A Sensor for Embedded Stress Measure of Concrete: Testing and Material Heterogeneity Issues

Concrete is well known to be a heterogeneous material that is usually considered homogeneous only referring to a scale of several centimetres. This characteristic makes measuring stresses inside concrete a particularly difficult task. Strains can be measured using several well-known devices. Nevertheless, it is almost impossible to derive a correct estimation of the stress within a concrete structure starting from strain measures as the modulus of elasticity is variable and unknown and creep strains superimpose elastic ones. A preliminary experimental campaign performed to test a stress sensor with the dimensions of a coin to be embedded in concrete is described in the present paper. The effects external applied load are measured comparing the results of short-term loading test performed directly on the sensor and on concrete specimens.