Furthermore, the air content in fresh mortars was measured in accordance with PN-EN 1015-7:2000P
standard . According to the WTA instruction , the air content for renovation plasters should not
be less than 25%.
The cellulose admixtures and the increase in mortar consistency associated with their
presence reduced the air content in the fresh mortar. For mortar containing no cellulose admixture, the
air content was 26.5%. With increasing viscosity of admixture and a constant w/c, the air content
slightly decreased, figure 3.
3.2. Study of the influence of cellulose admixtures on water retention in mortar
Figure 4a. shows changes in water retention depending on the viscosity of cellulose (for 2% solutions,
Brookfield viscosity gauge).
It can be concluded that there is a relationship between the viscosity of cellulose admixtures and the
WRV water retention by the mortar, figure 4a. This effect is uneven, with the greatest intensity observed
when the viscosity of cellulose admixtures changed from 6,000 mPa·s to 20,000 mPa·s in the case of
HPMC, from 6,500 to 14,000 mPa·s for MEHEMC, and from 6,000 to 31,000 mPa·s. A further increase
in the viscosity of cellulose admixtures had an increasingly lower effect on the change in WRV.
Analysing the obtained results, it can be stated that the HPMC- and HEMC-based admixtures had
the greatest influence on the water retention of renovation mortars. For the mortar containing no
cellulose admixtures, the value of water retention was approx. 75 %. For those above-mentioned
admixtures with a viscosity over 15,000 mPa·s, water retention values in mortars exceeded 95%.
Figure4b. shows the changes in water retention depending on the consistency of the mortar. Analysing th
graph, it can be concluded that cellulose admixtures with a comparable viscosity have a different effect
on the consistency, and a different effect on WRV water retention value.
Although the increase in viscosity of admixtures above 15,000 mPa·s clearly influenced the change of mortar consistency, it did not affect the water retention capacity. The increase in the viscosity of admixtures from 15,000 to 65,000 mPa·s, the resulted in WRV coefficient results being in a narrow range from 96 to 97%.