Technical ReportAdhesive and cohesive properties of glue cement mortars with addition of organic–mineral modifiers
Introduction
Most of glue cement compositions represent ordinary mixtures of Portland cement and fractions of sand with two main additives: water-retaining-cellulose ester and adhesive-redispersed polymer. If necessary other additives may be added in order to regulate the mixtures’ properties.
Compositions of glue construction mixtures are usually characterized by high Portland cement consumption, which is necessary to provide sufficient quantity of cement paste for achieving the required adhesive strength of mortars. Improving the adhesive and cohesive properties along with decreasing the cost of glue compositions is an important technological task that is the main aim of the present study.
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Theoretical background
Following the classic theory of the adhesion, it is resulted in mechanical interlocking of the adhesive and the substrate due to penetration of glue into the materials pores. Presently adsorption, electrostatic, diffusion and chemical adhesion theories are the most known theories. Following the adsorption theory, there is a “wetting” effect of the adhesive on the adherent surface due to inter-molecular forces. The adhesive layer is formed in two stages. First migration of adhesive’s molecules
The working hypothesis and aims of the study
Analysis of modern concepts on the mechanism of cement mortars’ gluing ability shows that improving the cohesive and adhesive properties of mortars at simultaneous decrease of cement consumption and achieving high physical and mechanical characteristics is possible just by adding highly dispersed silica fillers in combination with surface-active additives and polymers. Such compositions can be considered as organic–mineral modifiers (OMM) of cement glue mortars. This conclusion allows
Used materials and research methodology
The main initial components for dry and mortar mixtures were Portland cement CEM I [7], MS is a waste product of ferrosilicon production, coal fly ash of a local power station. The chemical composition of the materials is presented in Table 1. The cement was produced from clinker with the following mineralogical composition:
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tricalcium silicate С3S – 57.10;
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dicalcium silicate C2S – 21.29;
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tricalcium aluminate C3A – 6.85;
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tetra-calcium aluminoferrite C4AF – 12.18%.
The initial materials had the
Experimental procedure, results and discussion
The main feature of glue mortars, characterizing their adhesion to the given materials, is the adhesive strength at tearing off. Additional adhesive properties of mortars that are important for facing building, characterize the adhesion area, correction duration and ability of glued construction elements to crawling.
The adhesive strength of mortars at tearing off was obtained as follows. The surface of a concrete plate with a 100 mm thickness was covered by a glue mortar that included
Conclusions
Following the experimental results, obtained in the frame of this study, adding to cement glue mortars organic–mineral modifiers, including microsilica (MS) or milled fly ash (MFA), superplasticizer (SP) and redispersed polymer powder (RPP), allow providing high values of adhesive and cohesive strength.
The effect of modified glue mortars composition factors on possible decrease in shear strength of glue line under repeated freezing and thawing was studied. It was shown that adding OMM has a
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