Feuchtetransport über Materialgrenzen im Mauerwerk / Moisture transport through interfaces in masonry

Abstract

In order to get more information about the moisture transport through the interface of two capillary active materials, the capillary liquid transport for two types of layers of natural sandstone in ideal hygric contact was observed. The results show that the water absorption behaviour of the composite samples is strongly dependent on the sequence of its composition. This can be explained by the different water retention curves of the materials. Calculation shows in all cases good agreement between the measured and calculated values for the water absorption and for the moisture profiles. Examinations of the moisture transport between rendering and brick show that the moisture transport is reduced. Comparisons between measurement and calculation indicate that the introduction of a thin resistance layer between rendering (or mortar) and stone is necessary. With this layer the liquid transport through the interface can be simulated correctly.

Moisture transfer through mortar joints: A sharp-front analysis

“…After curing and edge removal, appropriately sized mould mortar 'joints' are obtained by further sawing. The mould mortar joints and brick facets are assembled with thin kaolin clay layers between the different materials, to ensure perfect hydraulic contact [1]. All samples are finally dried at 50 °C and 3 % RH: low temperature drying is preferred to avoid damage during drying and to avoid removing chemically bound water from the cementitious materials.…”

“…While its constituent materialsceramic brick and cement mortarare reasonably well understood, the hygric behaviour of masonry is often shown to deviate from the normal unsaturated flow theory. In this respect, most authors refer to an imperfect contact and hence an interface resistance in the brick-mortar bond plane [1][2]. The 'interface resistance' concept was introduced in [3], but in fact only for a non-bonded contact between building materials.…”

“…The extraction may similarly introduce interface resistances as it transports fine cement particles to the interface [7] and creates compaction pores near the interface [8]. While most authors [1][2][3][4] opt for 'introduced interface resistances' or 'modified hygric properties', [13] revealed that both influences simultaneously affect the moisture transfer in mortar joints. That study moreover demonstrated the relation between the modified hygric properties and introduced interface resistances and the water extraction during curing.…”

Influence of the nature of interfaces on the capillary transport in layered materials

“…Capillary transport in masonry, a multi-layered material composed of bricks and mortar joints, deviates from the classical capillary transport in a homogeneous material. In literature, the deviation is attributed to the presence of a hydraulic resistance at the brick-mortar interface [9][10][11] or to a change of the moisture transport properties of the mortar joint [12]. The change in moisture transport properties of mortar is explained by the curing conditions of the fresh mortar.…”

“…The change in moisture transport properties of mortar is explained by the curing conditions of the fresh mortar. The fresh mortar is placed between two bricks and extraction of water from the fresh mortar to the brick may result in a change of the water/cement factor and resulting properties of the mortar [10,[12][13][14]. Nyame and Illston [15] and Goto and Roy [16] show that porosity decreases with decreasing water-cement ratio for hardened cement paste.…”