Cement-based composites filled with carbon black of 120nm size were prepared, the composites contained 15% amount of CB was in the percolation threshold, and it showed good strain sensing ability, the resistivity of composites changed linearly with applied strain, suggesting that this kind of composites was a promising candidate for strain sensor used in concrete structures. Water ratio has obviously influences on the initial resistivity of the composites. Epoxy encapsulated was found a practicable way to insulate the composites from water, and make the resistance measurement practicable. Strain senser was maken with the composite contained 15% amount of CB, and applied in concrete column for strain monitoring, the results showed that the strain of the concrete column could be monitored by this kind of sensor.
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