Sample Placement Effect During Curing on Microwave Reflection Properties of Early Age Engineered Cementitious Mortar Specimens

Microwave reflection properties of early age (one to nine days) engineered cementitious mortar specimens with a different water-to-binder ratio (w/b) and different sample placements during curing were measured by an open-ended waveguide probe, and then, the effect of these curing conditions on microwave reflection properties was investigated. From this analysis, we note the following important points. First, microwave reflection properties measured from any side of the mortar specimen with higher w/b are, in general, greater than the corresponding properties measured from the same side of the mortar specimen with lower w/b (the effect of free-water content of mortar specimens with higher w/b). Second, the inclusion of fly ash into mortar mixtures retards the crossover of reflection properties of mortar specimens with different w/b values. Finally, curing conditions should be accounted for finding the correlation between the destructive compressive strength measurements and nondestructive microwave reflection properties.