Surface curing effect on reflection response of hardened cementitious mortar samples

Surface curing effect of hardened engineering cementitious mortar (ECM) samples with distinct water-to-binder ratios (w/b) is analyzed by recording amplitude of reflection response vertical bar Gamma vertical bar or conductance term g measured by a microwave open-ended waveguide probe. Frequency dependencies (between 3.95-5.85 GHz) of vertical bar Gamma vertical bar and g measured from various surfaces (top, bottom, and lateral) of ECM samples with w/b = 0.2 and 0.3 are presented at the 720th days of curing (hardened ECM). In addition, their temporal dependencies (over 1-9 and 720-815 days) are presented for the frequency value of 4.56 GHz. From our analysis, contrary to top and lateral surface behaviors, it is noted that crossover between g values measured from bottom surfaces of ECM samples with w/b = 0.2 and 0.3 delays for a long time (around 550 days). Propagation-related studies should take into account reflection profiles varying with wall height for accurate prediction.