2.3. Methodology of research on the influence of cellulose admixtures on the ability to retain water in
fresh renovation plaster
The retention of water in fresh mortar is described by the percentage of water that remains in the mortar
after a brief draining of water through the filter paper . In laboratory conditions, the measurement
consisted of placing fresh mortar in a plastic ring with a diameter of 140 mm and a thickness of 10 mm,
set on a filter paper and a plate also made of plastic. The mortar flow in the ring was covered with a
plastic plate and left for 5 minutes. The amount of water adsorbed by the filter paper was adopted as the
measure on the basis of which the water retention value (WRV) was calculated as a percentage
determined from equation (1):
WRV =100-W (1)
where: WRV - water retention value, W - relative loss of water in the mortar (%).
The water content in mortars was constant and amounted to 25% in relation to all dry ingredients,
the w/c ratio was 1.04.
2.4. Methodology of research on the influence of cellulose admixtures on the adhesion of hardened
mortars to the substrate
The adhesion of renovation plasters was determined in accordance with PN-EN 1015-12:2016-08E
standard , as the value of critical stress during which adhesive or cohesive detachment of the layer
of applied material from the substrate took place. For this purpose, the mortar was applied to a thickness
of 10 mm on a concrete block. After 28 days of seasoning, 50 mm diameter discs were cut out of the
plaster. After cleaning the surface of the samples, five steel discs were attached with epoxy glue at the
points of incision. The critical strain was measured using the "Pull-off" device on the ProceqDyna Pull
off Tester Z-16. The consistency of the mortars was constant at the flow of 170 mm±5 mm determined
by the flow table test.
3. Research results and discussion
The test results are shown in table 3.
3.1. Study of the influence of cellulose admixtures on the consistency of mortar
The results of the influence of cellulose admixtures, differing in the modification and viscosity, on the
consistency change determined using the flow table method are shown in Figure 2. To quantify the