ABSTRACT
In order to obtain representative measurements, three parallel and two diagonal measurements were made with help of theWenner probe and averaged (Figure 4).
To establish the influence of the partial drying out of the outer regions of the tunnel lining segment, insitu capillary absorption tests have been performed at an age of 300 days. To this aim, capillary sorption test set-ups have been placed directly over the MREs, on both sides of the segment. The set-up resembles a Carsten pipe and consists of a water container with an open connection to the concrete surface, fixed to this surface by bolts. The container is connected to a long capillary pipe (750 mm). The surface of the segment in the vicinity of the absorption cell is coated to prevent evaporation. At the onset of the capillary suction test, the water container and the capillary pipe is filled via the capillary. The absorption is measured by monitoring the drop in water level of the pipe. The water level in the capillary pipes was kept as much as constant possible at about 2/3 of its length so that the gravity effect on the measurements could be taken constant. The water uptake of the concrete has been measured at various times for 28 days. During this period, the electrical resistance has been measured with the MREs three times as well, to investigate if it was possible to follow the penetration front of the water in the concrete.
