Title: Monitoring of Concrete Hardening and Strengthening Using Results of Electrical Resistivity Measurements
Author(s): David I. Stackelberg, Boris I. Wilge, Shimon V. Boiko and Felix A. Goldman
Publication: Symposium Paper
Appears on pages(s): 84-101
Keywords: compressive strength, concrete, electric resistivity, hardening, monitoring, pore solution, strengthening
Hardening and strengthening of cement-concrete compositions (CCC) is a result of forming a moist capillary porous body. Physical water contained in pores and capillaries of the resulting structure is its most informative component. First, it is only the pore solution that is electrically conductive component, and, second, the liquid phase stays perpetually in a thermodynamic equilibrium with the solid surfaces by which it is adsorbed. Thus the physical-moisture state immediately responds to any change in the material’s solid skeleton of hardening CCC.
These effects serve as a physical basis for the CCC hardening and strengthening monitoring using the results ofcontinuous measurement of electric resistivity. Such monitoring is aimed at controlling various properties of the material: from the initial viscous fluid or viscous plastic state of fresh mixtures to the final elastic state of artificial stone. The results of measuring the electric resistivity are compared to those of standard tests. Thus established relationships “Electric resistivity ( ρ ) – Parameters ( i P )” (Parameters: W/C, Slump, Setting Time, Plastic strength, Compressive Strength) allow to carry out technological monitoring over the entire range of CCC hardening. All correlations Pi = f (ρ ) are described by linear relations with high correlation coefficients.
The linearity of the correlations “Strength – Electric Resistivity” is characteristic of various CCC: regular dense concrete, dry concrete mixtures (W/C ≈ 0.35), shotcrete, rising and plastic strengthening of aerated concrete at the stage of preautoclave hardening, etc.