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2. Subject of the study and research methodology used
The impact of cellulose ethers of different chemical composition and viscosity, obtained on the basis of
hydroxypropyl methylcellulose (HPMC), hydroxyethyl methyl cellulose (HEMC) and
methylethylhydroxyethyl cellulose (MEHEC), on the change of adhesion to the substrate, consistencies
and water retention properties were investigated. The research was carried using the original recipe of
renovation plasters.
2.1. Tested material.
An experiment was carried out consisting in preparing dry mixes of renovation plasters containing tested
cellulose admixtures in the amount of 0.3% against all dry ingredients. The admixture at the level of
0.3% was selected based on preliminary tests which had shown that this is the optimal amount of
admixture that allows to clearly assess its impact on the analyzed mortar property. Properties, the method
of cellulose admixtures modification and their viscosities determined in 2% solutions by Brookfield
method are presented in table 1.
The composition of the renovation mortars is shown in Table 2. The mortars were prepared in a
laboratory mixer, which is described in PN-EN 196-1:2006 standard [15]. The method of samples
mixing was in accordance with PN-EN 998-1:12 standard [16]. After adding water, the mortars were
mixed mechanically for 30 seconds, then manually for 60 seconds using a trowel, and then for 180
seconds mechanically. The agitator speed was 160/45 rpm.
2.2. Methodology of research on the influence of cellulose admixtures on the change of renovation
plasters consistency
The determination of the consistency of the fresh mortars was made using the flow table method in
accordance with PN-EN 1015-3:2006 standard [17]. The consistency tests were carried out after 30
minutes from the moment of mixing dry ingredients with water. This is conventionally the time that
elapses from mixing the ingredients with water until the mortar is applied in working conditions. In
laboratory practice of in mortar design, it is convenient to express the effect of admixtures on the
consistency with the amount of water that should be added to the dry ingredients in order to obtain the
same consistency.