University of applied sciences Nuremberg GEORG SIMON OHM

Improving the thermal insulation properties of thin-bed mortar Part I: Impact evaluations of various admixtures on material engineering parameters

1 A selection of modifiers for thin-bed mortar All authors
2 Gas adsorption measuring cell for determining the specific surface area (BET) of hardened thin-bed mortar fragments
3 Correlation of 7-day and 28-day compressive strength with the corresponding        28-day thermal conductivity values, λ10, dry, of thin-bed mortar samples in dependence on admixture of 10 vol.% modifier compared to the zero sample
4.1 Cumulative pore volume as a function of pore diameter within the 210 µm to 20 nm range for the thin-bed mortar zero sample and modified mortar mixes
4.2 Specific pore volume as a function of pore diameter within the 210 µm to 20 nm range for the thin-bed mortar zero sample and modified mortar mixes
5 Mercury porosimetry measuring cell (0.5 cm3 cell volume) filled with thin-bed mortar fragments
6.1 Cumulative pore volume as a function of pore diameter within the 210 µm to 20 nm range for the thin-bed mortar zero sample and modified mortar mixes
6.2 Specific pore volume as a function of pore diameter within the 210 µm to 20 nm range for the thin-bed mortar zero sample and modified mortar mixes
7 Correlation of compressive strength and porosity of hardened thin-bed mortar mixes dosed with 10 vol.% modifying admixtures compared to the zero sample
8 Radiographic analyses of a thin-bed mortar zero sample in comparison with a mortar sample containing 10 vol.% expanded perlite, a mortar sample containing 10 vol.% expanded type-II aluminosilicate, and a mortar sample containing 10 vol.% fumed silica at sample ages of 2, 7 and 28 days
9 Temperature-dependent (TG) loss of mass of a thin-bed mortar zero sample and modified mortar mixes containing 10 vol.% modifying admixture each after a curing time of 28 days in air
10 SEM micrograph of the fracture face of a thin-bed mortar (zero sample in 50-fold magnification)
11 SEM micrograph of the fracture face of a thin-bed mortar (sample containing 10 vol.% fumed silica in 50-fold magnification)
12 SEM micrograph of the fracture face of a thin-bed mortar (sample containing 10 vol.% perlite in 50-fold magnification)
13 SEM micrograph of the fracture face of a thin-bed mortar zero sample in 500-fold magnification
14 SEM micrograph of the fracture face of a thin-bed mortar sample containing 10 vol.% silica, in 1000-fold magnification
15 SEM micrograph of the fracture face of a thin-bed mortar sample containing 10 vol.% perlite, in 500-fold magnification

Monolithic walls erected with an appropriately modified thin-bed mortar should show superior thermal insulation properties. Admixing 10 vol.% fumed silica proved to reduce by 19% the thermal conductivity of a typical thin-bed mortar belonging to compressive strength class M 10. Simultaneously, it also improved the mortar’s compressive strength by nearly 16 %. The investigations also showed that an admixture of expanded perlite can increase the compressive strength by 99 %.

1 Introduction

Thin-bed cement mortar is often used for masoning up such precision-ground, monolithic wall-building materials as bricks, autoclaved aerated concrete units (Ytong), or building blocks of pumicite, expanded clay or sandy limestone [1–3]. The corresponding material engineering parameters are governed by the applicable DIN specifications [4–7], which prescribe, for example, a compressive strength level of βD ≥ 10.0 MPa for class-M 10 mortar after 28 days of curing [8].

According to one market analysis, the thermal conductivity of products in this mortar category has been stagnating...

TEXT Sebastian Schmidt1, Prof. Dr. Dr. Herbert Pöllmann2, Prof. Dr. Wolfgang Krcmar1
1University of Applied Sciences Nuremberg Georg Simon Ohm, Materials Technology Department, Nuremberg/Germany
2Institute of Geosciences and Geography, Mineralogy/Geochemistry Section, Martin-Luther-Universität Halle-Wittenberg, Halle (Saale)/Germany

This article appeared in

ZKG 6/2018

This article appeared in

ZKG 6/2018

Ressort:  Materials
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