Experimental investigations on water sorptivity in mortars with the use of X-ray micro-CT system

Abstract

The phenomenon of water sorptivity in prismatic mortar specimens was investigated in this experimental work. This phenomenon is closely linked to material durability. Sorptivity evaluated during a steady stage, combined with exposure conditions can be used for performing service life predictions. Water's initial and secondary sorptivity in unsaturated mortar specimens were measured in laboratory tests following the standard ASTM C 1585–04. The impact of initial porosity on sorptivity was investigated by varying the cement-to-sand ratio (c/s) and the water-to-cement ratio (w/c). In addition, the surface area of water intake was changed which was either vertical or horizontal in orientation. The water distribution in the test specimens was visualized using the 3D X-ray micro-CT system SkyScan 1173 which was a novelty. The mortar sorptivity was found to be highly responsive to the c/s ratio, varying by up to 100%, and to be moderately impacted by the w/c ratio, varying by up to 25% and the surface inflow direction, varying by up to 45%. The sorptivity increased with a decline in the c/s (in agreement with the existing literature data) and w/c ratio (in contrast with the existing literature data). According to micro-CT images, the water distribution in the specimens was found to be non-uniform and larger porosity contributed to the rise in water level but not to the total volume of absorbed water (in contrast to the literature data). The snap-off events were detected ahead of the waterfront.