PSI - Issue 78

Han Liu et al. / Procedia Structural Integrity 78 (2026) 1759–1766

1762

fifth layer, spaced 30 mm apart, to provide reinforcement. A schematic drawing of the printed specimen and detailed geometric dimensions are shown in Figure 2. Fabricated specimens were then cured in the laboratory for an additional 28 days to promote further hydration and enhance their mechanical properties, as is for standard concrete.

Fig. 2: Schematic drawing showing the (a) top view; (b) side view; (c) front view; and (d) 3D view of the printed Specimen.

2.3. Electromechanical model

The self-sensing behavior of cementitious composites primarily stems from their piezoresistive response under mechanical loading, which allows the electrical resistance to change in response to strain. Assuming only the internal resistance is a ff ected by the mechanical deformation Han et al. (2012); Dong et al. (2019), the conductive cement composite can be simplified as an ideal resistor with nominal resistance R 0 , expressed as:

d A

R 0 = ρ

(1)

where ρ is the bulk resistivity of the composite, d is the spacing between the sensing electrodes, and A represents the cross-sectional area perpendicular to current flow. To evaluate the sensing response, the fractional change in resistance (FCR) is used and defined as:

R − R 0 R 0

∆ R R 0

(2)

FCR =

=

where ∆ R is the resistance change from its initial value R 0 . In the case of a beam subjected to three-point bending, the maximum bending strain ε max , appearing at the outermost fibers (top and bottom surfaces of the beam) of the section, is a function of mid-span deflection δ and computed as:

6 · δ · h L 2

(3)

ε max =