, high cost, bad durability, and poor compatibility with concrete. The emergence of cement-based smart composites [8][9][10][11][12][13][14] provides a new sensing mean for structural health monitoring, and it has been well applied in civil engineering as embedded sensors. However, although the cement-based smart sensor has high sensitivity, good linearity, and well compatibility with concrete, it is greatly affected by environmental factors, especially temperature and humidity, and has poor plasticity.…”