3.3. Study of the influence of cellulose admixtures on adhesion to a concrete substrate
Analysing the results presented in Figure 5a, it can be concluded that with increasing viscosity of
The HEMC effect was slightly lower, although, in this case, the adhesion increases with the increase of the admixture viscosity. Admixtures based on MEHEC influenced theadhesion in a very diverse way. The highest adhesion was obtained for MEHEC with a viscosity of31,000 mPa·s. Further increase in the viscosity of this admixture caused a slight decrease in adhesion.
The standard requirements for the adhesion are mainly determined for repair mortars for concrete
and tile adhesives. In the case of renovation plasters, similarly to the other plasters, a value equal to the
tensile strength of the substrate is assumed to be sufficient adhesion.
Based on the opinion of practitioners, sometimes, despite the fulfilment of mandatory requirements, not all renovation plasters offered by commercial manufacturers show sufficient adhesion. In particular, this applies to the use of renovation plasters on poor substrates which are quite common in the renovation of objects of historical importance.
The author's technological practice shows that for renovation plasters, the adhesion should
not be lower than 0.5 MPa, with the optimal value at 0.8 MPa. In the aspect of the renovation plaster
under consideration, the highest adhesion was obtained for HPMC 52000.
The paper presented the influence of cellulose admixtures on consistency, water retention capacity and
adhesion to substrates. As a result of the examination, it was found that due to the shaping of physical
properties of renovation plasters, which were analysed in this paper, the best results can be obtained
with (hydroxypropyl)methyl cellulose HPMC and (hydroxyethyl)methyl celluloseHEMC, particularly:
KEY WORDS:#Cellulose Ethers#Plasters#Water Retention